TPT January 2013

Article

control temperature in serial was invented and it can achieve high grade shaped of complex roll shape. Based on various working condition, technical requirement and material type the heat treatment process was determined. Because of no ready production lines for working high chromium alloy roll to copy and imported, so all production processes included machining process and technical equipment must be designed by ourselves, specially to solve many problems on machining high precision hole curve of steel pipe roll, machining high hardness material, etc. The compared main process chart of new alloy roll with that of similar product made at home and abroad is as shown below. Because of developing success in the way of roll material and preparation method the process replaced forging by casting is achieved for producing straightening steel pipe roll, HFW/ ERW welding pipe roll and cold roll formed steel roll. 3.3 The compared effect of saving material and saving energy of new roll preparation method with that of traditional forging steel roll Through some examples to explain. According to fairly good process level included melting used of intermediate frequency furnace, forging, heat treatment and machining, to account the power consumption of every ton steel and to change into standard coal consumption from energy consumption of generation power at home at the present for finished roll of per ton in the example. 3.3.1 Straightening steel pipe roll and welding pipe roll with shallow hole shape The world’s biggest roll for straightening steel pipe mill as example, the finished roll weight is 4.584 ton. 3.3.1.1 The accounting result of comprehensive energy consumption of forging roll production process of similar products at home and abroad Total comprehensive energy consumption of every ton of finished product is 2.595 ton standard coal and the utilisation coefficient of material is 54.1 per cent.

The distribution of Mo element in each phase of high chromium alloy is about 50 per cent into Mo 2 C, about 25 per cent into M 7 C 3 carbide, it can be to enhance hardness and wear resistance. About 23 per cent of Mo element is into matrix to enhance quenching degree of material. W atom and C atom have strengthening combining force and they can enhance the stableness of high temperature resolution of material, so that red hardness is enhanced. When quenching in high temperature the part of W carbide is melted into matrix, the quenching degree is increased. Ni element can strengthen matrix and improve comprehensive property of material and can increase quenching degree. B element into matrix can enhance microstructure hardness and impacting toughness of the matrix, strengthen supporting action of carbide to matrix, so that the wear resistance is increased of the material. Ti and N elements can be fine eutectic structure and to form stable Tic unclear. After adding N carbon-nitrogen compound with high melt point can enhance the heat property. Adding Nb element can deposit out Nb particle, that is rigid phase, with high hardness (2,000Hv), high melt point, regular shape, small grain and even distribution, and it can effectively control the solidified deviation of alloy, so that to enhance comprehensive property and save Ni or Cr elements. Adding special complex modification agent can effectively improve and fine M 7 C 3 carbide changed strip shape distribution into block and spherical shape distribution, enhance the evenness of distribution, so that the strength and impacting toughness are increased, and another, it can bear a action to decrease adding number of Ni, Mo and Cu elements. Through a lot of testing and comprehensive various factors the new high chromium alloy material with high quality and extensive utilisation was designed. Pointing to some problems of complex roll shape, more product size, small production batch and poor pour property, etc, the new solidified casting process with intelligence

Main process chart A of new roll manufacture:

material

→

melting

→

casting

→

block

→

tempering

→

roughing

→

finishing

Main process chart B of new roll manufacture:

quenching and tempering

material

melting

casting

block

annealing

roughing

finishing

→

→

→

→

→

→

→

Main process chart of forging roll manufacture of similar product at home and abroad:

quenching and tempering

→

→

→

→

roll block annealing roughing → →

→

→

material

melting

billet

forging

finishing

100

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January 2013