Zhuojin Pipe Fitting Co., LtdApplication of Lincoln Electric Welding Wire in Composite Hardfacing of Slab Continuous Casting Rolls
Literature Overview
This 1995 paper by Zhou Wusheng from the Tianjin Metallurgical Spare Parts Repair Center reports the successful application of American Lincoln Electric welding equipment, consumables, and technology in the composite hardfacing of slab continuous casting rolls. Published in Tianjin Metallurgy (Vol. 1995, Issue 1, pp. 20-22), the study demonstrates a practical approach to extending the service life of critical continuous casting components through advanced hardfacing techniques. The reported life improvement of 1 to 2 times over un-hardfaced rolls represents a significant economic benefit for steel mills operating slab casting lines.
Core Technical Content and Process Description
The continuous casting roll is one of the most critical components in a slab caster, subjected to extreme thermal cycling, mechanical contact stress from the solidifying steel shell, and cooling water erosion. The composite hardfacing approach described in this paper involves applying a wear-resistant overlay layer onto the working surface of the roll to resist the combined degradation mechanisms.
Hardfacing Process Parameters
| Parameter | Typical Range | Purpose |
|---|---|---|
| Welding process | Submerged arc / Plasma arc | High deposition rate, low dilution |
| Shielding gas | Argon-based mixture | Prevent oxidation of hardfacing layer |
| Wire composition | High-carbon chromium-iron alloy | Form hard carbides (Cr7C3, Cr23C6) |
| Preheating temperature | 200-300°C | Reduce residual stress and prevent cracking |
| Interpass temperature | ≤350°C | Control cooling rate in HAZ |
| Number of passes | 2-3 layers | Achieve required overlay thickness |
| Post-weld treatment | Stress relief at 550-600°C | Eliminate residual stress |
Key Technical Points
- The Lincoln Electric consumable system provides consistent wire composition and shielding gas delivery, which is critical for achieving uniform overlay properties across the entire roll circumference.
- The composite nature of the hardfacing implies a multi-layer approach: a transition layer to ensure metallurgical compatibility with the roll substrate (typically 40Cr or similar alloy steel), followed by one or more wear-resistant layers.
- The 1-2 times life improvement suggests that the un-hardfaced roll life was limited primarily by surface erosion and thermal fatigue cracking, both of which are effectively mitigated by the hardfaced overlay.
Engineering Practice Insights
In my experience with continuous casting equipment maintenance, the hardfacing of casting rolls requires careful consideration of several factors beyond the basic welding parameters:
- Thermal management: The roll diameter and mass influence the heat input distribution. Large-diameter rolls (typically 600-800 mm for slab casters) have sufficient thermal mass to absorb welding heat without excessive distortion, but the circumferential welding sequence must be planned to minimize warping.
- Overlay adhesion: The bond strength between the hardfacing layer and the roll substrate is critical. Insufficient adhesion leads to spalling during service, which can damage the solidifying shell. The transition layer composition must be carefully matched to avoid excessive dilution or brittle intermetallic formation.
- Surface preparation: Prior to hardfacing, the roll surface must be machined to remove prior wear patterns and oxide layers. A roughened surface (through shot blasting or machining with specific tool geometry) improves mechanical interlocking.
- Post-weld machining: The overlay thickness must exceed the final machining allowance to ensure the final surface finish meets the smoothness requirements for proper shell contact and water flow distribution.
Study Reflection
This paper, though published in 1995, reflects an important era in Chinese metallurgical equipment maintenance when domestic hardfacing consumables were still developing. The adoption of Lincoln Electric technology represented a significant step forward in reliability. Today, domestic alternatives have largely matched these performance levels, but the fundamental principles of multi-layer composite hardfacing remain unchanged. The key lesson is that consistent consumable quality and disciplined process control are more important than the specific brand of equipment employed.