This document provides information on TRIP (TRansformation Induced Plasticity) steels from ArcelorMittal, including descriptions, applications, standards, availability, processing recommendations, and mechanical properties. TRIP steels offer high strength and ductility from their microstructure composed of islands of retained austenite and bainite in a ferritic matrix. They are suitable for automotive structural and reinforcement parts. The document discusses grades, coatings, formability, welding parameters, fatigue strength, and impact performance of TRIP steels. Technical support is available from ArcelorMittal for incorporating these steels.

1. Automotive Worldwide
TRIP (TRansformation Induced Plasticity)
steels
Extract from the product catalogue -European edition
Note: Information contained in this catalogue is subject to change.
Please contact our sales team whenever you place an order to ensure that your requirements are fully met.
Please contact us if you have a specific requirement that is not included in the range of products and services covered by this catalogue.
We are also reachable by the e-mail address automotive.request@arcelormittal.com.

2. We are also reachable by the e-mail address automotive.request@arcelormittal.com.
TRIP (TRansformation Induced Plasticity) steels
Advanced high strength steels
Description
TRIP steels offer an outstanding combination of strength and ductility as a result of their microstructure. They are thus suitable for structural
and reinforcement parts of complex shape. The microstructure of these steels is composed of islands of hard residual austenite and
carbide-free bainite dispersed in a soft ferritic matrix. Austenite is transformed into martensite during plastic deformation (TRIP:
TRansformation Induced Plasticity effect), making it possible to achieve greater elongations and lending these steels their excellent
combination of strength and ductility.
These steels have high strain hardening capacity. They exhibit good strain redistribution and thus good drawability. As a result of strain
hardening, the mechanical properties, and especially the yield strength, of the finished part are far superior to those of the initial blank.
High strain hardening capacity and high mechanical strength lend these steels excellent energy absorption capacity. TRIP steels also exhibit
a strong bake hardening (BH) effect following deformation, which further improves their crash performance.
The TRIP range of steels comprises 2 cold rolled grades in both uncoated and coated formats (TRIP 690 and TRIP 780) and one hot rolled
grade (TRIP 780), identified by their minimum tensile strength expressed in MPa.
Applications
As a result of their high energy absorption capacity and fatigue strength, TRIP steels are particularly well suited for automotive structural and
safety parts such as cross members, longitudinal beams, B-pillar reinforcements, sills and bumper reinforcements.
ArcelorMittal has extensive data on the forming and service characteristics of the TRIP family of steels. To integrate these steels at the
design stage, a team of experts is available to carry out specific studies based on modeling and experimental tests.
B-pillar reinforcement in electrogalvanized TRIP 780
(thickness: 1.2 mm)
Bumper cross member in electrogalvanized TRIP 780
(thickness: 1.6 mm)
Designation and standard
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3. Designation and standard
Euronorms VDA 239-100
TRIP 690 HCT690T (+ZE, +Z) CR400Y690T-TR (-UNC,-EG,-GI)
TRIP 780 HCT780T (+ZE, +ZF) CR450Y780T-TR (-UNC,-EG,-GA)
Euronorms
Uncoated (EN 10338 :2015): Steel grade name
Electrogalvanized (EN 10338 :2015 + EN 10152 :2017): Steel grade name +ZE
Galvannealed (EN 10346 :2015): Steel grade name +ZF
Extragal® (EN 10346 :2015): Steel grade name +Z
VDA 239-100
Uncoated: Steel grade name-UNC
Electrogalvanized: Steel grade name-EG
Galvannealed: Steel grade name-GA
Extragal®: Steel grade name-GI
Hot rolled Cold rolled
While the ArcelorMittal grades conform perfectly well to the indicated EN standards, ArcelorMittal grades generally offer tighter mechanical
properties (see table below).
The above indicative table summarizes the European and VDA standards corresponding to the ArcelorMittal product range.
Technical characteristics
Mechanical properties
Guaranteed for 20x80 mm ISO tensile specimens (uncoated sheets) with the tensile axix parallel to the rolling direction
YS (MPa) UTS (MPa)
ef
(%)
L0
= 80 mm
th < 3 mm
n BH2
(MPa)
TRIP 690 410 -510 690 -800 ≥ 25 ≥ 0,19 40
TRIP 780* 450 -550 780 -900 ≥ 23 ≥ 0,18 40
Hot rolled Cold rolled
* The product is also available with a minimum yield stress of 500 MPa
Typical cold rolled electrogalvanized TRIP 780
microstructure (residual austenite fraction about 18%)
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4.
Typical hot dip galvanized TRIP 690 microstructure (residual
austenite fraction about 10%)
Chemical composition (%)
C Mn Al +Si
Max Max Max
TRIP 690 0,200 2,0 2,0
TRIP 780 0,250 2,0 2,0
Hot rolled Cold rolled
Available coatings and Worldwide availability
Uncoated Electrogalvanized Extragal
®
EUR NAM SAM RSA CHI EUR NAM SAM RSA CHI EUR NAM SAM RSA CHI
TRIP 690
TRIP 780
Galvannealed Jetgal
®
EUR NAM SAM RSA CHI EUR NAM SAM RSA CHI
TRIP 690
TRIP 780
Hot rolled Cold rolled
Available in non-visible part quality Undergoing customer testing Under development Available in visible and non-visible part
quality (Z)
EUR : Europe Region -NAM : North America Region -SAM : South America Region -RSA : South Africa Region -CHI : China
X Available - O Under development
Recommendations for use and secondary processing
Forming
TRIP steels offer high ductility for their tensile strength. For example, cold rolled TRIP 780 has uniform elongation comparable to that of an
ArcelorMittal 04.
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5. The figure below shows examples of forming limit curves for cold rolled TRIP 690 and TRIP 780 steels in 1.5 mm thickness. Their formability
is superior to that of a lower strength Dual Phase 600 steel.
Forming limit curves for TRIP 690 and 780 (thickness: 1.5
mm)
Please consult us for more information about the forming of TRIP steels.
In order to fully exploit the potential of TRIP steels, the metal characteristics after forming rather than those of the initial blank should be used
in the design stage.
Because of their very good drawability, this family of steels can be used to make safety and structural parts with both simple and complex
geometries, provided springback is taken into account at the design stage.
Welding
Resistance spot welding
TRIP steels can be readily welded using conventional welding processes, provided the parameters are adjusted. Because of the high carbon
equivalent, electrode forces must be increased and welding cycles adjusted to obtain high-quality weld spots. The risk of interface fracture,
which can occur in TRIP-TRIP welds, can be reduced by optimizing the welding parameters.
The table below gives examples (indicative only) of spot welding parameters for TRIP 690 Extragal® and TRIP 780 electrogalvanized
matching joints, determined according to the ISO 18278-2 standard:
Coating
Thickness
(mm)
Max. intensity
(kA)
Nugget diameter
(mm)
Pure tensile
(kN)
Tensile-shear
(kN)
TRIP
690
Extragal® 1.0 8.3 6.5 6.7 13
TRIP
780
Electrogalvanized 1.0 7.7 6.7 5.5 13.7
Hot rolled Cold rolled
MAG arc welding
MAG (Metal Active Gas) arc welding employs a filler wire in a protective gas shield. It can be used for thicknesses greater than 0.8 mm. MAG
weldability of TRIP 780 has been assessed using CMOS technology according to the EN 288 and EN 25817 standards for 1.5 mm thick butt
joints. Heat input is of the order of 2 kJ/cm.
As a result of its chemical composition, TRIP 780 typically has a relatively high carbon equivalent of about 0.50. However, no particular
precautions are needed to prevent cold cracking. The small thicknesses employed (< 2 mm) minimize restraint stresses during welding.
The most appropriate combination for MAG welding of TRIP 780 in a thickness range of about 1.5 mm is the following:
Filler: G3Si1 type in accordance with EN 440;
Protective gas: Ar + 8% CO2
.
(M21 according to EN 439).
The CMOS evaluation shows satisfactory overall weld behavior meeting the mechanical strength criteria set out in the standards, given that:
bends are good up to 120° and crack on the reverse side at 180°;
all tensile test failures occur in the base metal, even with G3Si1 filler metal, as a result of the associated dilution.
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6. all tensile test failures occur in the base metal, even with G3Si1 filler metal, as a result of the associated dilution.
Laser welding
Laser welding tests have revealed no particular difficulties.
Laser lap welding is particularly suitable for TRIP/TRIP joining.
Based on long shop-floor experience in characterizing its products, ArcelorMittal can provide technical assistance in adjusting the welding
parameters for all steels in the TRIP range.
Fatigue strength
Due to their high mechanical strength, TRIP grades have significantly better fatigue properties than conventional steels.
Examples of Wöhler curves for a variety TRIP grades are shown in the two graphs below. The curves plot maximum stress versus number of
cycles to failure. They are calculated for two loading ratios: tension-compression R=-1 and tension-tension R=0.1.
Wöhler curves or S-N curves for TRIP steels
The graph below shows the low-cycle fatigue or E-N curves for the same steels. The curves plot strain amplitude versus number of reversals
to failure (one cycle corresponds to two reversals). Other high and low cycle fatigue data can be provided on request.
Low-cycle fatigue or E-N curves for TRIP steels
ArcelorMittal can make a TRIP steel fatigue database available to its customers.
Impact strength
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7. Impact strength
As a result of their very high tensile strength, TRIP steels are particularly suitable for parts designed to absorb energy in an impact.
TRIP steels have been characterized in dynamic axial compression tests using an omega structure with a spot-welded closure plate at an
impact velocity of 56 kph. These tests have demonstrated the very good impact behavior of these steels.
Mass reduction potential compared to that of an HSLA 380
steel (reference)
These results are obtained for specimens produced by bending. Strain hardening during drawing enhances the energy absorption capacity of
this grade. In order to fully exploit the potential of TRIP steels, the metal characteristics after forming (hardening) rather than those of the
initial blank should be used in the design stage. Crushing tests have shown a 9% gain in energy absorption of drawn parts compared to parts
obtained by bending.
© ArcelorMittal | Last update: 03-05-2018
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