A kind of rolling production method that reduces 42crmo hardness

Abstract

The invention belongs to the field of production machining of special steel of the metallurgical industry, and relates to a rolling production method capable of reducing hardness of 42CrMo. A 42CrMo casting blank serves as a raw material, and the method sequentially comprises following working procedures of heating, descaling, a rough rolling, cooling after rough rolling, continuous rolling, through water cooling, bar reducing sizing mill finish rolling, cooling bed cooling and finally obtaining a finished product bar; by the adoption of the technology, the site operation is simple, online automatic control is easily achieved, and operation labor intensity of a worker is reduced; through the online controlled rolling controlled cold technology, straightness of the 42CrMo steel grade is greatly improved; the subsequent heat treatment technology (annealing technology) is reduced, production cost is saved, the production period is shortened, and the steel market competitiveness is improved; the hardness value range of the obtained 42CrMo steel ranges from 220 HBW to 260 HBW; a metallographic structure comprises ferrite and pearlite; the banded structure is smaller than or equal to 2 levels; the grain size is larger than or equal to 8 levels; and the mechanical property can meet the national standard and user needs.

Description

Technical field [0001] The invention belongs to the field of special steel production and processing in the metallurgical industry, and relates to a rolling process, in particular to a rolling production method for reducing the hardness of 42CrMo. Background technique [0002] In recent years, with the rapid development of my country's economy, my country's automobile manufacturing industry and machinery manufacturing industry have developed rapidly. In this context, it is particularly important to accelerate the research and development of automotive steel. Due to its high strength, good hardenability, plasticity and toughness, 42CrMo steel has small deformation during quenching, and has high creep strength and enduring strength at high temperatures, it is widely used in automotive parts, such as automotive engine crankshafts, front axles, Knuckle etc. However, with the development of deep processing technology of steel, in order to improve the processing efficiency, the curren...

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Problems solved by technology

[0007] (1) In order to control the hardness value of 42CrMo steel, some iron and steel enterprises adopt a heat treatment process (annealing process) to solve the problem, but this process has high production costs, long turnaround time, and wastes energy, which is not conducive to environmental protection

[0008] (2) In order to control the hardness value of 42CrMo steel, the domestic iron and steel industry mainly ensures the hardness value of 42CrMo steel through high-temperature off-line high-temperature sawing, and timely slow cooling in the slow cooling pit. Although this method has certain effects, there are The following disadvantages: 1) This method increases the construction cost of the slow cooling pit; 2) Increases the labor intensity of the slow cooling operator; 3) Since 42CrMo is easy to bend, the bending degree after slow cooling seriously exceeds the standard, which increases the difficulty of straightening by the leveler; 4) If the off-line temperature is not controlled in time, it will easily lead to unqualified hardness

[0009] (3) Although the existing technology also adopts the controlled rolling process to control the hardness value of 42CrMo steel, but for the steel rolling workshop with long main rolling line and lower-line temperature below 300 °C, it is still very difficult to control the final rolling temperature only. It is difficult to control the hardness value of 42CrMo steel, especially for specifications ≤ 42CrMo steel

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