Cold rolling

[ben1793]

Does cold rolling effect the crystal structure of a material?

 

 

[Enthalpy]

Yes!

 

It can change the grain size, make the grains elongated, define their orientation.

Laminated alloy products have different properties in the lamination direction. That's why the yield strength uses to be measured in the transverse direction.

Even when warm-rolled: transformer cores have one better magnetic axis because of lamination orientation; manufacturers often desire this effect.

 

It can change the crystal lattice. That's common with austenitic stainless steel. When little nickel (17%Cr+7%Ni) leaves the austenite metastable, cold rolling transforms it partially to martensite, which helps hardening and also makes the alloy magnetic, as can be observed on stainless screws. Where much nickel (18%Cr+12%Ni) stabilizes the austenite, very little transforms to martensite and the alloy stays nonmagnetic - but it does harden though needing more deformation, so martensitic transformation is NOT the whole picture.

 

Almost any alloy hardens by cold rolling though keeping its lattice, for instance Al-Mg alloys, unalloyed copper...

 

Very few metals keep soft despite deep deformation. Gold is the best known and can be squeezed to ultra-thin foils; very pure (ppm) aluminium hardens little.

Some alloys are designed to harden during cold draw: the mentioned 17-7, the old X120Mn12, all alloys for stainless springs...

Cold draw can be followed by heat treatment, often a precipitation hardening, like in Cu-Be2, stainless spring... 10mn in a kitchen oven at 200°C improves both the strength AND the toughness of cold-rolled 17-7, which I suppose isn't precipitation hardening.

 

The effect is more important with polymers. Only fibre stretching at production makes polymer yarn, fabrics, ropes resistant. Here it's directly an effect of molecule elongation and orientation.

[John Cuthber]

Does cold rolling effect the crystal structure of a material?

No, it affects it.

http://grammar.yourdictionary.com/style-and-usage/affect-effect-grammar.html