Research On High Strength Bolt Thread Rolling Process

Nowadays there is a rapid development in all walks of life,such as engineering machinery?automobile?wind power?light industry?aviation and construction etc.The demand for high strength and precision thread fasteners are inevitable and steadily increasing in the above industry.Because there is complexity of high strength and precision thread process and the uncertain factors during rolling.If we depend on the experience of the staff to adjust the parameters,all those will bring great trouble to enterprise development of efficiency and quality,especially in the lot production for high-strength threaded business.Therefore,it is a great significance method to explore efficient and reliable thread rolling parameters for technicians.In this paper,first explain the theory of thread rolling,and briefly list of technical analysis during actual production process.Meanwhile illustrate theoretical calculation parameters of the thread rolling including bar diameter before grinding?rolling pressure and time value,etc.By comparing the theoretical calculation with the actual production parameters,there is still a deviation phenomenon,which gives the direction of the research.In order to study the relationship between rolling parameters,the paper summarizes the rolling pressure and time how to effect half of thread angle,pitch diameter and major diameter variation,with high strength balance bolt and oil pump bolt as the rolling test object.With the rolling pressure tending to a reasonable value,the feed roller play a very good role in metal flow diversion,even streamline the thread tooth side and lateral root and become more symmetrical and smooth,and the top gear forming effect is better.Then matched up the reasonable rolling time,those parameters including half of thread angle,pitch and major diameter gradually can reach to the theoretical value.All these prove that the rolling time and pressure are the key factors to influence the precision of the screw thread rolling.By drawing the rolling pressure and time curve,it is found that it is more consistent with the power function curve.So apply MATLAB software to fit curve with experiment data under the specific conditions.After the rolling test with parameters from the curve?observing the surface state of the thread and assembly with torque requirement,it is concluded that each type of bolts only needs to be tested once to get the rolling pressure and time parameter,which are selected to fit the curve equation and used for guiding production.It is feasible to use the curve equation to guide the thread rolling.In fact,the method saves labor costs and brings economic benefits.