How do you tell if a steel is classed as brittle or ductile?

[rattler]

I'm looking for some help please regarding the UK steel 826M40 condition Y, formerly En 26. The material properties listed are 0.2% proof strength 1080 MPa and UTS 1225 MPa. I need to know whether this material is considered to be brittle or ductile as I am trying to determine a suitable safety factor to apply. The material is used to make a pin subjected to shear loading, generally of a low level, but may be subjected to a large shock load.

Cheers
Rattler

 

[metengr]

Here is a web site that lists the mechanical properties for EN26 material.

http://www.interlloy.com.au/index.html

This alloy contains 2.5% Ni which indicates it is tough material for moderate to low temperature service in the quenched and tempered heat treat condition.

 

[metman]

rattler,
It depends to a large degree on the operating temperature for a given steel alloy.

thread330-24020 has some information that will help.

If the service conditions are ALWAYS at or above room temperature for this alloy it would be considered ductile. Actually the ductile to brittle transition temperature for En26 is likely somewhat below room temperature.

Since it is similar to AISI 4340 but with more Nickel it will be tougher for a given temperature.

4340 at 1240 MPa UTS has Izod impact strength of
47J or 35ft-lbf at room temp.

 

[Carburize]

In the absence of any crack-like effects a good measure of the material is the ductility before failure in a tensile test. If there are defects present then some parameter such as fracture toughness at the appropriate temperature and strain rate is more applicable - charpy impact tests give an approximate guide to the toughness.