With thank's to "Alvin the librarian", without who's help this page would never have happened.

Annealing
Annealing is used to soften steel, relieve stresses and refine grain. For a plain carbon steel with a carbon content between 0.50 to 1.00 percent the annealing temperature is between 790C and 815C.
Annealing temperature is usually 20 to 30 degrees above critical (Ac3) for a steel with less than 0.85 percent carbon. Followed by a slow cool down in an insulator such as Vermiculite or Wood Ash.

Soak times can generally be taken as one hour per inch of thickness. For example 15 minutes would be about right for a quarter inch thick blade.

Arrest points are points on the heating or cooling curve of a material (iron) at which a property change occurs in the material. For this reason they can also be referred to as critical or transformation points. The symbology for these points is french, Ar stands for arret refroidissement (cooling) and Ac stands for arret chauffage (heating), therefore Ar refers to points on the cooling curve while Ac refers to points on the heating curve. Ac points are usually 10 to 30 degrees higher than their corresponding Ar points.
There are 4 arrest points in Iron or Steel. These points are accompanied by a change (arrest) in the rate of heat absorbtion or heat loss at certain temperatures. The material uses or loses heat to transform from one allotropic form to another. This changes the rate at which the steel heats or cools and effects a change in the temperature gradient.
Transformations require time so by rapidly cooling a piece of steel through the transformation zone, from a temperature above Ar3 it is possible to eliminate the transformation that would normally occur and the iron or steel will acquire the desired conditio,(hardness) at room temperature. A key indicator that the steel is above Ar3, or Ac3 for that matter, is that it is non-magnetic so knifemakers will frequently use a magnet to judge if it is below, at, or above this arrest point. .

Arrest points in iron during a temperature drop.
1. Ar4 1403C
2. Ar3 906C
3. Ar2 768C
4. Ar1

Arrest points in iron during a temperature rise.
1. Ac4 1415C
2. Ac3 915-935C
3. Ac2 768C
4. Ac1

Duration of the vapor film in seconds vs. bath temperature in F.

A +40F change in plain water temerature increases the vapor film duration by twice, while a +20F change can do the same with 24% brine.

Severity of quench is 1.0 for still water.

Temperature as it relates to color.

	0390F Faint Straw 0199C 0445F Light Straw 0229C 0465F Dark Straw 0240C 0480F Brown 0248C 0500F Brown/Purple 0260C 0520F Purple 0271C 0540F Dark Purple 0282C 0575F Blue 0301C 0800F Dark grey 0427C 1000F Very slight red, mostly grey 0538C 1100F Slight red 0593C 1200F Dull red 0649C 1300F Medium red 0704C 1400F Red 0760C 1500F Bright red 0816C 1600F Orange red 0871C 1700F Orange 0927C 1800F Orange yellow 0982C 1900F Dark yellow 1038C 2000F Bright yellow 1093C

---

To use temperature converter enter a value on the left side.

Press the center button and viola, your value is converted