Steels continued heat treatment

Molten lead has a very good heat transfer abihty and is used in the continuous heat treatment process for the manufacture of high-carbon steel wire. This process demands a very rapid heating from room temperature to 450°C (temjjering after hardening) and a very quick cooling from 900°C to 550°C (so-called lead patenting). The lat-... 

The cracking susceptibility of a micro-alloyed HSLA-100 steel was examined and compared to that of a HY-100 steel in the as-received condition and after heat treatment to simulate the thermal history of a single pass weld. Slow strain rate tensile tests were conducted on samples of these alloys with these thermal histories in an inert environment and in an aqueous solution during continuous cathodic charging at different potentials with respect to a reference electrode. Both alloys exhibited reduced ductilities at cathodic potentials indicating susceptibility to hydrogen embrittlement. The results of these experiments will be presented and discussed in relation to the observed microstructures and fractography. 

One final test was conducted on a heat treated sample to elucidate the effect of heat treatment and sensitization on the fracture behavior of this steel. A CF sample was heated for 24 hours at 650°C to see if the fracture mode would continue to change with an even larger amount of carbide precipitation. Note in Figure 15-a this heavily sensitized steel has a fracture appearance that is completely dominated by small microvoids associated with carbides. The bimodal distribution of microvoids like those in Figure 7 has been eliminated. In fact, the fracture appearance is remarkably similar to that of the tritium-exposed-and-aged steels albeit at a different magnification (Figure 15-b). It appears that carbides in the microstructure affect the fracture mode in a similar manner as the decay helium bubbles but on a different scale. 

The results of low-temperature and intermediate-temperature specific heat measurements on stainless steel 31 OS (two heat treatment conditions) and Inconel X750 (four melting practice/heat treatment combinations) were presented and discussed at the 1975 International Cryogenic Materials Conference (ICMC) [% In a continuation of that work, measurements have been made on 10 more samples, consisting of Inconel X750 (HIP), Inconel 706, Kromarc 58, and Nitronic 33, in various metallurgical conditions. 

Bainite is a crystalline constituent that can be formed during heat treatment of steel by isothermal transformation or continuous cooling in the temperature range between those of perlite and martensite. Here, iron diffusion is no longer possible, while... 

Chilled iron shot or grit can be used for the removal of rust, mill scale, heat treatment scale, and old paint from forged, cast, and rolled steel. This abrasive breaks down gradually against steel substrates, so continual sieving to retain only the large particle sizes may be needed if a rough surface profile is desired in the cleaned surface. 

For hardening and subsequent tempering operations, the heat treatment contractor should be guided by the recommendations of the steel maker given in the data sheets for the material concerned. These heat treatment recommendations are derived from the chemical composition of the steel used. Material-specific, continuous and isothermal Time-Temperature-Transformation (TTT) diagrams, as shown in Figure 4.80, describe the transformation behaviour of the steel s microstructure [3]. 

A.V. Supov, N.M. Aleksandrova, S.A. Paren kov, R.V. Kakabadze, V.P. Pavlov, Metallographic problems of the production of parts from continuously cast high-speed steels, Metal Science and Heat Treatment, 9-10 (1998), 354-359. 

STEELS Processing Diffusion V Recrystaiiization V Isothermal transformation tiiagrams, continuous-cooling transformalion tiiagrams heat treating tor tempereil martensite Heat treatment of steels ... 

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