What You Need to Know About Magnesium Alloy Welding

Due to the low density of magnesium alloy, low melting point, high thermal conductivity and conductivity, high thermal expansion coefficient, vigorous chemical activity, easy oxidation, and the high melting point of oxides, a series of difficulties such as coarse crystal, oxidation, and evaporation, thermal stress, weld collapse, porosity, and thermal crack will occur in the welding process of magnesium alloy welding. The mechanical properties of the welded joint are not only related to the welding process parameters but also to the composition of the welding wire.

What Problems Need To Be Solved In Magnesium Alloy Welding?

Magnesium alloy has a low density and melting point, high thermal conductivity, conductivity, and thermal expansion coefficient, vigorous chemical activity, easy oxidation, and oxide melting, Due to the high point characteristics, the welding of magnesium alloy must solve the following series of problems:

• Coarse-grained magnesium has a low melting point and high thermal conductivity, so it is necessary to use a high-power welding heat source when welding. The welding seam and the near seam area are prone to overheating, grain growth, crystallization segregation, and other phenomena, which reduce the joint performance.

• Burn-out and collapse of thin parts During welding, because the melting point of magnesium alloy is low and the melting point of magnesium oxide is high, they are not easy to fuse, so it is difficult to observe the melting process of the weld during the welding operation. As the temperature increases, the color of the molten pool does not change significantly, which is easy to produce the phenomenon of burning through and collapsing.

• Oxidation and evaporation of magnesium are very strong oxidation, easy to combine with oxygen, and easy to form MgO in the welding process, The high melt point of MgO (2 500 ℃) and high density of MGO (3. 2 g Π cm-3) tend to form small sheet solid slag inclusion in welds, which not only seriously hinder weld formation but also reduce weld performance. At high welding temperatures, magnesium is also easy to combine with nitrogen in the air to produce magnesium nitride. Magnesium nitride slag inclusion will also lead to the plastic drop of weld metal so that the joint property deteriorates. The boiling point of magnesium is not high (1100 ℃), and it is easy to evaporate under high arc temperatures.

• It is easy to produce hydrogen pores when stomatal welding magnesium. The hydrogen solubility in magnesium also decreases sharply with the temperature decrease.

• Magnesium and its alloys are easy to oxidize and burn during welding in air environment, so inert gas or flux should be used for protection during welding.

Main Methods Of Magnesium Alloy Welding 

Argon tungsten arc welding is the most common welding method for magnesium alloys. It uses arc heat to melt base metal and filler metal under the protection of inert gas. Argon tungsten arc welding is the most common welding method for magnesium alloy welding. It uses arc heat to melt base metal and filler metal under the protection of inert gas. The reverse polarity connection method should be used in the welding of the DC power supply, to destroy and remove the oxide film on the surface of the base metal by cathode atomization and reduce or avoid the oxide inclusion in the weld. The reverse polarity connection method should be used in the welding of the DC power supply, to destroy and remove the oxide film on the surface of the base metal by cathode atomization and reduce or avoid the oxide inclusion in the weld.

Safety Code For Argon Arc Of Magnesium Alloy Welding

The following are some points that must be paid attention to during the magnesium alloy welding:

-The manual argon tungsten arc welding machine should be placed in a dry and ventilated place, in strict accordance with the operation instructions. The welder should be inspected thoroughly before use. Make sure there are no hidden dangers, then switch on the power. No load operation can be normal before welding. Ensure that the welding machine is properly connected and securely grounded to ensure safety. The switch on the power supply board controls the switch on and off of the welder power supply. It is strictly prohibited to switch the load to avoid burning the shaped contact.

-The working condition of the cooling water system of the argon arc welding gun should be checked frequently. If blockage or leakage is found, it should be solved immediately to prevent the burning out of the welding gun and affecting the welding quality.

-When the welder leaves the workplace or the welder is not in use, the power supply must be cut off. If the welding machine fails, it should be repaired by professionals and safety measures such as anti-electric shock should be taken during maintenance. The welder should be dusted and cleaned at least once a year.

-The high-frequency electromagnetic field produced by the high-frequency oscillator of the argon tungsten arc welding machine will make people feel dizzy and fatigued. Therefore, when welding, minimize the action time of the high-frequency electromagnetic field, and cut off the high-frequency power supply immediately after igniting the arc. The welding gun and the welding cable should be shielded by soft metal braided wire (one end of the hose is connected to the welding gun, the other end is grounded, and the outside is not insulated). If possible, crystal pulse arc starting should be used to replace high-frequency arc starting.