Weld thermal simulation of API 5CT L80 grade steel

The microstructure and mechanical properties of an API 5CT L80 casing grade steel (0.24C 0,4Si 1.4Mn CrNiCu) have been studied after performing weld thermal simulations (with and without subsequent tempering) applying a thermal cycle weld simulator. Specimens were subjected to three different peak temperatures (1300 °C, 1150 °C, 950 °C) and five different cooling rates (1 °C/s, 3 °C/s, 5 °C/s, 10 °C/s, 60 °C/s) through the austenite transformation temperature range. Based on the microstructure, hardness values, and toughness properties of the simulated specimens, thermal cycles were selected and recommended for welding of L80 components by the SAG-FW (shielded active gas forge welding) method.

Fibrous nano composite reinforced surface on WC-Co cemented carbide achieved by pulsed electron beam irradiation and subsequent tempering

Exotic microstructures can be tailored by extreme conditions with combined material processing techniques for desirable properties. In this work, an innovative 2-staged process was explored for WC-10Co cemented carbide surface modification. Firstly, rapid thermal cycles were induced by high current pulsed electron beam (HCPEB) irradiation at energy density of 6 J/cm2, during which the micro-WC/Co was melted and re-solidified into a nano-scaled equiaxed grain microstructure with metastable fcc-WC1-x as the majority phase in the surface layer (~2 μm). Thereafter, a subsequent tempering process was applied to the HCPEB-irradiated cemented carbide specimens and the nano equiaxed grains in the surface layer were gradually transferred into nano-scaled fibrous microstructure. Phase transformation was investigated using thermo-gravimetric analysis differential scanning calorimetry (TGA-DSC), confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM) and X-ray diffractometry (XRD). Analysis showed that the fibrous nano structure resulted from the decomposition of WC1-x at 600-700 ºC via fcc-WC1-x → hex-WC + hcp-W2C. After the 2-staged process, the surface microhardness was greatly improved.

Can Sub-zero Treatment at −75 °C Bring Any Benefits to Tools Manufacturing?

: Vanadis 6 ledeburitic tool steel was subjected to sub-zero treatment at −75 °C for different durations, and for different subsequent tempering regimes. The impact of these treatments on the microstructure, hardness variations, and toughness characteristics of the steel was investigated. The obtained results infer that the retained austenite amount was reduced to one fourth by sub-zero treatment (SZT), and the population density of add-on carbides was increased by factor of three to seven, depending on the duration of SZT. Tempering always reduced the population density of these particles. A hardness increased by 30–60 HV10 was recorded after sub-zero treatment but tempering to the secondary hardness peak induced much more significant hardness decrease than what was established in conventionally quenched steel. The flexural strength was not negatively influenced by sub-zero treatment at −75 °C while the fracture toughness tests gave worse values of this quantity, except the case of steel tempered to the secondary hardness peak.

Strengthening from Cu Addition in 0.2C-(1-2)Mn Steels during Tempering

The strengthening effects of Cu and Mn were studied in steels, which contained 0.2% C and were micro-alloyed with B and Ti. The experimental steels were austenitized and quenched in order to take Mn and Cu into solid solution. The subsequent tempering of martensitic structures resulted in higher strengths in the materials alloyed with Cu than in the steel without Cu addition. Tensile testing and metallographic analyses were performed. The kinetics and magnitude of precipitation strengthening were measured for different tempering temperatures and times. Presumed synergistic effects between Cu precipitation strengthening and higher levels of Mn were observed.

Development of Residual Stresses in a Railroad Wheel Through Rim Spray Heat Treatment

Understanding how residual stresses develop during a typical rim spray quench and subsequent tempering operation is a fundamental objective necessary to gain knowledge of how wheels behave when under service loads. In this study, we have used specially modified and validated ANSYS software to calculate plastic deformations as they develop during the heat treatment process. Plastic deformations, including creep, were determined to follow stages which were both dependent on time of quench and depth from the taping line. Residual stresses developed from these deformations are also discussed.