在焊（hàn）管生產過程中（zhōng），隻要進行焊接，焊管表麵就會產（chǎn）生應力和變形，隻是程度（dù）不同罷了。焊管（guǎn）在焊接過程中產生的焊接應力和各種變形，往往使焊接產品質量（liàng）下降，甚（shèn）至造（zào）成裂紋。焊（hàn）接變形造成焊件尺寸，形（xíng）狀的變（biàn）化，這種變（biàn）化超過一定的數（shù）值後，可能無法與其他焊管連接或沒有足夠的加工餘量無法進行（háng）切削加工。下麵我們說下應力（lì）和變形。
In the production process of welded pipe, as long as welding is carried out, stress and deformation will occur on the surface of welded pipe, but to varying degrees. Welding stress and various deformations of welded pipes in the welding process often cause the quality of welded products to decline, and even cause cracks. Welding deformation results in the change of weld size and shape. If the change exceeds a certain value, it may not be able to connect with other welded pipes or not have enough machining allowance for cutting. Now let's talk about stress and deformation. 首先是焊管的表麵應力，當材料在外力作用下不（bú）能產生位（wèi）移時，它的幾何形狀和尺（chǐ）寸將（jiāng）發生（shēng）變化，這種（zhǒng）形變就（jiù）稱為應（yīng）變。材料發生形變時其內部（bù）產生了（le）大小相等但方向相反的反作用力抵（dǐ）抗外力，把分布（bù）內（nèi）力在一點的（de）集度稱為應力，應力與微麵（miàn）積的乘積即為內（nèi）力，或物體由於外因(受力、溫度變化等)而變形時，在物體內各部分之間產生相（xiàng）互作用（yòng）的內力，以抵（dǐ）抗這種外因的作用，並力圖使物體從變形後的位置回複到變形前的（de）位置。
First is the surface stress of welded pipe. When the material can not produce displacement under external force, its geometry and size will change. This deformation is called strain. When a material is deformed, it produces internal reaction force of equal size but opposite direction to resist external force. The concentration degree of distributed internal force at a point is called stress. The product of stress and micro-area is internal force, or when the object is deformed by external factors (force, temperature change, etc.), the internal force interacts among various parts of the object to resist the effect of external factors. Make the object return from the position after deformation to the position before deformation.
從（cóng）力學角度來講，變形（xíng）是指結構(或其一部分)形狀的改變（biàn）。任何結構都是由可變（biàn）形固（gù）體材料組成，在外力作用下將會產生變形和位移。
From a mechanical point of view, deformation refers to the change of the shape of a structure (or part of it). Any structure is composed of deformable solid materials, which will produce deformation and displacement under the action of external forces.
在焊管生產過程中，即使能矯正，如機械或火焰矯正過來，這也不僅費時費力，而且又增加了焊管的（de）附加應力，對構建使用不利（lì）、由此（cǐ），我們必須對焊（hàn）接應力和變（biàn）形的產生原因、大小程度以及如何減小和避免焊接應力和變形進行了解。
In the production process of welded pipe, even if it can be corrected, such as mechanical or flame correction, it will not only take time and effort, but also increase the additional stress of welded pipe, which is unfavorable for construction and use. Therefore, we must understand the causes, magnitude and extent of welding stress and deformation, and how to reduce and avoid welding stress and deformation.
