Very high cooling rates leads to distortion and cracking in components. I am trying to understand the advantages of very high cooling rate in steels. Can anyone please help me in finding a suitable application where we use high cooling rate of magnitude 2000K/s approx is used in the field of metallic materials ? I am finding difficult to find such applications.
in industrial steel production you will hardly find cooling rates higher than 50 dg/s. It is because of real metal thickness and impossibility to apply cooling so accelerated as in specialized LAB conditions. As to advantages (within the indicated range), the faster cooling the stronger transformed structure (ferrite->bainite->martensite), depending on chem composition of course.
Thank You Mr. Zisman, In quenching dilatometer the cooling rate is 2500 k/s and I am questioning myself the purpose of this specification in steel application. The manufacturers are also not able to state an application. Is these cooling rates used for Research work, can you pl share your opinion ?
Among possible transformations in cooling, the martensitic temperature range THEORETICALLY depends only on chemical composition, however to find this range you should get sure that further accelerating cooling no more changes the transformation range. this case higher rates (hundreds deg/s) are helpful. ANOTHER possible application of ultimate cooling rates is simulation of phase transition near a weld joint. Particularly for laser or electron welding.
Dear Ajeet Babu Kumar,
In the case of steel, I have no more idea than Zisman has. However, broadly speaking, in the field of metallic materials, I can take the example of amorphous solids or non-crystalline solids. The most important factor in producing these materials is to cool them at a sufficiently rapid rate. This rate for many metals can be as high as 10E+6 C/s. Here I provide a link which may be useful for you, if you interest in amorphous solids.
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.384.2775&rep=rep1&type=pdf
The only application that I know is the manufacture of metallic glasses.
If you want you can contact with this group: http://www.fi.uba.ar/es/node/701
I attach an image that give an idea from the process.
Dears!
Quenching dilatometer is utilized to study solid state transformations, that's why rapid solidification is out of table during this discussion. But still amorphous metals are extremely interesting research field.
I am fully agree with A. A. Zisman that high cooling rates are present near the welding pool during its solidification. Thus it is possible to obtain strain data for the welded pars being cooled with such rates using your equipment.
Named cooling rate is also might be useful in low-hardenability steel studies. Such steels are used in Russia, Canada (and, of course, other countries), for example, for leaf spring production. By the way, low-hardenability steels can be utilized for producing a number of automotive parts.
But still I am not sure, that it is possible to apply by means of a dilatometer a constant cooling rate of 2500 K/s on a standard steel sample (D=10 mm, L=3 mm) from 900 to 300 C using helium or other gas coolant. May be hollow samples or spray cooling is used in the equipment. In case of hollow samples you face a problem of hardness measurements and steel decarburization.
For a somewhat related discussion at this forum, see ─ «Critical cooling rate and critical thickness to describe the glass forming ability (GFA)?»: https://www.researchgate.net/post/Critical_cooling_rate_and_critical_thickness_to_describe_the_glass_forming_ability_GFA
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