HSS Rolls are becoming popular choice in Steel Rolling Mills globally. HSS Rolls are successfully replacing other conventional rolls which are used in bar mills, structural mills and strip mills. Since the HSS Rolls have a longer product life the mills using these rolls vouch for lower roll costs per tonne, less mill down time in turn an increase in overall production.
Advantage of using HSS Rolls: Technical aspects
Chemical Properties: With the addition of certain chemicals like of Vanadium, chromium, tungsten, molybdenum, niobium etc. HSS rolls outer shell gets good thermal stability, high hardness under high temperature and excellent wear and tear resistance against hot material.
Centrifugal Casting: HSS rolls have a unique technology of centrifugal casting which ensures high hardness of the roll barrel surface and core being of less hardness which improves the bending strength of the rolls which is good for rolling strips and structure mills.
High Resistance to Temper Temperatures: Hardness of the ordinary rolls drops when temper temperature rises. On the other hand, HSS rolls hardness is always high even when the temper temperature is high. Due to this excellent feature HSS rolls has very high failure resistance.
Centrifugal Casting: HSS rolls have a unique technology of centrifugal casting which ensures high hardness of the roll barrel surface and core being of less hardness which improves the bending strength of the rolls which is good for rolling strips and structure mills.
High Resistance to Temper Temperatures: Hardness of the ordinary rolls drops when temper temperature rises. On the other hand, HSS rolls hardness is always high even when the temper temperature is high. Due to this excellent feature HSS rolls has very high failure resistance.
Bars made to Size: HSS rolls have high swelling factor and good thermal conductivity. Because of this the groove/pass sizes are more stable while rolling rebars and has better control of input material negative allowances. Thus bars are produced as per the size and specifications thus eliminating the chances of steel loss and ensuring correct product quality and standards.
Advantage of using HSS Rolls: Economical
As the wear and tear of these rolls is comparatively much less as compared to conventional rolls these rolls are capable of reducing the overall roll cost incurred per tonne of rolled steel. The following are the economical advantages of using HSS Rolls:
Lower Roll Cost per Tonne: It is estimated that the useful life of HSS rolls is almost 5-6 times more than that of conventional rolls. Meaning that over all cost of rolls consumed per tonne of finished steel produced is much less.
Increase in Production: Because of the longer product life of the HSS Rolls, the time required for repetitive changing of roll pass is considerably reduced. This regular change of roll pass consumes a lot of time and results in production loss. In addition to production loss, this also accounts for huge energy loss. In case of re-heating furnaces the heated billets/ ingots are forced to be soaked for a longer duration resulting in waste of energy and higher billet/ingot scaling losses. In case of hot charging designs the mill production team is forced to take the heated billet to the cooling bay, thus wasting thermal energy and making the entire system inefficient and cost extensive.
Zero wastage of raw material: Since the grooves/ passes of the HSS rolls have a greater resistance to wear and tear, the shapes of the grooves are stably maintained. Because of the high swelling factor of the HSS rolls with time the barrel swells in turn reducing the size of the worn out grooves. This is very helpful specially in the rolling of bars and re-bars as it give a better control of input material negative allowances.
Chemical Composition of HSS Rolls
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C
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Si
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Mn
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P
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S
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Ni
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Cr
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Mo
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W
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V
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1.50/2.20
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0.30/1.00
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0.40/1.20
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0.030
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0.025
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0.00/1.50
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3.00/8.00
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2.00/8.00
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0.50/8.00
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2.00/9.00
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