A kind of manufacturing method and mold structure of super large head long shank bolt

Abstract

The invention discloses a manufacturing method of an oversized-head pole bolt. The method comprises the following steps: 1, preparing a pole blank, wherein the cross-sectional area of a wire blank is equal to 1.5-1.8 times the radial cross-sectional area of a finally-molded pole; 2, preshrunking the screw part of a bolt, wherein the area ratio of diameter reduction is 20-25%; 3, shrunking and molding the screw part of the bolt, wherein the area ratio of diameter reduction is 20-25%; 4, premolding a bipyramid of an upset head, wherein the bipyramid comprises an upper positive pyramid and a lower inverted pyramid, the preserved cylindrical positioning guide clamping height of the upper positive pyramid is 3mm, the demolding inclination of the upper positive pyramid is 8-15 degrees, the demolding inclination of the lower inverted pyramid is 12-15 degrees, the height of the upper positive pyramid is 1-7.5mm less than that of the lower inverted pyramid The volume of the lower inverted pyramid occupies more than a half that of the bipyramid; during molding in a static mold, the transverse force borne by a conical die in a movable die is reduced, and the head molding stability is improved; 5, preforming a cylindrical body of the upset head; and 6, finally forming the upset head.

Description

technical field [0001] The invention belongs to the technical field of cold heading forming and fastener processing and manufacturing, and relates to a method for manufacturing super-large-head long-stem bolts; it is especially suitable for manufacturing super-large-head long-stem bolts when the upset-forging ratio is ≥ 4.5. Background technique [0002] As we all know, the upsetting ratio is the ratio of the length of the billet to be deformed to the diameter of the billet. Generally, when the upsetting ratio of the material is 3, the upsetting is likely to produce a double drum shape. If the upsetting ratio is greater than 3, the billet is prone to instability and longitudinal bending; If the ratio is too large and exceeds 4.5, longitudinal bending will appear in the upsetting blank, and interlayers will appear after flattening, resulting in product defects. [0003] For super-large-head long-stem bolts with an upset-forging ratio ≥ 4.5, it is usually necessary to increase...

AI Technical Summary

Problems solved by technology

[0007] The invention discloses a method for manufacturing super large-head long-stem bolts to solve the problem of low production efficiency and low material utilization rate in manufacturing super-large-head long-stem bolts in the prior art; high energy consumption and high manufacturing cost of hot heading processing; The forging angle of the upsetting die is small when the cold heading is large and the forging ratio is large, the height of the cylindrical positioning guide of the upsetting die is limited, and the structure of the spring ejector rod is added to the upsetting die.

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