Cryogenic treatment is an extension of the heating / quenching/ tempering cycle i.e. Conventional metallurgical practice.

 

a) 20 Hi Mill Rolls

b)Slitting Cutters

c) Tube Mill Rolls

It involves lowering of the temperature of the material of the material with the help of liquid nitrogen to -320 Degree Farenheight in a patented deep cryogenic treatment system controlled by a highly sophisticated microprocessor. This highly controlled thermal; cycle eliminates any possibility of thermal shocks. The tool life is substantially enhanced by 3 known mechanisms.

a) Cryogenic is the only known process where in a short period of 50-70 Hrs. There is a conversion of significant amount of retained Austanite to martensite which is the desirable molecular structure for dimensional stability to the material.
b) By cooling the material to about -320 degree farenheight and bringing it back to room temperature the material goes through a tempering process leading to formation of fine nitrogen carbides (ETA carbides) which enhances the wear resistance of the material.
c) Cryogenic treatment causes relief of residual stresses i.e., the removal of stress concentrators which prevent fractures and raises the fracture resistance and hence wear resistance of the material.

Cryogenic treatment can be applied to all known tools material to increase wear resistance. DEE TEE recommends that cryo be carried out post heat treatment before final finishing. Any increase of hardness is for the optimum benefit in the working of the tool material and will not make the tool brittle. It works equally well on coated tools.

1) Retained Austenite :

Austenite is a softer grain structure a part of it is always present after heat treatment. So after the steels are quenched from austenitising temperature( Hardening Temperature) a position of austenite always remains untransformed nd is referred as retained austenite. Higher the carbon content in steel higher is the content of austenite retained after quenching. By applying cryogenic treatment, retained austenite is transformed into the harder, more durable grain structure-martensite. The range of retained austenite in a material after heat treatment maybe as high as 50% or as low as 3% of the retained austenite is converted martensite. As greater amount of R.A is transformed, and wear resistant martensite is increased, the material.

2) Fine Carbide Precipitation :
Fine eta (n) carbide precipitates are formed during the cryogenic treatment. These are in addition to the larger carbide particles present before cryogenic treatment. These fine precipitates or fillers along with the larger particles, form A denser, more coherent and much tougher matrix in material.

Benefits of cryogenic treatment process :
 

• Cryogenically treated material shows a marked increase in wear resistance.

• While regrinding, less stock is removed from Cryo treated tools resulting in longer tool life.

• The most significant change is increased toughness.

• The process is also used extensively to relieve residual stresses

• The Cryo treated material becomes less brittle.
   

It has been observed at DEE TEE that the hardness of Cryo treated tools increase by 1-1.5 HRC after cryogenic treatment. DEE TEE recommends tempering after Cryo

Almost any kind of tool steel or dynamic part, for whatever application, will exhibit some kind of life increase. As less tools are needed there is substantial saving in consumption. Additional saving includes less downtime and less maintenance and changeover time, which brings production cost lower. Different material show following improvement in tool life, in term of wear resistence.


Change of entire structure : unlike surface treatments such as plating and carburizing, Cryo affects the entire structure of the part. A tool is not affected by subsequent grinding or sharpening. Only one treatment is necessary for the life of the tool. With the inner structure being stronger, wear is again reduced as the surface has more support behind it.



Denser Microstructure : Since the molecules pack together tighter, the surface is more even, the result is a larger contact area at the surface, reducing friction, heat and wear. The two samples above show this difference in material density. The treated sample on the right has a much finer and denser microstructure.

OTHER ARTICLES

NON DESTRUCTIVE TESTING OF COLD ROLLING MILL ROLLS
SUB ZERO TREATMENT (Reduction in Retained Austenite)
TUBE CUT OFF KNIVES
TIGHTER MANUFACTURING TOLERANCE FOR ROTARY
CUTTER, SLITTING KNIFE AND SPACER.
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