The roll manufacturer introduces the quenching process of new forged high speed steel roll material
The modern large-scale cold strip mill has completed headless and semi headless rolling. The requirements for the quality of the strip, such as the surface flatness and thickness difference of the cold-rolled strip, and the quality of the work roll, have been higher and higher. There has been great progress in both the requirements for the external surface hardness and the depth of the hardened layer. The following roll manufacturer Wuxi Taihu roll will talk about the new cast high-speed steel roll.
The research on the material of cold rolling operation roll has always been highly valued by the roll industry. From the initial bearing steel to 2% Cr, 3% Cr and 5% Cr section steel, its development is usually characterized by the continuous progress of chromium content. In recent years, semi high speed steel and high speed steel roll materials have been presented, and their arrangement and carbide research have been reported. The technicians of Anhui huanbowan high speed steel roll Co., Ltd. discussed the quenching process of a newly developed cast high speed steel cold rolling work roll data, and analyzed the influence of quenching temperature on high speed steel roll arrangement, grain size, residual austenite and hardness, so as to provide theoretical and experimental basis for the development of cold rolling work roll.
The experimental data of new cast high-speed steel roll are melted in 50kg vacuum induction furnace, and then cast at high temperature to form 100mm × 100mm × 250mm blank was annealed at 700 ℃ for 4H to obtain the original material for experiment. The metallographic sample is 15mm × 15mm × 15mm square, box type resistance furnace is selected for heating at different temperatures and air cooling quenching. 660rld / T Rockwell hardness tester is selected to detect hardness, x'perprox-ray diffractometer is selected to detect residual austenite, axiovert200mat optical microscope is selected to detect arrangement and grain size, and quanta400 scanning electron microscope is selected to investigate carbide.
The as cast arrangement of the new cast high-speed steel roll is lower bainite + ledeburite + a few martensite + strip carbide + granular carbide, in which the large strip carbide is the primary carbide precipitated during liquid steel condensation, and the granular carbide is the secondary carbide precipitated from austenite during cooling, with the carbide content of 3.6%. The discussion indicates:
(1) The quenching temperature affects the dissolution of carbides. With the increase of quenching temperature, the content of carbides in the quenching arrangement of high-speed steel roll is gradually reduced. When the temperature rises to 1200 ℃, the granular carbides have been fundamentally dissolved, leaving only a few massive carbides.
(2) With the increase of quenching temperature, the grain of high speed steel grows continuously. When the quenching temperature exceeds 1040 ℃, the grain growth trend is obvious. When the quenching temperature exceeds 1160 ℃, the grain size reaches grade 4.5, and the grain coarsening has been very serious.
(3) With the increase of quenching temperature, the content of residual austenite is added continuously. When the quenching temperature is steeper than 1080 ℃, the content of remaining austenite will increase sharply. When the quenching temperature reaches 1160 ℃, the content of residual austenite increases to 38%. Therefore, considering the control of residual austenite content, the quenching temperature should be lower than 1080 ℃
(4) When quenching at 1040 ℃, the hardness reaches the peak, which can reach 64.1hrc. At this time, the matching of roll arrangement, grain size and residual austenite content of high-speed steel is better.
(5) The quenching temperature of new cast high speed steel roll should be selected between 1020 ~ 1080 ℃.
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