Q: We have used EN16 (605M36) for the manufacture of a small component. Could EN8 (080M40) be used as an alternative?    
The use of EN8 as an alternative depends on the section size and the required mechanical properties. EN16 is a deeper hardening grade with in general higher tensile strength than EN8 for a particular cross-section

Q: Is there a cheap plain carbon steel for a component requiring a minimum yield stress of 385 MPa?    
There are a number of options:
• 080M40 (EN8) a nominally 0.40%C steel can be used up to section sizes of 60 mm.
• 605M36 (EN16)  for section sizes > 60mm.
The component will require heat treatment involving oil quenching to achieve these properties and should be designed accordingly.

Q: What is EN9 steel and is this specification still current?
EN9 is an old “Emergency No.” issued during the Second World War. These terminologies are still widely used by engineers but have been superseded. This is a plain carbon steel with a nominal 0.55%C, superseded by 070M55
Could it be used in an application requiring moderate wear resistance?
The carbon content offers this steel moderate wear resistance if heat treated to a hardness of about 350 Hb

Q: What is AISI 4140 grade steel?
The chemical analysis is available. The mechanical properties are available.
Is this a UK specification?
This is an American Standard for a grade commonly referred to in the UK as EN19 (709M40). The last two numbers of the AISI specification denote the carbon content, in this case 0.40%. It is a widely used CrMo steel.

Q: How can I improve the wear resistance of 709M40 (EN19)?
This grade of 1%Cr, 0.25%Mo steel is suitable for nitriding to increase the surface hardness and wear resistance. You must ensure that the mechanical properties of the substrate are not compromised by the treatment – the tempering temperature must have been higher than the nitriding temperature.

Q: Is 709M40 (EN19) suitable for an application requiring a minimum tensile strength of 850 MPa?    
Although quite a deep hardening steel, this strength can only be guaranteed for section sizes of up to 100mm.
For section sizes larger than this, a deeper hardening grade such as 817M40(EN24) might be appropriate.

Q: What is the normal grade of steel used for drill collars in the oil industry?
The most frequently used grade of steel for drill collars is steel to AISI 4140
Specification.  This is because it is widely available in large diameter bars and has good mechanical and wear properties in these sizes.

Q: What is steel grade EN24 (817M40) used for?
This is a general purpose alloy steel for a wide range of engineering parts. It is capable of being heat treated to produce a wide range of tensile strengths combined with good ductility and shock resistance. Tempering within the temperature range 300 to 500ºC leads to a drop in Impact properties.
What is the modern alternative?
BS EN 10088 replaces the old British Standard.

Q: What is steel grade AISI 4350? Can it be used instead of AISI 4340?    
This is a 0.50% carbon version of AISI 4340. All other elements are identical.
Extreme caution should be used when considering the use as an alternative as this steel suffers from a loss of impact properties when tempered in the range 200-400ºC.
Seek advice on individual circumstances.

Q: What can I replace 304 grade stainless steel strip with to give a higher hardness?    
A number of hardness levels are available or you may wish to consider using a different material such as a ferritic precipitation hardening grade.

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