A brief history and overview
of Cryogenic Processing

See also:
Case studies
Cryogenic FAQ

Cold treatments or sub zero treatments have been around for quite some time. There is documented research from as far back as the 1930's where German companies used it on components of Jumbo aircraft engines. 

Cryogenic processing had its US origins in the 1940s, be it all a primitive process compared to today's procedures. 

Steel cutting tools were immersed in liquid nitrogen for a brief period of time, removed from the liquid, allowed to warm up, and placed into service on production lines. As a result of the thermal shock associated with the rapid rate of cooling, tools tools would occasionally crack or chip. Some tools also became brittle because of the newly formed, untempered martensite. Of the tools that survived this crude quenching, many exhibited dramatically enhanced service life.

Research shows reference to cryogenic treatment in magazine articles as far back as the 1950s in magazines like 'Tooling and Production'. The most notable and persistent pioneer of cryogenics was Dr. Randall Barron of Louisiana Technical University. Papers written by Dr Barron are widely cited in the cryogenics industry.

In addition to developing the correct medium, a method to reduce thermal shock had to be developed. Elimination of thermal shock is critical. This is achieved by strict controls in the lowering and raising of  temperature in the treatment cycle that is critical to the commercial application and effectiveness of cryogenic processing. 

Cryogenics is a relatively new process, but one that using correct proceedures can bring substantial economic benefits. 

Cryogen Industries makes a clear statement that process doesn't work on everything nor is it a miracle cure-all. If a product is found by us not to be worth treating due to poor manufacture or the item will yield little to no return for the customer, we won't treat it.

What does Cryogenics do ? 

There are many benefits including:

• Reduces abrasive and adhesive wear. Treated material typically yield two to three times the production of non-treated material
• Permanently changes the structure of the metal resulting in improved machining properties. Treated components may be ground after treatment and the benefits of treatment are retained. 
• Reduce the frequency and cost of tool remanufacture. Worn treated tools require less material removal to restore a uniform cutting edge. Furthermore treated tools may be reground more times before falling below the minimum acceptable dimensions.
• Substantially reduce machine downtime caused by tool replacement. 
• Improved surface finishing on material being manufactured with treated tooling. Treated tooling stays sharper and in tolerance longer that untreated. 
• Reduces likelihood of catastrophic tool failures due to stress fracture.
• Stress relieves to reduce inherit/residual stress caused by manufacture.
• Increases the overall durability of the treated product.

Cryogenic processing makes changes to the structure of materials being treated, dependent on the composition of the material it performs three things:

1. Turns retained austenite into martensite

2. Refines the carbide structure

3. Stress relieves

Cryogenic treatment of ferrous metals converts retained austenite to martensite and promotes the precipitation of very fine carbides.

Most heat treatments at best will leave somewhere between ten and twenty percent retained austenite in ferrous metals. Because austenite and martensite have different size crystal structures, there will be stresses built in to the crystal structure where the two co-exist. Cryogenic processing eliminates these stresses by converting the majority of the retained austenite to martensite. 

An important factor to keep in mind is that Cryogenic Processing is not a substitute for heat-treating if the product is poorly treated cryogenic treatment can't help it, also if the product is overheat during remanufacture or overstressed during use, you may destroy the temper of the steel which is developed during the heat treatment process rendering the cryogenic process useless by default. Cryogenic processing will not in itself harden metal like quenching and tempering. It is an additional treatment to heat-treating.

This transformation itself can cause a problem in poorly heat treated items that have too much retained austenite it may result in dimensional change and possible stress points in the product being treated. This is why Cryogen Industries will not treat poorly heat treated items.

The cryogenic metal treatment process also promotes the precipitation of small carbide particles in tool steels and suitable alloying metals. The fine carbides act as hard areas with a low coefficient of friction in the metal that greatly adds to the wear resistance of the metals. 

A Japanese study in the role of carbides in the wear resistance improvements of tool steel by cryogenic treatment; concluded the precipitation of fine carbides has more influence on the wear resistance increase than does the removal of the retained austenite.

The process also relieves residual stresses in metals and some forms of plastics, this has been proven by field studies conducted on product in high impact scenarios where stress fractures are evident.

Cryogenic Processing is not a coating, it changes the structure of the material being treated to the core and in reality works in synergy with coatings. As cryogenics is a once only treatment you will never wear off the process like a coating but you will be able to sharpen, dress, or modify your tooling without damaging the process.

Tool Failure - Another good reason to cryogenically treat

Tooling failures that can occur are abrasive and adhesive wear, chipping, deformation, galling, catastrophic failure and stress fracture.

Abrasive wear results from friction between the tool and the work material. Adhesive wear occurs when the action the of the tool being used exceeds the material’s ductile strength or the material is simple too hard to process. 

Adhesive wear causes the formation of micro cracks (stress fractures). These micro cracks eventually interconnect, or network, and form fragments that pull out. This “pullout” looks like excessive abrasive wear on cutting edges when actually they are stress facture failures. When fragments form, both abrasive and adhesive wear occurs because the fragments become wedged between the tool and the work piece, causing friction this can then lead to poor finish or at worst catastrophic tool failure.

Catastrophic tooling failures can cause thousands of dollars in machine damage and production loss. This type of tool failure can cause warping and stress fractures to tool heads and decks as well rotating and load bearing assemblies.

Cryogenically treating industrial tools reduces abrasive wear and tool failures.