A historical overview of steel tempering parameters

Abstract

The results of the stress relieving and tempering processes are dependent on the temperature and time of the process, which may be correlated using a parameter such as Holloman's (Holloman-Jaffe) parameter or the Larsen-Miller parameter. These parameters are a measure of the thermal effect of the process on the metallurgical transformation of the steel during tempering. The processes that exhibit the same tempering parameter are expected to exhibit the same effect (such as hardness). However, these more traditional numerical expressions assume isothermal tempering processes which seldom exist in production tempering ovens due to the heat-up period prior to soaking

Addressing H-Material Interaction in Fast Diffusion Materials—A Feasibility Study on a Complex Phase Steel

“…From the constant strain rate indentation tests, the average hardness and Young’s Modulus were calculated to be 5.13 GPa and 233 GPa, respectively. Similar hardness values were reported for tempered martensite and martensitic steels with similar C content [ 56 , 57 ]. Figure 5 a depicts the load-indentation depth plot that corresponds to the strain rate jump tests and Figure 5 b shows the exemplarily resulting hardness and Young’s modulus over indentation depth.…”

Additive manufacturing of high tensile strength steel for offshore & marine 3D complex joint applications

“…This is consistent with previous discussions in Chapter 2.1.1.2, as the SLM process creates a very rapid cooling of the EH36 built specimens by staying on the left of the TTT curve (see Figure 2.2). This is also further evidenced in the high Vickers hardness numbers consistent with that of low carbon steel with asquenched martensitic microstructure [150], where Vickers hardness values are in the range of 300 to 400 for low carbon steel (see Figure 4.28). However, Zhao et al has shown that an optimised heat treatment process may improve impact toughness performance by up to 50% [151].…”

Critical Assessment 34: Are χ (Hägg), η and ϵ carbides transition-phases relative to cementite in steels?

“…Although empirical, the parameter is acknowledged widely to rationalise the combined effects of time and temperature during tempering [e.g. [29][30][31] Two conclusions can be drawn from Figure 3. First, that cementite seems to be the most stable phase over a wide temperature range when the strength of the heat treatment is greatest within the scope of the dataset.…”