| The key technology in the development and plant trial of nickel based corrosion resistant alloy G-3 and 825 oil pipe for high sour gas fields were investigated in this paper. After literature review and study on the present research status of nickel base corrosion resistant alloy domestic and abroad, the main work finished in this paper was as follows, The high temperature deformation and the corrosion resistance of G-3 and 825 were studied by thermal simulation tests and sensitizing tests. On the basis of thermal-dynamic calculation (Thermo-Calc) and X-Ray diffraction (XRD), the precipitated phases in the deformed alloys and their mechanisms were analyzed by means of optical microscopy (OM), scanning electron microscope (SEM), transmission electron microscope (TEM).The effect of cold-rolling rate on microstructure and mechanical property was explored by cold-rolling experiments and mechanical tests like tensile, impact tests, which gave some references to the production of bare tube.The corrosion resistance on cold rolling slab and performance evaluation on oil pipe were also finished in this paper. The following conclusions were obtained from all the study mentioned above:(1) If the strain and strain rate of G-3 & 825 were steady, the dynamic recrystallization took place completely more easily with the increase of deformation temperature, while the maximum stress and static stress decreased. The maximum stress and static stress of G-3 alloy are 85MPa and 70Mpa larger than that of 825, respectively. The dynamic recrystallization became difficult with the increase of strain rate, then the maximum stress and static stress became higher. And the maximum stress and static stress of G-3 were all 50MPa larger than that of 825. At the same tensile rate of 200mm/s, with the increase of temperature, the reduction of area increased firstly, reached the maximum at about 1150℃, then decreased rapidly. The reduction of area at high temperature of 825 was larger than that of G-3.(2) If calculated by Thermo-Calc, the phases existing in G-3 wereσ,M23C6,M6C when over 500℃. Theσ,M23C6 coexisted between 500℃～821℃and M6C appeared at 821℃. The precipitated phases M23C6,σand M6C would disappear successively with the increase of temperature and they dissolved completely at 1093℃. And theσ,M23C6 existed in 825 at 500℃-789℃. They dissolved at 931℃. The precipitation and dissolving of second phases in alloy after solution treatment were further analyzed by SEM and TEM which were similar with the Thermo-Calc results.(3) According to the hot deformation and precipitated phases, the appropriate hot forming temperature for 825 was 1050℃-1240℃and 1150℃-1240℃for G-3. The temperature region of 825 was obviously larger than G-3.(4) The effect of cold rolling rate on microstructure and mechanical property were studied by cold-rolling experiments and tensile tests. The results showed that the cold-working rate should be 17-28%for the production of 110ksi oil pipe, and 30-44%for 125ksi oil pipe. While the appropriate deformation rate of 825 were 30-35 %for 110ksi oil pipe and 41-45%for that of 125ksi.(5) The salt spray tests showed that there were no obvious corrosion both for G-3 and 825 with the average corrosion rate of 0.001mm/a and 0.0019mm/a, respectively. In the FeCl3 pitting test, the corrosion rate in G-3 was slower than that in 825. The inspection on bare tube, which included chemical composition, mechanical property, hardness and corrosion resistant test such as SSCC, HIC, Intergranular Corrosion, all the results were up to the standard. |
PDF Full Text Request