Semi-trailer welding process introduction and local welding process

he welding defect of the semi-trailer frame is one of the most serious defects in the welding structure of the whole vehicle, which will directly affect the product quality of the whole semi-trailer and even lead to sudden traffic accidents. The welding defects of semi-trailers are closely related to the metallurgical factors in the welding process and the mechanical factors in the use process, so the shape of the defects is directly related to the manufacturing.

Shape defects, namely the physical structure defects in component welding, include: cracks, holes, solid inclusions, non-fusion and non-penetration and a series of factors, among which cracks are the main defects in semi-trailer welding.

There are many reasons that lead to the crack, which are mainly reflected in the mechanical factors and metallurgical factors in the welding process. The main mechanical factor generated by cracks is restricted stress. In the welding process of all parts of semi-trailer, because the weld section is much smaller than that of the component, and the shapes and sizes of all parts are different, and the weld seam is complex, the restricted stress and deformation will be concentrated in the section. The greater the stress and strain in the welding zone, the greater the risk of welding crack.

The semi-trailer frame crack is the most dangerous defect of the whole vehicle body, and most of the damage accidents are caused by welding crack, which reduces the working section of the welded joint, thus reducing the bearing capacity of the welded structure, forming a serious stress concentration, and reducing the fatigue strength of the structure. Semi-trailer working environment is complex, surface cracks can hide dirt and dirt, which is easy to cause or accelerate the corrosion of the structure, and make parts fracture.

Semi-trailer production requires comprehensive welding quality control, which requires products from design, manufacturing, to the after sales service and so on all links to implement welding quality assurance and quality control, semi-trailer welding quality control including perfecting enterprise technology and equipment, improve the quality of operation personnel and strict management of welding technology, the goal is to have no defects of semi-trailer welding structure, It is very important to meet the requirements of semi-trailer welding products in the actual use process, especially the welding design and construction.

As the semi-trailer welding structure design, must consider the analysis of its specific structure form, technology and manufacturing conditions, in addition to the material welding performance and distribution of welding joints should also be considered. Its design requirements are as follows:

1, reasonable choice of weld size and form, under the condition of ensuring the bearing capacity of the structure, the design should be as far as possible to use a smaller weld size, because the weld size is large, not only the amount of welding, welding stress and deformation of the weld is also large;

2. Reasonably arrange the position of welds to avoid excessive concentration and crossover of welds and minimize unnecessary welds;

3. Fully consider the feasibility of ensuring the implementation of the welding process, the feasibility of various tests, whether the welding deformation is easy to control, whether the welding operation is convenient and safe, and whether the welding quality is guaranteed.

The material selection of welded structural parts should be based on three conditions: its service performance, welding process performance and economy. The specific material selection principles are as follows:

1. Under the premise of meeting the technical requirements, materials with lower strength level should be selected as far as possible;

2, according to the structure of the use of conditions, as far as possible to choose the automobile professional plate;

3. Under the condition that the welding process cannot be changed, try to choose materials with good welding performance.

Technology, production equipment, material consumption affect the choice of welding method, in the production of semi-trailer, choosing welding method should be on the premise of guarantee the quality of semi product and to meet the need of production circumstances, should try to choose low level of technology, production equipment is simple, low cost and less material consumption of welding method, in order to improve the economic benefit. Semi-trailer structure is more complex, welding seam is long and large, I steel should adopt submerged arc automatic welding, other beams and other short welding welding manual arc welding, generally small pieces of gas shielded welding.

After welding, shape factors, residual stress and deformation lead to fatigue fracture of related parts of semi-trailer, so post-welding treatment is required. After welding, the welding slag, welding spatter and other dirt on the surface of the weldment should be carefully cleaned, and local repair of the weldment should be carried out if necessary. Through mechanical processing, in order to change and improve the distribution of residual stress to reduce stress concentration caused by welding, weld in red heat, first with a small hammer knock weld, to offset the contraction of the weld metal and heat affected zone metal power, so as to reduce or eliminate internal stress, reduce or rectify deformation, when the hammer as far as possible to the weld transverse hammer, Spread the weld metal as horizontally as possible. And the blows should be dense, light and even.