Technological Superiority

ERW welded pipe is a longitudinal welded pipe produced through high-frequency welding technique. This product is widely applied in the fields of crude oil and natural gas delivery pipe and oil casing pipe. The API 5CT casing pipe of J55 steel grade (its diameter is 508 mm and wall thickness is 16.13 mm) is a high-end superior product researched and developed to meet the demand of ERW welded pipe market. Through welding line and appearance testing, the diameter and physical dimension of the oil casing pipe all reach the process design requirements.

Casing pipe is a channel which transports petroleum or other materials. It is praised by clients for its good performances in use. The oil casing pipe is heated under certain temperature. For 27MnCrV steel, the heating temperature in subcritical quenching is set between 740℃ and 810℃(AC1=736℃, AC3=810℃). If the heating temperature is 780℃, the subcritical quenching time is 15 min. After quenching, the temperature of tempering is set to 630℃ and the heat preservation period should be 50 min. The casing pipe has high strength and its toughness is improved at the same time. The quenching stress and deformation of oil casing pipe are reduced in low-temperature quenching. This method has ensured the successful heat treatment. At present, the heat treatment technique has been applied in diverse steel tube processing plants. Quality assurance data shows that for the heat treated steel tube, its yield strength Rt0.6 is between 820 MPa and 860MPa, tensile strength Rm is between 910 MPa and 940 MPa, impact toughness Akv is between 65J and 85J and its anti-destroy performance is 100% qualified. Statistics indicate that 27MnCrV steel tube is a superior high-grade oil casing pipe, and that the quenching technique is a great method to avoid high-temperature brittleness in steel production. The tensile strength, impact toughness and anti-destroy property of the pipe have been effectively improved through this heat treatment method.

27MnCrV is a new type of steel used for producing the casing pipes of TP110T steel grade. The conventional steels used for this purpose are 27MnCrV and 26CrMo4. Compared with the latter two steels, 27MnCrV contains less Mo elements and the production cost is vastly reduced. However, the 27MnCrV processed through the conventional austenitizing quenching technique has obvious temper brittleness. This would give rise to the instability of the impact toughness property of the oil casing pipe.
Generally, there are two methods to solve this problem. One method is to cool down the pipe quickly after tempering. The other method is to achieve incomplete austenitizing of the steels through subcritical quenching method in order to effectively reduce the harmful elements and impurities.