Challenges and solutions in repairing components with weld overlays for the steel industry

Let's start with the basics:

What are the current challenges in the Steel Production and Maintenance of various components?

The steel mills are producing more and more special steels, such as high strength steels. These steels cause more wear on caster rollers. Providing the right welding consumables to further improve the service life of caster rollers is a major challenge.

How does UTP answer the challenges of increased wear exposure?

Repairing parts is always more sustainable than replacing them with new parts. Therefore, we will continuously try to improve our products and services to offer the best solutions for steel manufacturers.

With the special welding products that we developed over the years, we can give the rollers a much better service life, which is up to 50% better than the old solutions. We will, of course, continue to work on new alloying concepts to meet the challenges ahead.

One outstanding project was with ArcelorMittal in Gent, Belgium. Their continuous casting line was experiencing driving roll issues. We introduced a 15% cobalt alloy filler metal that doubled the service life of the rolls — a real success story in the steel segment of the welding industry.

Could you give us some tips how to increase productivity by reducing wear on caster rollers?

How do rollers wear and what causes this wear?

Caster rollers are subject to extremely demanding working conditions. These rollers have to withstand high contact pressures, high temperatures, abrasive oxides and slag, as well as cyclic stresses —both thermal and mechanical. Over time, these conditions contribute to several types of wear mechanisms, including abrasive wear, adhesive wear, oxidation, plastic deformation, fatigue, corrosion, and, in some cases, even catastrophic failure.

That's quite a list of challenges! Can you break down some of these wear mechanisms for us, starting with abrasive and adhesive wear?

Abrasive and adhesive wear are primarily caused by contact with oxides, slag, and the slab itself. As the molten material solidifies and is extracted, the roller’s surface suffers from abrasive forces of the hardened oxides and slag that build up on the cast slab. These forces act to wear down the surface of the rollers over time.

How does oxidation contribute to wear on caster rollers?

Oxidation is especially important at high temperatures and in the presence of steam. This process results in the formation of surface oxides, that worsen abrasive wear. This oxidation process results in an “elephant skin” pattern on the roller surface — a result of oxidation along grain boundaries. This pattern weakens the surface, often leading to cracking and spalling of the material.

That sounds like a serious issue. And what about plastic deformation and fatigue - how do they affect the rollers?

Plastic deformation occurs when the roll surface deforms due to high contact pressure with the hot slab, especially when the rollers repeatedly encounter these forces.

Thermal and mechanical fatigue are also critical wear mechanisms. As the roller rotates, it experiences cyclic stresses from the slab’s passage and bending forces, as well as extreme temperature changes as the surface contacts the hot slab, which is up to about 600°C, and then is cooled by water spray. These repeated temperature changes cause a fine network of cracks known as “fire-cracking,” which is one of the leading causes of material loss in roughing stands.

How do corrosion mechanisms play a role in the deterioration of caster rollers?

Corrosion mechanisms such as pitting and crevice corrosion originate in aggressive acidic environments within the caster, often due to localized conditions favoring anodic dissolution of the steel. Mold-flux-induced corrosion is another issue, where water spray - often containing hydrofluoric acid from reactions with mold flux powder - creates a low pH environment. This environment accelerates pitting, crevice corrosion, and can lead to stress corrosion cracking, particularly at areas of surface discontinuities.

You mentioned catastrophic failures earlier. Can you explain how these occur?

Catastrophic failure can be either caused by improper material selection or the progressive wear mechanisms already mentioned. For instance, excessive spalling, surface degradation, or roll breakage can be traced back to wear mechanisms such as thermal fatigue, oxidation or corrosion. If left unchecked, they eventually lead to sudden, complete failure.

With so many wear mechanisms at play, how can operators prevent these issues? Are there any specific strategies or treatments that help?

You've mentioned the importance of material composition in the protective layers. Could you elaborate on specific design properties or materials that help protect caster rolls from these various forms of wear?

So it seems like a lot of attention goes into selecting materials that not only provide immediate hardness but also long-term resilience in extreme conditions.

Are there any additional steps that operators can take during maintenance to ensure these layers functioning optimally?

Yes, maintenance just as important as the initial material selection. During routine inspections, signs of premature wear such as pitting, cracking or corrosion between the beads can be detected. Any visible deterioration should be addressed immediately to prevent it from progressing. Adopting these strategies - both in terms of material choice and maintenance - helps operators maximize the lifespan of caster rolls while maintaining production efficiency.