In order to withstand the large-displacement deformation of pipelines caused by the tundra, land slide and earthquake etc.,and ensure the safety and integrity of the pipeline in service,the steel pipes applied therein shall be with high deformability. According to the foreign researches, the materials which can be used as the strain-based linepipe steel are: Ferrite(F)+Bainite(B) dual-phase steel,Bainite+M/A(Mastensite-Austenite constituent) dual-phase steel and acicular ferrite steel.By controlling the chemical compositions and the rolling process, the above-mentioned high-deformability linepipe steel can be obtained. The kind of linepipe steel features in low yield point, low Y/T ratio, high work hardening rate, high uniform elongation rate, and round-house type stress-strain curve. Trial production of high-deformability welded pipe for the China-Myanmar Oil & Gas Pipeline project was conducted and succeeded in 2011 by several domestic steel plants and pipe plants.The ferrite+ bainite dual-phase steel is commonly used as the high-deformability line pipe steel in China at present.%为了克服冻土带、滑坡带、地震带等条件对管线造成的大位移变形失效,保证服役管线的安全性和完整性,要求焊管具有较强的抗大变形能力.国外的研究表明,目前可作为抗大变形管线钢的材料有铁素体+贝氏体双相钢、贝氏体+M/A双相钢和针状铁素体钢,这些抗大变形管线钢可通过控制钢的化学成分、轧制工艺和热处理得到,双相管线钢具有低屈强比、高加工硬化指数、大均匀延伸率、圆屋顶型应力应变曲线等特点.国内的钢厂和管厂也联合进行了中缅油气管道抗大变形焊管国产化试制工作并获得成功,目前国内抗大变形管线钢普遍采用铁素体+贝氏体双相钢.
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