| Recently,the transport and storage of oil pipeline main use the corrosion resistant alloy steel grade. But the application of such steel will increase the cost of oil field. Research on a new material and the development of new manufacturing methods and processes become the focus of attention in the industry. It was suggested that a new low Cr steels use and development is an important way, The article aim at the new pipeline 5 Cr steels. Analyze the process performance and its performance through the research of the weldability.Finite element method was employed to conduct the numerical simulation calculation of temperature fields of 5Cr steel. Through the research of continuous cooling transformation organization under the welding condition to predict the organization, performance and hardness of weld heat affected zone. The results show that 5Cr steel can obtained the tissue types that contain ferrite in the wide range of cooling rate. So it has high strength and good mechanical properties.Research the matching of the selected welding wire and the base material. And research the formability and the crack resistance of the three kinds of joints. The results show that the weld of the YC-YD450 Q is good formability and surface bright. The weld of the ER308 is smooth and bright, with a slight modification. The deformation of the H08Mn2 SiA weld plates is small. The test of the Y-groove weld cracking results show that three corresponding wire welded joints have not cracks at 60℃and100℃preheating.The performance testing and microstructure observed of the three welded joints show that the connector fusion of the YC-YD450 Q and ER308 are good. The joint of H08Mn2 SiA obvious impatience corrosion, which joints is obviously not bright after the alcohol solution of nitric acid corrosion. The weld area organizations of the YC-YD450 Q is granular bainite, which average tensile strength of joint is 533.52 Mpa, The weld area organizations of the H08Mn2 SiA is Martensite and lower bainite, which average tensile strength of joint is 580.16 Mpa, The weld area organizations of the ER308 is bainite and ferrite, which average tensile strength of joint is 547.75 Mpa. The fracture morphology shows dimples, which have good ductility and toughness. The average load of the H08Mn2 SiA joint is 17 kN. The average load of the ER308 joint is 17 kN. The average load of the YC-YD450 Q joint is 8kN. The bending of the three joints is large and not fracture, which show that the bending properties of the three kinds of joints are good. The impact test results of the three kinds of joint show that the impact toughness is close to the base metal. The hardness distribution of the three joints is uniform. The central area of the weld is larger than heat affected zone. The base metals are lowest. The corrosion tests show that the average corrosion rate of YC-YD450 Q is 0.0397mm/a, the average corrosion rate of H08Mn2 SiA is 0.07675mm/a, the average corrosion rate of ER308 is 0.0496mm/a. The corrosion morphology shows that the joints of YC-YD450 Q and ER308 corrosion are not obvious. The joint of H08Mn2 SiA corrosion is serious. The results of the tightness and pressure tests show that the welds have not water leakage under the test pressure 3.2MPa, 5MPa, 10 MPa holding 10 min, and found that the pressure loss rate of less than 10%. So the tightness and pressure of the three joints is good. The results of X-ray diffraction test show that the joints of the YC-YD450 Q and H08Mn2 SiA have not appear inclusions,pores, cracks and other defects.The success of the research will change the current on structured application of 5Cr new steel grades, which can save the production cost, which is meaningful to the actual production. |
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