1.What are the advantages and disadvantages of an argon-helium mixture?
The most universal and optimal balance is achieved through argon providing stability and protection, while helium increases melting depth, speed, and improves the fluidity of the molten pool.
It has a wide process window, fast welding speed, good weld formation, and reliable protection.
The cost is higher than that of pure argon.
2.What are the core characteristics, advantages, and disadvantages of high-purity argon?
The safest and most protective inert gas. Completely isolates oxygen and nitrogen.
Advantages: The weld metal is the purest and has a bright silver appearance; the performance is stable and reliable.
Disadvantages: The potential for penetration and welding speed is slightly lower than that of mixed gas; the cost is high.
3.What are the four core factors in product selection decisions?
Four Core Factors in Steel Selection Decisions: Steel Grade and Composition (Decisive Factors)
Plain Carbon Steel (SPCC/SECC, etc.): Strict protection against nitrogen and oxygen intrusion is essential. High-purity argon or Ar-He mixtures are preferred.
High-Strength Steel/Advanced High-Strength Steel: Sensitive to thermal cycling. Ar-He mixtures offer better molten pool control and cooling rates, making them a safer choice.
Interstitial Atom-Free Steel (IF Steel): High-purity argon can be used. To reduce costs, Ar+ (<3%) N₂ mixtures can be explored, but rigorous bending, cupping, and aging tests must be conducted to verify the absence of embrittlement risk.
Welding Process Requirements
Speed: Higher welding speeds require more helium to increase energy input and stabilize the molten pool. Ar-He mixtures are preferred for high-speed welding.
Plate Thickness: Thicker plates require greater penetration depth. Increasing the helium proportion helps achieve greater penetration.
Subsequent Processing: If the weld needs to withstand severe deformation (such as in automotive structural parts), high-purity inert gases must be used to ensure the weld toughness matches that of the base material.
Weld Quality Indicators
Appearance: Requires a bright, silvery-white finish; high-purity argon-based gas must be used.
Mechanical Properties: Requires qualified weld strength and elongation; brittle fracture due to inadequate protection must be prevented.
Defect Control: Prevent porosity, undercut, and humps. Suitable gas optimizes molten pool flow and solidification.
Overall Cost Considerations
Total Cost of Ownership (TCO) Thinking: Do not only compare gas unit prices. Cheap gases may lead to:
Decreased welding speed → Loss of production output.
Increased strip breakage rate → Downtime losses and scrap.
Substandard weld quality → Customer claims or subsequent processing cracking.
Although Ar-He mixed gases have a higher unit price, their high speed and high stability often result in the lowest overall production cost.
4.What are the core operating procedures?
Gas purity: Must be ≥99.995% (4.5N grade), dew point <-40°C. Impurities are the main cause of porosity and embrittlement.
Gas delivery system:
Double-sided protection: A pre-shielding gas is provided at the front of the welding torch, and a sufficiently long trailing gas shield must be provided at the rear for delayed protection, covering the high-temperature cooling process.
Laminar flow protection: Ensure stable airflow and avoid turbulent air entrainment. Use a gas lens or diffuser.
Moderate flow rate: Front shielding gas is typically 15-25 L/min, trailing gas 10-20 L/min. Excessive flow disturbs the molten pool, while insufficient flow provides inadequate protection.
Equipment maintenance: Regularly check for gas leaks, nozzle blockages, and damage to the trailing gas shield.
5.What are some usage recommendations for laser welding of cold-rolled coils?
Preferred option: Ar (70%~80%) + He (20%~30%) mixture. This offers the best balance between quality, speed, and reliability.
Conservative/High-quality option: High-purity argon. Suitable for scenarios with extremely high quality requirements but less stringent speed constraints.
Absolutely avoid: Using low-purity gases to reduce costs or using nitrogen without verification.