1. A non oxidizing (nitrogen protected) roller bottom heat treatment furnace (normalizing furnace) heated by radiation tubes is used. After a period of use, the furnace rollers and bottom rollers may form nodules. The direct harm of nodules is the formation of pits on thicker steel plates, which affects surface quality. As shown in the figure below, please talk about effective measures to prevent nodules on the bottom rollers and the treatment methods after nodules.
2. The cast material has inherent deficiencies in tissue density such as pores and sand holes Pulling is the process of using hot-rolled bar material, which undergoes multiple processes such as perforation and tube pulling. In terms of uniformity and density of composition, it is better than casting, and the price alone is much higher. Without considering the brand, there is a significant difference between the furnace and the price. It all sounds like the same material. The lifespan is much better when pulled out.
3. Generally, there are nodules on the surface of the furnace rollers and bottom rollers in the atmosphere protection roller bottom furnace, which is a difficult problem to solve. I consulted Mr. Han Hengji, the president of SAC, and Mr. LOI Su. They believe that nodules on medium and thick plates in the roller bottom furnace are mainly caused by surface impurities such as oxide scales coming into contact with the roller conveyor at high temperatures, and once nodules occur, they will scratch the workpiece and exacerbate the nodules. The solution is to add a shot blasting unit in front of the furnace, remove oxide scale by shot blasting, and wash away impurities such as steel shot. Even with the addition of shot blasting units, it cannot be guaranteed that there will be no nodules at all. Regular inspections are necessary!
However, foreign experts say that it is better not to machine the outer surface of the roller using centrifugal casting, which can maintain a dense structure and have weaker adsorption force on iron oxide scale or other impurities at high temperatures. Nevertheless, the inner surface has been machined with an accuracy of 12.5, effectively ensuring the uniformity of the roller wall thickness.