What is MIG welding ?

MIG welding uses metal wire instead of tungsten electrode in welding torch. Others are the same as TIG welding. Therefore, the welding wire is melted by the arc and sent to the welding area. The electric drive roller sends the welding wire from the spool to the welding torch according to the welding needs.

The heat source is also DC arc, but the polarity is just the opposite to that used in TIG welding. The shielding gas used is also different. 1% oxygen should be added to argon to improve the stability of arc.

There are also some differences in basic processes, such as jet transfer, pulsating jet, spherical transfer and short-circuit transfer.

Pulse MIG welding editing voice

Pulse MIG welding is a MIG welding method that uses pulse current to replace the usual pulsating DC.

Due to the use of pulse current, the arc of pulse MIG welding is pulse type. Compared with normal continuous current (pulsating DC) welding:

1. Wider adjustment range of welding parameters;

If the average current is less than the lower critical current I0 of the injection transition, the injection transition can still be obtained as long as the pulse peak current is greater than I0.

2. Arc energy can be controlled conveniently and accurately;

Not only the size of pulse or base current is adjustable, but also its duration can be adjusted in units of 10-2 s.

3. Excellent backing welding ability of thin plate and all position.

The molten pool melts only in the pulse current time, and cooling crystallization can be obtained in the base current time. Compared with continuous current welding, the average current (heat input to the weld) is smaller on the premise of the same penetration.

MIG welding principle editing voice

Different from TIG welding, MIG (MAG) welding uses fusible welding wire as electrode and the arc burning between the continuously fed welding wire and the weldment as heat source to melt the welding wire and base metal. During the welding process, the shielding gas argon is continuously transported to the welding area through the welding gun nozzle to protect the arc, molten pool and its nearby base metal from the harmful effect of the surrounding air. The continuous melting of welding wire shall be transferred to the welding pool in the form of droplet, and the weld metal shall be formed after fusion and condensation with the molten base metal.

MIG welding feature editing voice

⒈ like TIG welding, it can weld almost all metals, especially suitable for welding aluminum and aluminum alloy, copper and copper alloy, stainless steel and other materials. There is almost no oxidation and burning loss in the welding process, only a small amount of evaporation loss, and the metallurgical process is relatively simple.

2. High labor productivity

3. MIG welding can be DC reverse connection. Welding aluminum, magnesium and other metals has a good cathode atomization effect, which can effectively remove the oxide film and improve the welding quality of the joint.

4. Tungsten electrode is not used, and the cost is lower than that of TIG welding; It is possible to replace TIG welding.

5. When MIG welding aluminum and aluminum alloy, sub jet droplet transfer can be used to improve the quality of welded joints.

⒍ as argon is an inert gas and does not react with any substance, it is sensitive to oil stain and rust on the surface of welding wire and base metal, which is easy to produce pores. The welding wire and workpiece must be carefully cleaned before welding.

3. Droplet transfer in MIG welding

Droplet transfer refers to the whole process in which the molten metal at the end of the welding wire or electrode forms droplets under the action of arc heat, which is separated from the end of the welding wire and transferred to the welding pool under the action of various forces. It is directly related to the stability of welding process, weld formation, splash size and so on.

3.1 force affecting droplet transfer

The droplet formed by molten metal at the end of welding wire is affected by various forces, and the effects of various forces on droplet transition are different.

⒈ gravity: at the flat welding position, the gravity direction is the same as the direction of droplet transition to promote the transition; Overhead welding position, hindering droplet transfer

2. Surface tension: maintain the main force of the droplet on the end of the welding wire during welding. The thinner the welding wire, the easier the droplet transition.

3. Electromagnetic force: the force generated by the magnetic field of the conductor itself is called electromagnetic force, and its axial component always expands from small section to large section. In MIG welding, when the current passes through the welding wire droplet electrode spot, the cross section of the conductor changes and the direction of the electromagnetic force also changes. At the same time, the high current density at the spot will make the metal evaporate strongly and produce a great reaction force on the metal surface of the droplet. The effect of electromagnetic force on droplet transfer depends on the arc shape.

4. Plasma flow force: under the contraction of electromagnetic force, the hydrostatic pressure generated by arc plasma in the direction of arc axis is inversely proportional to the cross-sectional area of arc column, that is, it gradually decreases from the end of welding wire to the surface of molten pool, which is a favorable factor to promote droplet transition.

5. Spot pressure

3.2 droplet transfer characteristics of MIG welding

During MIG welding and MAG welding, droplet transfer mainly adopts short-circuit transfer and jet transfer. Short circuit welding is used for thin plate high-speed welding and all position welding, and jet transfer is used for horizontal butt welding and fillet welding of medium and thick plates.

During MIG welding, DC reverse connection is basically adopted. Because the reverse connection can realize the fine jet transition, and the positive ion impacts the droplet at the positive connection, resulting in a large spot pressure to hinder the droplet transition, so that the positive connection is basically an irregular droplet transition. MIG welding is not suitable for alternating current because the melting of welding wire is not equal on each half cycle.

When MIG welding aluminum and aluminum alloy, because aluminum is easy to oxidize, in order to ensure the protection effect, the arc length during welding cannot be too long. Therefore, we cannot adopt the jet transition mode with large current and long arc. If the selected current is greater than the critical current and the arc length is controlled between jet transition and short-circuit transition, sub jet transition will be formed.

MIG welding is widely used to weld aluminum and aluminum alloy workpieces. [1]

Common editing voice

▲ gmt-skd11 > 0.5 ~ 3.2mm HRC 56 ~ 58 welding repair cold working steel, metal stamping die, cutting die, cutting tool, forming die and workpiece hard surface to make argon electrode with high hardness, wear resistance and high toughness. Heat up and preheat before welding repair, otherwise it is easy to crack.

▲ gmt-63 degree blade edge welding wire > 0.5 ~ 3.2mm HRC 63 ~ 55, mainly used for welding broach die, hot working high hardness die, hot forging master die, hot stamping die, screw die, wear-resistant hard surface, high-speed steel and blade repair.

▲ gmt-skd61 > 0.5 ~ 3.2mm HRC 40 ~ 43 welding zinc supplement, aluminum die casting mold, with good heat resistance and cracking resistance, hot gas die, aluminum copper hot forging mold, aluminum copper die casting mold, with good heat resistance, wear resistance and cracking resistance. General hot die casting dies often have tortoise shell cracks, most of which are caused by thermal stress, surface oxidation or corrosion of die casting raw materials. Heat treatment is adjusted to appropriate hardness to improve their service life. Too low or too high hardness is not applicable.

▲ gmt-hs221 tin brass welding wire. Performance features: HS221 welding wire is a special brass welding wire containing a small amount of tin and silicon. It is used for gas welding and carbon arc welding of brass. It is also widely used for brazing copper, steel, copper nickel alloy, etc. Suitable welding methods for copper and copper alloy welding wires include argon arc welding, oxygen acetylene welding and carbon arc welding.

▲ gmt-hs211 has good mechanical properties. Argon arc welding of copper alloy and MIG brazing of steel.

▲ gmt-hs201, hs212, hs213, hs214, hs215, hs222, hs225 copper welding wire.

▲ GMT – 1100, 1050, 1070, 1080 pure aluminum welding wire. Performance characteristics: pure aluminum welding wire for MIG and TIG welding. This kind of welding wire has good color matching after anodic treatment. It is suitable for power applications with good corrosion resistance and excellent conductivity. Purpose: Ship sports equipment power

▲ GMT semi nickel, pure nickel welding wire and electrode

▲ GMT – 4043, 4047 aluminum silicon welding wire. Performance characteristics: used for welding 6 * * * series base metal. It is less sensitive to thermal cracks and is used for welding, forging and casting materials. Uses: ships, locomotives, chemicals, food, sports equipment, molds, furniture, containers, containers, etc.

▲ GMT – 5356, 5183, 5554, 5556, 5A06 aluminum magnesium welding wire. Performance characteristics: this welding wire is specially designed for welding 5 * * * series alloys and filler alloys whose chemical composition is close to the base metal. It has good corrosion resistance and color matching after anodic treatment. Application: used in sports equipment such as bicycles, aluminum scooters, locomotive compartments, chemical pressure vessels, military production, shipbuilding, aviation, etc.

▲ gmt-70n > 0.1 ~ 4.0mm welding wire characteristics and application: bonding of high hardness steel, cracking of zinc aluminum die casting die, welding reconstruction, pig iron / cast iron welding repair. It can directly weld all kinds of cast iron / pig iron materials, and can also be used as the welding of mold cracks. When using cast iron welding, try to lower the current, use short-distance arc welding, preheat the steel, heat and cool slowly after welding.

▲ gmt-60e > 0.5 ~ 4.0mm characteristics and application: special welding of high tensile steel, priming of hard surface production, welding of cracks. High strength welding wire with high composition of nickel chromium alloy is specially used for anti cracking bottom welding, filling and backing. It has strong tensile force and can repair the cracking of steel after welding. Tensile strength: 760 n / mm & sup2; Elongation rate: 26%

▲ gmt-8407-h13 > 0.5 ~ 3.2mm HRC 43 ~ 46 die casting dies for zinc, aluminum, tin and other non-ferrous alloys and copper alloys, which can be used as hot forging or stamping dies. It has high toughness, good wear resistance and thermal corrosion resistance, good high-temperature softening resistance and high-temperature fatigue resistance. It can be welded and repaired. When it is used as punch, reamer, rolling knife, grooving knife, scissors… For heat treatment, it is necessary to prevent decarburization. If the hardness of hot tool steel is too high after welding, it will also break.

▲ GMT anti burst backing wire > 0.5 ~ 2.4mm HB ~ 300 high hardness steel bonding, hard surface backing and cracking welding. High strength welding support with high nickel chromium alloy composition is used for anti cracking bottom welding, filling and backing. It has strong tensile force, and can repair the cracking, welding and reconstruction of steel.

▲ gmt-718 > 0.5 ~ 3.2mm HRC 28 ~ 30 mold steel for plastic products such as large household appliances, toys, communications, electronics and sports equipment. Plastic injection mold, heat-resistant mold and corrosion-resistant mold have good machinability and pitting resistance, excellent surface gloss after grinding and long service life. The preheating temperature is 250 ~ 300 ℃ and the post heating temperature is 400 ~ 500 ℃. When multi-layer welding repair is carried out, the backward welding repair method is adopted, which is less likely to produce defects such as poor fusion and.

▲ gmt-738 > 0.5 ~ 3.2mm HRC 32 ~ 35 translucent plastic product mould steel with surface gloss, large mould, plastic mould steel with complex product shape and high precision. Plastic injection mold, heat-resistant mold, corrosion-resistant mold, good corrosion resistance, excellent processing performance, free cutting, polishing and electric corrosion, good toughness and wear resistance. The preheating temperature is 250 ~ 300 ℃ and the post heating temperature is 400 ~ 500 ℃. When multi-layer welding repair is carried out, the backward welding repair method is adopted, which is less likely to produce defects such as poor fusion and.

▲ gmt-p20ni > 0.5 ~ 3.2mm HRC 30 ~ 34 plastic injection mold and heat-resistant mold (copper mold). The alloy with low susceptibility to welding cracking is designed with nickel content of about 1%. It is suitable for PA, POM, PS, PE, PP and ABS plastics. It has good polishing property, no porosity and crack after welding, and good finish after grinding. After vacuum degassing and forging, it is pre hardened to HRC 33 degrees, the hardness distribution of the section is uniform, and the die life is over 300000. The preheating temperature is 250 ~ 300 ℃ and the post heating temperature is 400 ~ 500 ℃. When multi-layer welding repair is carried out, the backward welding repair method is adopted, which is less likely to produce defects such as poor fusion and.

▲ gmt-nak80 > 0.5 ~ 3.2mm HRC 38 ~ 42 plastic injection mold and mirror steel. High hardness, excellent mirror effect, good EDM and excellent welding performance. After grinding, it is as smooth as a mirror. It is the most advanced and best plastic mold steel in the world. It is easy to cut by adding easy cutting elements. It has the characteristics of high strength, toughness, wear resistance and no deformation. It is suitable for mold steel of various transparent plastic products. The preheating temperature is 300 ~ 400 ℃ and the post heating temperature is 450 ~ 550 ℃. When multi-layer welding repair is carried out, the backward welding repair method is adopted, which is less likely to produce defects such as poor fusion and.

▲ gmt-s136 > 0.5 ~ 1.6mm HB ~ 400 plastic injection mold, with good corrosion resistance and permeability. High purity, high specularity, good polishing, excellent rust and acid resistance, less heat treatment variants, suitable for PVC, PP, EP, PC, PMMA plastics, corrosion-resistant and easy to process modules and fixtures, super mirror corrosion-resistant precision molds, such as rubber molds, camera parts, lenses, watch cases, etc.

▲ GMT Huangpai steel > 0.5 ~ 2.4mm HB ~ 200 iron mold, shoe mold, mild steel welding, easy engraving and etching, S45C and S55C steel repair. The texture is fine, soft, easy to process, and there will be no pores. The preheating temperature is 200 ~ 250 ℃ and the post heating temperature is 350 ~ 450 ℃.

▲ GMT BeCu (beryllium copper) > 0.5 ~ 2.4mm HB ~ 300 copper alloy mold material with high thermal conductivity. The main additive element is beryllium, which is suitable for inner inserts, mold cores, die-casting punches, hot runner cooling system, heat transfer nozzles, integral cavities and wear plates of blow molds of plastic injection molding molds. Tungsten copper materials are used in resistance welding, electric spark, electronic packaging and precision mechanical equipment.

▲ gmt-cu (argon welding copper) > 0.5 ~ 2.4mm HB ~ 200 this welding support has a wide range of applications and can be used for welding repair of electrolytic sheet, copper alloy, steel, bronze, pig iron and general copper parts. It has good mechanical properties and can be used for welding and repair of copper alloy, as well as welding of steel, pig iron and iron.

▲ GMT oil steel welding wire > 0.5 ~ 3.2mm HRC 52 ~ 57 blanking die, gauge, drawing die, piercing punch, can be widely used in hardware cold stamping, hand decoration embossing die, general special tool steel, wear-resistant, oil cooling.

▲ GMT Cr steel welding wire > 0.5 ~ 3.2mm HRC 55 ~ 57 blanking die, cold forming die, cold drawing die, punch, high hardness, high bremsstrahlung and good wire cutting performance. Heat up and preheat before welding repair, and perform post heating action after welding repair.

▲ gmt-ma-1g > 1.6 ~ 2.4mm, super mirror welding wire, mainly used in military products or products with high requirements. Hardness HRC 48 ~ 50 maraging steel system, surfacing of aluminum die casting die, low pressure casting die, forging die, blanking die and injection mold. Special hardened high toughness alloy is very suitable for aluminum gravity die casting mold and gate, which can prolong the service life by 2 ~ 3 times. It can make very precise mold and super mirror (gate repair welding, which is not easy to use thermal fatigue cracks).

▲ GMT high speed steel welding wire (skh9) > 1.2 ~ 1.6mm HRC 61 ~ 63 high speed steel, with a durability of 1.5 ~ 3 times that of ordinary high speed steel. It is suitable for manufacturing cutting tools, welding repair broaches, hot working high hardness tools, dies, hot forging master dies, hot stamping dies, screw dies, wear-resistant hard surfaces, high-speed steels, punches, cutting tools Electronic parts, thread rolling die, die plate, drilling roller, roll die, compressor blade and various die mechanical parts, etc. After European industrial standards, strict quality control, high carbon content, excellent composition, uniform internal structure, stable hardness, wear resistance, toughness, high temperature resistance, etc. The properties are better than the general materials of the same grade.

▲ GMT – nitrided parts repair welding wire > 0.8 ~ 2.4mm HB ~ 300 is suitable for mold and parts surface repair after nitriding.

▲ aluminum welding wires, mainly 1 series pure aluminum, 3 series aluminum silicon and 5 Series I welding wires, with diameters of 1.2mm, 1.4mm, 1.6mm and 2.0mm.

Job hazard editing voice

Occupational Diseases

The harm degree of argon arc welding is relatively greater than that of general electric welding. It can produce harmful gases such as ultraviolet, infrared radiation, ozone, carbon dioxide and carbon monoxide and metal dust, which can lead to a variety of occupational diseases: 1) welder pneumoconiosis: long-term inhalation of high concentration of welding dust can cause chronic pulmonary fibrosis and lead to welder pneumoconiosis, with an average length of service of 20 years. 2) Manganese poisoning: neurasthenia syndrome, autonomic nerve dysfunction, etc; 3) Electro optic ophthalmia: foreign body sensation, burning, severe pain, photophobia, tears, eyelid spasm, etc.

Protective measures

(1) in order to protect eyes from arc light, a mask with special protective lens must be used during welding. (2) in order to prevent the arc from burning the skin, the welder must wear work clothes, gloves, shoe covers, etc. (3) in order to protect welding and other production personnel from arc radiation, protective screen can be used. (4) conduct occupational health examination every year.

 


Post time: Sep-16-2021