Melting and Forging
The alloy ingot for the blank of the forged steel rolls is usually melted by electric arc furnace. Through the oxidization, restoration and adjustment to the ingredients of the steel liquid, slagging reaction and slagging-off will reduce the content of harmful elements, thus to get qualified steel liquid. The demoulded steel ingot can go to next step after its surface is finished and cleaned.
The qualified steel ingot is pressed to the roll blank by the hydraulic forging machine after pre-heating, heating and even heating. The purpose of forging and pressing process is: the forging and pressing can reduce and compress the porosity, shrinkage and some pore; improve the macroscopic segregation (pattern segregation, V shape segregation) in the original structure of the steel ingot; shatter the gross liquation carbide and net carbide; crush and refine the gross grain. In order to acquire the optimized feature of the roll, we strictly control the forging ratio , not less than 3 for work rolls while more than 2.5 for large size backup rolls.
1. Using ladle furnace and vacuum degas to control material composition and gas content to guarantee anti-fatigue lifetime.
2. Advanced forging machine controls the forging ratio to guarantee density of materials and keep material a high strength. We keep the forging ratio above 3 for work rolls/intermediate rolls and above 2.5 for back-up rolls.
Pic.1 Electric Arc Furnace