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CSM Saw Steel

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CSM Saw Steel

The steel in a saw blank must be high quality, machined, heat-treated and handled properly.

There are two grades of steel most generally used in plates. These are plain carbon steel and nickel alloy steel.

Plain carbon steel is difficult to heat-treat properly and consistently. Nickel steel is easier to handle and gives good results.

Steel is generally known as Iron or Ferrite, and iron carbide compound known as Cementite. The two mixed make Pearlite. In annealed, or soft steel, these elements are separated in layers. When the steel is heated above its critical point, the elements merge with each other and form Austenite. If cooled slowly it will return to its original state. When the steel is cooled rapidly another transformation takes place changing the Austenite to Martensite and making the material hard and brittle, depending on its carbon content.

These changes are critical and affect the steel adversely if not done properly.

After rapidly cooling the steel, it is then necessary to temper it to reduce the brittleness and make it more uniform in structure and softer, but tougher.

Carbide saw blanks are tempered to approximately 40 to 42 Rockwell C. The Rockwell C scale is a standard test to determine the relative hardness of various steels.

The reason for discussing saw steel is to impress upon you the necessity of handling it with care. Many saws are ruined by faulty gumming and brazing techniques. If the steel turns blue when grinding, it changes its structure and causes a stress area. Steel begins its first transformation around 1400 F which is the first real critical temperature.

Silver solder melts at around 1300 F and thus it is very difficult to control the brazing temperature below the critical change in the steel structure.

If the brazing is performed too rapidly, the steel will change its structure directly behind the tooth or below it. This will create a very hard chill line because the cold plate cools the steel rapidly right where the steel change is taking place.

When the brazing is done more slowly the heat has a chance to run further into the plate and to draw the chill line out.

A simple test using a file behind the teeth will tell you if you have a hard chill line. The steel will resist the file if it is too hard.

Treat your saw steel with respect and handle it carefully.


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