Effect of Annealing Time and Temperature Parameters on the Microstructure, Hardness, and Strain-Hardening Coefficients of 42CrMo4 Steel

Abstract

The study presents the effect of annealing process parameters on the microstructure, hardness, and strain-hardening coefficients, that is, the strength coefficient c and the strain-hardening exponent n, of 42CrMo4 steel. Seven selected annealing time–temperature schemes are examined for superior steel formability in cold metal forming conditions. The c and n coefficients are first determined in experimental upsetting of annealed samples and then used in FEM (finite element method) simulations of the upsetting process. The results demonstrate that the strain-hardening coefficients (c and n) depend on the employed annealing scheme. Compared with the as-received sample, the annealing process reduces the true stress and effectively decrease the hardness of 42CrMo4 steel; improves microstructural spheroidization; and, consequently, facilitates deformability of this material. The annealing schemes, relying on heating the material to 750 °C and its subsequent slow cooling, lead to the highest decrease in hardness ranging from 162 to 168 HV. The results obtained with the SEM-EDS (scanning electron microscopy-energy dispersive spectrometer), LOM (light optical microscopy), and XRD (X-ray diffraction) methods lead to the conclusion that the employed heat treatment schemes cause the initial ferritic-pearlitic microstructure to develop granular and semi-lamellar precipitation of cementite enriched with Mo and Cr in the ferrite matrix. In addition, the annealing process affects the growth of α-Fe grains. The highest cold hardening rate, and thus formability, is obtained for the annealing scheme producing the lowest hardness. The results of FEM simulations are positively validated by experimental results. The obtained results are crucial for further numerical simulations and experimental research connected with developing new cold metal forming methods for producing parts made of 42CrMo4 steel.

Hot Workability of Ultra-Supercritical Rotor Steel Using a 3-D Processing Map Based on the Dynamic Material Model

“…Figure 21 shows the distribution of flow line on various state. It can be concluded from Figure 21 that the grains are oriented in the direction of the material flow [38]. It is shown that the simulation results are consistent with the microstructure photos and the proposed method that integrates the 3-D processing map into the finite element software FORGE ® , is able to predict the formability of X12CrMoWVNbN10-1-1 alloy steel during its hot forging process.…”

FEM analysis of the manufacturing of hollow forgings from a tube billet

“…Geometrical models of the extrusion and forging processes are presented in Figure 2. The present study is a continuation of previously published results [13,14,[16][17][18][19][20] regarding the project entitled: New metal forming technique for producing flanged hollow parts for the mining industry.…”

“…The tools were modelled as rigid objects. Material model of annealed 42CrMo4 grade steel was obtained as a result of an upsetting test [13]. Its rheology is expressed by the following equation:…”

Influence of Nitrogen Content on the Corrosion Behavior of Powder Metallurgy Nickel‐Free Austenitic Stainless Steel

“…Figure 2 shows the metallographic structure and XRD pattern of the sintered alloy denitrified at 1100 °C for 2 h. Figure 2(a) shows that the sintered alloy was divided into three layers from the surface toward the center. e inner layer had single equiaxed grains; the middle layer had the structure of a grain boundary network or granular precipitated phases; and the outermost layer had several lamellar structures similar to pearlite colonies (ferrite/cementite lamellar) [26,27]. Cr 2 N and CrN peaks were observed in the XRD pattern shown in Figure 2(b), suggesting that the precipitates in Figure 2(a) were Cr 2 N and CrN [28,29].…”