Φ244.48 mm×13.84 mm R95套管拉伸性能和几何尺寸超标原因分析

Reason Analysis on Non-conformity of Tensile Property and Geometric Dimension of Φ244.48mm× 13.84mm R95 Casing

某公司生产的Φ244.48 mm×13.84 mm R95套管热处理后出现批量性力学性能超标和几何尺寸不合格现象,主要表现为屈服强度大于标准值,不合格率90%;外径普遍增大0.23~0.56 mm,但未超标;壁厚减少0.05~0.21 mm,30%超标;10%椭圆度超过2 mm;10%管端直度超标。经分析,屈服强度不合格主要由回火炉温度控制不均匀、回火温度过低、回火保温时间不够等因素综合引起;外径、壁厚淬火后数值增大、回火后数值减小主要是由热处理组织变化以及淬火、回火影响程度不同而决定;椭圆度超标是由于管端长时间高温受热而发生了“坍塌”;直度不合格主要是热处理后套管发生了形状畸变而导致。针对屈服强度超上限和尺寸变化,提出了解决措施及建议,保证了Φ244.48 mm×13.84 mm R95套管后续生产质量。

After heat treatment of Φ244.48 mm×13.84 mm R95 casing produced by a company,the phenomena of batch non-conformity of mechanical properties and geometrical size appeared.The yield strength was greater than the standard value with an unqualified rate of 90%.The outer diameter generally increased by 0.23~0.56 mm but not exceed the standard.The wall thickness reduced by 0.05~0.21 mm,which resulted in an exceeding standard rate of 30%.Ovality of 10% of the casing exceeded 2 mm and end straightness of 10% of the batch exceeded standard.Through analysis,the unqualified yield strength is mainly caused by the integrated factors such as uneven furnace temperature,too low tempering temperature,insufficient tempering holding time and so on.The values of outer diameter and wall thickness increase after quenching and decrease after tempering mainly due to the change of heat treatment microstructure and the different effects of quenching and tempering.The phenomenon of “burning down” occurred at the end of the tube which was heated at high temperature for a long time.The unqualified straightness after heat treatment is mainly caused by the shape distortion of casing after heat treatment.In view of the yield strength exceeding the upper limit and the size change,the measures and suggestions are put forward to ensure the quality of Φ244.48 mm×13.84 mm R95 casing in subsequent production.