Analysis of defects in the welding of metal materials and countermeasures to discuss

Metals have a very distinctive characteristic of weldability. The so-called metal welding is a process that uses heat, high temperature or high pressure to produce molecules or atoms and unite two metal objects that are not together. When it comes to the method of metal welding is also characterized by diversity, using each method has its own advantages and disadvantages and different impacts, which is attracting more and more attention.
1 Defects in the welding of metal materials
1.1 Welding cracks
In the welding of metals, there is a relatively common situation is cracks, and cracks are mainly the crystallization state of the different changes between each other and produced. Cracks do not appear for a long time, sometimes immediately apparent or stop for a moment that is visible, and its location is often in the welding base metal and the junction of the fusion line, cold and hot is the main classification of cracks.
Hot cracking is basically occurring in the position of segregation. The reason for its formation is mainly left in the molten pool in the melting point of low freezing point high ice clean shaping low strength of poor impurity crystals, due to the many defects of these impurity crystals and lead to be bound in the time it is easy to be pulled apart, this is the formation of hot cracks. In contrast to the cold crack, first of all, the time on the hot cracks later, during or after welding, and when the low temperature comes down there will be cracks, and even some of the cold crack time is more lagging, in a few days before appearing, such a situation is very easy to affect the normal use of structural safety.
1.2 The phenomenon of unwelded, unfused
When the metal is not all welded to the deepest part of the joint is the root of the time, resulting in wood metal can not be completely melted off, thus causing the so-called unsoldered, it is mainly for the object is wood. This situation is also known as the disadvantages of the unwelded through very much, frequently make the effective area of the weld will gradually become smaller, and then also make the joint strength continues to weaken, and finally lead to the fatigue strength of the weld continues to decline. Another situation that is similar to the unwelded joint is the unfused, as the name suggests, is that the metal is not perfectly fused to the joint, which brings the defect of reducing the load-bearing area, making the gathering of stress is very difficult.
1.3 Slagging
In the welding process there will be some residual slag left in the weld, we can simply call it slag. There are many reasons for the formation of slag, for example, when the current strength is not enough or large or small, welding speed or fast or slow, the choice of welding rod is not reasonable, the bevel angle is not appropriate or the electrode off-center and other reasons will make the edge of the weld left slag.
1.4 Other defects
(1) The organization of the weld may not meet the requirements, or the chemical composition may not meet the standards, or the chemical composition of the weld metal may be unstable due to elemental burns during welding. All of this will continue to weaken the mechanical ability of the weld, and thus more seriously make the corrosion resistance of the joint also suffered;
(2) Bite edge also occurs in the welding process, mainly due to high current or inappropriate electrode angle and then seal the weld edge of the pit is not good in the first time to fill the metal and caused. This kind of phenomenon may make the use of metal material area greatly reduced, along with this also makes the structure of the pressure resistance index is difficult to meet the requirements, more serious is due to the reaction force greatly gathered and lead to cracks.

2 Preventive measures in welding of metallic materials
All kinds of defects are very easy to appear in the welding process of metal materials, so we have to worry about the quality of metal materials, so it can be seen, when we face these defects, timely and appropriate preventive measures are very necessary.
2.1 Measures to prevent cracks
Measures to prevent cracking mainly have the following points: First, we should strictly abide by the rules related to it, carefully consider the welding procedure they want to choose, strictly adhere to the standard of welding rod, carefully identify its acidity and alkalinity, in order to achieve better results can be placed in a stable insulation room, when we need to use it out; Second, we should carefully clean up the interface, to ensure that there is no moisture, oil or other leftover traces; Third, we should carefully clean up the interface, to ensure that no moisture, oil or other leftover traces. Is other leftover traces; Third, when we are in the welding period, pay attention to the choice of smaller current, and then choose multiple welding passes, a variety of levels to be strictly enforced, so that it is very good to make the chances of cracks greatly reduced, but also to improve the shape of the weld, so that the stress of welding is also reduced.
2.2 Measures to prevent non-welding penetration and non-fusion
When the welding has not yet begun, we have to do some preparatory work, such as reasonable selection of the bevel angle and size, the correct selection of the diameter of the welding rod. Secondly, the current size and welding speed should also be carefully selected. In the process of welding, we should also pay attention to the proper swinging of the upper chain, concentrate on observing the changes on both sides. It is important to ensure that all processes are carried out in accordance with the correct technique and construction specifications.
2.3 Measures against slagging
The first thing is to pay special attention to the choice of welding electrodes, the requirements of which differ between acid and alkaline. The second is to have the right bevel angle and to be able to control the welding speed, which should not be too fast.
2.4 Enhancement of welders' skills
Welding on the welder is also a certain technical requirements, training in basic skills is very necessary, training content is mainly how to choose the materials to be used and the specific construction environment, and in the welding process should maintain what posture and control are also need to learn more, so that the welding work in the absence of any external influences under the smooth running, so that the disadvantages can be further minimized. The disadvantages can be further minimized. At the same time, for the welder's self-control should also be further enhanced, to make each welder can be qualified, the quality and skills of its strict control.
2.5 Other comprehensive measures
In addition, we also need to pay attention to other comprehensive measures, for example, for the construction of the environment should be more requirements, if the temperature is relatively low, we must use the material for a certain degree of heating, in the construction area to establish a certain degree of cleanliness, but to ensure that during the work of the ventilation, air humidity as far as possible to be less than ninety percent, and to ensure that argon concentration should be greater than ninety-nine percent and so on. A series of measures.
The rapid development of the economy, industry still occupies its own impregnable important position, which undoubtedly also brought about the extensive use of metal, more and more on the daily production of life has an important impact. The popularity of metal also triggered the accelerated development of welding technology, however, through this article we can clearly recognize that there are a variety of disadvantages of metal welding, it will be directly unfavorable to the welded structure, and even more serious injury to people's personal safety. Therefore, no matter what for its starting point, we have to maximize to overcome all the shortcomings, the development and implementation of a variety of measures, the welders put forward higher requirements, and continue to develop better welding methods, so that the quality of welding gradually climbed.