Heat treatment is the controlled heating and cooling of steel in its solid state to set qualities such as hardness, strength and ductility. Buck says heat and subsequent cooling change "the physical and structural properties (but not the chemical composition)" of a solid metal. Steelmakers publish the sequence as hardening, quenching and tempering, and state the result as a hardness range.
Alleima publishes these steps for its own knife steels; they are a steelmaker's program, not a home forge method.
Where a freezing step goes depends on the maker. Alleima's 14C28N datasheet says deep freezing raises hardness by about 1 to 2 HRC. Crucible's S30V sheet says a freezing treatment "may be used between the first and second tempers", its MagnaCut sheet says a cold treatment "may be used after the quench", and Buck tempers its blades "through a heating, freezing and reheating system".
Alleima's 14C28N piece-hardening program lists 59, 57 and 55 HRC after 2 hours of tempering at 175, 225 and 350°C. The tempering temperature a knife maker picks moves the result along that list, and Alleima publishes a recommended range for 14C28N, 55 to 62 HRC, rather than one figure. Crucible's S30V and MagnaCut sheets call their values typical: "Normal variations in chemistry, size and heat treat conditions may cause deviations from these values."
A steel name on a listing tells you whose published program and hardness range apply to the alloy, not which temper the knife maker chose. Each product page's spec table lists what the product data for that knife states; Knives Now does not test heat treatment, and the Steel Lab works from published datasheets and independent references.