Effect of Cooling Rate After Rolling on Microstructure and Mechanical Properties of 22 mm Thick X80M Hot Rolled Strip Steel
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摘要: 通过热模拟试验测定X80M管线钢铸坯的连续冷却转变（CCT）曲线，确定了合理的冷却速率范围；利用2 250 mm热连轧机组进行工业试制试验，研究了冷却速率（5，15，25℃·s-1）对X80M带钢显微组织、力学性能和抗落锤撕裂性能的影响，确定了最佳冷却速率；在最佳冷却速率下进行22 mm厚X80M带钢的批量生产，研究了其显微组织、力学性能和抗落锤撕裂性能。结果表明：当冷却速率为20～30℃·s-1时，可得到有利于试验钢性能的由针状铁素体、粒状贝氏体和弥散分布M/A岛组成的显微组织；当冷却速率由5℃·s-1提高到25℃·s-1时，工业试制带钢组织中的M/A岛变得细小，分布更加弥散，最佳冷却速率为25℃·s-1；批量生产X80M带钢的晶粒细小，组织均匀，其抗落锤撕裂性能、拉伸性能和冲击韧性均满足中石油管线采购要求。
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关键词:
- 落锤撕裂试验(DWTT) /
- CCT曲线 /
- 针状铁素体 /
- 冷却速率
Abstract: Continuous cooling transformation (CCT) curves of X80M pipeline steel ingot were measured by thermal simulation test, and a reasonable cooling rate range was determined. The industrial trial manufacturing test was conducted with a 2 250 mm continuous hot rolling mill. The effects of cooling rate (5, 15, 25℃·s-1) on the microstructure, mechanical properties and resistance to drop-weight tearing of the X80M strip steel were studied, and the optimal cooling rate was determined. At the optimal cooling rate, the 22 mm thick X80M strip steel was produced in batches, and its microstructure, mechanical properties and resistance to drop-weight tearing were investigated. The results show that when the cooling rate was between 20-30℃·s-1, a microstructure consisting of acicular ferrite, granular bainite, and dispersed M/A island was obtained, which was beneficial to the performance of the test steel. When the cooling rate increased from 5℃·s-1 to 25℃·s-1, the M/A island in the structure of the industrial trial manufactured strip steel became smaller and the distribution was more diffuse; the optimal cooling rate was 25℃·s-1. The batch-produced X80M strip steel had fine grains and a uniform structure, and its resistance to drop-weight tearing, tensile properties and impact toughness all met the requirements of PetroChina pipeline procurement standards.-
Keywords:
- drop-weight tear test (DWTT) /
- CCT curve /
- acicular ferrite /
- cooling rate
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