Tungsten carbide roll and roll consumption calculation

 Rolls made by powder metallurgy with tungsten carbide and cobalt as raw materials were born with the development of the metal processing industry after the advent of powder metallurgy technology in 1909. As the finishing mill works under high speed and high stress, cast iron rolls and tool steel rolling rolls

(Poor wear resistance, short groove life, frequent repairs and loading and unloading, affecting efficiency, and no longer suitable for finishing rolling production requirements) has been replaced by combined tungsten carbide rolls.

Main ingredients

Tungsten carbide rolls of different compositions correspond to different working conditions, and even the composition of rolls of different stands in the same finishing mill is different. The rolls for high-speed wire rod mills are mainly tungsten carbide rolls with cobalt as the binder. A few continuous casting and rolling mills also use Co-Ni-Cr tungsten carbide rolls as binders due to poor water quality, and the cost is also low. The metallographic structure is composed of the matrix phase WC and the binder phase Co. The hardness of the carbide roll increases with the increase of the WC content; while the toughness increases with the increase of the binder phase content.

Product performance

Tungsten carbide rolls have high hardness and are less affected by temperature. The hardness at 700°C is 4 times that of high-speed steel; and the modulus of elasticity, compressive strength, bending strength, and thermal conductivity are also more than one time higher than tool steel. Tungsten carbide rolls have much better wear resistance and deformation resistance than tool steel rolls in the working process, thereby ensuring the smoothness and dimensional constancy of the roll grooves, which is essential to ensure the surface quality and dimensional accuracy of the wire rod. Important. Due to the high thermal conductivity of the tungsten carbide roll, the heat dissipation effect is good, and the time that the roll surface is at a high temperature is relatively short, so that the high temperature reaction time of the roll and the harmful impurities in the cooling water is relatively short. Therefore, tungsten carbide rolls are more resistant to corrosion and thermal fatigue than tool steel rolls.

Production method

Tungsten carbide rolls are produced by powder metallurgy using tungsten carbide powder and cobalt powder (a small amount of other hard phases or alloying elements can also be added) as raw materials. The above two powders were wet-milled and mixed with a ball mill. After the materials are uniformly mixed, they are dried and sieved to become the intermediate product-cemented carbide mixture. The mixture is pressed and sintered to become a roll blank. The roll blank is polished or re-grooved to become a production roll.

Quality standards and influencing factors

The quality standards of tungsten carbide rolls include: material porosity, WC grain size, total carbon and free carbon content, density, hardness, magnetic saturation strength, coercive force, bending strength, impurity content, etc. In addition, there are also the processing accuracy and surface roughness of the roll. The level of each index reflects the quality of the roll and indicates its performance. The factors that affect the quality of the roll include: the dispersion, particle size and particle size distribution of WC powder and Co powder in the mixture, total carbon, free carbon, oxygen, iron content, etc.; the type and quantity of rubber used for pressing, the temperature and time of degumming , Sintering temperature, time and atmosphere, etc. In addition, the precision of the grinding machine for processing the roll and the quality of the diamond grinding wheel all affect the quality of the roll. Gangde Company passed the ISO9001 international quality assurance system certification in 2009, providing customers with high-quality and stable cemented carbide products.

Prospects

Tungsten carbide rolls have been used in various fields of metal plastic processing. Tungsten carbide rolls are used from non-ferrous metals to steel, from hot-rolled wire rods and pipes to cold-rolled foil strips and rebar. General manufacturers can only produce tungsten carbide rolls from φ8 to φ300mm(Gangde’s characteristic products are all kinds of ultra-thin, ultra-thick, ultra-long, ultra-wide cemented carbide products, and the maximum diameter of tungsten carbide rolls can reach φ400mm).

With the high speed of wire finishing, people are exploring ways to improve the hardness and strength of tungsten carbide rolls. This is mainly to add a small amount of TaC, NbC, Ni, Cr, Mo and other elements to the tungsten carbide roll; and through hot isostatic pressing, vacuum sintering-low pressure hot isostatic pressing, heat treatment and other means to produce better quality rolls.

1. The unit consumption of the roll

The unit consumption of the roll depends on the number of re-turns of the roll and the amount of metal rolled per re-turn, which can be calculated according to the following formula:

△W=∑m*W/(n+1)/T

△W: unit consumption of rolls (kg/t) m: the number of rolls in a set of each rolling mill

W: the weight of each roll (kg, the weight of the new roll after finishing) n: the number of re-turns of the roll

T: The amount of metal rolled once per heavy car (t)

2. Roll consumption of various rolling mills (kg/t)

Name of mill or roll	main products	Roll material	Unit consumption
Blooming mill	Billet	Forged steel	0．10～0．12
Rail and beam rolling mill	Rails, steel beams	Forged steel, cast steel	2．4～3．0
Large rolling mill	Square, round, profile	Forged steel, ductile iron	3．5～4．0
Medium Rolling Mill	Square, round, profile	Cast steel, ductile iron	3．0～4．0
Small rolling mill	Small wood	Cast steel, chilled cast iron	1．0～2．5
Wire rod mill	Wire rod	Cast steel, chilled cast iron, tungsten carbide	1．5～2．0
Thick plate rolling mill	Thick plate	Cast steel, forged steel, chilled cast iron	2．0～2．5
140 seamless unit	Seamless pipe	Forged steel, ductile iron	1．0～1．4
76 seamless unit	Seamless pipe	Forged steel, ductile iron	1．0～1．4
Semi-continuous steel plate rolling mill	Hot rolled plate	Forged cast steel, ductile cast iron	2．5～3．0
1700 cold rolling work roll	Cold rolled sheet	Forged steel	1．4～1．5
1700 cold rolling backup roll	Cold rolled sheet	Forged steel	0.4
1200 cold rolling work roll	Cold rolled sheet	Forged steel	2.5
1200 cold rolling backup roll	Cold rolled sheet	Forged steel	1.2
1700 Hot Continuous Rolling Steel Plate Mill	Coil	Forged steel	0.89