[Abstract] This article starts with the common problems of gas shielded welding, starting from the five links of human, machine, material, method, and environment. It focuses on the analysis of welding defects caused by welding equipment failures, welding processes, and improper welding operations, identifies the causes of gas shielded welding defects, and proposes corresponding countermeasures.
[Keywords] Gas shielded welding; Problem; countermeasure

With the continuous improvement of welding technology in Chinese enterprises, the gas shielded welding process has been continuously developed due to its advantages of high quality, high efficiency, energy saving, low cost, and low environmental pollution; With the recent CO2 welding technology promotion and application exchange conferences, gas shielded welding technology has been vigorously promoted and applied in the mechanical metal structure industry, laying the foundation for the sustained, stable, and vigorous development of CO2 welding technology. Gas shielded welding not only meets the requirements of automation development, but also promotes enterprise progress and industrial upgrading, so gas shielded welding occupies a dominant position in many mechanical manufacturing, construction and other enterprises. However, there are also some shortcomings in its development that affect its further growth.

1. Welding personnel factors
People are the foundation of quality. Any manufacturing and installation quality formation process cannot be separated from human operation and management. Human skills, quality awareness, rigorous style, and psychological state are key factors and the main reasons for defects. In enterprise production, there are often problems such as inadequate staffing of welding personnel, improper work arrangements for welding personnel, and low skills and qualities of welding personnel.
The allocation of welding personnel should be based on the scale of the enterprise and the size of the welding project. Welding personnel should include: welding administrative personnel, welding technical personnel, welding quality inspection personnel, various types of welders (spot welders, welding welders, repair welders, etc.), welding heat treatment personnel, and necessary auxiliary personnel. The problem of low skills and quality of welding personnel should be addressed by increasing their training efforts.

2 Welding equipment factors
If the welding machine is not adjusted properly, it may result in uneven wire feeding, wire feeding motor stopping or motor running without wire feeding, uneven flow of protective gas, arc craters during welding parameter changes, wire curling, knotting at the wire feeding roller and hose inlet, and welding current imbalance; Not meeting the regulatory requirements, specifically manifested in:
2.1 Uneven feeding of welding wire
The reasons for the occurrence are as follows: improper adjustment of the pressure of the wire feeding roller, wear of the V-shaped groove of the wire feeding roller, gearbox failure, loose power plug of the wire feeding roller motor, poor contact of the welding gun switch or control circuit, loose or blocked wire feeding hose joint or inner spring tube, poor winding of the welding wire, sometimes loose and sometimes tight or bent, poor contact of the conductive part of the welding gun, and unsuitable hole diameter of the conductive nozzle.
Specific measures: Adjust the pressure of the wire feeding wheel, replace the roller with a new one, inspect, tighten, repair, replace one reel or rewire the straightened welding wire.
2.2 The wire feeding motor stops running or does not feed wire while the motor is running
The causes are as follows: motor failure (including carbon brush wear), damage to motor power transformer, fuse burnout, wire feeding wheel slippage, relay contact or wire coil burn, fusion of welding wire and conductive nozzle, poor contact of welding gun switch or open circuit of controller circuit, damage to control button, wire coil stuck at the wire inlet pipe, speed control circuit and failure, silicon component breakdown, control transformer damage, poor contact or broken wire, transistor and thyristor breakdown, poor contact of potentiometer.
Specific measures: repair or replace carbon brushes, fuses, adjust the tightening force of the wire feeding wheel compactor, replace conductive nozzles, replace switches or repair control circuits.
2.3 Uneven gas flow generates pores
The causes are as follows: gas blockage or joint leakage, insufficient or even no gas in the gas cylinder, electromagnetic valve failure, nozzle hole blockage, preheater not powered on, insufficient gas flow, oil stains on the welded parts, and large air convection in the workplace.
Specific measures: Check the air circuit and tighten the joints; Replace with a new bottle; overhaul; Clean the nozzle; Repair the preheater circuit; Add atmospheric flow; Clean the welding parts to be welded; Install measures such as wind deflectors to prevent wind.
2.4 Changes in welding parameters: Unstable welding arc during welding process
The causes are as follows: wear of the wire feeding roller; Inappropriate welding parameters; The conductive nozzle is severely worn; The bending angle of the welding wire is too large; Welding components and welding wires are not clean; poor contact.
Specific measures: Replace and adjust welding parameters; Repair the wire feeding roller; Replace the conductive nozzle; Straightening welding wire; Clean the welding wire and the area to be welded.
2.5 The welding wire may curl or knot at the inlet of the wire feeding roller and hose
The reasons for this are as follows: the wire feeding roller, hose connector, and guide wire connector are not in a straight line; The inner hole of the conductive nozzle is too small; The conductive nozzle is stuck to the welding wire; Excessive pressure on the wire feeding wheel; Welding wire deformation; Small blockage in the inner hole of the wire feeding wheel; The distance between the wire feeding wheel and the inlet of the hose joint is too far.
Specific measures: straightening; Replace the conductive nozzle; Adjust pressure; Clean or replace the hose; Shorten the distance between the two.
2.6 Welding current and voltage imbalance
The reasons for this are as follows: faults in the wire feeding motor or its circuit; Welding circuit malfunction; The thyristor speed control circuit is faulty.
Specific measures: Replace the appropriate conductive nozzle; Tighten the joint; Check the electric motor and power supply system; Tighten the connection; Tighten the nut.

3 Welding process factors
3.1 The specific manifestations of the problems and causes are as follows:
Inexperienced operation and unclear standards, such as unclear specific dimensions of fillet welds and the hazards of excessive height, resulting in problems such as excessive fillet weld size and poor weld appearance; Excessive gas flow will increase the oxidation reaction of the weld seam, causing a large amount of carbon, manganese, and silicon elements to be burned, resulting in a decrease in joint strength and often causing problems such as excessive undercutting and large arc craters; Due to the lack of emphasis on spot welding quality and incomplete understanding of requirements, improper welding procedures have led to poor quality of sealing welds.
3.2 In response to the above issues, the proposed countermeasures are as follows
The general principle is to strengthen training, standardize operational processes, implement an assessment system, and combine self inspection and mutual inspection. In response to the issue of excessively high weld leg dimensions and their impact on appearance, the following standards are set: the size of fillet welds is determined according to engineering requirements, and if there are no specific requirements, the thickness of the thinner side of the workpiece is used as the standard. Excessively high welds cause stress concentration, increased deformation, waste of welding materials, and increased welding hours. In response to the series of problems caused by excessive current, appropriate welding operation manuals and welding process cards are developed based on standards and welding process evaluations, with clear regulations on the range of welding current and welding voltage usage. Minimize welding joints as much as possible. For areas where welding joints cannot be avoided, effective protection should be provided at the joints to save gas and ensure that the weld seam is aesthetically pleasing and meets the required strength. And attenuate the current before extinguishing the arc; Fill the arc pit. In response to the issue of excessive undercutting, strictly follow the welding parameters specified in the process card, adjust the welding gun angle in a timely manner, and observe the molten pool clearly during welding, with more stops on both sides. In response to the problem of poor quality of sealing welds, on the one hand, the sealing welds have been cancelled, and the welding procedures have been arranged reasonably. The sealing welds have been changed from direct transition welding to ordinary intermediate joints; On the other hand, when sealing welding is necessary or if there are defects in the sealing area that need to be repaired, the welding current should be reduced and a short-circuit transition arc welding method should be implemented.

4 Material factors
Welding materials mainly refer to the base metal and welding materials, and the possible problems are that the chemical composition and physical properties of the base metal and welding materials do not meet the requirements.
In response to the common problems with welding materials, it is necessary to strengthen the quality inspection of base materials and welding materials, and never allow a single unqualified material to enter the welding operation site. There should be a dedicated area for stacking welding materials, and the use of welding materials should be managed and distributed by specialized personnel.

5 Common Malfunctions in Gas Shielded Welding Process
Gas shielded welding does not meet the specified requirements in terms of porosity, burn through, slag inclusion, cracks, large spatter, insufficient penetration depth, and weld formation. The specific manifestations are:
5.1 Pores
Due to poor gas protection effect, oil, rust, and water on the surface of the welding wire, low gas purity, insufficient manganese silicon content in the welding wire, excessive swing of the welding gun, and improper angle, many pores appear. The proposed countermeasures for the phenomenon of air holes include increasing atmospheric flow, paying attention to wind protection, and cleaning nozzles; Clean the weldment and welding wire before welding; Welding gas purity>99.5%, CO2 gas, Ar gas>99.95%; Select appropriate welding wire; Adjust the perspective of training operational skills.
5.2 Burning through
Due to excessive gap at the root of the groove, small blunt edge, slow welding speed, and high current, burn through phenomenon occurs. The proposed countermeasures for this phenomenon include adjusting the current according to the process; Processing grooves, increasing blunt edges or reducing current; Reasonably select parameters.
5.3 Slag inclusion
Due to the previous layer of welding slag not being removed; Low current, slow welding, and excessive deposited metal; When using the left welding method, the slag flows to the front of the molten pool; The welding gun swings too much, causing slag to be drawn into the molten pool and resulting in slag inclusion. The proposed countermeasures for this phenomenon include removing interlayer welding slag; Adjust the current and accelerate the welding speed; Change the operating method and angle; Reduce oscillation and perform multi pass and multi-layer welding.
5.4 Cracks
Due to the presence of oil rust and moisture in the welding wire and components, the melting depth is too deep, resulting in significant internal stress in the welded parts after welding. In multi-layer welding, the first layer of the weld seam is too small, and the CO2 gas has a high moisture content, leading to cracking. The proposed countermeasures for this phenomenon include cleaning the welded parts; Reasonably select welding parameters; Reasonably select the welding sequence; Eliminating stress; Strengthen the quality of the first layer weld seam; Dehydration and drying of CO2 gas.
5.5 Large splashes
Due to excessive or insufficient inductance during short-circuit transition; The arc swings during welding; Incomplete cleaning of welding wire and components; There is a phenomenon of large splashing. The proposed countermeasures for this phenomenon include adjusting the inductance; Replace the conductive nozzle; Thoroughly clean the welded components and welding wires.
5.6 Insufficient melting depth
Due to the low welding current; The extension length of the welding wire is too long; Uneven wire feeding; Welding speed is too fast; The bevel angle and root gap are too small; Due to factors such as excessive blunt edges, insufficient melting depth may occur. The proposed countermeasures for this phenomenon include increasing the welding current; Adjust the extension length of the welding wire; Check the wire feeding mechanism; Slow down the welding speed; Adjust the groove size.

6 Conclusion
To ensure welding quality, it is necessary to strictly control the five links of personnel, machinery, materials, methods, and environment in welding construction. From welding management personnel, welding technicians to welding construction personnel, each link should be strictly monitored, and every factor that may cause welding defects should not be overlooked. Welding management and technical personnel should combine standards with reality, and establish reasonable management systems and welding operation documents; Welding operators should conduct self inspection and mutual inspection, control the quality themselves, and ensure that the welding products meet the specified requirements.