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Benefits of Sub Zero Treatment
1. Life of Rolls Increases
2. Soft Spots are reduced
3. Wear resistance improves
4. Dimensional stability is achieved
5. Higher Hardness and more depth of hardening
6. Less Susceptible to surface cracks.
SUB ZERO TREATMENT
The structure of steel when heated to austenitic temperature( hardening
temp) and cooled rapidly (quenched) gets converted to martensite. The
formation of martensite gives wear resistance and increases the hardness of
steel. However , during quenching process complete transformation of
structure from austenite to martensite does not take place because of high
stability of austenite. This is especially for steels containing alloying
elements like Cr, Mo, W, V, Ni, Mn, etc. Hence some austenite remains in the
structure of steel after quenching. Presence of austenite reduces
dimensional stability of steel as well as wear resistance, Normally,
austenite tends to get transformed to martensite by tempering at 250 degree
Centigrade and above, depending composition of steel, but the process does
not result in complete transformation. To reduce quantity of retained
austenite sub zero treatment is given to steel. It increases life of work
rolls.
PROCESS :-
Rolls are hardened as per normal H.T. Cycle. Then after initial tempering
they re cooled to sub zero temperature i.e between – 70 degree centigrade /
80 degree centigrade. At this temperature retained austenite is transformed
to martensite. Rolls are held at this temperature got 6 to 8 hours. Finally
rolls go through tempering cycle to attain suitable hardness.
Due to stabilization of metal, stresses and strains are removed and better
life is obtained. OTHER ARTICLES
NON
DESTRUCTIVE TESTING OF COLD ROLLING MILL ROLLS
TUBE CUT OFF KNIVES
TIGHTER
MANUFACTURING TOLERANCE FOR ROTARY
CUTTER,
SLITTING KNIFE AND SPACER.
CRYOGENIC
TREATMENT
HINTS & TIPS ON THE APPLICATION OF
SLITTER TOOLING
GUIDELINES
FOR RAW MATERIAL SELECTION FOR SLITTING LINE TOOLING
SHEAR BLADES AND MACHINE KNIVES
PRECAUTION & ORDERING
TIPS FOR FRICTION SAWS
FINS AN IMPORTANT
COMPONENT OF TUBE MAKING
IMPORTANT FACTORS
IN COLD ROLLING MILL ROLLS
DEE TEE FORGES YET AHEAD IN SEARCH OF
EXCELLENCE
SLITTER TOOLING OVER ARM
SEPARATORS |
