There are M7C3 type eutectic carbides with high hardness (1200~1800HV) in the room temperature microstructure of the wear-resistant plate, and they are isolated from each other and not connected into a network, which greatly reduces the splitting effect on the matrix and makes the material stronger. The toughness is improved at the same time, and it has excellent abrasive wear resistance and good fracture resistance. It is precisely based on these excellent properties of wear-resistant plates that they have been widely used in mineral processing, electric power, road construction, engineering, agriculture and other machinery since their inception. As we all know, the quantity, morphology, size and distribution of carbides, which are the anti-wear phase of wear-resistant plates, have a great influence on the mechanical properties of wear-resistant plates. The type of carbide phase is in turn related to the composition, more precisely, closely related to the Cr/C in the wear-resistant plate. At the same time, in addition to rationally selecting the chemical composition of the wear-resistant plate, heat treatment can also change the structure of the matrix and strengthen the supporting effect of the matrix on carbides, thereby improving the performance of the wear-resistant plate. Commonly used heat treatment processes for wear-resistant plates include high-temperature quenching, tempering, subcritical heat treatment, pearlitization pretreatment, etc. Compared with high-temperature heat treatment, subcritical heat treatment not only avoids problems such as decarburization, oxidation, deformation, and cracking of the workpiece during high-temperature quenching, but also can reduce energy consumption, save resources, and improve workers' operating conditions. This article mainly studies the structural changes and phase transformation rules of wear-resistant plates with different Cr/C during subcritical heat treatment, analyzes and discusses the experimental results, and explores the hardening mechanism of Cr/C wear-resistant plates during subcritical heat treatment and its effect on the wear-resistant plate. Effect of hardness.
The materials used in the experiment are wear-resistant plates with different Cr/C, respectively: 4.8, 7.0, 8.6, and the same addition amount of other alloy elements. Put the small as-cast sample (10mm×10mm×100mm) into a box-type resistance furnace (SX-12-12), heat it to 540, 580 and 620℃ at a rate of 250℃/h, and keep it at 0, After 2, 4 and 6 hours, take it out and cool it in air.
Subcritical heat treatment has different effects on wear-resistant plates with different Cr/C. When Cr/C is low, heat treatment has little effect on its hardness. Only when Cr/C is high, heat treatment will have a greater impact on its hardness. Impact. When the wear-resistant plate is subjected to subcritical heat treatment, carbon and chromium will precipitate in the form of secondary carbides, which reduces the supersaturation of carbon and chromium in the austenite, increases the Ms point, increases the content of martensite in the matrix, and the alloy Increased hardness. When the wear-resistant plate is subjected to subcritical heat treatment, the precipitation of secondary carbides and the increase in martensite content in the matrix increase the alloy hardness, while the martensite microhardness decreases and the secondary carbides aggregate and grow, causing the alloy hardness to decrease. These strong and weak mechanisms work together, so the wear-resistant plate will have a peak value during subcritical heat treatment. Wear-resistant plates with different Cr/C have different peak times at the same heat treatment temperature, and wear-resistant plates with the same Cr/C have different peak times at different heat treatment temperatures.
