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Tianjin lefin Industrial
TIANJIN LEFIN STEEL GROUP containing Tianjin lefin Industrial Co.,Ltd. 、Tianjin lefin steel import & export Co.,Ltd and Tianjin Shengqifeng International Trading Co., Ltd. -
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Steel Pipe Processing
Our main products include 1/2inch to 16 inch ERW PIPE/GI PIPE which has been produced according to BS1387/ASTM A53/EN10219/EN10255/EN10217 Standard -
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Our steel pipes are suitable for oil, natural gas, shipbuilding, chemical industry, water conservancy, electrical, steel structure, construction and other related fields.
What Is The Bright Heat Treatment Of Steel Pipes And What Is Its Significance?
Release time：
2026-05-20
I. What is the bright heat treatment of steel pipes
The bright heat treatment of steel pipes：
(commonly referred to as bright annealing/BA, delivered in the NBK state) is a heat treatment process where the steel pipes are heated to the recrystallization/transformation temperature in a vacuum or protective atmosphere (H₂, N₂, H₂ + N₂), held for a certain period of time, and then cooled under controlled conditions.
The entire process is oxygen-free, no oxide scale is formed, and after cooling, the inner and outer surfaces maintain the original metal color and high glossiness.
Core process key points
- Atmosphere: Pure hydrogen/nitrogen-hydrogen mixture/vacuum, anti-oxidation, decarburization prevention.
- Temperature
Carbon steel/low alloy steel: 700–850℃ (recrystallization annealing).
Stainless steel： 1000–1150℃ (solution annealing).
- Cooling： Rapid cooling under protective gas to prevent oxidation and lock in the structure.
- Surface: No oxide layer, no decarburization layer roughness Ra ≤ 0.4–0.8 μm.
II. The Core Significance of Bright Heat Treatment
1. Surface Quality: No need for acid washing, high gloss, high cleanliness
- No oxide scale / no decarburization: Eliminates the need for acid washing, phosphating, and polishing, reducing costs and preventing hydrogen embrittlement.
- Mirror-like surface finish: Bright surface, low Ra value, suitable for high-cleanliness scenarios such as food, medical, and semiconductor industries.
- Inner wall cleanliness: No residual oxides, prevents medium contamination, and reduces transportation resistance.
2. Mechanical Properties: Stress Relief, Toughness Enhancement, DimensionStabilization
- Elimination of Cold Work Hardening: After cold drawing/cold rolling, the hardness is high and the plasticity is poor; annealing treatment softens the base material and restores plasticity, facilitating subsequent bending, flaring, and flattening.
- Release of Residual Stress:Significantly reduces internal stress (by 80%+), prevents deformation, cracking, and dimensional drift, and enhances long-term stability.
- Fine grain refinement, uniform microstructure: Balance of strength and toughness, without loss of strength, improvement in toughness, better fatigue and impact resistance.
3. Corrosion Resistance: Resistant to rust, resistant to various media, long service life
- Stainless Steel (304/316): Solution treatment dissolves carbides and restores chromium content, avoiding areas with low chromium content, significantly enhancing corrosion resistance.
- Carbon Steel/Low Alloy Steel: No oxide scale and no grain boundary depletion, stronger resistance to atmospheric/weak media corrosion.
4. Economy and Efficiency: Cost Reduction, Efficiency Enhancement, High Added Value
- Process Simplification: Elimination of acid washing/ polishing, shortening of the process, reduction of equipment and energy consumption.
- High Yield: No oxide scale loss, no acid washing corrosion, yield increases by 3% - 5%.
- Stable Precision: Low internal stress, stable dimensions, controllable tolerances (h8 - h9 grade), suitable for precision hydraulic/ pneumatic components.
III. Typical Application Scenarios
- Precision hydraulic/ pneumatic steel pipes: High polish, no oxidation, stable dimensions, leak-proof, suitable for high pressure.
- Food/medicine/semiconductor pipelines: High cleanliness, no impurities, corrosion-resistant, in line with hygiene standards.
- Automotive/aerospace precision pipe fittings: Stress relief, anti-fatigue, easy welding, suitable for harsh conditions.
- High-end decoration/mechanical structure pipes: Bright surface, no painting required, beautiful and durable.
IV. Key Differences from Ordinary Annealing (Air Furnace)
| Comparison Item | Bright Heat Treatment (BA/NBK) | Ordinary Annealing (Air Furnace) |
| Atmosphere | Protective gas/vacuum, anaerobic | Air, aerobic |
| Surface | No oxide scale, metallic luster, low Ra value | Thick oxide scale, dull, requires acid washing |
| Subsequent processes | No acid washing or polishing | Must acid wash, phosphating and polishing |
| Internal stress | Low Dimensional stability | High prone to deformation |
| Corrosion resistance | Good, no chromium depletion/decarbonization | Poor, with oxide scale and decarburization layer |
| Cost | Medium-high (atmosphere equipment) | Low (simple equipment) |
| Applicable scenarios | Precision, cleanliness, high-end | Ordinary structure, low requirements |
Summary
Lightning heat treatment is not merely about "brightening the surface", but rather a comprehensive improvement in surface quality, mechanical properties, corrosion resistance, and economy. It is the core process for high-end precision steel pipes, determining the product grade and application boundaries.
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Address: Hengtai Road,Daqiuzhuang Town,Jinghai County,Tianjin,China
Mob: +8615122229899(whatspp)
Phone: +86 22 58171905
Fax: +86 22 58171902
E-mail:info@lefinsteel.com
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