Frequently Asked Questions
These are some of the questions that we frequently get asked.
- What Is Stainless Steel?
- When was stainless steel discovered?
- What is stainless steel used for?
- Does stainless steel corrode?
- What forms of corrosion can occur in stainless steels?
- How many types of stainless steel are there?
- What are the correct standards for stainless steel?
- Is stainless steel non-magnetic?
- Can I use stainless steel at low temperatures?
- Can I use stainless steel at high temperatures?
- What surface finishes are available on stainless steels?
- How do I choose which stainless steel to use?
- What is 'multiple certification'?
Can I use stainless steel at low temperatures?
Austenitic stainless steels are extensively used for service down to as low as liquid helium temperature (-269 deg C). This is largely due to the lack of a clearly defined transition from ductile to brittle fracture in impact toughness testing.
Toughness is measured by impacting a small sample with a swinging hammer. The distance which the hammer swings after impact is a measure of the toughness. The shorter the distance, the tougher the steel as the energy of the hammer is absorbed by the sample. Toughness is measured in Joules (J). Minimum values of toughness are specified for different applications. A value of 40 J is regarded as reasonable for most service conditions.
Steels with ferritic or martensitic structures show a sudden change from ductile (safe) to brittle (unsafe) fracture over a small temperature difference. Even the best of these steels show this behaviour at temperatures higher than -100 deg C and in many cases only just below zero.
In contrast austenitic steels only show a gradual fall in the impact toughness value and are still well above 100 J at -196 deg C. See Selection of stainless steels for cryogenic applications.
Another factor in affecting the choice of steel at low temperature is the ability to resist transformation from austenite to martensite. This factor is discussed in more detail in Composition effects on the magnetic permeability of austenitic stainless steels.