Microstructure and Mechanism of Three Spheroidizing Treatment for the Carbide of GCr15 Steel

Abstract

Three groups of GCr15 steel were heat-treated respectively by conventional spheroidizing annealing, circulation spheroidizing annealing, 1050°C for 30min oil cooling quenching + 700°C tempering. The final heat treatment of these GCr15 steel was 840°C oil cooling quenching + 150°C tempering. The microstructure of the heat-treated GCr15 were observed and the mechanism of three spheroidizing treatment were discussed in this paper. The results showed that: There is obvious difference among the three groups carbide of GCr15 for the mechanism of three spheroidizing treatments is different. The GCr15 has 1050°C for 30min oil cooling quenching + 700°C tempering showed the best result of carbide spheroidizing. The microstructure of GCr15 after 840°C oil cooling quenching + 150 °C tempering was tempered martensite and carbide which is fine, round and widely distributed.

Effect of High Magnetic Field in Combination with High-Temperature Tempering on Microstructures and Mechanical Properties of GCr15 Bearing Steel

“…As mentioned above, the high-temperature tempering of high-carbon steel is accompanied by the precipitation and coarsening of carbides [6,30,41]. In comparison, the tempering in the HMF results in the smaller mean size of the carbides and higher density (Figure 4).…”

“…It is realized that TS structures with granular carbides distributed in the ferrite matrix can be obtained [6,30] when the as-quenched high-carbon steel is tempered at a high temperature. In this work, the block-like structure in Figure 3 is the TS.…”

“…Two types of heat treatment, i.e., spheroidization annealing and high-temperature tempering, are often used to obtain this kind of structure [5]. The tempering and quenching (Q&P) process can effectively improve the size and distribution of carbides [6][7][8] and is an important method to adjust the microstructures and properties of steels [7,9]. During the high-temperature tempering of steels, the TS structures can be obtained [8,10], with a uniform distribution of finer carbides [6,8], providing the most effective pinning at sub-grain boundaries [11], which is conducive to the improvement of the fatigue life [12].…”

“…For high-carbon steel, Wang et al [27] reported that HMF could enhance the decomposition of the retained austenite in M50 steel during tempering at 200-530 • C. From these studies, it is realized that HMF has the capacity to modify the microstructure and performance of steels during tempering. However, for high-carbon steels, tempering at a relatively high temperature (such as 600 • C) can significantly cause the recovery of the matrix and the coarsening of carbides [30], finally obtaining TS structures [6,8]. The majority of the previous studies regarding tempering in HMF have focused on the tempering of steels at relatively lower temperatures.…”

Fracture Analysis of GCr15 Steel Ball Screw Nut

“…By controlling heated temperature and holding time of spheroidize annealing, carbide networks can be refined and even eliminated. When heated temperature increases and holding time extends, carbide networks becomes less and less [6] . Studies [7] have pointed out that optimal process of GCr15 steel should be holding for 4 hours at 725˚C after heated to 820˚C.…”