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制约钢管抗挤毁强度的主要因素有屈强比、残余应力和尺寸精度。提高屈强比,将大大改善钢管的抗挤毁性能。对D/S值(外径与壁厚之比)较小的钢管,即D/S≤20的钢管更是如此。在这类钢管中,屈服强度是导致塑性挤毀的主要因素。因此,在设计钢种时,降低含碳量和细化晶粒,是达到这一目的的有效措施。新日铁开发了一种可以提高热轧低碳带钢强度的新工艺,此工艺是在带钢热轧期间,控制轧材高温机械性能的控制轧制工艺。采用这项新工艺,用热轧带钢不经淬火与回火便能直接生产出552MPa级的高强度电阻焊石油套管,而淬火与回火一直是常规轧制不可缺少的过程。将减少含碳量的冶炼方法与以细化晶粒为目的的高温机械性能控制轧制方法相结合,能大幅度地改善钢材的屈强比。因此,由这一新工艺生产的电阻焊石油套管,其抗挤毁强度等同或优于传统工艺轧制,即热轧、淬火、回火工艺流程所生产的产品。要实施热轧工艺的这一革新,即只采用热轧就能获得低碳高强的细晶粒钢材,须将终轧温度准确地控制在Ar_3点之上,并在轧后冷却区的前半段进行急冷,以及降低带钢的打卷温度。
The main factors restricting the collapse resistance of steel pipe are yield ratio, residual stress and dimensional accuracy. Improve yield ratio, will greatly improve the anti-collapse of steel performance. For D / S value (diameter and wall thickness ratio) smaller steel pipe, that is, D / S ≤ 20 steel pipe is even more so. In this type of pipe, the yield strength is the main factor leading to plastic collapse. Therefore, in the design of steel, reduce the carbon content and grain refinement is an effective measure to achieve this goal. Nippon Steel has developed a new technology that can improve the strength of hot rolled low carbon steel strip, a controlled rolling process that controls the high temperature mechanical properties of the rolled strip during hot strip rolling. Using this new process, hot-rolled strip can be directly produced without quenching and tempering 552MPa-class high-strength resistance welding oil casing, and quenching and tempering has been an indispensable process of conventional rolling. Combining the smelting method of reducing the carbon content with the high-temperature mechanical property control rolling process for grain refinement can greatly improve the yield ratio of steel. Therefore, the resistance welding oil casing produced by this new process is equal to or better than the traditional process rolling, that is, the products produced by the process of hot rolling, quenching and tempering. To implement this innovation in the hot rolling process, that is, using only hot rolling to obtain low-carbon high-strength fine grain steel, the finishing temperature must be accurately controlled above the Ar_3 point and the first half of the cooling zone after rolling Quench, and reduce the strip rolling temperature.