Will the degreasing treatment have an impact on the performance of stainless steel welded pipes

The influence of degreasing treatment on the performance of stainless steel welded pipes needs to be analyzed based on the process principle. The following are the specific impacts and differences:

1. Chemical degreasing performance impact

Corrosion resistance: Under normal process conditions (weak alkaline solution with pH ≤ 10 and temperature <60°C), the degreasing process does not damage the passivation film, and the salt spray test (5% NaCl solution) lasts for ≥ 500 hours without rust; if the reagent residue exists, it may cause local pitting corrosion.

Mechanical properties: Without mechanical external force, the tensile strength (σb) and elongation (δ) are consistent with the base material (such as 304 steel σb ≥ 520 MPa), and there is no risk of stress concentration.

Welding compatibility: The surface cleanliness is high (oil residue ≤ 5mg/m²), the porosity of the weld bead is reduced to <1%, and the uniformity of the weld penetration is improved. 

II. Performance Impact of Mechanical Degreasing

Corrosion Resistance: Abrasive blasting (with abrasive hardness > HV400) may damage the surface passivation film, and the salt spray test's corrosion resistance time is shortened by 10%-20%; subsequent passivation treatment (such as nitric acid passivation) is required to restore the film layer.

Mechanical Properties: Mechanical friction may cause surface hardening (hardness increases by 10-15HV), thin-walled tubes (with wall thickness <1mm) may develop microcracks, affecting fatigue strength (life decreases by 5%-10% under cyclic loading).

Welding Compatibility: Increased surface roughness (Ra > 1.6μm), residual flux is prone to remain, which may cause slag inclusion in the weld seam; secondary cleaning (such as ultrasonic water washing) is required. 

III. Key Performance Comparison Table

Chemical degreasing (standard operation)

Salt spray resistance: No rust for 500-800 hours

Surface hardness: Consistent with the base material (HV150-200)

Welding porosity rate: <1%

Fatigue strength (10⁶ cycles): σa = 210 MPa (for 304 steel) 

Mechanical degreasing (conventional sandblasting)

Salt spray resistance: 400-600 hours (requires passivation)

Surface hardness: Local HV170-230 (hardened layer depth 5-10 μm)

Weld porosity rate: 1.5%-3% (requires pre-treatment)

Fatigue strength (10⁶ cycles): σa = 190-200 MPa (304 steel) 

IV. Process Selection Suggestions

For high corrosion resistance scenarios (such as in healthcare and food industries): Chemical degreasing must be performed, and the residual chemicals must be verified (electrical conductivity detection ≤ 10 μS/cm);

For components subjected to dynamic loads: Avoid mechanical degreasing to prevent surface hardening that leads to stress concentration;

For workpieces that require subsequent passivation treatment: Mechanical degreasing can be prioritized (with high efficiency in removing heavy oil stains), but an additional passivation step is necessary to restore corrosion resistance.