Abstract
This paper shows the latest progress in steel grades and in case hardening technology for gear components.
To answer the demand for fuel-efficient vehicles, modern gear boxes are built much lighter. Improving fatigue resistance is a key factor to allow for the design of thin components to be used in advanced vehicle transmissions. The choice of material and the applied heat treat process are of key importance to enhance the fatigue resistance of gear components.
By applying the technology of Low Pressure Carburizing (LPC) and High Pressure Gas Quenching (HPGQ), the tooth root bending strength can be significantly enhanced, compared to traditional heat treatment with atmospheric carburizing and oil quenching.
Besides heat treatment, significant progress has been made over the past years on the steels being used for gear components. The hardenability of case hardening steels such as 5130H, 5120H, 20MnCr5, 27MnCr5, 18CrNiMo7-6 etc. has been stepwise increased in recent years. An important factor for fatigue resistance is the grain size after heat treatment. Therefore, grain size control is a key goal when developing new modifications of steel grades.
After enhancing grain size control, it was possible to increase the carburizing temperatures over the past years from 930°C to 980°C (1700°F to 1800°F) which resulted in shorter heat treatment cycles and thus in significant cost savings.
With the introduction of new microalloyed steels for grain size stability, carburizing temperatures can now be even further increased to temperatures of up to 1050°C (1920°F), leading to even more economic process cycles. By adding microelements such as Niobium or Titanium in the ppm-range, nitride and carbonitride-precipitates are formed. These precipitates effectively limit the grain-growth during the heat treatment process.
International Journal of Engineering Research and DevelopmentIJERD Editor
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Aerospace Engineering.
International Journal of Engineering Research and DevelopmentIJERD Editor
Electrical, Electronics and Computer Engineering,
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Aerospace Engineering.
Comparative study of behaviour of cold formed steeland hot rolled steel secti...eSAT Journals
Abstract Cold-formed steel is used in large number of products. For example in metal building construction, for wall coverings, floor decking etc. Cold-formed steel is a basic component in construction of lightweight prefabricated structures like stud frame panels, trusses and portal frames.The Cold formed steel term itself make it different from hot rolled steel due to difference in manufacturing methods. Typically columns, beams and angles etc. are different globally. At room temperature cold formed steel members are formed by bending flat sheets. Cold formed steel sections mainly created using two methods those are break press through and rolling. Where hot rolled steel members are precasted. Therefore cold formed steel sections can be easily available at any place where hot rolled sections are not available. The cold formed steel components can be used for larger and complex structures. The Comparison of cold formed steel section and Hot rolled steel section of equal cross sectional area is done in this research paper. Sections were experimentally tested under axial compression in universal testing machine. Simultaneously, ultimate compressive strength of cold formed members and hot rolled members has been investigated. Also, different properties of the sections such as stresses induced in the sections, strain in the section, axial deflection, and lateral deflection are obtained experimentally. For measuring strain experimentally strain gage foils were used. The validation of results is done by preparing finite element model in ABAQUS software. From experimental work it is observed that cold formed steel sections has more load carrying capacity as compared to hot rolled steel section. Keywords: Ultimate compressive strength, buckling, cold formed steel, deflection, stress, strain, ABAQUS
Effect of Subzero Treatment on Microstructure and Material Properties of EN...IJMER
Cryogenic treatment of steels has been widely used for enhancing mechanical properties
like hardness, toughness and stable metallurgical structure. Application such as gears, kicker rods,
bolts are made of medium carbon alloy steels like EN-24 steel. In these applications, percentage of
retained austenite has considerable effects on the life of the material. A comparative study on
conventionally heat-treated (CHT) and shallow cryogenic treated (SCT) EN-24 steel was done to
evaluate the effect of shallow cryogenic treatment (SCT) on hardness, toughness and the amount of
retained austenite present in the structure of EN24 steel. The microscopic structure of cryogenic
treated EN24 steel revealed the formation of carbides, both primary and secondary carbides. An
estimated amount of 15% retained austenite after CHT tempered condition was less than 2% after SCT
tempered condition. Tensile test fractography of subzero treated (SCT) specimen revealed ductile
fracture. The maximum hardness observed in case of SCT tempered samples was 415BHN, 15%
increase from CHT tempered samples. The maximum impact strength observed in case of SCT
tempered samples was 240kJ/m2, 11% increase from CHT tempered samples. Further SCT tempered
samples, tempered at 650°C resulted in ductility increase by 55% as compared to CHT tempered
samples without sacrificing hardness.
Heat treatment 1 By
P.SENTHAMARAI KANNAN,
ASSISTANT PROFESSOR ,
DEPARTMENT OF MECHANICAL ENGINEERING,
KAMARAJ COLLEGE OF ENGINEERING AND TECHNOLOGY,
VIRUDHUNAGAR, TAMILNADU.
INDIA.
Comparative study of behaviour of cold formed steeland hot rolled steel secti...eSAT Journals
Abstract Cold-formed steel is used in large number of products. For example in metal building construction, for wall coverings, floor decking etc. Cold-formed steel is a basic component in construction of lightweight prefabricated structures like stud frame panels, trusses and portal frames.The Cold formed steel term itself make it different from hot rolled steel due to difference in manufacturing methods. Typically columns, beams and angles etc. are different globally. At room temperature cold formed steel members are formed by bending flat sheets. Cold formed steel sections mainly created using two methods those are break press through and rolling. Where hot rolled steel members are precasted. Therefore cold formed steel sections can be easily available at any place where hot rolled sections are not available. The cold formed steel components can be used for larger and complex structures. The Comparison of cold formed steel section and Hot rolled steel section of equal cross sectional area is done in this research paper. Sections were experimentally tested under axial compression in universal testing machine. Simultaneously, ultimate compressive strength of cold formed members and hot rolled members has been investigated. Also, different properties of the sections such as stresses induced in the sections, strain in the section, axial deflection, and lateral deflection are obtained experimentally. For measuring strain experimentally strain gage foils were used. The validation of results is done by preparing finite element model in ABAQUS software. From experimental work it is observed that cold formed steel sections has more load carrying capacity as compared to hot rolled steel section. Keywords: Ultimate compressive strength, buckling, cold formed steel, deflection, stress, strain, ABAQUS
Effect of Subzero Treatment on Microstructure and Material Properties of EN...IJMER
Cryogenic treatment of steels has been widely used for enhancing mechanical properties
like hardness, toughness and stable metallurgical structure. Application such as gears, kicker rods,
bolts are made of medium carbon alloy steels like EN-24 steel. In these applications, percentage of
retained austenite has considerable effects on the life of the material. A comparative study on
conventionally heat-treated (CHT) and shallow cryogenic treated (SCT) EN-24 steel was done to
evaluate the effect of shallow cryogenic treatment (SCT) on hardness, toughness and the amount of
retained austenite present in the structure of EN24 steel. The microscopic structure of cryogenic
treated EN24 steel revealed the formation of carbides, both primary and secondary carbides. An
estimated amount of 15% retained austenite after CHT tempered condition was less than 2% after SCT
tempered condition. Tensile test fractography of subzero treated (SCT) specimen revealed ductile
fracture. The maximum hardness observed in case of SCT tempered samples was 415BHN, 15%
increase from CHT tempered samples. The maximum impact strength observed in case of SCT
tempered samples was 240kJ/m2, 11% increase from CHT tempered samples. Further SCT tempered
samples, tempered at 650°C resulted in ductility increase by 55% as compared to CHT tempered
samples without sacrificing hardness.
Heat treatment 1 By
P.SENTHAMARAI KANNAN,
ASSISTANT PROFESSOR ,
DEPARTMENT OF MECHANICAL ENGINEERING,
KAMARAJ COLLEGE OF ENGINEERING AND TECHNOLOGY,
VIRUDHUNAGAR, TAMILNADU.
INDIA.
presentation is divided into three parts,
1)spur gears failure
2)Beam Strength while designing spur gears
3)Wear Strength while designing spur gears
this is not all for spur gears,just a part of design
This presentation briefly tells about the classification of Gears. It includes information about spur, helical, bevel, herringbone, rack and pinion, internal and external gears.
Unit 6- spur gears, Kinematics of machines of VTU Syllabus prepared by Hareesha N Gowda, Asst. Prof, Dayananda Sagar College of Engg, Blore. Please write to hareeshang@gmail.com for suggestions and criticisms.
ALD Holcroft® - Low Pressure Carburizing for Large Transmission PartsALD Vacuum Systems Inc.
Often, the required hardness qualities of parts manufactured from steel can only be obtained through suitable heat
treatment. In transmission manufacturing, the case hardening process is commonly used to produce parts with a hard and
wear-resistant surface and an adequate toughness in the core. A tremendous potential for rationalization, which is only
partially used, becomes available if the treatment time of the case hardening process is reduced. Low pressure carburizing
(LPC) offers a reduction of treatment time in comparison to conventional gas carburizing because of the high carbon
mass flow inherent to the process (Ref. 1).
By increasing the carburizing temperature, a further significant increase in productivity is obtained, which is not
possible in gas carburizing systems to this extent due to furnace component and process limitations (Ref. 2). By adding micro-alloy elements such as aluminium, niobium and titanium as well as properly adjusting the nitrogen content, modern case hardening steels have become sufficiently fine-grain resistant even in temperatures above 1,000°C (1,830°F)
(Ref. 3). Today’s vacuum carburizing systems are suited for heat treatment in temperature above 1,000°C.
A low-carbon steel wire of AISI 1022 is used to easily fabricate into self-drilling tapping screws,
which are widely used for construction works. The majority of carbonitriding activity is performed to improve
the wear resistance without affecting the soft, tough interior of the screws in self-drilling operation. In this
study, Taguchi technique is used to obtain optimum carbonitriding conditions to improve the mechanical
properties of AISI 1022 self-drilling tapping screws. The carbonitriding qualities of self-drilling tapping screws
are affected by various factors, such as quenching temperature, carbonitriding time, atmosphere composition
(carbon potential and ammonia level), tempering temperature and tempering time. The quality characteristics of
carbonitrided tapping screws, such as case hardness and core hardness, are investigated, and so are their
process capabilities. It is experimentally revealed that the factors of carbonitriding time and tempering
temperature are significant for case hardness. The optimum mean case hardness is 649.2HV. For the case
hardness, the optimum process-capability ratio increases by about 200% compared to the original result. The
new carbonitriding parameter settings evidently improve the performance measures over their values at the
original settings. The strength of the carbonitrided AISI 1022 self-drilling tapping screws is effectively improved.
Low-Alpha Technology: The innovative refractory solution for steel devices su...Refratechnik Group
In modern steel production, plant reliability is playing an increasingly important role. Innovative and comprehensive refractory concepts are decisive when it comes to optimizing steel production processes in terms of performance and costs. In close cooperation with our customers, we develop, test, and supply perfect solutions.
Effect of Hardness and Wear Resistance on En 353 Steel by Heat Treatment IJMER
En 353 steel is an easily available and cheap material that is acceptable for heavy duty
applications. Heat treatment on En 353 steel is improved the ductility, toughness, strength, hardness and
relive internal stress in the material. Spectrographic method is used to analyze the composition of the
alloy material. The experimental results of hardness and dry wear testing on pin-on-disc are done to get
idea about heat treated En 353 steel. It is found that the hardness and wear resistance of the En 353 steel
is improved after the heat treatment and the microstructure is changed from ferrite to martensite.
Inventors and entrepreneurs have vocations fueled by passion. Many would have done it for free or as a hobby if it hadn’t become a profession. Mark Rosenzweig is a natural creator, driven by his passion. This fuel has led Mark to develop his ideas into viable products and innovations that he has been patenting since 2003. From an innovative filter sensor and indicator for vacuum cleaners to a basket for deep fryer and methods of cooking food products to a compact cyclonic bagless vacuum cleaner. Sometimes independently and often as part of creative teams, Mark has patented just under one hundred innovative inventions between 2003 and 2017.
This presentation features ALD's DualTherm® two chamber Vacuum Furnace and it's numerous design and performance benefits including convective heating for faster cycles and minimized distortion, faster to temperature uniformity reversible gas flow during quenching, it's Dynamic-Quench® and that it can be integrated into automated lines.
Production Integrated Vacuum Heat Treatment Systems in the Automotive IndustryALD Vacuum Systems Inc.
To secure the required properties of highly stressed parts from the automotive industry these parts need to be heat treated, in many cases case hardened. This is traditionally performed in central hardening shops. However, the separation between machining and heat treatment involves great efforts regarding transport and buffering of parts leading to extended throughput times and therefore additional costs. The use of modern vacuum heat treatment technologies and the introduction of flexible, modular heat treatment systems allows for the integration of heat treatment into the mechanical production environment, and as of recently also directly into the process chain of part manufacturing.
by V. Heuer, T. Leist, G. Schmitt
ABSTRACT:
Controlling distortion is of key importance during the case
hardening process for the production of automotive and
non-automotive metallic components. By effective control of
distortion and the variation of distortion, significant costs in
post heat treatment machining processes can be avoided. In
some cases it is even possible to eliminate all post-machining.
In other cases it may be possible to avoid the press-quenching
of individual components, resulting in huge cost-benefits.
A recently introduced new vacuum furnace design allows the
treatment of small batches in a single layer of parts (“2D-treatment”)
which allows for easy automated loading and unloading
of the fixture-trays. By using the small batch concept,
a continuous flow of parts can be established (“One Piece
Flow”). There is no need to wait until enough parts are collected
to build a large batch with multiple layers (“3D-batch”).
This compact furnace unit can be implemented into the heart
of the production chain and provides heat-treatment processes
which can be fully synchronized with the green and hard
machining-operations. When performing case hardening, the
components are Low Pressure Carburized (LPC) at high temperatures
(1050 °C) followed by gas quenching. The treatment
in single layers offers an optimum in quality regarding: temperature
homogeneity, quench homogeneity and distortion
control. Typical components for this technology come from
the automotive, aerospace and tool industry. The directly following
contribution in this Journal (A. Schüler et al., p. 90-98)
shows more results achieved with this technology on selected
truck-components such as gears and sliding-sleeves.
Distortion of Gears and Sliding Sleeves for Truck Gear Boxes – a Systematical...ALD Vacuum Systems Inc.
Case hardening is the most common heat treatment for gears,
shas and synchronizer parts used in gear boxes for automotive
and commercial vehicle applications. A combination of high fatigue
resistance as well as good machinability and reliable process
stability in heat treatment ensures transmission components with
maximum strength, excellent performance and cost efficient production.
Enhancing Energy Efficiency of Thermochemical Vacuum-Processes and SystemsALD Vacuum Systems Inc.
The energy optimization of thermoprocessing equipment is of great ecological and economical importance. Thermoprocessing equipment consumes up to 40% of the energy used in industrial applications in Germany. Therefore it is necessary to increase the energy efficiency of thermoprocessing equipment in order to meet the EU’s targets to reduce greenhouse gas emissions. In order to exploit the potential for energy savings, it is essential to analyze and optimize processes and plants as well as operating methods of electrically heated vacuum plants used in large scale production.
High Temperature Vacuum Carburizing for Large Carburizing Depths in Highly St...ALD Vacuum Systems Inc.
In order to complete the existing heat treatment
shop and expand capacity, the chain
works HEKO in Wickede was looking for a
modern, clean, ecological and, most of all,
flexible heat treatment process as an alternative
to conventional gas carburizing with
oil quenching.
MWF Heat Treatment: Solutions for a Critical Process by Dr. Neil CanterALD Vacuum Systems Inc.
When the topic of metalworking is raised, most of us think of drilling a hole in a piece of metal or bending a metal part to form a component for an automobile. Not as many individuals realize that another process included under the realm of metalworking is heat treating or quenching.
Heat treatment is utilized to adjust the physical and mechanical properties of metals so that they can be used in subsequent metalworking applications. These properties are changed by the controlled heating and then cooling of metals. In many cases, the objective of heat treatment is to increase the strength of a specifi c metal alloy. Most operations are conducted on steel alloys, but nonferrous metals such as
aluminum and titanium also can be heat treated.
Integrating heat treatment into the manufacturing line has been a topic of discussion for many years. Today’s production philosophy for gear components
usually relies on the traditional separation between
soft machining, heat treatment, and hard machining. Heat
treatment is performed in a central hardening shop, and
there is no continuous flow of production parts between
the different operations such as soft machining, heat
treatment, shot peening, and hard machining. Instead the
parts are first collected into batches and then moved from
operation to operation, so large numbers of production
parts are being stored in buffers or are in transit between
the different operations. A continuous flow of production
parts between operations is only occurring today between
some of the soft machining operations and some hard
machining operations. This discontinuous flow of production
results in increased logistical and documentation
efforts, increased turnaround times and, ultimately, in
increased production costs.
Dual chamber vacuum furnace for Low Pressure Carburizing (LPC) and High Press...ALD Vacuum Systems Inc.
Dual vacuum furnaces with separated heating and cooling processes are providing several advantages when compared to single chamber vacuum furnaces. This includes faster heating up, less energy consumption, more quenching severity and less maintenance. Accordingly a new, “second
generation” of dual vacuum furnace for low pressure carburizing and high pressure gas quenching, DualTherm®, was developed using proven technologies from the ModulTherm® series of vacuum furnace systems.
The first furnace was recently installed at a commercial heat treater and is now in three-shift-operation.
Overview of the fundamental roles in Hydropower generation and the components involved in wider Electrical Engineering.
This paper presents the design and construction of hydroelectric dams from the hydrologist’s survey of the valley before construction, all aspects and involved disciplines, fluid dynamics, structural engineering, generation and mains frequency regulation to the very transmission of power through the network in the United Kingdom.
Author: Robbie Edward Sayers
Collaborators and co editors: Charlie Sims and Connor Healey.
(C) 2024 Robbie E. Sayers
Student information management system project report ii.pdfKamal Acharya
Our project explains about the student management. This project mainly explains the various actions related to student details. This project shows some ease in adding, editing and deleting the student details. It also provides a less time consuming process for viewing, adding, editing and deleting the marks of the students.
NO1 Uk best vashikaran specialist in delhi vashikaran baba near me online vas...Amil Baba Dawood bangali
Contact with Dawood Bhai Just call on +92322-6382012 and we'll help you. We'll solve all your problems within 12 to 24 hours and with 101% guarantee and with astrology systematic. If you want to take any personal or professional advice then also you can call us on +92322-6382012 , ONLINE LOVE PROBLEM & Other all types of Daily Life Problem's.Then CALL or WHATSAPP us on +92322-6382012 and Get all these problems solutions here by Amil Baba DAWOOD BANGALI
#vashikaranspecialist #astrologer #palmistry #amliyaat #taweez #manpasandshadi #horoscope #spiritual #lovelife #lovespell #marriagespell#aamilbabainpakistan #amilbabainkarachi #powerfullblackmagicspell #kalajadumantarspecialist #realamilbaba #AmilbabainPakistan #astrologerincanada #astrologerindubai #lovespellsmaster #kalajaduspecialist #lovespellsthatwork #aamilbabainlahore#blackmagicformarriage #aamilbaba #kalajadu #kalailam #taweez #wazifaexpert #jadumantar #vashikaranspecialist #astrologer #palmistry #amliyaat #taweez #manpasandshadi #horoscope #spiritual #lovelife #lovespell #marriagespell#aamilbabainpakistan #amilbabainkarachi #powerfullblackmagicspell #kalajadumantarspecialist #realamilbaba #AmilbabainPakistan #astrologerincanada #astrologerindubai #lovespellsmaster #kalajaduspecialist #lovespellsthatwork #aamilbabainlahore #blackmagicforlove #blackmagicformarriage #aamilbaba #kalajadu #kalailam #taweez #wazifaexpert #jadumantar #vashikaranspecialist #astrologer #palmistry #amliyaat #taweez #manpasandshadi #horoscope #spiritual #lovelife #lovespell #marriagespell#aamilbabainpakistan #amilbabainkarachi #powerfullblackmagicspell #kalajadumantarspecialist #realamilbaba #AmilbabainPakistan #astrologerincanada #astrologerindubai #lovespellsmaster #kalajaduspecialist #lovespellsthatwork #aamilbabainlahore #Amilbabainuk #amilbabainspain #amilbabaindubai #Amilbabainnorway #amilbabainkrachi #amilbabainlahore #amilbabaingujranwalan #amilbabainislamabad
Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
Using recycled concrete aggregates (RCA) for pavements is crucial to achieving sustainability. Implementing RCA for new pavement can minimize carbon footprint, conserve natural resources, reduce harmful emissions, and lower life cycle costs. Compared to natural aggregate (NA), RCA pavement has fewer comprehensive studies and sustainability assessments.
NUMERICAL SIMULATIONS OF HEAT AND MASS TRANSFER IN CONDENSING HEAT EXCHANGERS...ssuser7dcef0
Power plants release a large amount of water vapor into the
atmosphere through the stack. The flue gas can be a potential
source for obtaining much needed cooling water for a power
plant. If a power plant could recover and reuse a portion of this
moisture, it could reduce its total cooling water intake
requirement. One of the most practical way to recover water
from flue gas is to use a condensing heat exchanger. The power
plant could also recover latent heat due to condensation as well
as sensible heat due to lowering the flue gas exit temperature.
Additionally, harmful acids released from the stack can be
reduced in a condensing heat exchanger by acid condensation. reduced in a condensing heat exchanger by acid condensation.
Condensation of vapors in flue gas is a complicated
phenomenon since heat and mass transfer of water vapor and
various acids simultaneously occur in the presence of noncondensable
gases such as nitrogen and oxygen. Design of a
condenser depends on the knowledge and understanding of the
heat and mass transfer processes. A computer program for
numerical simulations of water (H2O) and sulfuric acid (H2SO4)
condensation in a flue gas condensing heat exchanger was
developed using MATLAB. Governing equations based on
mass and energy balances for the system were derived to
predict variables such as flue gas exit temperature, cooling
water outlet temperature, mole fraction and condensation rates
of water and sulfuric acid vapors. The equations were solved
using an iterative solution technique with calculations of heat
and mass transfer coefficients and physical properties.
About
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Technical Specifications
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
Key Features
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface
• Compatible with MAFI CCR system
• Copatiable with IDM8000 CCR
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
Application
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
RAT: Retrieval Augmented Thoughts Elicit Context-Aware Reasoning in Long-Hori...
Improved Material and Enhanced Fatigue Resistance for Gear Components
1. 15FTM02
AGMA Technical Paper
Improved Materials and
Enhanced Fatigue
Resistance for Gear
Components
By Dr. Volker Heuer,
Dr. Klaus Loeser,
and Gunther Schmitt
ALD Vacuum Technologies GmbH
Hanau, Germany
3. 2 15FTM02
Improved Materials and Enhanced Fatigue Resistance
for Gear Components
Dr. Volker Heuer, Dr. Klaus Loeser, and Gunther Schmitt
ALD Vacuum Technologies GmbH – Hanau, Germany
Introduction
For decades, the gear industry has addressed the challenge to produce high-performance components in
a cost-effective manner. To meet design intent, vehicle transmission components need to be heat treated.
In many applications, the high demands regarding service life of components can be reached only by the
application of a customized case hardening. This case hardening process results in a wear-resistant
surface layer in combination with a tough core of the component.
Enhanced fatigue resistance of the components has become more and more important. This is mainly
driven by the need for weight reduction and by the introduction of higher durability claims. Some vehicle
OEMs have introduced a 100000-mile warranty for the powertrain.
When trying to improve fatigue properties, two important areas need to be focused on: improvements of
material and improvements in heat treatment technology. This paper describes the advances in these
fields over recent years.
Improved Material
Traditionally, gear components are made of case hardening steels such as 8620H, 8625H, 5120H,
5130H, 9310H, 16MnCr5, 20MnCr5, 27MnCr5, 18CrNiMo7-6, and others. The chemical composition of a
steel grade defines its hardenability, with the most important elements being carbon, manganese,
chromium, nickel, boron and molybdenum. The hardenability of a steel grade can be quantified either with
“DI-values” or with “Jominy-curves.”
The use of DI-values is popular in North America. DI stands for “ideal diameter” and means the largest
diameter of a given steel composition which under maximum quench conditions still reaches 50%
martensite in the core [1]. This means that a high DI-value corresponds with a good hardenability of the
steel.
The use of Jominy-curves is very popular in Europe. The Jominy hardenability curve is a standardized
test as described in ASTM A255 [2] using cylindrical specimen with 25mm and 100mm height as test
probes. After austenitizing, the probe is hung vertically and quenched with a water jet of well-defined
intensity. The water jet is directed towards the lower face of the cylindrical specimen. This means that
with increasing distance from this face, the quench rate inside the probe is continually reduced.
After completion of the quench, the hardness profile is measured in an axis-parallel line with 0.4mm
distance to the surface. The resulting curve is the so-called Jominy-curve. This curve describes the
relation between the distance from the lower face of the probe in mm or in 1/16 of an inch (so-called
“Jominy-value“) and the achieved hardness in HRC. Besides the experimental method as described
above, the curve can be calculated from the chemical composition of the steel grade, as well. Fig. 1
shows typical Jominy-curves of case hardening steels.
4. 3 15FTM02
Fig. 1 – Typical Jominy-curves of case hardening steels
(hardness as a function of the Jominy-distance)
Each standardized steel grade has a defined range of hardenability, meaning that each grade has a
minimum and maximum Jominy curve. However, many producers have restricted this range further.
Doing so will result in the following benefits:
- improved distortion control;
- reduced variation of core hardness and case hardening depth (CHD) after heat treatment;
- reduced variation of microstructure (e.g. avoiding bainite formation in the surface area) after heat
treatment.
Over recent years, in many applications the hardenability-range was restricted to the upper end of the
standard range. The tightest range, which can be supplied by the steel industry today, is a band of
4 HRC. Fig. 2 shows an example of the grade 18CrNiMo7-6 with the standard range and with the
restricted hardenability. The so-called HH-grade (high hardenability) has a range of hardenability which
is restricted to the upper third of the standard range.
5. 4 15FTM02
Fig. 2 – Standard range and restricted range of hardenability
for the case hardening steel 18CrNiMo7-6
In the following three examples of successful restrictions of hardenability are given.
Levers made of 8620H-material were initially supplied using the standard range with a minimum DI=1.7
inches (see Fig. 3). This resulted in significant variations of core hardness and case hardening depth
(CHD). After restricting the material to a minimum DI=2.6 inches, these variations were minimized and a
consistent quality was achieved after heat treatment.
Fig. 3 – Lever made of 8620H-material
Shafts made of 28MnCrB7-2-material were initially supplied in a rather wide range of hardenability with
DI=2.2 to 3.4 inches (see Fig. 4). This led to significant variations in core hardness, and additionally,
resulted in problems achieving consistent microstructure after heat treatment. After restricting the
hardenability to a range of DI=2.7 to 3.1 inches, those variations were eliminated successfully.
Fig. 4 – Shafts made of 28MnCrB7-2-material
Final Drive Ring gears made of 4121M-material were initially supplied with DI-values ranging from 2.7 to
3.1 inches (see Fig. 5). This led to significant variations in core hardness. After improving the
hardenability to a range of DI=2.9 to 3.3 inches, those variations were reduced and core hardness
specification (28HRC min.) was safely reached.
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Fig. 5 – Final Drive Ring gears made of 4121M-material
Advanced heat treatment technology
The high demands regarding service life of transmission components for most applications can be
reached only by the application of a customized case hardening. This case hardening process results in a
wear-resistant surface layer in combination with a tough core of the component. Over the past 15 years,
the technology of Low Pressure Carburizing (LPC) and High Pressure Gas Quenching (HPGQ) was
established in serial production. LPC is often referred to as Vacuum Carburizing as well. Typical
applications include gear parts, machine components, and bearing components, as well as injection
systems for engines.
The Low Pressure Carburizing (LPC) process takes place in a pressure range between 5mbar and
15mbar and a temperature range between 870°C to 1050°C. In most cases, the carburizing temperature
is between 940°C and 1000°C. During the complete process, the treated components are not exposed to
any traces of oxygen [3].
Fig. 6 shows the LPC process in a schematic diagram. First, the charge enters the furnace chamber
under vacuum, followed by convective heating under a nitrogen atmosphere close to 1bar. Convective
heating offers a quicker and more homogenous heating of the load compared to vacuum heating alone.
Subsequently, another heating phase under vacuum takes place. The actual carburizing and diffusion
starts after all parts have reached the specified carburizing temperature. Carburizing takes place by
applying a routine of alternating pulses and diffusion-steps. Acetylene is used in most applications as the
carbon source.
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Fig. 6 – Schematic diagram of the Low Pressure Carburizing (LPC)
and High Pressure Gas Quenching (HPGQ) process
Once the targeted carbon profile is obtained, the parts are quenched. Quenching can be initiated either
from carburizing temperature or from a lower hardening temperature. In most cases, High Pressure Gas
Quenching (HPGQ) with either nitrogen or helium is applied after LPC [4]. In a few applications, oil-
quenching is applied after LPC.
Table 1 – Comparison of treatment times for LPC and Atmospheric Gas Carburizing
The high mass transfer of carbon into the components during LPC leads to significantly shorter treatment
times compared to conventional gas carburizing (see Table1).
When combining LPC with High Pressure Gas Quenching (HPGQ), the process provides the following
advantages compared to Gas Carburizing combined with Oil Quenching:
- excellent carburizing homogeneity even for components with complex shape;
- avoiding intergranular oxidation (IGO) and surface oxidation;
- shorter cycle times;
- potential for further reduction of cycle time when applying High Temperature LPC;
8. 7 15FTM02
- possibility to integrate heat treatment into the production line [5];
- no conditioning of the equipment necessary (meaning no stepwise heating-up and no saturation of
the furnace insulation necessary);
- clean surfaces of parts after heat treatment, no washing of parts necessary;
- environmentally friendly process (small consumption of resources; no disposal of oil or salt bath
residues);
- potential to reduce heat treat distortion [6].
Altena studied, in particular, the field of carburizing homogeneity. Fig. 7 shows the hardness profile after
LPC & HPGQ compared to Gas Carburizing & Oil Quenching [7]. When using LPC & HPGQ, the
hardness profile at the root is almost identical to the profile at the flank.
Fig. 7 – Hardness profiles of tooth flank and tooth root;
comparison of Gas Carburizing and LPC [7]
In the next step, Altena studied if the carburizing or the quenching step was the deciding factor for the
improvement of hardness results. Fig. 8 compares the differences in CHD between root and flank when
using Gas Carburizing & Oil Quench, LPC & Oil Quench and LPC & Gas Quench. When using Gas
Carburizing, the difference was 18 to 19%. When using LPC, the difference was 7 to 8%, regardless of
the quench method. Therefore, Altena concluded that the carburizing step was decisive for the improved
results.
9. 8 15FTM02
Fig. 8 – Case hardening depth (CHD) of tooth flank and tooth root;
comparison of Gas Carburizing and LPC [7]
Carburizing temperature and microalloyed steel grades
The costs of the heat treatment process are largely driven by the cycle time. As shown in Table 1, the
high-mass transfer of carbon into the components results in significantly shorter treatment times of LPC,
compared to atmospheric gas carburizing. The advantage of LPC can be further enhanced by increasing
the carburizing temperature. With increasing carburizing temperature, the diffusion rate rises sharply, and
thus carburizing time is significantly reduced (see Fig. 9).
Furthermore, the limit for carbide precipitation shifts to higher values. According to the iron-carbon
diagram, the precipitation limit is increased in unalloyed steel (i.e. C15) from 1.3% C at 930°C to 1.65%C
at 1030°C. Consequently, high temperature carburizing allows one to target higher surface carbon
contents in each carburizing pulse. The now higher concentration gradient leads to a further reduction of
treatment time. This additional reduction of carburizing time is not even reflected in Fig. 9.
Table 2 illustrates the treatment times for LPC of 18CrNiMo7-6 at different temperatures for a case depth
of 1.5mm. It shows that the total process time is reduced by 40% if carburizing temperature is elevated
from 930°C to 1030°C.
The potential for improvement is increased with higher case depth requirements. For material 15CrNi6
and a case depth of 3mm, for example, a total process time reduction of 55% was verified when the
carburizing temperature was increased from 950°C to 1050°C [8].
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Fig. 9 – Carburizing depth as a function of carburizing temperature and duration
(without heating; with case hardening depth CHD610 = EHT610 defined at 610 HV) [9]
Table 2 – Treatment times for LPC of 18CrNiMo7-6 at different temperatures (CD = 1.5 mm)
Fig. 10 shows the comparison between a conventional LPC process at 960°C and a high temperature
LPC process (HT-LPC) at 1050°C. For a given CHD of 0.65mm, the cycle time is reduced from 180min to
40min. Combined with gas quenching, the HT-LPC process offers a rapid case hardening process with
low values of heat treat distortion.
11. 10 15FTM02
Fig. 10 – Process cycle of Low Pressure Carburizing (LPC) and High Temperature–Low Pressure
Carburizing (HT-LPC); CHD= 0.65mm for both cases [5]
Over recent years, the carburizing temperatures were risen steadily (see Fig. 11). This led to enormous
cost reductions and to dramatic savings of energy.
Fig. 11 – Commonly-used carburizing temperature over the past years
when applying Low Pressure Carburizing (LPC)
12. 11 15FTM02
However, when using today’s conventional case hardening steels, there are limitations. When applying
high carburizing temperatures above the range of 980°C to 1000°C, this may lead to an unwanted grain
growth. Components with coarse or mixed grains have the following disadvantages:
- higher macroscopic heterogeneity;
- less toughness, especially in the carburized area;
- lower tooth root bending strength.
Especially for dynamically loaded parts, the formation of coarse grains can reduce service life
substantially. As a countermeasure, steel suppliers started several years ago to develop new micro-
alloyed steel grades to prevent unwanted grain growth [10], [11]. These micro-alloying elements form
precipitates during the steel production process which act as grain boundary pinning particles and thus
inhibit abnormal grain growth during heat treatment at high temperatures.
For high temperature carburizing up to 1050°C, such steels often have a controlled amount of nitrogen, N
(120–170 ppm) and aluminum, Al (250–350 ppm). Furthermore, a small amount of niobium, Nb (320–400
ppm) is being added to the steel. The steel production process route is controlled in a way that an
optimum size and distribution of the Al(N)- and Nb(C,N)- precipitates are being secured. Several micro-
alloyed steel grades have been developed and successfully tested jointly by steel suppliers and gear
manufacturers [12], [13].
Currently, several gear manufacturers are in the process of adjusting their material specifications to use
these materials in high temperature heat treatment. No negative influence of micro-alloying on the gear
machining processes has been reported.
Furthermore, the material needs to have a sufficient and controlled hardenability to allow for quenching
with moderate quench intensities. High quench intensities should be avoided to facilitate a cost-effective
gas quench process. Typical steel grades suited for that process are 20MnCr5-HH, 23MnCrMo5,
27MnCr5, 18CrNiMo7-6 or 20NiMoCr6-5, 5120, 5130, or 9310.
The use of microalloyed materials is necessary to exploit the vast potential of process time reduction
through high temperature carburizing by means of LPC.
Improvements in fatigue resistance
Fig. 12 illustrates the stress distribution on running gears. The highest stress appears at the flank and the
root of the teeth.
Fig. 12 – Stress on running gears
(Source: WZL-RWTH Aachen)
13. 12 15FTM02
One popular test method to quantify tooth root fatigue is the Imbalance-Excited Resonance Pulsator—
also called the “Pulsator test.” Fig. 13 shows the set-up of the test rig.
Fig. 13 – Set-up of Imbalance-Excited Resonance Pulsator (test)
(Source: WZL-RWTH Aachen)
The tested gear is part of a mechanical oscillation system with a sinusoidal load applied. The components
are tested with different loads, and as a result, the S/N curve (Wöhler curve) is generated. This curve
assigns—for a certain failure probability—the achievable number of load cycles to each load level.
The German drivetrain research association (FVA) has determined S/N-curves in order to compare test
gears heat treated with Gas Carb. & Oil Quenching and test gears treated with LPC & HPGQ [14]. These
S/N curves were determined by using the Pulsator test. The components were not shot-peened. Fig. 14
shows a comparison of the tooth root bending strength in the range of limited fatigue life at N = 3 ·104
load cycles for 50% failure probability. Two different materials were tested. For both materials 20MnCr5
and 18CrNiMo7-6 the gears treated with LPC demonstrated higher bending strength than the gas
carburized ones. When comparing the gears made of 18CrNiMo7-6 treated with LPC at 940°C with those
treated at 1050°C the later ones showed significantly lower strength. This can be explained with the grain
growth which occurred during treatment at 1050°C. The test gears were made of a standard grade
without micro-alloys, therefore formation of large grains was not avoided.
Fig. 14 – Tooth root bending strength in the range of limited fatigue life at N = 3x104
load cycles;
50% failure probability; derived from Pulsator test; comparison of “Gas Carb. & Oil Quench” and
“LPC & Gas Quench” and different carb. temperatures; [14]
14. 13 15FTM02
The nominal bending stress number (endurance limit) is given in Fig. 15. Again, the LPC-treated gears
demonstrate higher strength compared to the gas carburized gears.
Fig. 15 – Nominal bending stress number (endurance limit); derived from Pulsator test;
comparison of “Gas Carb. & Oil Quench” and “LPC & Gas Quench” [14]
A summary of the tooth root endurance limit as a function of the carburizing method and the carburizing
temperature is given in Fig. 16. Clearly, the LPC-treated gears demonstrate higher tooth root endurance
limit (meaning strength against tooth break at the tooth root) compared to gas carburized gears. When
analyzing pitting on the tooth flank, the same results were obtained when comparing LPC-treated and gas
carburized test gears [14].
15. 14 15FTM02
Fig. 16 – Tooth Root Endurance Limit (nominal bending stress number) as a function of the
carburizing method and the carburizing temperature [14]
Summary and future works
Improvements in heat treatment technology and improvements of material are key factors to enhance the
fatigue resistance for gear components. A clear trend towards
- a restriction of hardenability of the steel, and
- an increase of hardenability of the steel
could be observed over recent years. As a result, the variations in core hardness and case hardening
depth (CHD) after heat treatment were significantly reduced. Another important benefit when restricting
material hardenability is an improvement of distortion control, which was described in earlier publications.
The application of advanced heat treatment technologies such as Low Pressure Carburizing (LPC) in
combination with High Pressure Gas Quenching (HPGQ) offers a lot of benefits. One of them is an
enhancement of tooth root bending strength compared to the technology of Gas Carburizing with Oil
Quenching.
With the introduction of newly-developed microalloyed case hardening steels, the LPC temperatures
can be increased up to 1050°C (1920°F), and even higher. Raising carburizing temperature results in
a dramatic reduction of cycle time, and therefore in great savings of production costs and energy.
16. 15 15FTM02
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