There are many types of metal materials, including stainless steel, copper, aluminum, carbon steel, zinc, alloy materials, etc. Each has different characteristics, and its related metal laser welding machines also have different processes for welding and cutting related materials. Process and these require experienced users to overcome these difficulties, such as: what types of lasers are needed to weld stainless steel and copper materials, how to configure its power, how to control the welding operating equipment, etc. These require a certain amount of technical experience. , and materials with relatively good conductivity, such as aluminum and copper, have low laser absorption rates, and laser welding is also in certain difficulties. How to better achieve the welding of various metals, we must first divide the boards into some Characteristics of metal-like materials!

1. Stainless steel laser welding

The thermal conductivity of austenitic stainless steel is only 1/3 of carbon steel, and its absorption rate is higher than that of carbon steel. Therefore, austenitic stainless steel can obtain a slightly deeper welding penetration (5%-10% deeper) than ordinary carbon steel. Laser welding has small heat input and high welding speed, and is very suitable for welding Ni-Cr series stainless steel. Martensitic stainless steel has poor weld ability, and the welded joints are usually hard and brittle, with a tendency to cold crack. When welding stainless steel with a carbon content greater than 0.1%, preheating and tempering can reduce the tendency of cold cracking and embrittlement. Ferritic stainless steels are generally easier to weld with laser welding than other welding methods.

2. Carbon steel laser welding

Both low carbon steel and low alloy steel have good weld ability, but when laser welding is used, the carbon content (carbon equivalent C) of the material should not be higher than 0.25%. Carbon equivalent calculation formula: C=C%+Mn/6%+Ni/15%+Cr/13%+Cu/13%+Mo/4% For materials with a carbon equivalent exceeding 0.3%, the tendency of welding cold cracking will increase, a certain amount of shrinkage of the weld is taken into account in the design, which is beneficial to reducing the residual stress and crack tendency of the weld and heat-affected zone. When materials with a carbon equivalent greater than 0.3% and materials with a carbon equivalent less than 0.3% are welded together, the use of offset welds will help limit the transformation of marten site and reduce the occurrence of cracks. When the carbon equivalent of the material exceeds 0.3%, reducing the quenching speed can also reduce the crack tendency.

Galvanized steel, because the vaporization temperature of zinc (903°C) is much lower than the melting point of steel (1535°C), the zinc evaporates during the welding process, causing serious pores in the weld, so it is difficult to use laser welding, especially penetration In welding, there are now experiments to set a 0.1mm gap between the upper and lower materials to release the zinc vapor from the gap. However, in actual production, the operation of the gap is more difficult.

Sulfur and phosphorus content have a certain impact on welding cracks. Steel with sulfur content higher than 0.04% or phosphorus content higher than 0.04% is prone to cracks during laser welding.

Due to the high carbon content on the surface of steel that has been carburized, it is easy to produce solidification cracks and cracks in the carburized layer, and is generally not suitable for laser welding.

3. Laser welding of titanium and its alloys

Titanium alloy has low density, high specific strength, high temperature resistance, corrosion resistance and other excellent properties. Titanium and titanium alloys are very suitable for laser welding, and high-quality, plastic welded joints can be obtained. But titanium is sensitive to oxidation and must be welded in an inert atmosphere. Therefore, special attention should be paid to the cleaning and gas protection of the joints. Titanium and titanium alloys are not sensitive to hot cracks, but delayed cracks will appear in the heat-affected zone during welding. Hydrogen is the main cause of such cracks. The main way to prevent this kind of crack is to reduce the hydrogen source of the welded joint. If necessary, vacuum annealing can be performed to reduce the hydrogen content of the welded joint. When laser welding titanium alloys, the welding speed is generally high (80-100m/h), and the welding penetration rate is about 1mm/kW.

4. Laser welding of copper, aluminum and their alloys

The reflectivity of red copper to CO2 laser is very high, but the reflectivity to Nd:YAG laser is very low, so it is still possible to weld red copper with laser. In addition, surface treatment can be used to improve the material's absorption of laser light.

Brass is unweldable because it contains more zinc than is allowed for laser welding. Zinc has a relatively low melting point and vaporizes easily, causing a large number of welding defects such as pores.

Due to the high reflection and high thermal conductivity of aluminum alloy. Laser welding of aluminum alloys requires relatively high energy density. However, many aluminum alloys contain volatile elements, such as silicon, magnesium, etc., and there are many pores in the welds. The above problems do not exist when laser welding pure aluminum. At this stage, high energy, large pulse width, surface removal of oxidation, and sufficient argon gas protection are generally used for welding, and the effect is good. In addition, composite welding is now used to weld aluminum alloys. Using 8KW laser power to weld aluminum alloy materials with a thickness of 12.7mm, the welding penetration rate is approximately 1.5mm/kW.

Through the above content, we can better understand the characteristics of laser welding of various common metals, better avoid various shortcomings during metal laser welding, and better complete metal welding!