Cold Heading Steel Bright Bar
Introduction:
ML20Cr cold heading steel bright bar is a high-precision alloy structural steel specially optimized for cold forging, cold extrusion and cold upsetting forming, complying with GB/T 6478 standard. Produced with ultra-low impurity control, uniform chemical composition and fine grain microstructure, the material delivers excellent cold plastic toughness and stable mechanical consistency.
Product Overview
ML20Cr cold heading steel bright bar is a high-precision alloy structural steel specially optimized for cold forging, cold extrusion and cold upsetting forming, complying with GB/T 6478 standard. Produced with ultra-low impurity control, uniform chemical composition and fine grain microstructure, the material delivers excellent cold plastic toughness and stable mechanical consistency. According to customer precision and surface requirements, finished products can be selectively processed by cold drawing, centerless turning (peeling) and centerless grinding. The bright bar features ultra-smooth mirror surface, no oxide scale, no surface decarburization and precise dimensional tolerance, effectively avoiding cracking and deformation during high-speed cold heading. With stable carburizing and quenching performance, the finished parts achieve high surface hardness and wear resistance after heat treatment, while retaining sufficient core toughness and excellent fatigue resistance. Through strict internal and surface quality control, zero inclusion and zero porosity are guaranteed, making it the preferred high-end material for automotive, electrical and mechanical high-strength precision fasteners and cold-formed components.
Representative Grades
Representative Grade: ML20Cr
Core Characteristics & Application: ML20Cr is low-carbon chromium alloy cold heading steel. It features superior cold formability, uniform hardness, low internal stress and excellent carburizing hardenability. It can withstand one-time complex cold upsetting forming without cracking. After carburizing and quenching, it obtains high surface hardness and wear resistance while retaining sufficient core toughness. It is mainly used for manufacturing medium and high-strength fasteners, precision bolts, screws, pins and cold-extruded mechanical parts that require wear resistance and fatigue resistance.
Grade Description
ML20Cr is coded according to Chinese cold heading steel naming rules. The prefix "ML" indicates special steel for cold heading; "20" stands for average carbon content of 0.20%, ensuring excellent cold plastic toughness and avoiding cracking during cold forming. The Cr (chromium) element significantly improves hardenability, surface hardness and wear resistance after carburizing treatment, and enhances structural stability and fatigue life. Standard chemical composition: C: 0.18–0.23%, Si: 0.10–0.30%, Mn: 0.60–0.90%, Cr: 0.90–1.20%, S≤0.025%, P≤0.025%, Alt≥0.020%. Standard mechanical properties: Tensile Strength ≥785MPa, Yield Strength ≥588MPa, Elongation ≥10%, Section Shrinkage ≥40%, Delivery Annealed Hardness ≤179HB. It is widely applicable for precision cold forming and heat-treated fastener products.
Product Specifications
Basic technical parameters of ML20Cr cold heading steel round bar (table in pure English):
|
Item |
Technical Parameter |
|
Product Name |
ML20Cr Cold Heading Steel Round Bar |
|
Executive Standard |
GB/T 6478 |
|
Common Diameter Range |
Φ16mm–Φ200mm (Custom sizes available) |
|
Delivery Condition |
Hot Rolled / Annealed |
|
Delivery Hardness |
≤ 179 HB (Annealed state) |
|
Surface Quality |
Mirror bright, oxide-free, crack-free, fold-free, zero decarburization layer |
|
Cold Heading Performance |
Qualified for 1/2, 1/3, 1/4 cold upsetting test |
|
Dimension Tolerance |
National standard precision tolerance, high precision customizable |
|
Custom Service |
Fixed-length cutting, straightening, polishing, stress relief annealing |
Core Advantages
1. Superior Cold Forming Performance: The bright bar is delivered with low hardness, uniform microstructure and excellent plastic toughness, ensuring no cracking or deformation during high-speed cold heading and cold extrusion molding.
2. Ultra-Clean Steel Quality: Strict control of S, P impurities and gas content, internal structure compact without inclusions or porosity, greatly improving finished fastener yield and stability.
3. Zero Surface Decarburization Defect: Optimized rolling and annealing process eliminates surface decarburization, ensuring consistent thread strength, surface hardness and assembly accuracy of precision fasteners.
4. Stable Heat Treatment Performance: Excellent carburizing hardenability with minimal quenching deformation, ensuring high dimensional accuracy and stable fatigue resistance of heat-treated parts.
5. Excellent Batch Consistency: Uniform composition and mechanical properties across different batches, perfectly matching fully automated mass production of high-precision fasteners.
6. Flexible Precision Processing Options: Support cold drawing, centerless turning (peeling) and centerless grinding processes to meet different precision, surface roughness and tolerance requirements of high-end cold-formed parts.
Main Application Fields
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Automotive Industry
Automotive engine fasteners, chassis bolts, studs, pins and precision cold-formed structural parts.
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Mechanical Equipment Industry
High-strength bolts, screws, rivets and connecting fasteners for general machinery and engineering equipment.
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Electrical & Hardware Industry
Precision standard parts, instrument fasteners and small wear-resistant cold-forged components.
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New Energy Equipment
Structural fasteners and precision cold-extruded parts for new energy vehicles and energy storage equipment.
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Mold & Processing Industry
Medium-hardness wear-resistant mechanical parts requiring carburizing and quenching strengthening.
Packaging & Services
- 1. Executive Standard: GB/T 6478, fully compliant with national cold heading steel precision manufacturing standards.
- 2. Complete Inspection Items: Chemical composition analysis, tensile test, hardness test, cold upsetting performance test, decarburization layer detection, metallographic grain inspection, internal defect detection.
- 3. Material Certification: Provide EN10204 MTC 3.1 mill test certificate; support SGS, BV third-party inspection and factory witness testing.
- 4. Professional Exclusive Packaging for Bright Bars: Adopts special scratch-proof and rust-proof precision packaging for bright bars, wrapped with thickened waterproof film on the outer layer and firmly bundled and fixed. High-precision and long-size products can be customized with solid wooden box packaging, completely avoiding collision, scratches, deformation and rust during transportation, suitable for long-distance sea and land transportation.
- 5. MOQ & Shipment: Flexible order quantity, support small-batch trial order and large-batch bulk supply, mixed-specification container loading acceptable.
- 6. Custom Deep Processing: Optional cold drawing, centerless turning (peeling), centerless grinding, fixed-length cutting, straightening, polishing and stress relief annealing customization.
- 7. Professional Technical Support: Provide targeted technical services such as cold heading process optimization, heat treatment scheme matching and steel grade selection guidance.
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- WhatsApp: +86-185 9567 2991
- Email: martinliu@rongtianmetal.com
- Tel: +86-185 9567 2991
- Address: 8F, Bldg 2, Jinke Zhihui Valley No. 65 Hongyuan Rd., Jinshui Dist. Zhengzhou, China.
