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苏联卡拉干达钢铁公司的罩式炉装入3个25t重的镀锡厚板带卷,采用两段式加热工艺进行退火,带钢的硬度不能符合新标准ГОСТ13345—85规定的硬度值。经试验研究发现带卷靠中心的20～30％长度,也就是温度最低的部分硬度最高;再延长退火时间也不能使这一部分的硬度符合要求。该公司根据研究结果制定了三段式加热工艺,第二段加热温度为520℃和590℃,第三段提高到640～650℃,第一段比原先低,以减小第一阶段带钢的同卷温度差和同炉温度差,从而使同卷和同炉带卷的硬度差大为减小。
Furnaces from the Karaganda Iron and Steel Company of the Soviet Union were loaded into three 25-tonne tin-plated plate coils, which were annealed in a two-stage heating process. The hardness of the strip did not meet the new hardness requirement of ГОСТ13345-85. The experimental study found that the tape around the center of 20 to 30% of the length, that is, the lowest temperature part of the highest hardness; and then extend the annealing time can not make this part of the hardness meet the requirements. The company developed a three-stage heating process based on the results of the study, the second heating temperature of 520 ℃ and 590 ℃, the third paragraph increased to 640 ~ 650 ℃, the first paragraph was lower than the original, in order to reduce the first stage strip Of the same volume temperature difference and the same furnace temperature difference, so with the same volume with the coil with the hardness difference greatly reduced.