Heat Treating Silver Steel

heating silver steel with blow torch

This article is all about heat treating silver steel. There are many different types of steel, silver steel a really useful material for the hobbyist if you learn about heat treating it.

heating silver steel to a cherry red

Heat uniformly to 770-780°C until heated through. Quench in water. Sizes up to 8mm or 5/16” dia may be oil hardened from 800-810°C.

In this particular instance I’m hardening a piece of silver steel that is to be used as a rivet punch. Hence it has a concave dome machined into one end.

I’m hardening just the end that fits over the rivet.

The colour of the steel can be used as a rough guide to it’s temperature and the table below gives that relationship.

Colour Temperatures

The colour of a piece of steel may be used as a guide to it’s temperature. These are particularly useful when hardening or tempering steel.

Colour°C
Pale yellow221
Straw230
Golden yellow243
Brown254
Brown to purple266
Purple277
Bright blue288
Blue293
Dark blue316
Just visible red500 to 600
Dull cherry red700 to 750
Cherry red750 to 825
Bright cherry red825 to 875
Brightest red900 to 950
Orange950 to 1000
Light orange1000 to 1050
Lemon1100 to 1200
White1200 to 1300
Note: These should only be used as a guide.

Quenching

The difference in quenching media determines how fast the steel is cooled, with water cooling the fastest and air cooling the slowest.

quenching silver steel in water

Tempering

From the first quench from “cherry red” the steel is very hard. It is so hard that it can not be used as a tool without breaking. It is too brittle.

When you temper, you are taking a piece of steel that is as hard as glass from the first quench, and making it just a little softer. This redeuces the brittleness and makes it tougher.

heating silver steel in a blow torch

After quenching, heat the part back to around 100°C to 150°C. I’ve done this again in a blow torch, but it is better if this temperature and time is better controlled. As the temperature is within the range of a conventional household oven it is possible to anneal it at 150°C for 30 minutes.

The higher the temperature the lower the final hardness, but also the less brittle it will be.

Further Notes:

Silver steel bar is supplied annealed.

When hardening consideration should be given to heat treatment temperatures, including rate of heating, cooling and soak times. Note that soak times will vary due to a number of factors such as the shape and size of each silver steel component.

Other considerations during the heat treatment process include the type of furnace, quenching medium and the work piece transfer facilities. 

About Nigel 278 Articles
Have been making models since I was around 7 years old and using a lathe from the age of 11, a self taught engineer with a passion for making model engines.

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