What Materials Are Tool Wraps Made From?

What Materials Are Tool Wraps Made From?

Stainless steel 321 and 309 grade foils are used as tool wraps because of properties that make them favourable. Why 321 and 309 stainless steel? And why 321 rather than 309 stainless steel? We’ll take a look at their similarities before understanding what makes them different.

Similarities

Annealing

Both 309 and 321 stainless steel tool wraps are annealed. Annealing reduces the hardness while increasing their ductility, allowing them to be deformed without being brittle. This is important for tool wraps, as the slightest break can cause the entire work piece it is wrapping to be scrapped.

Heat Resistance

Both 309 and 321 stainless steel have high temperature resistance. Both of these grades can withstand temperatures above 1,000 Degrees Celsius for up to four hours without the risk of contamination, making them ideal for use in heat treatment processes.

Can Be Produced In Thin Sheets

Both 309 and 321 stainless steel can be produced in thin sheets. In the case of tool wraps, they can be produced to be as thin as two thousandths of an inch (.002”). Being so thin allows them to be used for wrapping all the while still maintaining their shape as a metal sheet.

Differences

Next, let’s find out what makes them different; why you would choose one grade of stainless steel over another as a tool wrap. Let’s first look at 309 stainless steel.

309 Stainless Steel

309 stainless steel is generally considered to be a heat-resisting alloy. It does not corrode, melt nor oxidise at temperatures up to 1226 degrees Celsius or 2240 degrees Fahrenheit. It retains these properties even in thin sheet form, which makes it favourable for use as a tool wrap.

321 Stainless Steel

Next, let’s look at 321 stainless steel.

A 321 stainless steel tool wrap differs from its 309 counterpart because it contains titanium. The titanium content protects the tool from decarburization and pitting by quickly reacting with oxygen left inside the envelope. When carbon on the tool does not have time to react with oxygen, the result is a clean surface, free from decarburization.

321 stainless steel can withstand temperatures up to 1032 degrees Celsius or 2000 degrees Fahrenheit.