TY - JOUR ID - TI - Effect of Heat Treatment and Bake Hardening on the Mechanical Properties and Microstructure of Dual Phase Steel AU - Abbas Fadhil Abbas AU - Abbas Abdul Hussein Abid PY - 2019 VL - 12 IS - 3 SP - 84 EP - 94 JO - DIYALA JOURNAL OF ENGINEERING SCIENCES مجلة ديالى للعلوم الهندسية SN - 19998716 26166909 AB - This research is concerned with study of the effectheat treatment and the bake hardening process on dualphase steels which can be obtain by intercritical annealingprocess. Hardness, microstructure and tensile specimenswere prepared according to standards. Used specimenswas with different carbon content (0.12, 0.096 and 0.064).The normalizing heat treatment was conducted on lowcarbon steel, to remove the effect of the previousmanufacturing processes. Intercritical annealing was usedas a heat treatment to obtain the dual phase steel, thecarbon steel was quenched from760 ºC this temperaturelies between the critical points. It has been found thatafter intercritical annealing process has transformationaccrue from pearlite structure resulting from thenormalization process to a new structure contain ferriteand martensite. The hardness of dual-phase steel obtainedby intercritical annealing is higher than of the steel thatwas normalized as well as the carbon content of the steelaffects the hardness. Tensile test results showed that theultimate tensile strength and yield strength increased afterintercritical annealing process compared to otherspecimens were normalized ,content of carbon also effecton the ultimate tensile strength and yield point. The dualphase steel is characterized with no visible yield point dueto the dislocations movement are restricted. Dual phasesteel yield point re-appear after pre-strained at 3, 5, 8,10%., and baked to 170 ° C. The ultimate tensile strengthand the yield point for the pre-strained and bakedspecimens were higher than the other tensile specimenswhich conducted with normalizing or intercriticalannealing only due to the diffused carbon atoms that pindislocations and prevent it is movement. Baking processis affected by several factors such as carbon ratio and theamount of prestrain. It is found that when carboncontent increase, the number of diffused carbon atomswill increase. Amount of pre-strain effect on themechanical properties after baking process, where it wasfound that when the mount of pre-strain increase theultimate tensile strength and yield point stress willincrease.

ER -