Factors Affecting on Shrinkage Stresses of Weld Under Restraint
Factors Affecting on Shrinkage Stresses of Weld Under Restraint
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约束焊缝收缩应力的影响因素
DOI：
10.2207/qjjws1943.33.6_439
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发表时间：
1964
期刊：
影响因子：
--
通讯作者：
K. Satoh
中科院分区：
文献类型：
--
作者：
K. Satoh
焊接开裂受冷却过程中的反应应力和焊缝金属及热影响区的性能共同影响。因此，对焊缝开裂问题的研究不仅要从冶金学的角度出发，还要从反应应力的角度出发。研究了冷却或约束时的反应应力对焊缝开裂的影响，特别是对一些低碳钢和高强钢的约束焊缝的一道焊裂进行了研究。在研究项目的早期阶段，需要了解哪些因素对约束下的反应应激有影响，以便进行合理的研究规划。本文件是作为后续测试计划的初步资料编写的。在图1所示的约束系统中，收缩力将由冷却期间首道焊缝金属的受阻收缩或拉伸产生。对焊缝金属的拉伸进行了分析研究。该分析基于假设母板(B)和约束构件(C)在冷却过程中表现为弹性，但在焊缝金属在图3所示的应力-应变关系下会产生一定的塑性变形。由whw/ph⋅λwn+λw= sph和pwhw分别为母板和焊缝金属单位延伸所需的单位长度刚度或单位长度力，S为母板约束长度(l)之间的自由收缩。在s的几个值下，λw与刚性比pwhw/ph的关系如图4所示。较小的刚性比和较大的自由收缩会导致焊缝金属产生较大的拉伸。自由收缩S受长度为l的母板的热输入和整体冷却行为的影响。在一定的热输入下，长度为l的母板的总冷却速率或热损失随着热容量或母板长度(l)和厚度(h)的减小而增大。因此，在给定的热输入下，焊接金属在给定温度下的反应应力受以下因素的影响：1)约束系数(p)，包含约束长度(l)和母板与约束构件的截面积之比。2)母板厚度(h)。3)母板的约束长度(l)。4)焊缝金属刚度（pwhw）。图8和图9给出了l和h对焊缝延伸影响的计算实例。
Weld cracking is influenced by both reaction stress during cooling and properties of weld metal and heat-affected zone. The problems of weld cracking, therefore, should be explored not only from metallurgical standpoint but also from standpoint of reaction stress. Researches on effect of reaction stresss during cooling or restraint on weld cracking are now undertaken by the authors, especially for first-pass-weld-cracking of restrained welds of some mild and high strength steels. At earlier stage of the research project, informations on what factors influence to reaction stress under restraint were wanted for reasonable research planning. The present paper was prepared as preliminary informations for the subsequent test planning.In a restrainning system shown in Fig. 1 shrinkage force will be produced by hindered contraction or extension of first-pass weld metal during cooling. Analytical investigation was conducted on the extension of weld metal. The anaiysis is based on the assumptions that behavior of mother plate (B) and restraining members (C) is elastic during cooling, however, in the weld metal will be produced some plastic deformations under the stress-strain relation as shown in Fig. 3. The extension (λw) of weld metal at a given temperature below about 300°C is obtained bypwhw/ph⋅λwn+λw=Swhere ph and pwhw are rigidity or force per unit weld length required for unit extension of mother plates and weld metal respectively, and S is free contraction between restrained length (l) of mother plate. Relations of λw versus rigidity ratio pwhw/ph are shown in Fig. 4 for a few values of S. Larger extension of weld metal will be produced under smaller rigidity ratio and larger free contraction.Free contraction S will be influenced by heat input and overall cooling behavior of mother plate of length l. Under a given heat input the overall cooling rate or heat loss from the mother plate of length l will be increased as the decrease of heat capacity or length (l) and thickness (h) of mother plate.It will be concluded, therefore, that under a given heat input reaction stress of weld metal at a given temperature is influenced by the following factors ;1) restraint coefficient (p), which contains restrained length (l) and ratio of sectional area of mother plate to restraining members.2) thickness (h) of the mother plate.3) restrained length (l) of the mother plate.4) rigidity of weld metal (pwhw).Figs. 8 and 9 show some calculated examples of the effect of l and h on the extension of weld metal.