Mechanical Properties of High-strength Bolts Material after High Temperature

In order to investigate the mechanical properties of high-strength bolts after high temperature, the tensile test of the specimen of 10.9 grade M22 big six angle high-strength bolts after high temperature was carried out.The variation rules of yield strength, tensile strength and elastic modulus of high-strength bolts material under different heating temperatures and cooling methods were studied.The results show that the mechanical properties of high-strength bolts material are basically the same under the two different cooling methods.When the heating temperature is not more than 400℃,the yield strength and tensile strength of high-strength bolts material are basically not affected by the heating temperature.When the temperature does not exceed 300℃,the elastic modulus is nearly unchanged.With the increase of temperature, the yield strength, tensile strength and elastic modulus of high-strength bolts material decrease rapidly.When the temperature reaches 600℃,the yield strength, tensile strength and elastic modulus of high-strength bolts material decrease to 70%~78% of normal temperature.According to the test results, the formulas of reduction factors of yield strength, tensile strength and elastic modulus of high-strength bolts material after high temperature are obtained by fitting.The results of yield strength reduction factors and tensile strength reduction factors in this paper are consistent with those of some scholars, but the results of elastic modulus reduction factors of different scholars are quite different, which need to be studied further.