Mechanical properties "near the surface" : at what depth ?

[stanislasdz]

In many manufacturing specification we can found impositions abour méchanical properties on steel parts near the surface, mid-thickness end centre.

My question what is teh depth of the "near surface" ?

is there any specification with deal with the depth of the "near surface" location.

 

[unclesyd]

One are that near surface applies has to with selection of metals based on hardenability alone. It is normally measurements in 1/16" increments from the end-quench hardenability tests. You can use the end-quench hardenability tests alone or with the cooling rate curves to select material.
You will see numbers (in) like 4/16, 6/16.

 

[metengr]

stanislasdz;
Most internationally recognized specifications, like ASTM, have descriptive and illustrative locations in the specification itself where test samples for tensile or impact are to be removed for castings, forgings and bar product forms.

If you are dealing with a specific manufacturing specification, I would go back and ask for clarification for "near surface". As you can see, there will be many interpretations regarding this term and the only one that counts is from the originator of the specification.

 

[arunmrao]

Normally steels are not considered to be section sensitive as cast irons are. However, there can be differences in properties if you traverse from the surface to the core in thick section (>200mm,please correct if wrong). This is exhibited due to differences in cooling rate and resulting solidification structure. Also in near surface samples you could experience decarburizing,scaling and other surface defects related to processing of the ingot or the forgings.