TPT January 2013

102 / 108

100 January 2013
Article
The distribution of Mo element in each phase of high chromium
alloy is about 50 per cent into Mo2C, about 25 per cent into M7C3
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 M7C3 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
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.
material melting billet forging roll block annealing roughing
quenching
and
tempering
finishing
material melting casting block annealing roughing
quenching
and
tempering
finishing →
→ → → → → → → →
→ → → → → →
material melting casting block tempering roughing finishing → → → → → →
Main process chart A of new roll manufacture:
Main process chart B of new roll manufacture:
Main process chart of forging roll manufacture of similar product at home and abroad: