SHINHOP laser

There are many types of metal materials, including stainless steel, copper, aluminum, carbon steel, zinc, alloy materials, etc. Each has its own characteristics, related to their respective applications.Metal laser welding machineThere are also different processing techniques for welding and cutting related materials, which require experienced users to overcome these difficulties. For example, what types of lasers are needed for welding stainless steel and copper materials, how to configure the power, how to control the welding operation equipment, etc. All these require certain technical experience. Materials like aluminum and copper, which have good conductivity, have a lower absorption rate for lasers, making laser welding also face certain difficulties. To better achieve welding of various metals, we first need to understand the characteristics of different metal materials!
1. Stainless steel laser welding
The thermal conductivity of austenitic stainless steel is only 1/3 of that of carbon steel, and its absorption rate is higher than that of carbon steel. Therefore, austenitic stainless steel can achieve a slightly deeper welding penetration (5%-10% deeper) than ordinary carbon steel. Laser welding has a small heat input and high welding speed, making it very suitable for welding Ni-Cr series stainless steels. Martensitic stainless steel has poor weldability, and the welded joints are usually hard and brittle, with a tendency for cold cracking. When welding stainless steel with a carbon content greater than 0.1%, preheating and tempering can reduce the tendency for cold cracking and brittleness. Ferritic stainless steel is usually easier to weld with laser welding than with other welding methods.
2. Carbon steel laser welding
Low carbon steel and low alloy steel have good weldability, but when using laser welding, the carbon content (carbon equivalent C) should not exceed 0.25%. The formula for calculating carbon equivalent is: C=C%+Mn/6%+Ni/15%+Cr/13%+Cu/13%+Mo/4%. For materials with a carbon equivalent exceeding 0.3%, the tendency for cold cracking during welding increases. Considering a certain shrinkage of the weld in the design is beneficial to reduce the residual stress and cracking tendency in the weld and heat-affected zone. When welding materials with a carbon equivalent greater than 0.3% together with those less than 0.3%, using a biased weld seam form is beneficial to limit the transformation of martensite and reduce the occurrence of cracks. When the carbon equivalent exceeds 0.3%, reducing the quenching rate can also decrease the tendency for cracks.
Galvanized steel is difficult to laser weld because the vaporization temperature of zinc (903°C) is much lower than the melting point of steel (1535°C). During the welding process, zinc evaporates, causing serious porosity in the weld seam, making laser welding particularly difficult, especially for penetration welding. Currently, experiments have been conducted to set a 0.1mm gap between the upper and lower materials to allow zinc vapor to escape from the gap, but in actual production, operating the gap is quite challenging.
The sulfur and phosphorus content has a certain impact on welding cracks. Steel with a sulfur content higher than 0.04% or a phosphorus content higher than 0.04% is prone to cracking during laser welding.
Steel that has undergone carburizing treatment is prone to solidification cracks and shrinkage cracks due to its high carbon content on the surface, and is usually not suitable for laser welding.
3. Titanium and its alloy laser welding
Titanium alloys have a low density, high specific strength, high-temperature resistance, and corrosion resistance. Titanium and titanium alloys are very suitable for laser welding, achieving high-quality and ductile welded joints. However, titanium is sensitive to oxidation and must be welded in an inert atmosphere. Therefore, special attention must be paid to the cleanliness of the joints and gas protection issues. Titanium and titanium alloys are not sensitive to hot cracking, but delayed cracks may appear in the heat-affected zone during welding, with hydrogen being the main cause of these cracks. The main way to prevent these cracks is to reduce the hydrogen sources in the weld, and if necessary, vacuum annealing can be performed to reduce the hydrogen content in the weld. When laser welding titanium alloys, the welding speed is generally high (80-100m/h), and the penetration rate is about 1mm/kW.
4. Copper, aluminum, and their alloy laser welding
Copper has a high reflectivity to CO2 lasers but a low reflectivity to Nd:YAG lasers, so it is still possible to laser weld copper. Additionally, surface treatment can be used to improve the material's absorption of laser.
The non-weldability of brass is due to the zinc content exceeding the allowable range for laser welding. Zinc has a relatively low melting point and easily vaporizes, leading to numerous welding defects such as porosity.
Due to the high reflectivity and high thermal conductivity of aluminum alloys, laser welding of aluminum alloys requires relatively high energy density. However, many aluminum alloys contain easily volatile elements such as silicon and magnesium, which lead to many pores in the weld seam. There are no such issues when laser welding pure aluminum. Currently, high energy, large pulse width, surface oxidation removal, and sufficient argon protection measures are generally used during welding, which can yield good results. Additionally, composite welding methods are now used for welding aluminum alloys. Using 8KW laser power to weld 12.7mm thick aluminum alloy materials, the penetration rate is about 1.5mm/kW.
Through the above content, we can better understand the characteristics of various common metal laser welding, which can help avoid various shortcomings during metal laser welding and better complete metal welding!