Preforming method for high-strength steel variable-diameter tubular part

A preforming method for a high-strength steel variable-diameter tubular part, comprising:

• selecting a tubular blank;
• and
• preparing a tubular blank forming mold, wherein the tubular blank forming mold comprises a preforming mold and a final forming mold;
• sealing and pressurizing the tubular blank;
• heating the tubular blank by using electrodes;
• preforming the tubular part at a constant temperature, wherein performing the tubular part comprises heating the tubular blank to a temperature T;
• enabling the temperature T to be larger than or equal to 300° C., and smaller than or equal to 1200° C.;
• maintaining the temperature T of the tubular blank for 5-20 s, then closing the preforming mold;
• compressing the tubular blank;
• and opening the preforming mold after the tubular blank is compressed;
• maintaining a temperature T1 and moving the preformed tubular part to the final forming mold, wherein maintaining the temperature T1 and moving the preformed tubular part to the final forming mold comprises continuously maintaining the temperature T1 of the preformed tubular part for 5-20 s, enabling the temperature T1 to be larger than or equal to 700° C., and smaller than or equal to 1300° C., and then moving the preformed tubular part to the final forming mold;
• and
• finally forming the tubular part.