What impact does the degreasing treatment of 201 stainless steel welding pipes have on the subsequen

1. Positive Effects

Improvement of Welding Quality: Removing surface oil, oxide scale, and other impurities through degreasing reduces weld porosity (such as H₂ porosity), slag defects, and prevents molten pool splashing caused by oil combustion and CO₂ generation.

Optimization of Fusion Effect: Cleaning the surface enables better wetting between the welding material and the base material, reduces the risk of incomplete fusion in the weld, and enhances joint strength (tensile strength can be increased by 10%-15%). 

II. Potential Risks and Mitigation

Residual Deodorizer Impact

Risk: If the deodorizer (containing chlorine or sulfur components) remains, it will decompose at high temperatures, generating corrosive gases, which can cause intergranular corrosion or stress corrosion cracking of the weld seam.

Mitigation: After deodorization, thoroughly rinse with deionized water (chloride ion content <25 ppm), dry with hot air (temperature ≤ 60°C), and wipe with white cotton cloth to check for no residue.

Change in Surface Passivation Film

Risk: Strongly alkaline deodorizers may damage the surface chromium oxide passivation film, resulting in an oxide layer during welding, affecting corrosion resistance.

Mitigation: Use neutral deodorizers (pH value 7-9), weld within 2 hours after deodorization, or lightly sand the surface before welding to activate it.

Hydrogen Embrittlement Hazard

Risk: If the deodorizer contains strong reducing agents (such as sulfites), they may penetrate the lattice and generate hydrogen atoms, which will accumulate at high temperatures during welding, causing hydrogen embrittlement.

Mitigation: Choose deodorization processes without hydrogen (such as solvent deodorization), and perform low-temperature baking (120°C × 2h) after deodorization to remove hydrogen.

Welding Parameter Compatibility

Risk: After deodorization, the surface cleanliness is high, and changes in thermal conductivity may cause welding heat input deviation (such as local overheating).

Mitigation: Adjust the welding current (reduce by 5%-10%), use pulsed TIG welding to reduce the heat affected zone, and control the interlayer temperature ≤ 150°C. 

III. Process Connection Suggestions

Optimal interval time: Complete welding within 8 hours after degreasing to avoid prolonged exposure to dust; if the interval exceeds 24 hours, the surface needs to be wiped again.

Welding protective gas: Use high-purity argon gas (purity ≥ 99.99%) with a flow rate increased by 10% compared to the conventional level to prevent secondary oxidation of the cleaned surface. 

IV. Quality Verification Methods

Weld Inspection: Penetrant Testing (PT) is used to confirm that there are no microcracks on the surface, and X-ray Testing (RT) is employed to detect internal pores and slag inclusions.

Corrosion Resistance Test: The welded joints undergo a 5% nitric acid immersion test (for 48 hours), and a weight loss rate of ≤ 0.5g/m² is considered. 

By controlling the type of degreasing agent, the cleaning and drying process, as well as the welding parameters, the optimization effect of degreasing on welding quality can be fully exerted. At the same time, the risks of residue and hydrogen embrittlement can be avoided, ensuring the mechanical properties and corrosion resistance of the welded joints of 201 stainless steel pipe.