When the seamless steel tube is tempered at 650 °C, its impact toughness value is the lowest, that is, the temper brittle zone, so it is not suitable to temper in this temperature range. It should be noted that the Wuxi seamless steel pipe is quenched below 1100 ° C, and the medium grain of 4-6 grade is obtained, and there is no secondary hardening peak. When the temperature exceeds 1150 ° C, the crystal grain grows obviously. In addition to the above strict control, seamless steel pipe needs to be extended.
After the perforation of the seamless steel pipe, the dimensional accuracy of the capillary tube, the internal and external surface quality and performance can not meet the requirements of the product technical standards, and must be further processed to meet the requirements. The purpose of the extension process is to reduce the wall thickness of the seamless steel tube to make it close to or meet the requirements of the finished product.