Different welding methods have different welding processes. Welder welding process is mainly based on pieces of material, grade, chemical composition, structure type weldments, welding performance requirements to determine. First, to determine the welding methods, such as arc welding, submerged arc welding, TIG welding, MIG welding gas, etc., many types of welding methods, only according to specific circumstances. Determine the welding method, and then to develop welding process parameters, welding parameters of different types, such as arc welding, including: electrode model (or brand), diameter, current, voltage, welding power source type, polarity connection, welding layers, number of channels, testing methods, and so on.
Atlas of welding Carbon Steel Welding Rod points
⑴ warm in preheated help reduce the high carbon steel heat-affected zone hardness, prevent cold cracking, which is the main carbon steel welding process measures, but also to improve the joint warm-up plastic, reducing the residual stress after welding. Typically, 35 and 45 steel preheat temperature of 150 ~ 250 ℃ or higher in carbon content due to the thickness and stiffness of large, cracks tend to large, pre-heating temperature can be increased to 250 ~ 400 ℃.
If the weldment is too large, the overall warm-up difficulty, can be partial preheating, the heating range of local warm-up on each side of the weld 150 ~ 200mm.
⑵ electrode preferred alkaline conditions permit electrode.
⑶ groove weldment try to open the form of a U-groove-type welding. If casting defects, shovel dug the groove shape should be smooth, and its aim is to reduce the base metal melt into the weld metal in proportion to reduce the carbon content of the weld, to prevent cracks.
â‘· welding parameters due to the first layer of base metal molten weld metal in the highest proportion of 30%, so the first layer of seam welding, should maximize the use of small current, slow welding speed, to reduce the base metal melting deep.
⑸ weld heat treatment after welding, welded parts immediately the best stress relief heat treatment, especially for the large thickness of the weldments, structural parts and high rigidity under severe conditions (dynamic load or impact load) weldment work and even more so. Eliminate stress tempering temperature 600 ~ 650 ℃.
If post-weld stress relief heat treatment can not be carried out immediately after the heat treatment.
Basic knowledge of welding technology welding by heat, pressure, or both, so that the two atoms combine to produce the workpiece processing and connection mode. Welding is widely used, both for the metal, can also be used for non-metallic.
Welding methods are more than 40, divided into welding, pressure welding and brazing three categories.
Welding in the welding process will be heated to melt the workpiece interface, the state, without pressure to complete the welding method. When welding, heat welding the two workpieces to be rapid heating and melting at the interface to form a pool. Move forward with the heat bath, cooling to form a continuous weld and connect the two parts into one.
In the welding process, if the atmosphere in direct contact with the hot bath, atmospheric oxygen will be oxidized metal and various alloying elements. Atmospheric nitrogen, water vapor from entering the pool, but also in the subsequent cooling process in the formation of pores in the weld, slag, cracks and other defects, deterioration of weld quality and performance.
In order to improve the welding quality, it developed a variety of methods of protection. For example, gas-shielded arc welding is to use argon, carbon dioxide and other gases isolated from the atmosphere to protect the welding arc and weld pool rate; Another example is the steel welding, welding drug in the skin by adding the oxygen affinity of large ilmenite powder oxygen, can protect the electrode in the beneficial elements manganese, silicon and into the pool from oxidation, after cooling to obtain high-quality welds.
Bonding in the pressure conditions, so that the two parts between atoms in the solid state to achieve integration, also known as solid-state welding. The bonding process is commonly used resistance welding, when the current through the connector when the two parts, where the temperature rise due to a large resistance when heated to a plastic state, under pressure in the axial connection to become one.
A variety of bonding methods in common is pressure in the welding process without additional filler material. Most bonding methods such as diffusion bonding, high frequency welding, cold welding and so there is no melting, and therefore not as useful as alloying elements welded burning, invasive and harmful elements in the weld problems in order to simplify the welding process, improved welding safety and health conditions. And because the heating temperature is lower than welding, heating time is short, so a small heat-affected zone. Difficult to melt the welding of many materials, can often be welded into a bonding strength with the same high quality base metal joints.
Brazing is the use of lower melting point than the piece of metal for brazing, and brazing the workpiece heated to above the solder melting point, lower than the melting temperature of the workpiece, the workpiece using liquid solder wetting, filling the gap and the interface with the workpiece to achieve inter-atomic diffusion, in order to achieve welding methods.
Solder connections are formed when the two connected body known as the weld seams. Both sides of the weld will be welded in the welding heat effect, and the occurrence and properties change, the region known as the heat affected zone. Welding due to workpiece material welding material, welding current is different, after welding the weld and heat affected zone may overheat, embrittlement, hardening or softening, but also the weldment performance, deterioration of weldability. This need to adjust the welding conditions, weld preheating before welding pieces of the interface, welding heat and weld heat treatment can improve the welding quality of weldments.
In addition, welding is a rapid local heating and cooling process, the welding area of ​​the body parts due to four weeks and not binding free expansion and contraction, after cooling it in the weldment in the welding stress and deformation. Important products are required after welding to eliminate welding stress, correction of welding distortion.
Modern Welding Technology has been able to weld the inside and outside the defect-free, mechanical properties equal to or higher than the body of the weld connection. Welded body position in space of each other as welded joints, in addition to the strength of joints affected by the weld quality, but also its geometry, size, force and working conditions and so on. The basic form of butt joints, lap, T-connection (positive transfer), and fillet and so on.
Butt joint weld cross-sectional shape, determined to be welded prior to welding the thickness of the body and the two sides of the groove in the form received. Welding thick steel plates, in order to penetration in the access edges out of shape groove in order to more easily into the welding rod or wire. Groove in the form of single-sided welding of both sides of the welding groove and the groove. Choose the form of groove, in addition to ensuring penetration welding should be considered outside the convenience, less filler metal, welding deformation and beveling low cost factors.
Two different thickness steel docking, in order to avoid drastic changes in cross-section cause severe stress concentration, often to the edge of a thick plate gradually thinning, connected to two edges of equal thickness. Butt joint static strength and fatigue strength higher than other joints. In alternating, low impact loading or high-pressure containers in the work of the joint, often give priority to the use of butt joint welding.
Lap joint welding preparation work is simple, convenient assembly, welding deformation and residual stress small, so unimportant in the site installation of the structure of joints and is often used. In general, the lap joint is not suitable for alternating loads, corrosive medium, high or low temperature conditions.
The use of T-joints and corner joints is usually due to structural needs. T-connector on the lack of penetration of the working characteristics of fillet fillet with similar lap joint. When the weld and when they become a force perpendicular to the front fillet, then the surface shape of the weld can cause varying degrees of stress concentration; penetration of the fillet and butt joint force similar to the situation.
Angle connector carrying capacity is low, generally not used alone, only in the penetration, or both inside and outside corner welds when the improvements are used for closed-shaped structure around the corner.
Welding Electrodes than riveting, castings and forgings, light weight, the means of transport is to reduce weight and save energy. Welded seal, suitable for manufacturing various types of containers. Development of joint processing, so that welding and forging, casting combination can be made large, the economy and reasonable structure and forge welding welding cast structure, economic efficiency is very high. Using the effective use of welding materials, welding structure can be different in different parts of the performance of the material, give full play to the strengths of various materials to achieve the economic, high-quality. Welding has become an indispensable modern industry, but increasingly important processing method.
In the modern metal processing, welding than casting, forging technology development later, but the fast pace of development. Welded structure weight of about 45% of steel production, aluminum and aluminum alloy welded structures the proportion is increasing.
The future of the welding process, on the one hand to develop new welding methods, welding equipment and welding materials, welding quality and to further improve the safety and reliability, such as improvement of existing electric arc, plasma arc, electron beam and laser welding energy; the use of electronic technology and control technology, to improve the performance of electric arc process, the development of reliable methods to track the arc light.
On the other hand to improve the welding mechanization and automation, such as welding to achieve process control, digital control; the development process from the preparation, quality control of all welded to a special welding process automation; in automatic welding production line, to promote and expand CNC welding robot and welding robot, welding can increase the level of production, improve health and safety conditions for welding.