The consequences of high impurities in stainless steel seamless elbow materials
Excessive impurity content in stainless steel seamless elbow materials will cause multiple performance degradation and safety hazards.
1. Risk of mechanical performance collapse
Strength and toughness attenuation:
Sudden drop in blast resistance pressure: Impurities such as sulfur and phosphorus cause grain boundary embrittlement, resulting in a drop of over 18% in blast pressure for DN100 elbows under 10MPa conditions.
Low temperature brittle fracture: In the -20 ℃ impact test, the crack propagation speed in the impurity enriched zone is increased by three times.
Welding failure:
Impurities vaporize to form pores (diameter>0.5mm), resulting in a 25% loss of weld strength.
Sulfide segregation in the heat affected zone causes microcracks, resulting in a 50% reduction in fatigue life.
2. Comprehensive deterioration of corrosion resistance
Localized corrosion acceleration:
Pitting penetration: Micro cells are formed around non-metallic inclusions (such as Al ₂ O ∝), and a 0.5mm pitting can penetrate the tube wall within 3 months.
Uncontrolled intergranular corrosion: Carbide impurities precipitate at a sensitization temperature of 650 ℃, and the corrosion rate of the chromium poor zone at the grain boundary increases by 5 times.
Stress Corrosion Cracking (SCC):
Pure 316L: critical Cl ⁻ concentration>10000ppm; Cracking time>1000 hours.
Sulfur content>0.02%: critical Cl ⁻ concentration<500ppm; The cracking time is less than 200 hours.
The consequences of high impurities in stainless steel seamless elbow materials
Excessive impurity content in stainless steel seamless elbow materials will cause multiple performance degradation and safety hazards.
1. Risk of mechanical performance collapse
Strength and toughness attenuation:
Sudden drop in blast resistance pressure: Impurities such as sulfur and phosphorus cause grain boundary embrittlement, resulting in a drop of over 18% in blast pressure for DN100 elbows under 10MPa conditions.
Low temperature brittle fracture: In the -20 ℃ impact test, the crack propagation speed in the impurity enriched zone is increased by three times.
Welding failure:
Impurities vaporize to form pores (diameter>0.5mm), resulting in a 25% loss of weld strength.
Sulfide segregation in the heat affected zone causes microcracks, resulting in a 50% reduction in fatigue life.
2. Comprehensive deterioration of corrosion resistance
Localized corrosion acceleration:
Pitting penetration: Micro cells are formed around non-metallic inclusions (such as Al ₂ O ∝), and a 0.5mm pitting can penetrate the tube wall within 3 months.
Uncontrolled intergranular corrosion: Carbide impurities precipitate at a sensitization temperature of 650 ℃, and the corrosion rate of the chromium poor zone at the grain boundary increases by 5 times.
Stress Corrosion Cracking (SCC):
Pure 316L: critical Cl ⁻ concentration>10000ppm; Cracking time>1000 hours.
Sulfur content>0.02%: critical Cl ⁻ concentration<500ppm; The cracking time is less than 200 hours.