Method for forecasting retained austenite change of Q&P steel after transformation under different temperatures
A technology of retained austenite and martensitic transformation, applied in the direction of testing metals, material inspection products, etc., can solve the problem that the law of austenite transformation cannot be accurately predicted, the law of austenite transformation cannot be represented, and it is difficult to apply to the automotive industry. and other problems, to achieve the effect of reducing time cost and economic cost, easy implementation and accurate implementation
Active Publication Date: 2014-05-07
SHANGHAI JIAO TONG UNIV
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Therefore, the austenite transformation law in the traditional deformation process based on room temperature tests and isothermal conditions cannot represent the actual stamping process, and cannot accurately predict the phase transformation law of retained austenite in the actual stamping process, and it is difficult to apply it to the automotive industry
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[0030] This embodiment relates to a method for predicting the change in volume fraction of retained austenite after deformation of Q&P steel at different temperatures, including the following steps:
[0031] (1) In this example, take the 1.2mm QP980 sheet as an example, prepare the single-drawn sample of Q&P steel sheet and the environment box, and measure the volume fraction of retained austenite before deformation by X-ray diffraction method as V A0 =10.61%;
[0032] (2) Then put the sample in the environmental chamber, and carry out the uniaxial tensile test at four ambient temperatures (298, 333, 373, 413K), unload after loading to a certain strain and measure the residual value of the central point of the sample Austenite volume content;
[0033] (3) The retained austenite content obtained in step (2) and the corresponding equivalent plastic strain data are used to establish an expression for the retained austenite content after uniaxial stretching at different ambient t...
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The invention discloses a method for forecasting a retained austenite change of Q&P steel after transformation under the different temperatures. The method comprises the following steps of firstly measuring an initial austenite volume fraction of a plate material, stretching the plate material to presupposed strain under the different temperatures, unloading and measuring the retained austenite volume fraction, and fitting to obtain a relationship of the content of the retained austenite of the plate material different environment temperatures under different environment temperatures along with equivalent plastic strain in an isothermal state based on test data; deducing a strain induction Markov phase change rate equation to the relationship between the retained austenite volume fraction after plate material transformation and the equivalent plastic strain at any temperature path through integration on the equation; and accurately forecasting the retained austenite volume fraction change of the Q&P steel after transformation under different temperatures by measuring the equivalent plastic strain after transformation, and combining with the transformation process temperature. The method provided by the invention has the advantages that the method is simple and exact, the cost is low, the method is easy to implement, the retained austenite volume fraction of the plate material after stamping is exactly forecasted according to the method, and the basis is provided for the improvement of a stamping technology.
Description
technical field [0001] The invention relates to the field of performance measurement of steel stamping parts, in particular to a method for predicting the change of retained austenite after deformation of Q&P steel at different temperatures. Background technique [0002] In the face of the continuous improvement of manufacturing costs, body weight reduction and passive safety requirements of the modern automobile industry, the application of high-strength and lightweight materials such as advanced high-strength steel has attracted widespread attention. In 2003, J. Speer et al. proposed the quenching-partition (Quenching and Partition) process. The carbon distribution process enriches carbon atoms from martensite to austenite, and obtains low-carbon martensite and stable high-carbon austenite at room temperature. Body organization. The Q&P (Quenching and Partition) steel obtained by this process is a new type of advanced high-strength steel with TRIP effect. Its production c...
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IPC IPC(8): G01N33/20
Inventor 李淑慧邹丹青何霁来新民
Owner SHANGHAI JIAO TONG UNIV
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