工件底孔直径对Q460高强度钢冷挤压内螺纹的影响

试验研究了工件底孔直径对Q 460高强度钢冷挤压内螺纹的影响,包括分析工件不同底孔直径下内螺纹牙形、表面残余应力、硬度及端面表面形貌的变化。结果表明,冷挤压加工后内螺纹端面堆积体呈两边高、中间低的凹陷形,随着工件底孔直径的减小,端面堆积的高度不断增加,堆积程度也就变得愈加严重,螺纹牙顶、牙侧与牙根处表层硬度与表面残余压应力均升高。工件底孔直径的选择,在正确保证螺纹质量和丝锥寿命的前提下应尽可能取最大值,但是,一般情况下没有必要过分要求最高的牙高率,否则将给内螺纹挤压成形带来许多困难。Q 460高强度钢冷挤压内螺纹的工件底孔直径最佳取值范围为21.20～21.30 mm,牙高率超过80%,完全符合螺纹质量要求。

Effect of Hole Diameter of Work on Q460 High-Strength-Steel Internal Thread Formed by Cold Extrusion

The effect of hole-diameter of the work on Q460 high-strength-steel internal thread formed by cold extrusion is studied.And the changes of thread form,surface residual stress,hardness and surface topography of head face caused by different hole-diameter are investigated.The results show that the accumulation body of the head face of the internal thread formed by cold extrusion is higher on both sides,in the middle of the depressed shape form low.With the decreased hole-diameter of the work,the stack height of the head face is increasing,and the accumulated level is also becoming serious.The hardness and the residual pressure stress at crest,flank and root of the thread are increased.For ensuring the quality of the thread and the tap life,the hole-diameter of the work should select maximum value as far as possible.But it is unnecessary to pursue the highest thread high rate,otherwise extrusion forming of internal thread is attended with much difficulty.The best range of hole-diameter of Q460 high-strength-steel work is between 21.20 mm and 21.30 mm,the thread high rate exceeds 80%,and it completely meets the requrement of the quality of the thread.