Precautions for using electric soldering irons
In addition, welding is a local rapid heating and cooling process. The welding area cannot expand and contract Free expansion due to the constraints of the surrounding workpiece body. After cooling, welding stress and deformation will occur in the weldment. Important products need to eliminate welding stress and correct welding deformation after welding.
Modern welding technology has been able to produce welds without internal and external defects, with mechanical properties equal to or even higher than the connected body. The mutual position of the welded body in space is called a welded joint, and the strength at the joint is not only affected by the quality of the weld seam, but also related to its geometric shape, size, stress situation, and working conditions. The basic forms of joints include butt joints, overlap joints, T-joints (positive joints), and corner joints.
The cross-sectional shape of the butt joint weld seam is determined by the thickness of the welded body before welding and the groove form of the two edges. When welding thicker steel plates, various shapes of grooves are made at the edges in order to penetrate, making it easier to feed the welding rod or wire. There are two types of groove types: single-sided welding groove and double-sided welding groove. When selecting groove form, in addition to ensuring penetration, factors such as convenient welding, less Metallicity filling, small welding deformation and low groove processing cost should also be considered.
When two steel plates with different thicknesses are connected, in order to avoid severe stress concentration caused by sharp changes in the cross-section, the thicker plate edges are often gradually thinned to achieve equal thickness at the two joint edges. The static strength and fatigue strength of butt joints are higher than those of other joints. Welding of butt joints is often preferred for connections that work under alternating, impact loads, or in low-temperature and high-pressure vessels.
The pre welding preparation of lap joints is simple, easy to assemble, and has low welding deformation and residual stress. Therefore, it is often used for installing joints and unimportant structures on construction sites. Generally speaking, lap joints are not suitable for working under conditions such as alternating loads, corrosive media, high or low temperatures.
The use of T-joints and corner joints is usually due to structural needs. The working characteristics of incomplete fillet welds on T-joints are similar to those of lap joints. When the weld seam is perpendicular to the direction of external force, it becomes a positive fillet weld, and the surface shape of the weld seam will cause varying degrees of stress concentration; The stress situation of the fully welded fillet weld is similar to that of the butt joint.
Corner joints have low load-bearing capacity and are generally not used separately. They can only be improved when welded through or when there are corner welds inside and outside, and are mostly used at the corners of closed structures.
Welding products are lighter in weight than riveted parts, castings, and forgings, and can reduce self weight and save energy for transportation vehicles. The sealing performance of welding is good, suitable for manufacturing various types of containers. Developing joint processing techniques that combine welding with forging and casting can produce large, economically reasonable cast welded and forged welded structures with high economic benefits. The use of welding technology can effectively utilize materials, and welding structures can use materials with different properties in different parts, fully leveraging the strengths of various materials, achieving economic and high-quality results. Welding has become an indispensable and increasingly important processing method in modern industry.
In modern metal processing, welding developed later than casting and forging processes, but at a rapid pace. The weight of welded structures accounts for approximately 45% of steel production
