Al content in low alloy steel forging

[deaconp]

Quick scream for help.

I am looking at ordering billets of low alloy steel forgings, idealy I was looking for an aluminium content of between 0.15- 0.35%, I am curently being offered materials with contents below 0.1%

what i am looking at is what is the relationship of Al in steel and I am looking in the right direction?

My belief is that it aids the grain structre growth enabling hardnability of the metal, and also providing a degree of corrosion resistance to the material?

will a reduction to 0.1% Al have a drastic effect on the material?

thanks in advance to any help

Paul

 

[TVP]

Are you sure about the placement of the decimal for the range "0.15-0.35%"? Al is usually specified in the range of 0.020-0.080% by mass in order to deoxidize the steel and to form particles that refine the austenitic grain size.

 

[metengr]

Agree with TVP. Also, there is no increase in corrosion resistance afforded by aluminum additions in steel or low alloy steel for deoxidation or for grain refinement.

I would suggest that you specify the alloy steel forging to a recognized international standard like ASTM.

 

[deaconp]

my error sorry although it is stipulated as 0.15% - 0.035% Al content, this is for an ASTM A336, grade F-22 modified material.

This is what I curently have specified anyway, it is possible that it may need revising, but the values are stipulated in a componany material specification?

 

[metengr]

No. Stick with the ASTM A 336 Specification. I reviewed ASME SA-336 Standard Specification (identical to A-336) for Grade F22, and there is no specified aluminum addition, only silicon, which is used for deoxidation as well, and is specified at 0.50% max.

The aluminum in your specification could be added for grain refinement - however fine grained steel may not be what you want because the creep strength will be reduced. This material is used for elevated temperature service - so I see no reason for using aluminum as a deoxidizer or for grain refinement.

 

[stanweld]

Some companies require relatively low temperature toughness requirements for this material and the operating condition is in the low temperatrure creep range and component is in Hydrogen service. Control of residual elements sulfur, phosphorous, tin, arsenic, antimony, etc are required. Aluminum is added as a grain refiner and should be between 0.02% and 0.04%.

 

[Carburize]

deaconp - what is the application? I have seen this alloy used in oil-field applications as well as its traditional higher temperature service.

 

[deaconp]

Carburize- This material is indeed for oilfield service and is therefore H2 Service as well as being machined for pressureretaining components up to 10Ksi

 

[Carburize]

In your application I would specify an 0.035% max aluminum level this is typical of the value from other oil field users.

 

[arunmrao]

Higher residual Al content in steels leads to rock candy type of fracture. Long and continuous inclusion network as with higher Al ,nitrogen gets picked up forming aluminium nitride. Best advice is to maintan Al content as low as possible and use other deoxidants like Si and Mn.