Patent ID: 6038771
Filing Date: 2000-03-21
Classification: B21H,B21K,B23P,B62D,F16C,Y10T

Abstract:
A method of manufacturing a tie rod bar having a uniform wall thickness for use in a steering linkage of a motor vehicle, said method comprising:providing a steel pipe of a given length and a given wall thickness;a multistage forging step including a first stage of forming on said steel pipe a first diameter section by performing a cold forging while maintaining said given wall thickness in a state that a mandrel is inserted into said steel pipe so that a large diameter portion remains in one end portion of said steel pipe at a location corresponding to a location where a spherical section is to be formed, while an opposite end portion of said steel pipe is shank-reduced to form said first diameter section, a second stage of shank-reducing a first portion of said first diameter section from a location in a central portion of said steel pipe to one end thereof by cold forging to form a second diameter section smaller in diameter than said first diameter section while maintaining said given wall thickness, a third stage of shank-reducing a second portion of said first diameter section from a location in a central portion of said first diameter section toward said one end portion of said steel pipe by cold forging to provide a diameter equal to that of said second diameter section so that said second diameter section extends further toward said one end portion of said steel pipe while maintaining said given wall thickness, a fourth stage of shank-reducing a portion of said second diameter section at said opposite end portion of said steel pipe by cold forging to form a third diameter section smaller in diameter than said second diameter section while maintaining said given wall thickness, and a fifth stage of forming said spherical section at said large diameter portion of said steel pipe by cold forging while maintaining said given wall thickness and further forming a hexagonal section with a hexagonal cross section at a portion of said second diameter section adjacent said third diameter section;a neck section forming step of forming a neck section at a portion of said first diameter section adjacent said spherical section;a boot groove forming step of forming a boot groove at a given position on said second diameter section;a screw section forming step of forming a screw section on said third diameter section;a heat treatment step of performing a heat treatment for removing residual stresses from components formed in said multistage forging step, said neck section forming step, said boot groove forming step and said screw section forming step to thereby increase strengths and improve ductility thereof; anda coating step of coating the heat-treated components for rust prevention.