HVHD thermal spray coating and a specialized laser cladded alloy
BASIC OXYGEN FURNACE (BOF) Hood Tube Protection
The failure of Basic Oxygen Furnace (BOF) hood tube is often a result of a combination of two main factors – thermal fatigue stress and slag accumulation, causing corrosion and erosion.
The BOF hood assembly aids to direct, cool and exhaust BOF gases from the furnace. The cyclic temperatures (due to fluctuations in BOF gas temperatures) results in a large variance in water temperature, causing thermal fatigue failure. This, coupled with potentially high corrosive gas species and erosive slag, perpetuates material fatigue resulting in premature tube failures.
Whertec’s offers two effective and long-lasting solutions:an HVHD thermal spray coating and a specialized laser cladded alloy, protecting the surface from corrosion and erosion. The cladded surface is further protected by Whertec’s proprietary corrosion resistant and high emissive sealant. Whertec’s technology provides surface protection to mitigate tube material loss from corrosion and erosion, and also helps to improve the cooling and heat transfer of the furnace gas through the hood duct.
During operation, slag from the furnace deposits onto the EAF hood assembly. As the deposit of slag increases, it impedes the heat transfer performance of the hood, resulting in decreased efficiency of the water-cooled hood assembly to reduce the furnace gas temperature. Furnace operators frequently remove the slag deposit from the hood by abrasive blasting. However,as foreign material enriches the furnace gas with chlorides, sulfates and other highly corrosive gaseous species, the hood tubes begin to experience premature failure due to pitting and deposit beneath the slag layer.
Through the use of Inconel overlay cladding technology, hood assemblies can be protected from the effects of corrosion.
Enhance your protection with Whertec: Through the Whertec process, a second corrosion-resistant and high emissivity barrier layer is applied to the overlay cladding to enhance the heat transfer efficiency of the hood. Through this process, corrosion protection is improved and the tenacity of the slag deposit is reduced.
In the steel forming process, rolls are used in several areas of production, including thetin mill line (TML), galvanizing line, continuous casting, and pinch rolls.
To extend the life of these rolls, weld overlay is applied by sub arc welding with martensitic grade 400 series stainless steel. Through this conventional method, high heat enters the process and dilution of the base material occurs in the range of 25 to 30 per cent. This dilution deteriorates the base material, and after subsequent reapplication, the base material reaches a point when it becomes no longer serviceable by welding.
Decrease dilution up to 30 per cent with Whertec: Through the Whertec approach, a low heat input LaserCladding process is used to protect the rolls. The laser beam welding process minimizes the dilution that occurs to less than 2%, significantly increasing the life of the rolls.
Optimized performance and cost savings with LaserCladding: As the LaserCladding surface is much smoother than sub arc welding — resulting in much quicker machining time — through the reapplication of Whertec’s LaserCladding, our customers can achieve tremendous performance and significant cost savings.
Specifically engineered for you:Unlike sub arc welding, LaserCladding also allows for specific alloy blends to be used. For example, Whertec has developed a proprietary martensitic 400 series powder that incorporates engineered alloying metallurgy to increase both the heat and wear resistance of our cladding process. Additionally, the flexibility of LaserCladding allows Whertec engineers to design specific alloy blends beyond what is currently available with sub arc welding wire.
Through design, the use of Tungsten Carbide, Hastelloy, Cobalt, Inconel and other alloying compounds may be incorporated to produce a custom-tailored alloy finish. This flexibility in design allows Whertec to create a surface cladding finish that can be engineered to the specific needs of our clients. Whertec’s LaserCladding approach optimizes performance, design life and the long-term cost of operating the roll.