The 3D Thermo-mechanical Couple Simulation In Bar Hot Rolling Ad The Develop Of High Boron HSS Compound Sleeve Rolls

Milling roll is one of the major expenditure for steel makers, the cost of rolls in rolling process is about 5 to 15 percent of the total production cost. And it has been the major obstacle to productivity, quality and cost since the dawn of iron age. In marketing terms, the indefinite chill cast iron work roll is the main products which has been developed in the 1930s in America. The whole roll is rejected when the worklayer is finished. If we choose the sleeve rolls, about 60 percent of the roll could reused and the ring can make a better performance through materials choosing and heat treatment. Thus, steelmakers throughout the world can find a new way to achieve higher production outputs of higher quality products while holding down costs. For decades the engneers of roll shop and rolling mills have investigated this task. A major obstacle to this quest has been the security and materials.In this paper, with the steel bar hot rolling process and the rolls as the researching object, the basic laws of the temperature evolement and plastic rheology of the bar, the temperature evolvement and thermal expand of the milling rolls are systematically researched, the effects of alloy elements on the high-speed steel rolls materials are analyzed, and a sort of milling ring material possessing higher wear resistance, higher strength, higher toughness and higher thermal edurance and its bi-metal composite casting process is developed. Based on these, a new collar for bar hot rolling is developed. It is proved by the use of factory that the usage life of this assembled high-speed steel composite roller is higher.The research mainly includes the following parts:Firstly, the 3-dimensional thermo-mechanical couple elsto-plastic larger deformation finite elements model for bar hot rolling process, and the boundary conditions for heat transfer and mechanical are established, the iterative arithmetic, the flow for analysis by MARC and its convergent criterion are proposed, so the theory basis for 3-dimension simulating of the bar hot rolling process is established. Secondly, the 3-dimensional thermo-mechanical couple elsto-plastic finite elements simulateion for the finished stand of bar hot rolling process are accomplised, the problems of geometry nonlinear, materials nonlinear and the boundary nonlinear are considered in the simulation. The contact heat transfer beween the bar and the roller is considered to be a function of rolling pressure, the yielding strength of bar, the conductivity of bar and roller, the surface morphologies, the evolvment of temperature field and stress field are obtained. And the result can direct the structure design and analysising of compound sleeve rolls.Thirdly, the assembly interference of assembled roller is obtained by experience, and the heat equivalent methods to simulate the temperature field and stress field of the core and sleeve of the roller in the bar hot rolling process is proposed; the heat transfer equation, the model for thermal stress analyzing and its boundary conditions are established, the sta(?)ilize distribution of temperature is obtained. Through the calculating of thermal expandance, contact stress and equivalent stress of roller in the process of bar hot rolling, the feasibility for the interference assembly project to assembled roller is demonstrated, and then the contact stress and equivalent strss under the different diameter of roller core are compared, the appropriate core diameter is obtained. The security of compound sleeve rolls in rolling process is demonstrated.Fourthly, via the analysis of invalidation and materials of rolls, the idea of materials design was put forward. Rolls could have better performance through improve heat transmition and hot hardness of the roll material. The conception of "HIGH BORON HSS" is first put forward which combine the matrix of HSS and boride. The effects of the alloy elements on the high-steel roll materials is analyzed, a sort of composite roll material with excellent synthesize performance such as higher toughness, higher wear resistance and higher thermal cracking resistance is developed, the physical and mechanics performance of this kinds of material is tested, the inlayed-cast process is developed, and the microsturcture of this bimetallic sleeve is analyzed by microscope. Based on above researches, a kind of high boron HSS compound sleeve roll is manufactured.The study done in this paper can provide reference for the the control of roll casting technics, design of bar hot roll-caster, and the exploiture of rolls for bar hot rolling, this assembled high-speed steel composite rolls possess tremendous application foreground and important meaning to improve the economical benefit for the bar rolling industrials.