Production process optimization of high-quality steel for engineering machinery
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摘要: 工程机械用热轧钢板不仅对产品力学性能要求严格，而且对钢板表面质量要求极为苛刻。南钢从合金成分设计着手，通过控制钢水冶炼过程、降低奥氏体化温度和二次开轧温度，成功获得显微组织由铁素体和珠光体组成，拉伸性能稳定、低温冲击均值高达220 J、晶粒度10级以上无带状组织的高品质工程机械热轧钢板。研究表明：洁净钢冶炼技术提升、低温奥氏体化技术结合低温轧制冷却工艺,减少钢板表面铁橄榄石生成量，钢板表面可形成致密稳定不易破碎的5 µm厚度的氧化铁皮，氧化铁皮的存在避免了钢板在运输储存过程中表面的二次破坏，保证了客户使用质量。在满足了工程机械用钢对产品表面及性能的高要求的同时，企业也获得了高品质工程机械用钢的工艺研究成果及成套工业化制造技术。Abstract: Hot-rolled steel plates used in engineering machinery have strict requirements not only on mechanical properties but also on surface quality. NISCO successfully produced hot-rolled steel plates for high-quality engineering machinery by optimizing chemical composition design, controlling molten steel smelting process, and reducing austenitizing temperature and second stage rolling temperature. The obtained steel achieved ferrite and pearlite microstructure, fine grain size of ASTM 10 without strip structure presence, and stable tensile properties as well as excellent low temperature impact value up to 220 J. The combination of smelting technology of clean steel, low temperature austenitizing technology and low temperature rolling and cooling process can reduce the iron olivine formation on steel plate surface and therefore promote a dense, stable and unbreakable oxide scale with the thickness of 5 µm. The existence of the oxide scale avoids the secondary damage of the plate surface during transportation and storage, and ensures the use quality for customers. Through this research the industrial manufacturing technology of high-quality steel of engineering machinery had been obtained.
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Key words:
- hot-rolled steel /
- engineering machinery /
- mechanical properties /
- surface quality /
- microstructure
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图 2 钢水中夹杂物的转变形式
(a) LF处理后; (b) RH真空后; (c) 中包
Figure 2. Transformation form of inclusions in molten steel
图 4 不同奥氏体化温度钢板表面氧化铁皮厚度
Figure 4. Scale thickness on the surface of steel plate during reheating with different austenitizing temperature
(a) 1 220 °C; (b) 1 180 °C; (c) 1 150 °C
图 5 不同二次开轧温度下钢板氧化铁皮的形貌
Figure 5. Morphology of oxide scale of steel at different secondary rolling temperatures
(a) 930 ℃; (b) 900 ℃; (c) 870 ℃
图 6 不同返红温度钢板内应力示意
(a) 常规返红; (b)在线淬火
Figure 6. Schematic diagram of internal stress of steel with different reddening temperatures
图 7 拉伸性能控制
(a) 屈服强度; (b) 抗拉强度; (c) 延伸率; (d) 屈强比
Figure 7. Tensile properties results of obtained steel
图 9 厚度方向钢板的显微组织
(a) 表层; (b) 1/4处; (c) 芯部
Figure 9. Microstructure of steel plate across thickness direction
表 1 工程机械用钢板化学成分要求
Table 1. Chemical composition of steel used in engineering machinery
% C Si Mn P S Al N Ceq ≤0.22 ≤0.15 ≤1.5 ≤0.025 ≤0.035 ≥0.015 ≤0.015 ≤0.50 
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表 2 工程机械用钢板的力学性能要求
Table 2. Mechanical properties of steel used in engineering machinery
Rp0.2/MPa Rm/MPa A/% −29 ℃冲击功/J ≥290 ≥430 ≥20 ≥11
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表 3 工程机械用钢板的规格要求
Table 3. Specification requirements for steel for engineering machinery
mm 钢板厚度 钢板宽度 钢板长度 厚度公差 宽度公差 18 3160 12000 −0.3~+0.8 0～+20
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表 4 工程机械用钢化学成分设计
Table 4. Designing chemical composition of steel for engineering machinery
% C Si Mn P S Nb V Ti Al N Ca Ceq 0.16～0.19 0.10～0.15 1.30～1.40 0.020 0.005 0.01～0.30 0.01 0.01～0.05 0.020～0.060 0.005 0.0005～0.0030 0.44
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