High cr cast iron having excellent heat resistance and its heat treatment

Abstract

PROBLEM TO BE SOLVED: To provide a high-Cr cast iron superior in heat-cracking resistance for an abrasion-resistant member receiving a heat cycle involving an impact, and to provide a heat treatment method therefor. SOLUTION: The high-Cr cast iron comprises, by mass%, 2.5-3.5% C, 0.2-1.0% Si, 0.6-2.0% Mn, 11-22% Cr, 1.0-3.0% Mo, 0.01-0.15% N, and the balance Fe with unavoidable impurities, while controlling a ratio Cr / C of a Cr content to a C content into a range of 4.5 to 6.5, and a product Mn×Mo of a Mn content and a Mo content into a range of 1.8 to 2.5. The heat treatment method includes cooling the surface of the high-Cr cast iron at a cooling rate of 5°C / sec or lower in the step of quenching, to control a residual γ phase in a structure to 30% or less by volume ratio. Thus, the high-Cr cast iron acquires improved heat-cracking resistance.

Description

technical field [0001] The present invention relates to a wear-resistant member that is excellent in not only wear resistance but also heat crack resistance and is suitable for exposure to high-temperature thermal cycles, in particular, rollers or elevators for conveying high-temperature steel materials ( lifter), or around blast furnaces in steelworks and sintering plants, etc., high-Cr cast iron for parts such as linings that come into contact with or collide with high-temperature ores and coals. Background technique [0002] In steel rolling lines such as steel bars, wear resistance is required for rolls used to transport high-temperature steel. Traditionally, as this kind of roller, what has been used is to thermally spray a layer of 13Cr martensitic stainless steel or tungsten carbide or chromium carbide cermet ( cermet) material, etc. hard layer. [0003] However, the above-mentioned rollers for conveying steel materials are also subjected to a heat cycle due to inte...

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Problems solved by technology

Therefore, neither the existing high-Cr cast iron nor the above-mentioned control of carbides in the structure of high-Cr cast iron can sufficiently suppress the occurrence of the above-mentioned hot cracks, and the peeling of the surface layer of the roller caused by this is not conducive to the transportation. Damage caused by steel in

[0012] Therefore, in the wear-resistant parts such as the above-mentioned rollers for conveying steel materials that are subjected to thermal cycles accompanied by collisions, there has been no high-Cr cast iron capable of preventing surface thermal cracking.

In addition, the application of the above-mentioned patent documents 2 and 3 etc. is for rolls and cutting tools, because the high Cr cast iron itself has low toughness, so the high Cr cast iron itself is not suitable for these applications.

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