Development Of Sumerged ARC Welding Wire Steel H08SG For Pipeline Steel

With the rapid development of the "west to east gas pipeline project", oil and gas pipeline construction in China has entered a rapid development period. The pipeline steel should be welded by welding wire into welding pipe, to reach service conditions of oil and gas. Therefore, higher requirements for the pipeline steel welding material quality have been put forward. The welding wire steel H08 SG for welding X60-X70 pipeline steel by submerged arc welding was developed by shougang steel company. This work can break international market monopoly, and reduce pipe manufacturing costs, which has great social benefits.Two kinds of alloy system four groups of welding wire have been designed.According to the design of welding wire steel composition, the vacuum induction furnace has been used for smelting. After skinned, forging, rolling, heat treatment and wire drawing process, the test welding wire was processed. Using different flux combination,the welding test has been carried out. The microstructure of deposited metal was observed and its mechanical properties were tested.Test results show that, the welding wire after welding are mainly acicular ferrite, and contains a small amount of proeutectoid ferrite. This organization has good tenacity to cooperate, can satisfy the requirement of the western pipeline welding. The current process can be smoothly producted H08 SG steel, and succeed rate is 100%. H08 SG composition can be controlled within a narrow range. The wire rod average P content is0.0075% and the average S content is 0.0066%.By flux matching test, H08 SG wire match with flux CHF101 well. The optimization of weld seam impact toughness can be obtained. By H08 SG X60 pipeline steel wire, the welding joint tensile specimens were all broken in the parent metal. The tensile strength is510-535 MPa. Bending and reverse bending at 180 ° are intact. Strength of welded joint is appropriate, and plasticity is very well.The butt joint rigidity restraint welding crack test was carried out in the summer environment(temperature 32 ℃, relative humidity 75%) and winter environment(temperature 0 ℃), respectively. No preheating welding was adopted. The surface crack rate of the butt joint, fracture crack rate, root crack rate are all zero, which shows that thecracking sensitivity of the developed H08 SG wire welding by shougang trial-manufacture for X60 pipeline steel is very low.By industrial manufacture test was caiied out for H08 SG wire welded deposited metal, in which, H08 SG match CHF101 flux welding wire. The monofilament submerged arc welding and double wire submerged arc welding welding for X60 pipeline steel were adopted. The various performances fully meet the welding joint technical requirements for west-east gas of X60-X70 steel pipe.