Quenching and tempering

Carbon content is usually about 0.15% but may be higher in bolting steels and hot-work die steels. Molybdenum content is usually between 0.5 and 1.5% it increases creep—mpture strength and prevents temper embrittlement at the higher chromium contents. In the modified steels, siUcon is added to improve oxidation resistance, titanium and vanadium to stabilize the carbides to higher temperatures, and nickel to reduce notch sensitivity. Most of the chromium—molybdenum steels are used in the aimealed or in the normalized and tempered condition some of the modified grades have better properties in the quench and tempered condition. 

P/M steels can be heat treated in the same manner as cast or wrought steels. They may be austenitized, quenched, and tempered. Surface hardening includes pack or gas carburization or nitriding, ie, heating in a nitrogen-containing atmosphere. Because of the greater amount of exposed surface area in the form of porosity, a protective atmosphere is needed (see Metal surface treatments). 

Many steels used for gears and bearings are surface-hardened by carburizing, quenching, and tempering. Molybdenum is frequendy used in carburized steels, and carburized Ni—Mo steels have been shown to provide optimum resistance to fatigue and impact effects (28). 

Fig. 20. Transforniation diagram for quenching and tempering martensite. The product is tempered martensite.

The tendency toward lower carbon steels has minimized the utilization of peadite as a stmctural constituent. The growing use of HSLA steels has greatiy reduced the quenching and tempering of carbon steels to provide slightly stronger materials without the use of expensive alloys. Normalizing is stiU used to reduce variability in hot-roUed material if the economics can be justified. 

Quenched and Tempered Low Carbon Constructional Alloy Steels. A class of quenched and tempered low carbon constmctional ahoy steels has been very extensively used in a wide variety of appHcations such as pressure vessels, mining and earth-moving equipment, and in large steel stmctures (see Tanks and pressure vessels). 

Fig. 4. Microstructure of AISI T15 tool steel (quenched and tempered) produced (a) from particles and (b) by the conventional technique (picral etch). In (a), the median and maximum carbide sizes are 1.3 and 3.5 mm, respectively in (b), 6.2 and 34 mm, respectively.

For use at temperatures below -29 through (-20 through -50 F) tliis material must be quenched and tempered. 

These quenched and tempered stainless steels are ideal for things like non-rusting ball-bearings, surgical scalpels and kitchen knives." ... 

Most other rotor parts in gas turbines are individually forged. This includes compressor wheels, spacers, distance pieces, and stub shafts. All are made from quenched and tempered low-alloy steels (Cr-Mo-V or Ni-Cr-Mo-V) with the material and heat treatment optimized for the specific part. The intent is to achieve the best balance of strength, toughness with ductility, processing and nondestructive evaluation capability, particularly when it is recognized that some... 

In water solutions containing hydrogen sulfide, austenitic steels fail by stress corrosion cracking when they are quenched and tempered to high strength and hardness (above about Rockwell C24). 

Tabic 3.9. Comparison of Mild and Low-Alloy Quenched and Tempered Steels (111... 

Stecl a was quenched and tempered to a tensile, strength of 830 N/min and a yield strength of 670 N/inin, and steel b to 620 and 450 N/mm, respectively. It was considered that the maximum thickness of metal that could be welded onsite was 38 mm. 

Heat treatment by quenching and tempering improves the low temperature ductility of steels such as 0.5 Cr, 0.5% Mo, 1% Ni Type V. For lower-temperature application (below -196°C), up to 9% nickel is used as the sole alloying element. 

The tool joints made by forging are heat treated by quenching and tempering. They are either friction welded or flash welded to the pipe body. For friction... 

Drillstring subs are made from AISI 4140 or 4145H steel and sometimes from AISI 4340 or 4340H steel. The steel is quenched and tempered to a hardness range of 285 to 341 Bhn. 

Heavy-wall drillpipe has approximately twice the usual wall thickness and is usually made from AISI 4140-4I45H. The steel is quenched and tempered to the Rockwell C hardness of various grades from 20 to 28 for grade E, 27 to 30 for grade X-95, 30 to 34 for grade G-105 and 34 to 37 for S 135. 

The rotary drill bits are generally made from quench and tempered steel alloys such as AISI 3115 to 3120, 4620, 4815 to 4820 and 8620 to 8720. The only corrosion related problem that can arise may result from a hydrogen sulfide environment. The bearing in the roller rock bits can be damaged by H S contamination of drilling fluid. However, a well conditioned drilling fluid at... 

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