1. Utilizing a radiation tube-heated, oxide-free (nitrogen-protected) roller bottom heat treatment furnace (normalizing furnace), after a period of use, the furnace roller and bottom roller develop scale. The direct harm of this scale is to cause pitting on thicker steel plates, thereby affecting surface quality, as shown in the following image. Please discuss effective preventive measures against roller bottom scale formation and the methods for dealing with it after the scale has formed.

2. Castings inherently have defects like pores and sand holes in their tissue density. Extrusion involves hot-rolled billets that are pierced and drawn through multiple processes. In terms of component uniformity and density, extrusion surpasses casting, and the price is significantly higher, even without considering brand. This is why there is a vast difference in prices between different furnaces. It's all the same material, yet the service life of extruded products is much better.

3. Typically, protective atmosphere roller hearth furnaces suffer from the issue of scale formation on the roller and hearth surfaces, which is a difficult problem to resolve. I consulted Mr. Han Hengji, President of SAC, and Mr. LOI of LOI, who believe that the scaling of medium and thick plates in roller hearth furnaces is primarily caused by surface impurities such as oxide skins contacting the roller under high temperatures, and once scaling occurs, it can scratch the workpiece, exacerbating the scaling. The solution lies in adding shot blasting units at the furnace front, using shot blasting to remove oxide skins, and washing away steel shots and other impurities. Even with the addition of shot blasting units, it cannot be guaranteed that scaling will be completely avoided; regular inspections are necessary!

However, the foreign expert stated that it is better not to machine the outer surface of the roller cast by centrifugal casting, as it maintains a dense tissue. In high temperatures, it has a weaker attraction for iron oxide scale or other impurities. Nevertheless, the inner surface has been mechanically machined to an accuracy of 12.5, effectively ensuring the uniformity of the roller's wall thickness.