How does the burning process under the flux layer of the submerged arc welding machine affect the welding quality?

The welding process of the Submerged Arc Welding Machine is to burn the arc under the flux layer. This unique process has a profound impact on the welding quality. The presence of the flux layer not only protects the welding area, but also significantly improves the performance of the weld through a series of physical and chemical effects. The following is a detailed analysis of how the burning process under the flux layer affects the welding quality:

Mechanism of action of the flux layer
The flux plays multiple roles in the submerged arc welding process, which directly affect the welding quality:
(1) Protecting the welding area
The flux melts at high temperature and forms a layer of cover that isolates the welding area from the air and prevents harmful gases such as oxygen and nitrogen from invading the molten pool.
This protective effect effectively avoids the formation of oxides and nitrides during welding, thereby improving the purity and mechanical properties of the weld.
(2) Metallurgical reaction
The components in the flux (such as oxides and fluorides) will react metallurgically with the metal in the molten pool to remove impurities (such as deoxidation and desulfurization) and form beneficial alloying elements.
These reactions can optimize the chemical composition of the weld and improve its strength, toughness and crack resistance.
(3) Heat conduction and heat distribution
The flux layer can absorb part of the welding heat and release it slowly, playing a certain role in heat preservation. This heat conduction property helps to reduce the cooling rate, reduce welding stress and crack risk.
At the same time, the flux layer can also guide the arc heat to concentrate on the weld area, improve the penetration depth and welding efficiency.
2. Specific impact on welding quality
(1) Weld formation
The existence of the flux layer makes the surface of the molten pool evenly covered with liquid flux, which can smooth the weld surface and form a beautiful and regular weld shape.
The flux can also control the distribution of slag by adjusting the fluidity, thereby avoiding slag inclusions or irregular shapes in the weld.
(2) Welding heat input
The arc combustion of submerged arc welding is carried out under the flux layer, and the welding heat input is high and evenly distributed, which makes the molten pool deeper and wider, suitable for thick plate welding.
Although high heat input improves welding efficiency, it may also lead to coarse grains in the overheating zone and reduce the toughness of the weld. Therefore, it is necessary to balance the heat input by optimizing welding parameters (such as current, voltage and speed).
(3) Metallurgical properties of welds
Alloy elements in the flux can enter the weld through metallurgical reactions and change its chemical composition. For example, adding elements such as manganese and silicon can improve the strength and hardness of the weld.

Flux can also improve the crack resistance and corrosion resistance of the weld by removing harmful impurities (such as sulfur and phosphorus).
(4) Reduction of welding defects
The protective effect of the flux layer significantly reduces the occurrence of welding defects such as pores, slag inclusions and oxides.
The slow cooling characteristics of the slag also help to release the gas generated during the welding process, further reducing the porosity.
3. Key factors affecting welding quality
(1) Flux type
Different types of flux (such as acid flux and alkaline flux) have different effects on welding quality:
Acid flux: Suitable for welding of carbon steel and low alloy steel, with good process performance, but the impact toughness of the weld is low.
Alkaline flux: Can provide higher weld purity and toughness, but the process performance is slightly worse and it is easy to produce pores.
Flux particle size also affects welding quality. Finer flux particles can improve the fluidity of the slag, but may increase spatter; coarser flux particles are more suitable for high current welding.
(2) Welding parameters
Current: The current determines the welding heat input and penetration depth. Too high current may cause overheating and reduced weld performance, while too low current may result in incomplete fusion.
Voltage: Voltage affects arc length and weld width. Too high voltage may cause the weld to be too wide and increase spatter, while too low voltage may cause the weld to be too narrow.
Welding speed: Welding speed affects heat input and weld formation. Too fast speed may cause uneven cooling of the weld, while too slow speed may cause overheating and deformation.
(3) Flux recovery and reuse
The recovery and reuse of flux may introduce impurities (such as iron filings or dust), which will affect the welding quality. Therefore, flux cleaning and screening are very important.
4. Optimization strategies in practical applications
(1) Selecting the right flux
Select the right flux type according to the base material, welding position and performance requirements. For example, for high-strength steel, basic flux can be selected to improve weld toughness.
(2) Optimize welding parameters
Optimize the combination of welding current, voltage and speed through experiments and simulations to ensure that the welding heat input is moderate and avoid overheating or rapid cooling.
(3) Post-weld treatment
For some special materials (such as high-strength steel or stainless steel), post-weld heat treatment (such as annealing or normalizing) can be used to further improve weld performance and reduce residual stress.
(4) Automated control
Use automated submerged arc welding equipment to improve welding consistency and reduce human errors by real-time monitoring of welding parameters (such as current fluctuations and weld shape).

The combustion process of the submerged arc welding machine under the flux layer significantly improves the welding quality by protecting the welding area, promoting metallurgical reactions and optimizing heat conduction. The selection of flux, optimization of welding parameters and flux recovery management are the key to ensuring high-quality welding. In addition, with the development of automation and intelligent technology, the quality control of submerged arc welding will be further improved.