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The inner and outer spline shape dimensions are directly guaranteed by cold extrusion. According to the actual situation of use, the end face is not machined to avoid the burrs generated by the processing. In addition to the outer end of the large end gear, the outer diameter of the gear is 0.75mm, and the rest is 0.5mm, to ensure that the machining of the rear machine can be processed to the required size. The preformed hole has a diameter of 7.3 mm and a depth of 7.5 mm. Cold extrusion for parts.
The part extrusion process is based on the dimensions of the cold extrusion part of the part. Considering that the preformed hole is to be drilled, the volume of the extruded blank is calculated to be 8708 mm3 according to the principle of volume. The blank is a 16mm fine-drawn round steel, and the blank is used to prepare a high-quality lathe blanking method. The length of the blanking is 26.8mm. The process of the extrusion process is: lathe blanking, pre-forming hole annealing, softening, rolling, pickling, phosphating, Saponified squeezing. The squeezing deformation degree check adopts the squeezing and composite forming process, and the degree of deformation of the upset and the positive squeezing must be checked, and the degree of deformation of the upset portion is generally expressed by the height reduction rate h. h=(H0-H1)/H0100=62 (H0 is the height before the thickening, and H1 is the height after the thickening). The degree of deformation of the positively squeezed portion is represented by the reduction ratio of the section f, f = (F0 - F1) / F0100 = 53 (F0 is the cross-sectional area before the positive extrusion, and F1 is the cross-sectional area after the positive extrusion). The 20Cr allowable deformation degree can reach 65-70, so both are smaller than the allowable deformation degree, and the part allows the squeezing composite forming process.
When the squeezing force is calculated, the force required for the gear end to be thick is large, so the equipment can be selected as long as the roughing force is calculated. According to the formula and unit pressure in the data, the upset force is calculated to be 1900kN. A four-column universal hydraulic press with a nominal pressure of 2000kN was selected as the extrusion equipment.
The mold structure parts are extruded and formed using a universal ferrous metal extrusion formwork. The punch mold cap is fastened to the punch seat by the punch fixing sleeve. The lower mold adopts upper and lower split concave molds. The upper and lower split molds are all in the form of a three-layer combined die to save mold material. The parting surface of the upper and lower split die is selected to be 1 mm above the tangent point on the outer corner of the outer corner of the mold cone to polish the concave mold cavity. The convex and concave mold materials are made of W6Mo5Cr4V2 high speed steel, and the other working parts are Cr12MoV, and the heat treatment hardness is HRC6163. The reinforcing ring material is 40Cr, the medium reinforcing ring heat treatment hardness is HRC4244, the outer reinforcing ring is HRC3840, and 200 low temperature tempering is performed to eliminate internal stress.