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制造44800和19500 kg的两根70Cr3Mo钢支承辊大锻件。钢锭采用EAF+LF+VD+VC冶炼浇注,1锭锻制2件,锻后球化退火,出炉冷却后,毛坯进行超声波探伤检查。结果发现:小辊超探合格踩线,大辊在冒口端辊颈部分存在超标缺陷。为了探究锻造工艺合理性,切掉大辊两端辊颈部分,利用辊身合格的坯料改锻成小辊。改锻后的小辊经超声波探伤发现,除辊身外两端辊颈部分均存在超标密集缺陷。通过一系列试验,对孔洞缺陷和夹杂物进行了分析,确定了导致支承辊超探不合格的原因:铸锭缺陷中广泛分布的非金属夹杂物分割了钢基体的连续性,恶化了钢的性能,导致超探不合格。此外,分析了夹杂物的来源及其危害性,并提出了相应的工艺改进措施。
Two large 70Cr3Mo steel backup rolls were manufactured for 44800 and 19,500 kg. Steel ingot EAF + LF + VD + VC smelting pouring, 1 ingot forging 2, after forging ball annealing, after cooling out, the blank for ultrasonic testing. The results showed that: a small roller super-qualified step on the line, a large roll in the riser roll neck portion excessive defects exist. In order to explore the rationality of forging process, cut off the roll neck at both ends of the roll part, the use of qualified body blanket forging into small rolls. After the forging of the small roller by ultrasonic testing found that in addition to roller body at both ends of the roll neck are excessive excessive defects. Through a series of experiments, the hole defects and inclusions were analyzed to determine the cause of unsuccessful ultrasonography of the backup roll: extensive distribution of non-metallic inclusions in the ingot defects segmented the continuity of the steel matrix and deteriorated the steel Performance, leading to ultra-probe failed. In addition, the sources of inclusions and their harmfulness were analyzed, and the corresponding process improvement measures were put forward.