不同组配P91钢焊接接头断裂性能的试验研究

采用JR阻力曲线试验方法，研究了强度组配对P91钢焊接接头不同区域断裂性能的影响规律，并分析了不同组配P91钢焊接接头的硬度分布。结果表明，焊接热循环对其热影响区的性能没有明显的影响；低组配焊接接头焊缝区的断裂阻力要高于高组配焊接接头焊缝区的断裂阻力，即强度低组配有利于提高P91钢焊缝的抗断性能；对于熔合线区域，试验结果体现出类似的规律，即随组配比的降低，熔合线区域的抗断性能升高；而无论何种强度组配的P91钢焊接接头。其焊缝金属的抗断性能均优于熔合线区域。     

基于焊接接头断裂性能要求的焊条强度选择

焊接接头大量存在的裂纹及类裂纹缺陷是焊接接头破坏的主要原因之一，本文通过研究焊接接头强度组配对焊接接头断裂性能的影响，指出了不同位置的裂纹对焊接接头强度组配的要求是不同的，就焊条材料强度选择的问题提出了新的见解。     

裂纹深度和强度组配对焊接接头断裂性能的影响

利用弹塑性有限元计算和三点弯曲试验对不同裂纹深度，不同强度组配焊接接头试样的断裂性能进行了研究，着重讨论了裂纹深度和组配的不同对焊接接头试样加载过程中塑性区形状及大小，深浅裂纹分界点，抗断性能，裂纹尖端张开位移ＣＴＯＤ，Ｊ积分的影响。结果表明，裂纹越浅。加载时塑性区域大，断裂韧性值越高，高组配焊接接头试样加载时由于塑性区扩展到母材而具有较大的塑性区，低组配焊接接头试样加载时塑性区被抑制在焊缝中，尺     

焊接接头断裂抵抗力工程估计方法的数值研究

针对符合幂硬化性能的材料所连接而成的焊接接头,采用有限元计算方法,讨论了平面应变状态下,不同裂纹几何及材料组配的中心裂纹焊接接头的载荷与位移曲线。在此基础上,应用柔度变化率方法分析了各种组配接头的断裂性能,进一步通过曲线拟合的方法,得到了适合于焊接接头断裂韧度值的工程估算方法。     

焊接接头高应变率下的动态断裂韧度分析

对采用Hopkinson气炮加载－Charpy V形冲击试样试验方法对焊接接头高应变率下的动态断裂韧度数据进行了分析研究，通过对试样断口形貌、冲击吸收功、断裂韧度及其影响因素进行分析，表明在高应变率加载条件下，焊接接头冲击试样断口形貌有特殊的表现，延伸带或钝化区的尺寸大小反映了裂纹萌生前的塑性变形大小，也反映了裂纹萌生功的变化趋势。同时说明焊接接头在高速动态冲击载荷作用下，其断裂韧度参量受组配强度、冲击速度及环境温度等因素影响显著，焊接热影响区的断裂韧度值关系到焊接接头断裂韧度的好坏。     

焊接接头强度组配对CTOD的影响

利用模拟焊接接头试样三点弯曲试验的方法,就焊接接头强度组配对其断裂性能的影响进行了研究。发现不同的焊接接头强度组配对其断裂韧性和裂纹扩展驱动力有不同程度的影响,在考虑强度组配对焊接接头的断裂性能的影响时,必须从材料的断裂韧性变化和裂纹扩展驱动力变化的两个方面来考虑。     

LPG储罐焊接接头低温抗断裂性分析

通过ＣＯＤ试验测定了两种用于ＬＰＧ储罐建造的结构钢焊接接头低温抗断裂性能，研究了材料与工艺组合、试验温度等因素对焊接接头低温抗断裂性的影响，所得结果为ＬＰＧ储罐的选材与焊接工艺制定、结构的抗断裂分析提供了基础数据。     

为较高强度的结构钢选择焊接材料须考虑的两个因素

研究了焊缝金属相对宽度和焊缝金属强度对接头性能的影响。结果表明：随低强焊缝金属相对宽度变小,接头抗拉强度增大;焊缝金属相对宽度不大时,焊缝与母材实际等强的接头具有最优抗脆断性能,按实际等强原则选择焊接材料可提高焊接结构的可靠性,焊缝低强组配较超强组配合理。焊缝过分超强或过分低强均使接头抗脆断性能恶化。     

焊接接头损伤条件下的断裂力学参量数值模拟

利用弹塑性损伤-应变耦合有限元方法研究了不同强度匹配焊接接头中母材区断裂应变的变化对焊缝区裂纹断裂力学参量J积分的影响规律.结果表明,对于强度高匹配、等匹配和低匹配的焊接接头,在焊缝区各项力学性能参数保持不变的条件下,随着母材区断裂应变的减小,焊缝区的塑性应变及裂纹扩展驱动力J积分均有明显的提高;随着接头强度匹配比M的降低(母材屈服强度的升高),母材区断裂应变的变化对J积分值的影响作用减小.     

复合加载方式作用下熔合线上含裂纹焊接接头的裂端场与断裂参量

针对复合载荷作用下熔合线含裂纹的焊接接头,应用弹塑性有限元方法分析了其裂端应力场的分布规律.并对不同组配焊接接头的COD断裂参量及其复合角进行了数值计算,讨论了加载角度和接头强度组配对焊接接头断裂行为及断裂参量的影响机制.研究结果表明,对于复合载荷作用下的熔合线含裂纹焊接接头,其裂端应力场同时受到加载角度以及材料非均匀性的影响.当加载角度较小时,复合载荷对接头性能的影响相对于接头组配的影响更为显著.而当加载角度达到并超过30°时,情况与之相反.     

复合材料界面裂纹焊接接头塑性发展方向与复合角依存关系的数值分析

针对熔合线含裂纹的不同强度组配焊接接头,应用弹塑性有限元方法对其裂端场塑性区和复合角进行数值计算,讨论了强度组配与裂端场塑性区的发展规律以及裂端场塑性区发展方向与复合角的关系.结果表明,强度匹配对其裂端场塑性区发展规律有很大影响,即裂端场塑性区优先向屈服强度较小的材料发展;在同一载荷作用下,低组配接头裂端场塑性区比高组配大;裂端场塑性区随着复合角的增大而减小,对于不等组配接头,在载荷小于裂纹两边材料中较小的屈服强度值作用下,其塑性区发展方向与复合角呈现线性关系,而在载荷大于裂纹两边材料中较小的屈服强度值作用下则呈现非线性关系.     

弹性状态低匹配焊接接头弯曲等承载设计准则与设计方法

弹性状态以低匹配接头能够达到与母材“弯曲等承载能力”（EBLCC）为目标，对低匹配对接接头焊缝几何形状临界条件进行了理论分析，推导了低匹配接头满足弯曲等承载条件的最低余高以及最小熔宽，并给出了弹性状态低匹配弯曲等承载接头设计准则.分析了圆弧替代抛物线曲线的可行性，给出了适用于工程应用方便的三圆相切低匹配弯曲等承载接头设计方法，并进行了弯曲试验验证.结果表明，设计的三圆相切低匹配弯曲等承载接头能够达到与母材弯曲承载能力，满足弯曲等承载要求.文中给出的设计准则与设计方法可使低匹配接头按照母材的弯曲承载能力进行设计，为弹性状态低匹配接头弯曲承载能力设计提供重要的理论依据.     

提高P91耐热钢焊接接头冲击韧度的研究

探讨了影响P91耐热钢焊接接头冲击韧度的工艺因素,对P91钢的常规焊接工艺进行调整,并模拟该工艺进行焊接试验。最后通过拉伸、弯曲、冲击试验、断口扫描和金相观察检验接头组织及性能。结果表明,在模拟焊接工艺下,P91耐热钢可以获得良好的焊接接头。焊缝拉伸强度高于母材;焊缝侧向弯曲试验外弧面未发现开裂;焊接接头的显微组织为回火板条马氏体,未出现非正常组织,焊缝晶粒明显细化;接头冲击韧度得到了大幅度提高。     

12Cr1MoVG焊接接头高温短时拉伸及可靠性评价

分别对焊态和焊后热处理(PWHT)的12Cr1MoVG钢焊接接头进行300~600℃高温短时拉伸试验,根据该试验结果可以推算出接头的持久强度。结果表明,随测试温度的升高,两种接头的高温短时拉伸强度降低,伸长率升高。断口形貌分析表明接头的断裂机制由剪切断逐渐过渡到正断。焊态接头的高温短时拉伸强度均高于PWHT态接头。510℃时,焊态及PWHT态接头的持久强度下限(σ105783)分别为61 MPa和86 MPa,均大于某电站锅炉的额定蒸气压力(30.35 MPa)。PWHT态12Cr1MoVG钢接头具有较高的持久强度,因而具有更高的服役可靠性。     

Evaluation of the effect of strength mismatch in undermatched joints on the static tensile strength of welded joints by considering microstructure

High-tensile strength 950 MPa steel, HT950, which is steel used in penstocks, was developed to provide two vital properties: fracture arrest to stop brittle fracture and high weldability. This steel has been already used for penstocks in some hydropower plants in Japan. To widely apply high-tensile strength steels in penstocks in the future, fewer restrictions against their welding conditions such as pre-heat and post-heat temperature controls are required. One proposed solution is to undermatch the strength of the filler metal to that of the base material. This allows less pre-heating, or no pre-heating at all, and the use of conventional rod and process management is easier. Previous studies have shown that there are softening conditions under which the strength of the joint can be considered as that of the base material. However, the shape and distribution of the soft region are assumed to be ideal. In this study, the method for calculating the change of the strength in heat-affected zone (HAZ) during the welding process is discussed. Then, the influence of the strength distribution of HAZ and welded zone to the strength of the joint is investigated by a wide plate test in both experiment and elastic–plastic analysis. Applicability of undermatched joints to penstock fabrication is considered by these discussions. As a result, it is concluded that the Vickers hardness distribution in the HAZ can be estimated by the method which is proposed in this study and the strength of the under-matched joints is high enough in both experiment and analysis in which the Vickers hardness distribution is considered. From these conclusions, the applicability of undermatched joints, of which the weld metal is the HT570 class, to penstock fabrication is conformed.     

火电站新型中厚板异种钢焊接接头残余应力场数值模拟研究

基于因次分析法和方程分析的相似准则及高斯热源建立TIG焊数值模拟模型,以此模拟了T23与T/P91和TP347H与T/P91两种耐热异种钢中厚板焊接接头的应力场。在T23与T/P91中,低匹配残余拉应力稍高,落在焊缝区,高匹配残余拉应力低,但区域较宽;在TP347H与T/P91中,无论从冶金还是力学的角度来看,镍基匹配的焊接接头性能最好。     

火电站新型中厚板异种钢焊接接头残余应力场数值模拟研究

基于因次分析法和方程分析的相似准则及高斯热源建立TIG焊数值模拟模型．以此模拟了T23与T／P91和TP347H与T／P91两种耐热异种钢中厚板焊接接头的应力场。在T23与T／P91中，低匹配残余拉应力稍高，落在焊缝区，高匹配残余拉应力低，但区域较宽；在TP347H与T／P91中，无论从冶金还是力学的角度来看，镍基匹配的焊接接头性能最好。     

Influence of Multi-Thermal Cycle and Constraint Condition on Residual Stress in P92 Steel WeldmentEI北大核心CSCD

P92 steel is a typical 9%similar to 12% Cr ferrite heat-resistant steel with good high temperature creep resistance, relatively low linear expansion coefficient and excellent corrosion resistance, so it is one of important structural materials used in supercritical thermal power plants. Fusion welding technology has been widely used to assemble the parts in thermal power plant. When the supercritical unit is in service, its parts are constantly subjected to combination of tensile, bending, twisting and impact loads under high temperature and high pressure, and many problems such as creep, fatigue and brittle fracture often occur. It has been recognized that welding residual stress has a significant impact on creep, fatigue and brittle fracture, so it is necessary to study the residual stress of P92 steel welded joints. The evolution and formation mechanism of welding residual stress in P92 steel joints under multiple thermal cycles were investigated in this work. Based on SYSWELD software, a computational approach considering the couplings among thermal, microstructure and mechanics was developed to simulate welding residual stress in P92 steel joints. Using the developed computational tool, the evolution of residual stress in Satoh test specimens was studied, and welding residual stress distribution in double-pass welded joints was calculated. In the numerical models, the influences of volume change, yield strength variation and plasticity induced by phase transformation on welding residual stress were taken into account in details. Meanwhile, the hole-drilling method and XRD method were employed to measure the residual stress distribution in the double-pass welded joints. The simulated results match the experimental measurements well, and the comparison between measurements and predictions suggests that the computational approach developed by the current study can more accurately predict welding residual stress in multi-pass P92 steel joints. The simulated results show that the longitudinal residual stress distribution around the fusion zone has a clear tension-compression pattern. Compressive longitudinal residual stresses generated in the fusion zone and heat affected-zone (HAZ) in each pass, while tensile stresses produced near the HAZs. In addition, the numerical simulation also suggests that the transverse constraint has a large influence on the transverse residual stress, while it has an insignificant effect on the longitudinal residual stress.