This document provides an overview of metallurgy and material properties. It discusses the main classes of steels including carbon steels, alloy steels, and stainless steels. It also covers alloying elements, heat treatment processes, mechanical properties testing, and non-destructive testing methods. The key information presented includes the classifications of steels based on chemistry, the effects of common alloying elements, and standard tests used to evaluate material properties and integrity.

1. Metallurgy 101
Brought to you by
Houston Subsea Supplier Development
Joel Russo, CTG Metallurgist

2. Classes of Steels
• Carbon Steels – steels have no specified minimum quantity of
alloying elements, basically just carbon and manganese. Very
limited through hardenability. (e.g. 10XX XX = carbon equivalent)
• Alloy Steels – steels containing specific alloying elements other
than carbon (typically chromium and moly)
– A steel is considered to be an alloy steel when the maximum of
the range given for the content of alloying elements exceeds one
or more of the following limits
• Manganese …………. 1.65%
• Silicon ……………… 0.60%
• Copper ……………… 0.60%
e.g. 41XX 41 = Chrome + moly, 43XX 43 = chrome +
moly + Nickel
Low alloy steels are approved for H2S service at 22 HRC
max. for H2S service, the steels must contain less than
1% nickel.

3. Free Machining Steels
• Free Machining Steels—contain elements that allow faster
machining of parts. The main free machining additives are
extra sulfur, phosphorus or lead. These materials have higher
inclusion contents and lower toughness than regular steels.
Free machining grades are not approved for H2S service per
NACE MR0175/ISO 15156. Examples of these types of
steels are 1144, 12L14, and 1215.

4. Classes of Steels
• Stainless Steels – possess unusual ability to resist attack by
corrosive media at atmosphere and elevated temperatures.
These properties are due principally to the addition of
relatively large amounts of chromium, and also nickel and/or
molybdenum. Need 11% minimum chrome to be a stainless.
• There are several main types of SS:
– Austenitic—e.g. 18Cr-8Ni, 304, 316—nonmagnetic. These
stainlesses can not be hardened by heat treatment, but can be
hardened by cold working. Approved for H2S service at 22 HRC
max.
– Martensitic—e.g. 410, F6NM—magnetic. These steels can be
hardened by quenching and tempering. Approved for H2S service at
22 HRC max for 410, and 23 HRC max for F6NM.
– Precipitation hardening (PH)—e.g. 17-4PH. Magnetic and heat
treatable by solution annealing, quenching and aging. Can be
hardened to over 180K yield
– Duplex SS – Dual phases-austenite (for corrosion resistance) and ferrite
(for strength). Example 2205, F51-regular duplex yield strength approx.
60K. Super duplex – Zeron 100 (UNS S32760), 25-7 (UNS S32750). One
problem with duplex is distortion during machining.

5. Nickel Based Alloys
• Nickel (Ni) gives phase stabilization, resistance to stress corrosion
cracking (SSC) and general corrosion resistance. For example, 304
and 316 stainless steels are susceptible to SSC due to chlorides, at
temperatures above 50 C.
• Chromium (Cr) gives resistance to oxidizing corrosives such as
nitric acid.
• Molybdenum (Mo) gives resistance to pitting corrosion, due to
chlorides, salts, and reducing acids, such as hydrochloric acid.
• Note: 945 is a new nickel base alloy produced by Special Metals
Corp (SMC). It will be sold through Howco and Castle Metals. I
have been told that stock will be arriving soon at Howco in the size
range of 2” through 8” diameter. 945 is supposed to be priced
slightly lower than 718, but this is dependent on quantities and
market conditions. It is covered in FMC Materials Specification
M40146.

6. Pitting Resistance Number

7. Nickel Based Alloys

8. Alloying Elements
• Manganese (Mn)
– Generally present in all commercial steels
– Essential for melting and rolling of steels
– Combines with sulfur to improve hot working characteristics and to provide better surface
finish
– Improves transformation of steel phases during heating and cooling
– Major contributor to deep hardening
• Silicon (Si)
– The major reason silicon is used in alloy steel is for its strong deoxidizer ability in molten
steel
– Increases hardenability and strengthens low alloy steels
• Nickel (Ni)
– Increases the internal strength and elastic limit of steels depending on the level of carbon
present in the steel
– Steels containing nickel in sufficient quantities are very easily heat treated because nickel
lowers the critical cooling rate and allow quenched steel to attain higher levels of hardening
– Nickel containing steels have a greater resistance to impact at subzero temperatures
– In combination with chromium, nickel produces alloy steels with higher elastic ratios, greater
hardenability, higher impact, and fatigue resistance than carbon steel

9. Alloying Elements
• Chromium (Cr)
– Is a hardening element and is frequently used with toughening elements
such as nickel to produce superior mechanical properties
• Molybdenum ( Mo)
– Steels containing molybdenum when hardened require higher tempering
temperatures to achieve the same degree of softness as compared to
carbon or even other alloy steels. This ability to retain hardness is
beneficial for applications where the material is subjected to relatively high
temperatures
• Carbon (C)
– When used with iron forms steel
– Essential element for transformation
– Typical surface hardness upon heat treating is increased with increase in
carbon content up to approximately 0.6% carbon.

10. AISI Numbering System
• A four numeral series is used to designate graduations of
chemical composition of carbon steel, the last two numbers of
which are intended to indicate the approximate middle of the
carbon range.

11. Material Chemistries

12. Material Chemistries

13. Material Chemistries

14. Material Performance

15. Heat Treatment
• An operation or combination of operations involving the heat
and cooling of steels in the solid state for the purpose of
obtaining certain desirable mechanical, micro-structural, or
corrosion resisting properties.
• Normalizing (1575ºF – 1725ºF) Typical 1650ºF
– Provides grain refinement and uniformity
– Performed after forging or hot working
– The normalizing temperature should be the highest temperature in the steel
processing
– Air cooled
• Annealing (1100ºF – 1450ºF)
– Used to soften metals
– Used to improve machinability
– Cooled in furnace and is slower cooled than in normalizing

16. Heat Treatment
• Austenitizing (1500ºF – 1650ºF ) Typical 1600ºF.
– Used to transform material to a harder phase
– Usually followed by quenching
• Quenching
– Rapid cooling to increase hardening
– Quenching medium include water, oil, polymer. Use fastest quench that won’t crack the
material.
– The higher the cooling rate of the quench medium the higher the hardness
• Tempering (Typically 950ºF – 1325ºF)
– Tempering relieves stresses built up after quenching and insures better dimensional stability
– Material has temper, the softer the material lower yield.
– The higher the temper, the softer the material, the lower the yield strength, the
lower the hardness, and the higher the toughness (e.g. charpy values)
– Lowering the tempering temperature increases the yield strength, increases the
hardness, but lowers the toughness.

17. Heat Treatment
• Stress Relieving
– Can be done after straightening operation to lessen stresses induced
after straightening bars.
– Normally done at 50 to 100º F less than the tempering temperature
• Quench Cracking Prevention
– Avoid sharp corners, sharp radii and other stress concentrations
– Normalize after trepanning and prior to quench and tempering
– Avoid quenching bar or metal parts with small diameter holes (e.g. less
than 2”)

18. Mechanical Properties
• Hardenability – The ability of a ferrous alloy to form martensite
when quenched from a temperature above the upper Critical
Temperature.
– Hardness - Hardness is defined as the ability of a material to resist
permanent penetration. Depending on the method used, the
larger/deeper the indentations made by a hardness tester the softer the
material.

19. Mechanical Properties
– Brinell (HBW)
• Approved by API (minor and major loads applied)
• Most common method easily portable for field and large parts
• Indention diameter is measured and converted to Brinell hardness
units.
– Rockwell HRC or HRB)
• Approved by API (minor and major loads applied)
• Hardness is determined by depth of indention made by constant load
and not the diameter
• Most accurate method, accepted over Brinell
• B and C scales most common used

20. Material Hardenability
– Ranking of materials of lowest hardenability to highest. One method to
assess hardenability is the Ideal Diameter (D.I.) Method. It is a way of
quantifying the strength of the chemistry. The D.I. is the theoretical
largest diameter bar that would through harden if quenched in an ideal
quench. The major elements that affect the material hardenability are
Cr, Mo, Ni, and V.
– 1018 (Range of D.I.:0.5” to 0.7”)
– 1040 (Range of D.I.:0.8” to 1.2”)
– 4130 (Range of D.I.: 2.5” to 3.5”)
– 4140 (Range of D.I.: 4.0” to 6.0”)
– 8630 Mod (Range of D.I.: 5.0” to 8.3”)
– 4340 (Range of D.I.: 6.0” to 8.0”)
– 4330V (Range of D.I.: 8.0” to 11.0”)
– F22 (Range of D.I.: 9.0” to 11.0”)

21. Methods of Measuring Material Properties on Raw
Material
• Prolongation – An extension of the bar or forging, removed after
heat treatment. This gives a fairly accurate assessment of the
strength and toughness of the material. Some codes require testing
at mid radius, while others allow testing closer to the surface (e.g.
1.25” below the surface).
• QTC (Qualification Test coupon) – A QTC is approx. 4”X4” by 6” to
8” long. It does not give a true representation of the actual
properties of the bar or forging unless the diameter is similar.
Designers must take this into account. When the QTC
accompanies the parts during the heat treat process, there can at
least be some assurance that the parts were properly heat treated.
Some codes allow the QTC to be heat treated by itself in a separate
furnace. This is called a “capability” test and gives the least
assurance of proper heat treatment of the parts.

22. Destructive Testing
– Tensile (Tension) Testing
• Test specimen machined to specific size and shape (bar bell)
• Used to provide information of strength of materials
• Results: yield strength, elongation, general strength, reduction of
area
– Charpy Impact (V notch)
• Determines toughness at a specific temperatures
• Test specimen machined to specific size and shape
• .400” (10mm) x .400” (10mm) x 2” (standard) with “v” notch in middle
• Material tested at temperatures from ambient down to -150ºF.
Typical is -75ºF.

23. Tensile and Yield

24. Stress Strain Curve

25. Non-destructive Testing
– Magnetic particle testing
• Ferrous material testing
• Used to identify surface indications (cracks, etc.)
– Liquid penetrate testing
• Ferrous or non-ferrous material testing
• Used to identify surface indications
– Ultrasonic Testing
• Ferrous and non-ferrous material testing
• Used to identify indications below the material’s surface
• Use of calibrated standards required

26. Video Tour of a Melt Shop

27. Metallurgy 101 Test