All Saw Steel Is Not The Same
General Properties of Saw Blade Alloy Steel
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Do you ever wonder what goes into the steel saw body you buy from Peerless? What makes it stand up when it’s under stress from high temperature, shock or heavy loading? What characteristics does it offer that are unique? Really, what makes it better than any other brand of saw steel?
There’s really quite a story behind the selection and the logic for choosing the special alloy used in Peerless Saw bodies. First of all, we set out to supply our customers with the finest saw steel available in the world. Our customers are supplying the tooling in some of the toughest industrial applications imaginable. Quite often there are high temperatures, extreme shock, bending and all sorts of abuse that lesser qualities of steel just won’t take. We order a steel type designed to handle this kind of stress and abuse.
For more than fifty years, Peerless has used a high nickel, high carbon alloy tool steel. When comparing other alloys with carbon steels, Peerless saw steel provides additional strength, ductility and toughness. A close examination shows this alloy has a relatively high carbon content for cutting edge retention, nickel and molybdenum for toughness and chromium for corrosion resistance. This special grade tackles the challenges of industrial carbide tipped saw applications and maintains its strength and excellent abrasion resistance under high and low temperature operations.
What is an Alloy?
Alloy steel is a grade of steel in which one or more alloying elements have been purposely added or blended to give it special properties that cannot be obtained with a carbon steel. The elements of saw steel can be likened to a football team, where each player has a specific job to do. Let’s meet the players of the Peerless alloy team. The chemistry ‘line up’ is:
CARBON: Is present in practically all ferrous alloys and, like a quarterback, calls the play on hardness. It is the principal hardening element in steel, and as carbon is increased, the hardness of steel increases. Ductility and weldability decrease with increasing carbon.
NICKEL: This element’s toughness improves performance. It helps corrosion resistance and lessens distortion in quenching.
CHROMIUM: It’s like the blocking back fending off the attacks of corrosion. In this grade it also improves hardenability and resistance to wear and high temperatures.
MOLYBDENUM: Remember “moly” as the hard-nose element, small but tough. It promotes hardenability and close control during heat treatment.
MANGANESE: As Manganese increases in steel, so does tensile strength & durability. Manganese also aids in hardenability.
Here is the chemical makeup of the Peerless 8670 alloy:
C = .64/.75, Ni – .70/1.00, Cr = .30/.50, Mo = .05/.10, Mn = .40/.60, Si = .20/.35, S & P = .025 max
To ensure a cleaner, sounder product, Peerless saw steel must be melted in electric furnaces. Only a few steel companies in the world can supply this special alloy. All follow our special recipe, which is custom made, not a standard AISI alloy. All must meet quality standards that include dimension of sheet, crown, thickness variation and certification of chemical analysis.
Peerless inventories many thicknesses of alloy saw steel. This selection reduces the amount of grinding necessary to reach finished thickness.
As received from the steel mill, the alloy is in a dead soft, annealed form. During the heat treatment process, when the steel is heated above its critical point, the elements merge. If cooled slowly, it will return to its original state. However, when the steel is cooled rapidly, another transformation takes place, making the material hard and brittle, depending on its carbon content. These changes are critical to the quality of the finished saw steel and are controlled closely in the Peerless factory. After rapidly cooling or quenching, the alloy hardness is measured at approximately 62-64 Rockwell “C” scale. It is then necessary to temper to reduce the brittleness and make it more uniform in structure and softer, but tougher. These heat treatment stages are integral steps in providing a saw body that is tough and flat.
After the saw bodies are hardened, a second furnace is used to temper or anneal the steel. This operation is done under pressure to ensure the best flatness.
Peerless saw bodies are tempered to several standard hardness ranges, made to order:
- 38-42 Rc (target 40) is the standard hardness and the most popular. Most stock saw sizes held in inventory are made to this range.
- 42-46 Rc (target 44) is selected by some customers for special applications. Thin kerf, guided edger saw bodies are made to this hardness unless otherwise specified. This is also the standard hardness for solid, steel tooth saws that are set and sharpened.
- 46-48 Rc (target 47) is a special hardness for applications where you can risk brittleness to gain a stiffer saw plate.
- 47-50 Rc (target 49) is most commonly found on hollow ground, solid tooth saws for wood or metal cutting. Circular slitter knives, stiffening collars and paper tube cutting saws are also made to this hardness.
- 56-60 Rc (target 58) is the norm for M-2 circular knives.
It’s important to understand that many saw bodies are ruined by faulty gumming or brazing techniques. If the steel turns blue during grinding, its structure changes and causes a stress area. The Peerless alloy’s first transformation takes place around 1300ºf. Remember, most silver solder melts at around 1200ºf. You can see how important it is to keep the brazing temperature as low as possible, preventing a critical change in the steel structure.
If the brazing is performed too rapidly or the saw body is overheated, the steel will change its structure directly behind the tooth or below it. This could create a very hard heat affected zone (HAZ) due to the rapid cooling of the alloy after the heat is removed.
A simple test using a file behind the tooth will tell you if you have overheated (and hardened) the steel. The steel will resist the file if it is too hard. Saws found in that condition need to have their shoulders annealed to reduce the hardness.
The alloy steel used in Peerless saw bodies is selected with great care. We offer the finest product of its kind due to this selection and the care taken during laser cutting, heat treating, surface grinding and smithing. Our customers put their reputations on our saw bodies. For over 80 years we’ve been proud to hear our customers say, “You can depend on Peerless Saw steel!”