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ProductsDiscover Ruibaolong's full range of High-Performance PC Steel Wire, PC Steel Bar, and Cold Drawn Wire. We specialize in SWRH82B Spiral Ribbed, Plain, and Indented surfaces, as well as Hose Reinforcement Wire. ISO 9001 certified manufacturer for PCCP and infrastructure projects.
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About UsTianjin Ruibaolong Prestressed Steel Strand Co., Ltd. is a leading ISO 9001 certified manufacturer established in 2010. We specialize in producing and exporting high-quality PC wire and steel bars globally.
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Blog
12
2026
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01
Why SWRH82B Spring Wire Breaks During Drawing: Root Cause Analysis & Solutions
Introduction — Understanding Wire Breakage Starts with Materials Science
SWRH82B high-carbon steel wire is widely used in spring wire, prestressing wire, and other high-strength engineering applications due to its excellent fatigue resistance and mechanical performance.
However, during deep drawing, manufacturers sometimes experience transverse cracking or sudden wire breakage, even when using qualified raw materials.
At Ruibaolong, we believe that preventing failures starts with understanding the mechanism behind them.
In this article, we analyze real fracture cases of SWRH82B wire and explain how surface condition, microstructural transformation, and process control directly influence drawing stability.
1. The Phenomenon — What Happens Inside a Fractured Wire?
To identify the root cause, fractured SWRH82B wire samples were examined using laboratory metallographic analysis.
After polishing and etching the cross-section with 4% nitric acid alcohol, the following features were observed:
Surface cracks with depths of approximately 0.18 mm
Distinct abnormal microstructure near the surface layer
A clear contrast between the brittle surface zone and the ductile core
🔍 Key Insight:
Wire breakage is rarely random — it is the result of localized structural failure.
2. The Mechanism — Stress Concentration & Martensite Formation
Why does SWRH82B wire crack during drawing?
The primary mechanism behind most drawing fractures is the formation of brittle martensite in localized surface zones.
What Happens During Cold Drawing of High-Carbon Steel?
Average temperature rise per pass: 100–160°C
Under poor lubrication or surface defects, local temperatures may rise much higher
Chain Reaction Leading to Fracture
Lubrication Failure
Residual oxide scale or damaged phosphating film reduces lubrication efficiency.
Stress Concentration
Scratches or surface defects act as stress concentrators.
Phase Transformation
High stress and friction-induced heat cause localized austenite to transform into martensite.
Brittle Fracture
Martensite is extremely hard but brittle and cannot withstand subsequent deformation.
3. Key Factors Influencing SWRH82B Drawing Quality
Drawing stability depends on control at several critical stages:
| Factor | Typical Issue | Resulting Risk | Control Focus |
|---|---|---|---|
| Raw Material | Central cavity, segregation | Internal crack propagation | Billet quality & NDT |
| Surface Condition | Residual scale, scratches | Lubrication failure | Complete descaling |
| Lubrication System | Phosphate film peeling | Friction overheating | Stable phosphating |
| Drawing Parameters | Excessive reduction | Local heat accumulation | Optimized drafting |
| Microstructure | Surface martensite | Brittle fracture | Mechanical testing |
📌 Engineering takeaway:
Most failures originate from the surface, not the core.
4. How Ruibaolong Prevents Drawing Fractures
To ensure stable performance of SWRH82B-based products, Ruibaolong implements a strict Process Control System:
✔ Raw Material Selection
Controlled chemical composition
Internal quality verification using non-destructive testing
✔ Surface Management
Complete oxide removal
Uniform and stable phosphating film for reliable lubrication
✔ Drawing Process Optimization
Rational reduction ratios
Proper die matching to avoid surface overheating
✔ Rigorous Mechanical Testing
We perform strict torsion and reverse bending tests, which are the most effective methods to detect surface brittleness.
If any abnormal martensite layer exists, the wire will fail ductility tests immediately — ensuring no defective product leaves our factory.
Conclusion — Quality Is Engineered, Not Assumed
Wire breakage during drawing is not caused by SWRH82B itself, but by:
Uncontrolled surface conditions
Lubrication failure
Localized microstructural transformation
By eliminating surface stress concentrators, maintaining stable lubrication, and strictly testing mechanical properties, manufacturers can significantly reduce fracture risks.
At Ruibaolong, we apply materials science–driven process control to deliver reliable SWRH82B spring wire and prestressing steel products for demanding engineering applications.
📩 Looking for stable-quality SWRH82B wire or PC Steel Wire?
👉 Contact our engineering team to discuss your technical requirements.
FAQ — SWRH82B Wire Drawing & Fracture Control
Q1. Is SWRH82B inherently prone to wire breakage?
No. SWRH82B is a mature steel grade. Most fractures result from process-related issues rather than material defects.
Q2. Why does martensite form during cold drawing?
Localized overheating combined with high stress can trigger martensite transformation in surface zones.
Q3. Can better lubrication alone solve drawing fractures?
Lubrication is critical, but it must work together with surface quality, billet integrity, and proper drafting schedules.
Q4. How does Ruibaolong detect hidden fracture risks?
By monitoring torsion and reverse bending test results, we can easily detect surface brittleness caused by abnormal microstructures.
Q5. Is SWRH82B suitable for prestressed concrete wire?
Yes. With proper processing and quality control, SWRH82B is widely used for PC Wire production.
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Tianjin Ruibaolong Prestressed Steel Strand Co., Ltd. is one of the professional manufacturers specializing in the research, development, production, and operation of prestressed steel wires, cold-drawn steel wires, and steel wires for roll welding machines.
Address: No. 3, Tianyu Road, Tianyu Science and Technology Park, Jinghai District, Tianjin
Email: globaltrade@rblprestress.com
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