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热机械处理工艺(TMT)同时包含加工硬化、晶粒细化、固溶强化和沉淀强化等手段。采用电渣重熔(ESR)工艺制备了4种合金,它们的基本成分为:0.28%C,1.0%Mn,4.2%Cr,1.0%Mo,0.34%V。分别添加了微量Ti和Nb,增加Cr和V含量到4.8%和0.48%。在电渣重熔后的淬火态和回火态条件下,其中两种合金的屈服强度超过1550MPa。通过热机械处理进一步提高钢的屈服强度。通过析出物的稳定性计算、热挤压试验、不同冷却条件下冷却速率的确定以及TTT和CCT曲线模拟来优化热机械处理工艺参数。工艺过程包括将电渣重熔锭在1200℃预轧成中间坯,接着从950℃开始到850℃经两道次热轧将中间坯轧制成板,单道次变形量为25%。然后将试样立即在空气、聚合物水溶液(1∶1.5)和油等冷却介质中分别冷却。加Ti和高Cr、高V的合金经油冷后,屈服强度超过1750MPa。尽管电渣重熔铸态合金有很高的强度,但和基本成分合金一样,加Nb的合金试样并未得到强化,这是由于高温均热下晶粒长大。空冷试样的强度最低,油冷试样的强度最高。
Thermo-mechanical processing (TMT) includes both work hardening, grain refinement, solution strengthening and precipitation hardening. Four kinds of alloys were prepared by electroslag remelting (ESR) process. Their basic compositions were as follows: 0.28% C, 1.0% Mn, 4.2% Cr, 1.0% Mo and 0.34% V. Trace amounts of Ti and Nb were added, respectively, to increase the contents of Cr and V to 4.8% and 0.48% respectively. In the quenched and tempered condition after ESR, the yield strengths of the two alloys exceed 1550 MPa. Thermomechanical treatment to further improve the yield strength of steel. The thermomechanical processing parameters were optimized by the calculation of the stability of the precipitates, the hot extrusion test, the cooling rate determination under different cooling conditions, and the TTT and CCT curve simulations. The process includes pre-rolling the ESR ingot into an intermediate billet at 1200 ° C, followed by two hot rolling from 950 ° C to 850 ° C to roll the intermediate slab into plates with a single pass deformation of 25%. The sample is then immediately cooled in air, aqueous polymer solution (1: 1.5), and cooling medium such as oil. Plus Ti and high Cr, high V alloy after oil cooling, the yield strength of more than 1750MPa. Although ESR as-cast alloys have high strength, as with the base alloy, Nb-alloyed samples have not been strengthened due to the grain growth under soaking at high temperature. Air-cooled specimens have the lowest strength and the oil-cooled specimens have the highest strength.