Effects of Fe and O contents, heat treatment process and microstructure of impurity elements on mechanical properties of gr.17 titanium-palladium alloy. The results show that the content of Fe and O is the main factor affecting the mechanical properties of the sheet, so it should be strictly controlled. The uniform fine equiaxed alpha microstructure enables gr.17 ti - pd alloy to obtain good comprehensive mechanical properties. Between 680 ~ 740 ℃ annealing, can make the plank to achieve good plasticity and strength matching. Through this research, the yield strength of the sheet has been reduced obviously (0.2). The plasticity and strength have reached the standard.
Gr.17 is an alloy gr.1 (first-grade industrial pure titanium)+0.04%~0.08%Pd, belonging to alpha titanium alloy. Since ti-pd alloy not only retains excellent corrosion resistance of industrial pure titanium in oxidizing medium, but also significantly improves corrosion resistance in reducing medium, especially the ability to resist local corrosion in high temperature (above boiling point) chloride. In addition, Pd belongs to the slow eutectoid type, and the sensitivity of hydrogen embrittlement can be reduced by increasing the content of Pd. Therefore, gr.17 titanium palladium alloy is widely used in petroleum, chemical and metallurgical fields due to its strong corrosion resistance, hydrogen absorption resistance and crack corrosion resistance.
This paper mainly introduces the influence of impurity element Fe, O content and its heat treatment process and microstructure on the mechanical properties of gr.17 titanium palladium alloy, finds out the corresponding rules, and optimizates the reasonable heat treatment system, Fe, O content and its microstructure, which significantly reduces the yield strength and meets the technical standard of 200629. It provides the technological basis for mass production of the alloy sheet.
The experimental method
Gr.17 alloy ingots smelted in the vacuum arc furnace of the casting plant were used for inspection, and the slab was forged into square slab by the forging plant. After the slab was polished and ground, the slab was then hot-rolled to 8.0mm thick hot rolled plate on the 3,300mm four-high reversing mill. Alloy phase transition point is 880 ℃.
(1) Fe and O contents of impurity elements were 0.02% and 0.05% respectively; 0.03%, 0.06%; Mechanical properties of 0.04% and 0.08% 8.0mm plates were tested.
(2) the same chemical composition and processing technology of the 8.0 mm plate respectively to 680 ℃, 710 ℃, 740 ℃, 770 ℃, 790 ℃ for 1 h annealing, mechanical performance inspection after annealing.
(3) on the different grains of isoaxial structure (the same chemical composition, the same processing process, different temperature anneal appear 8.0mm plate mechanical properties test.
Results and discussion
Effect of main impurity elements Fe and O content on the mechanical properties of the plate the mechanical properties of 8.0mm plate with different impurity elements Fe and O content were tested.
With the increase of Fe and O content, the strength increases gradually and the elongation decreases gradually. The impurity elements Fe and O can form interstitial solid solution with titanium, which causes serious lattice distortion, strongly hinders dislocation movement, improves strength and reduces plasticity, and is also very harmful to fatigue performance, creep resistance, thermal stability and notch sensitivity. Therefore, the content of impurity elements Fe and O should be strictly controlled. In this study, due to the rigorous yield strength (0.2sigma) index, in order to further reduce the yield strength of the sheet to meet the technical standard 200629, the content of Fe and O in the ingot and the oxidation and oxygen increase in the processing process should be strictly controlled. Effect of heat treatment process on mechanical properties of sheet metal the mechanical properties of sheet metal after annealing at different temperatures with the same chemical composition and processing technology are tested.
(1) the content of Fe and O, impurities, are the main factors affecting the yield strength of gr.17 titanium palladium alloy sheet, and the content of Fe and O, as well as the oxidation and oxygen increase during the processing must be strictly controlled.
(2) the optimization of heat treatment temperature of 680 ~ 740 ℃.
(3) uniform fine equiaxed microstructure is beneficial to the reduction of yield strength and the improvement of plasticity. Through the above analysis of the factors affecting the yield strength of gr.17 titanium palladium alloy sheet, the correlation and laws are obtained. Based on the optimization of parameters, the reasonable chemical composition, thermal processing technology and heat treatment system are determined, which can significantly reduce the yield strength of finished sheet and improve its plasticity. The mechanical properties of the sheet reached the standard of 200629. It provides the technological basis for mass production of the alloy sheet in the future.