Forming and Oxidation Behavior During Forging with Consideration of Carbon Content of Steel

Abstract

Developments in technology rely increasingly on the numerical simulation of single process steps up to whole process chains using commercially available or user-written software systems, mostly based on the finite element method (FEM). However, detailed simulations require realistic models. These models consider the relevant material-specific parameters and coefficients for the basic material, surface phenomena, and dies, as well as machine kinematics. This knowledge exists to some extent for certain materials, but not in general for groups of steel that depend on alloying elements. Nevertheless, the basic material and its behavior before, during, and after hot deformation must be understood when designing and describing die-forging processes by experimental and numerical simulations. This is why a new mathematical approach has been formulated for forming behavior and recrystallization kinetics, taking into account the carbon content of the base material, the initial microstructure, and the reheating mode. Furthermore, there have been no studies investigating the influence of varying a single chemical element, such as the carbon content, with regard to the oxidation behavior, including the internal structure (e.g., pores) at high temperatures. In this context the majority of studies were performed with steel grade C45 (material no. 1.0503), which was chosen as base material for the experiments conducted. To identify the effects of the alloying element carbon on the material and oxidation behavior, steel grades C15 (material no. 1.0401) and C60 (material no. 1.0601) were also investigated. The investigations revealed a dependence of the material behavior (microstructure and surface) on the alloying system. Based on the experimental results, the mathematical models formulated were parameterized and implemented in the FE-software Simufact Forming (Simufact Engineering GmbH, Hamburg, Germany) by means of user subroutines. Furthermore, a correlation between the thickness of the oxide scale layer and friction was determined in ring compression tests and accounted for in the software code. Finally, real forging tests were carried out under laboratory conditions, with all three investigated steels for calibration of the materials as well as the FE models.

Influence of Austenite Grain Size on Mechanical Properties after Quench and Partitioning Treatment of a 42SiCr Steel

“…While the microstructural and mechanical effects of austenite grain size are relatively small, they nevertheless provide important outlooking information for forging processing of the 42SiCr alloy: as shown, e.g., in [11], different grain sizes occur over the cross-section of the final component after die forging as a result of recrystallization processes. If such a forged component is subjected to a subsequent Q-P treatment, different austenite grain sizes will also be present after austenitizing.…”

Effect of Cryogenic Treatment on Microstructure, Mechanical Properties and Distortion of Carburized Gear Steels

“…If the internal stress exceeds the yield strength of the steel, it will be deformed. Internal stresses in steel can lead to cracking and also inhibit the transformation of austenite to martensite [38,39]. The distortion schematic diagram is shown in Figure 11b, where the original shape of Nary C-rings was marked as 1 and the final one was marked as 2.…”

Friction Mechanism Features of the Nickel-Based Composite Antifriction Materials at High Temperatures

“…It is known the FeO, Fe 2 O 3 and, Fe 3 O 4 oxides exist in the system [38,39]. The intensive carbide oxidation occurs at temperatures above 1273 K and depends on the carbon amount in steel [40]. Oxidation resistance increases at the carbon amount growth.…”

“…Subsequently, this causes formation of the oxides in proportional amount. References include information about impurities located on the boundaries of particles that form a diffusion barrier to the oxygen penetrating into the powder particles, and protect nickel against oxidation [40,[43][44][45]. Thus, the more oxides of other chemical elements were formed, the slower was nickel oxidation.…”