【作者】 蔡星周；

【导师】 郭宝峰；

【作者基本信息】 燕山大学 ， 材料加工工程， 2014， 博士

【摘要】 油气管道是当今能源输出的主要载体。目前，管线工业对管线钢管的要求越来越高，而低端产品已经出现过剩。大口径直缝埋弧焊管是管线钢中具有良好性能的高品质产品，更符合经济社会的发展需求。管线钢的塑性变形引起材料强度性能指标的改变。在钢管的成形及性能测试过程中，会产生Bauschinger效应和加工硬化现象。前者使材料的屈服强度下降，而后者使材料的屈服强度上升。研究管线钢强度指标随塑性变形的变化规律，建立管线钢强化模型，确定毛坯板与制品之间的近似关系，对于促进管线钢的生产、完善管线钢成形的应用基础理论，具有非常重要的意义。本文针对在大口径直缝埋弧焊管制造领域最主要的UOE和JCOE成形方法，通过对其UO、JCO以及机械扩径成形工艺过程进行有限元数值模拟，分析和研究了板料在两种成形及机械扩径过程中的变形过程、变形特征和应力应变分布规律，确定了UOE及JCOE成形过程中的变形特征点，绘制了特征点周向应变变形历程曲线图。通过对特征点的周向应变历程分析，揭示了各部分板料的变形程度和变形历程，提供了建立管线钢管材料性能预测模型的基础。通过管线钢单轴正向加载试验和单轴反向加载试验，给出了不同加载路径下X80管线钢的材料性能随预应变量变化的规律。结合管线钢单轴反向加载试验，分析出X80管线钢的强化模型符合混合强化模型的特征，得到了混合强化系数随着预应变量的增大而增大的变化规律，并根据试验数据结果确定了混合强化系数和混合强化模型参数。制作了与UOE成形具有相同等效应变的X60管线钢弯曲试件，采用APISPEC5L标准关于矩形压平试样拉伸试验方法，分析得到了X60管线钢在不同弯曲变形程度下的材料性能变化规律。建立了用于反推X60管线钢管毛坯板力学性能的数学模型。在上述研究的基础上，根据在某制管厂完成的工业试验，分别对X60、X70、X90管线钢试验数据进行了研究，得到X60管线钢管坯在成形前后其材料性能的变化规律，与之前建立的X60管线钢力学性能的反推数学模型中呈现的变化规律相符；得到X90高钢级管线钢管坯的屈服强度在JCO成形后低于毛坯板、在机械扩径后高于毛坯板的变化趋势。更多还原

【Abstract】 Oil and gas pipeline is the main carrier of today’s energy output. At present, thepipeline industry has an increasingly high demand on pipeline steel while the low-endproducts have been excess.Large diameter longitudinal submerged arc welded pipes arehigh quality pipe with good properties of pipeline steel and more in line with the needs ofeconomic and social development. The plastic deformation of the pipeline causes thechanges in materials strength performance index. It can produce Bauschinger effect andhardening phenomenon in forming process and during the performance test of the pipe.The Bauschinger effect makes the yield strength of the materials decrease, and thehardening phenomenon makes the yield strength of the materials increase. Researching thepipeline strength index variation with plastic deformation, establishing the pipelinehardening model and determining the approximate relationship between the blank and theproducts have very important significance on the pipeline steel production and theapplication of the basic theory of pipeline steel forming.Aiming at the UOE forming and JCOE forming methods, which are the two mainforming methods in large diameter SAWL pipe manufacturing field, the deformationprocess, deformation characteristics and the distribution of stress and strain of plates intwo different forming processes and the following mechanical expanding processes wereanalysed by numerical simulation on UO、JCO and the following mechanical expandingforming technological process. Deformation feature points in UOE and JCOE formingprocesses were determined. The tangential strains deformation history graph of the featurepoints was drawed. The extent of deformation and deformation history of each part of thesheets were revealled by analyzing the tangential strains deformation history of the featurepoints. The basis for the establishment of line pipe material performance prediction modelwas provided.By the pipeline steel uniaxial positive loading test and uniaxial reverse loading test,the variation rule of the X80pipeline steel yield strength with the variation of thepre-strains under different loading paths were achieved. The features of X80pipeline steelharding model is analysed to be in line with the mixed hardening model by uniaxial reverse loading test for pipeline steel. The variation rule was obtained, which the mixedhardening model coefficient increases with the increasing of the pre-strain. The coefficientand parameters of the mixed hardening model were determined according to the results ofthe test data.X60pipeline steel bending specimen was produced which has the same equivalentstrain with UOE forming. According to API SPEC5L standard tensile tests on specimensflattened rectangle method, the materials performance variation rule of X60pipeline steelunder different degrees of bending was analyzed. Mathematical model which is forachieving the mechanical properties of X60pipeline steel blank was established.Based on the above studies, according to the completed industrial test in some pipeplant, test datas of X60, X70and X90pipeline steel were studied respectively. Variationrule of X60pipeline steel blank material properties before and after forming was obtained.It was in line with the variation rule of the mathematical model of the mechanicalproperties of X60pipeline steel established previously. The variation trend of X90highgrade pipeline steel blank was achieved, whose yield strength is lower than the blank afterthe JCO forming process while higher than the blank after the mechanical expandingprocess.更多还原