Specifying properties of 4140 castings? 2

[smslab]

I'm looking for advice from someone who has experience with 4140 castings or similar.

The intent is to produce a cylindrical part whose largest diameter is 3.5 " Service temperatures are anticipated to range from -30 F to 100 F.

Desired yield strength is 60-70 ksi, desired impact energy is 65 ft-lb Izod.

It looks like specifying 4140 cast, normalized and then oil quenched and tempered at 1300 F will give a higher strength than required for wrought material and more than adequate impact energy, but I cannot find anything for castings.

I've dug through my ASM handbooks and scoured the web so if I have missed a source of info I'd be very grateful if someone could help me out.
Is there

 

[metengr]

First, you need to specify a standard for purchasing the castings, I would suggest ASTM A 958 "Steel Castings, Carbon and Alloy, with Tensile requirements, Chemical Requirements Similar to Standard Wrought Grades". This specification contains mechanical property requirements or you can supply them under your own requirements for purchase.


I would suggest searching the internet for a copy of the Steel Castings Handbook, Supplement 2 from the Steel Founders Society or obtain a copy of ASTM A 958. Now that you have a standard specification for ordering cast 4140 (J14045) steel, you need to specify acceptance criteria for the casting (level of defects). This is up to you to determine and should be based on service application. Search through ASTM Standards for acceptance criteria for steel castings.

 

[GRoberts]

Unlike most wrought forms, castings will typically have weld repairs. Specifying 4140 (with the high carbon content) will only make that more difficult- especially when it gives you more strength than you really need. You might take a look at some of the more weldable grades in ASTM A487, or better yet, work with your local foundry to use thier expertise on their casting process, and they can suggest a specification that meets all of your properties, but is still easy for them to produce.

 

[dbooker630]

You may want to look at a version of ASTM A148 material and reduce the max carbon below .30% for weldability, and compensate with manganese to get the strength you need. Grade 120-95 is an example.

 

[smslab]

Thanks for the info so far.
I forgot to mention that this is a shaft with a spline that needs to be hardened. The logical choice would have been 8620 with a carburization but for reasons which I do not completely understand (this is on behalf of a friend) the foundry is unwilling or unable to produce castings out of 8620 on a time scale that he considers acceptable. It sounds like a case of 'we've got 4140, take it or leave it.' So he was looking to 'take it' and then induction harden the spline. Not optimum, but if it works he'll live with it to meet a deadline. This is the old story of having trouble getting parts made if you are only doing small runs.

 

[mfgenggear]

just a note

for small lots 1 - 500 pcs

for our customers we make gears from wrought bar or forgings 9310 0r 4340 (Aircraft Application)

normally core hardness 33-43 Hrc & case harden gear teeth, I like 4340 because it's very stable during heat treat. by means of through harden & Induction Harden

 

[arunmrao]

smslab,
That is blasphemy or hara kiri. Casting to produce a shaft,not advised, you could easily buy 8620 round rods and move on. Apparently you may see cost savings now,but pain will be maximum later.

metengr et al,
I have a question to ask. Sorry for hijacking the thread.

Between 4140 casting and forging,if tested for sub zero impact properties,will the values be the same?

Chocolates,men,coffee: are somethings liked better rich!!
(noticed in a coffee shop)

 

[smslab]

arunmrao I am not going to disagree with you but this is not my call to make. At this point I am doing what I can to dig up info - I am a heat it and beat it / mechanical tester myself so this is not an area I feel comfortable giving advice. I'll pass everything on so pleas ekeep it coming.

also arunmrao now that you have hijacked the thread (ok by me) I have not seen any data for subzero impact values on 4140. The closest I've seen in the ASM Metals Handbook Vol 19 is nil ducility transition temps for a variety of cast carbon and low alloy AISI grades including 4330 as a function of yield.