Study On Control Of Mechanical Properties Uncertainty Of HJ Company Pipeline Steel

Mechanical property testing is an important link in the quality assurance of pipeline steel products.Its uncertainty is the standard deviation of parallel testing data,which represents the credibility of testing results and is related to the risk of misjudgment.Based on the application of DMAIC method and TRIZ theory in quality management and management process optimization at home and abroad,this paper explores a new idea of HJ Company to control the uncertainty of mechanical property testing.In recent years,the uncertainty of mechanical property test of HJ Company is higher than that of other similar enterprises.The unqualified products determined for the first time are changed into qualified products after re inspection.In this paper,the measurement uncertainty of pipeline steel mechanical properties of HJ Company is taken as the improvement goal,the key quality characteristics of pipeline steel product testing data are analyzed and studied by combining DMAIC method and TRIZ theory,and the measurement uncertainty evaluation model is established according to the influencing factors.Through fish bone diagram,Pareto Diagram and correlation analysis,it is found that the poor controllability of the deflection of the mechanical property test sample will lead to the deviation of its lower yield strength from the true value,and then affect the evaluation value of the uncertainty component of the lower yield strength in the mechanical property test uncertainty.Aiming at the problem of controlling the deflection of the specimen,two schemes of controlling the deflection are put forward by using the material field model in TRIZ Theory:(1)reducing the influence of the deflection on the lower yield strength by using a flattening machine;(2)Change the shape of the sample into a round bar to eliminate the deflection.After the implementation of the improvement project,two different improvement schemes are compared and analyzed from multiple angles.It is found that the mechanical property test index of the round bar sample is stable,and the uncertainty of the lower yield strength of the round bar sample is reduced from4.1mpa to 3.8mpa.In addition,the error rate in the mechanical property test report of HJ Company decreased from an average of 0.81% to 0.46%,a drop of 43.2%.The spot check error rate of test samples increased from 98.7% in 2019 to 99.6% in 2020.The z-ratio score of mechanical property test of HJ Company from the end of 2019 to 2020 was in a stable state,and the annual test cost decreased by about 1.1 million yuan.The implementation of the project not only significantly reduces the uncertainty of mechanical property testing of HJ Company,but also reduces the risk of misjudgment in the testing process of the enterprise,significantly improves the accuracy of testing and steadily improves the cost performance of products,providing a feasible scheme for the testing institutions in the enterprise to carry out process control and risk prevention and control.