What does this ADS entry mean “zerolling”?

I was looking up how to say “below zero” temperatures and this associated entry caught my eye:零下温度压延加工

But the definition (in the ADS dictionary) merely says:
noun. zerolling

A Google search showed nothing but ice cream scoops by a company called “Zeroll”

Does “zerolling” mean anything to anybody?
I got a couple of relevant hits when I google the term.

Effect of Zerolling on Properties of Modified Type 347 Stainless Steel
...showed that working stainless steels at subzero temperatures resulted in greatly increased tensile strengths. If these “zerolled” stainless steels are heated to temperatures up to 800 F, additional strengthening takes place.


Cryoforming or Zerolling:
It is a slight variation of isoforming in which for example, the metastable austenitic stainless steels such as AISI 301 and 304 are deformed at low temperatures, where some martensite forms during the straining. Due to the formation of some martensite, the plastic deformation of which also occurs alongwith austenite, high rate of work hardening takes place. The yield strength, tensile strength and hardness increase. It is one of the important methods of strengthening austenitic stainless steels (18/8) as well as semi-austenitic precipitation hardenable steels to a tensile strength of over 1550 MPa. It is more effective process for stainless steels than ausforming.

In steels, whose Ms temperature is raised by cold working and may become higher than the cold working temperature, some metastable austenite transforms to martensite Thus, the steels are austenitised, and quenched to sub-zero temperatures, where, then cold working is done.

As Ms temperature is raised by plastic deformation, the amount of martensite formed depends on the extent Ms is raised higher than the deformation temperature. Cold working is done at sub-zero temperatures as it has to be below the Md temperature of the steel as well as the amount of martensite formed depends on the difference between Ms-deformation temperature. If it is too low, austenite may completely transform to martensite during initial stages of rolling.

That is why it is called zerolling (rolling at 0°C). A crying sound is heard when rolling is done at these temperatures due to deformation and transformation occurring simultaneously.

At any given deformation temperature, the yield and tensile strengths increase rapidly with the amount of cold reduction, but the ductility decreases; more significant increase in tensile strength occurs at lower temperatures of deformation. At a constant strength, the ductility is higher at lower deformation temperature.

In zerolling, due to increasing amount of martensite formed, heavy amount of cold working has to be done to achieve high strength. Thus, such high strength steels can be obtained only in the form of strips and require very hard rolls.

The strength obtained by cold rolling of such steels is due to the combined effects of the following factors:

1. Strain hardening of retained austenite which achieves around 80% of the strength.

2. The amount of martensite in structure.

3. The strain hardening of martensite.

Zerolling invariably retains some austenite untransformed, which may transform later on during service causing brittleness as well as stresses in the steels.
Likes: JD
A ha! Thank you for that.....I had made no connection to material science, and the “read the characters one by one” method failed me too.