Cladding welding is a process in which a material with specific properties (abrasion resistance, corrosion resistance, or unique properties) is deposited on the surface of a welded part through welding, or a process to repair old metal parts that do not conform to the shape. cladding is used in a wide range of applications, such as manganese and silicon cladding welding on automotive rotating axes to increase abrasion resistance, and shovel tooth surface cladding welding on excavators to increase abrasion resistance to improve service life. Commonly used engineering parts, comfortable to wear out, so the use of proper overlay welding, can improve the service life of components, save manufacturing and maintenance costs, but also shorten the time to repair and replace parts, reduce downtime, stop production losses, thereby improving productivity and reducing production costs. As a result, overlay welding is an important manufacturing and repair method in the mechanical industry and is widely used in a wide range of manufacturing and repair work
The key to the metal cladding welding process is to get the performance of the product that is needed.
Cladding welding technology has a wide range of applications in ships, vehicles, aviation, boilers, motors, smelting equipment, petrochemical machinery, mining machinery, lifting machinery, construction and defense industries.
Cladding welding to repair old metal parts is the key to reducing the cost of the business and improving the service life of the product. Incomplete statistics show that 72.2% of the total amount of cladding welding alloys is mainly used to repair old parts. For example, the cost of repairing a plain old roll is about 25 percent of the cost of a new turn, which doubles the service life after repair. The use of overlay welding in the manufacture of mechanical parts not only enables the working potential of the metal material and the overall technical performance of the parts to be realized but also saves a significant amount of precious metals. For example, hot forging dies using 8CrMnMo or 6CrNiMo alloy steel monolithic die manufacturing, and 45Mn2 cast steel as the hot forging die base of manufacturing the same performance, saving costs and improving production efficiency.
Several standard methods of overlay welding
Welding cladding is a vital welding method and process measure, as well as a means of surface heat treatment. The purposes of coating are fusion welding, brazing, pressure welding, spray welding, and other process methods. At present, the main ones used are gas protection arc welding overlay, gas welding overlay, and welding electrode arc welding overlay.
Gas protected arc overlay
There are two types of gas-protected arc overlay, tungsten-argon arc overlay, and melting-argon arc overlay.
1）TIG equipment, including welding machine, welding torch, air supply system, cooling system, control system, etc. The automatic adjustment of the melting pole automatic argon arc welding machine works the same as submerged arc welding. When the fine wire is selected, an equal-speed wire feeding system is used, with a slow-drop external characteristics of the welding power supply; when the coarse wire is selected, a variable-speed wire feeding system is used, with steep-drop external features of the welding power supply. This method is usually used when welding flawlessly deposited metal on new structural parts and is not generally used to repair parts. Cold welding wire helps to reduce thermal and cold cracks in the weld. This method is usually used when welding flawlessly deposited metal on new structural components and is not generally used to repair parts.
(2) Melting pole gas protection arc overlay welding, generally divided into melting pole active gas protection welding, melting pole inert gas protection welding, and carbon dioxide gas protection welding. Melting pole gas protection welding equipment, using a DC reverse power supply, using N2, CO2, Ar, or a mixture of CO2 and Ar as the gas protection gas, using solid or flux-cored welding wire. For abrasion-resistant overlay welding, the slow deposition rate requires a reduction in the pool temperature and the use of multiple layers and multiple passes to meet the weld requirements.
Welding of arcs on rods.
The overlay welding of the electric arc of welding rod is flexible and adaptable, with a wide range of applications, easy to disperse welding stress and control welding deformation, simple equipment, low cost, not limited by the location of the overlay welding and the size and shape of the workpiece, can be carried out in all positions of overlay welding, complex cross-section and irregular size of the parts are particularly suitable. He also has the disadvantage of low productivity, high dilution, and difficulty in obtaining a thin and uniform cladding welding layer.
For arc welding of welding rods, different rods must be selected according to different requirements. The rods used for patch cladding welding are based on the principle of equal or similar composition. Carbon steel wire is used for the carbon steel base material and alloy wire for the alloy base material. The quality of the weld is guaranteed by first removing the rust and oil from the surface before cladding welding. When cladding welding the second weld, it is necessary to melt 1/3 to 1/2 of the width of the first weld, to make a tight connection between each weld, and to prevent defects such as slagging and unwell through. Shaft overlays can be made with longitudinal symmetric overlays and transverse spiral overlays.
Gas overlay welding
We are using gas welding equipment, including pressure reducer, torch, oxygen bottle, acetylene bottle, LPG bottle, hose, etc. First, remove oil, rust, and other surface contaminants from the weld surface before cladding welding the alloy layer. For cladding welding punches, scissors, dies, etc., a groove needs to be made out of the edges before multiple layers of cladding welding can be carried out.
With the continuous development of computer technology, to improve and stabilize the quality of overlay welding, the development of automation, intelligence, modularity is getting faster and faster, the expert system of overlay welding, that is, to achieve a high degree of controllability and self-actualization, to find that the weld does not meet the requirements, that is, the machine and equipment testing whether it can be overlay welding, and then judge how to better go to overlay welding. The practice and theory of cladding welding are becoming more productive and more consistent in quality.