{"id":26,"date":"2022-06-13T05:19:00","date_gmt":"2022-06-13T05:19:00","guid":{"rendered":"https:\/\/mewelding.com\/?p=26"},"modified":"2022-06-14T13:03:30","modified_gmt":"2022-06-14T13:03:30","slug":"welding-distortion-and-warpage","status":"publish","type":"post","link":"https:\/\/mewelding.com\/welding-distortion-and-warpage\/","title":{"rendered":"Welding Distortion and Warpage"},"content":{"rendered":"\n
Warpage in welding and residual stresses occurring in welds are a nuisance for any welding engineer. The distortion spoils the aesthetic appeal of the product, and affects its usability for the intended purpose. Residual stresses can give rise to initiation of fracture in the metal, which can result in catastrophic failure.<\/p>\n\n\n\n
Therefore, it is important to understand why these phenomena happen, and how to control them. This article will address what is warping in welding, how it occurs, causes of distortion or warpage in welding, types of distortion, and ways to control it. <\/p>\n\n\n\n
Also, warpage and distortion in welding mean almost the same thing. Hence, in this article, these terms have been used interchangeably.<\/p>\n\n\n\n
Warpage definition in the dictionary says that it is the result of being bent or twisted out of shape, typically as a result of the effect of heat. In welding, the warpage meaning is same. <\/p>\n\n\n\n
Due to the heat involved in welding, the base metal gets distorted out of shape. This spoils not just the aesthetic appeal of the joint, but also renders the component unusable for its intended application. The extent of distortion depends on various factors which we shall see later in this article.<\/p>\n\n\n\n
First let us see what causes <\/em>warpage or distortion in welding.<\/p>\n\n\n\n When a piece of metal is heated to a high temperature, it expands equally in all directions. This is the property of metals. Likewise, when it cools \u2013 it wants to contract by the same amount in all directions. In welded joints, the weld metal that is cooling down from its\u2019 molten state is not allowed to contract in all directions \u2013 since it is integral with the base metal.<\/p>\n\n\n\n As a result, the metal distorts \u2013 because cool it must, and therefore contract it must. This is \u2013 in simple terms \u2013 the reason behind distortion, warpage, and residual stresses in welding.<\/p>\n\n\n\n The amount of expansion and contraction is directly proportional to the amount of temperature change. The change in dimensions of the metal depends on a physical property of the metal, which is denoted by its thermal coefficient (\u03b1). <\/p>\n\n\n\n Restating the case – in welding, the weld metal is not unrestrained. So it cannot shrink equally in all directions. This is because it is part of a larger piece of metal that is not heated to the same temperature as a whole. This non-uniform heating, differential cooling, and partial restraint is the main cause of thermal distortion and warpage that occur in welding. <\/p>\n\n\n\n This may be illustrated by a simple example. See the figure below. When this cube is heated, it expands \u2013 as shown \u2013 equally in all directions. Likewise, when it cools, if it is unrestrained – it contracts equally in all directions. In this cube, no distortion would occur.<\/p>\n\n\n\n