Study on Improving Accuracy of Measurement of Seamless Steel Tube Yield Strength

Tested are the degrees of influences on measured yield strength value of the seamless steel tube by such elements as tensile test stress rate, specimen holding-position and the yield strength index.And analyzed is the reason for deviation of the measured yield strength value from the true one.Accordingly relevant suggestion is proposed to improve the accuracy of the measured value.It is identified via the analysis that increasing the tensile teat stress rate imroves to some extent the measured yield strength value;the specimen holding-position affects the said measured value so obviously;and the yield strength index affects the measured value by less than 5 MPa.In order to improve the measurement accuracy oftheyieldstrength, itis suggested to get the stress rate limited as 10~25 MPa/s, try to get the specimen clamped in the middle position as vertically as it can be, and use the bilateral variable extensometer.Also suggested here is to determine the yield strength index according to what is specified under applicable product specification.In case that no correspondent requirement is found in the product specification, the index will be determined based on the specified total elongation rate etc.