Casting HSLA parts

[arunmrao]

Asteryx,any reason for considering the casting route? What is the part you intend to cast?
Will the foundry be able to handle the small batches? As in the case of plates,there is no grain refining or strengthening mechanism due to mechanical working for castings. For cast parts,it is essentially, grain refinement and microstructure control ( by heat treatment) that will enable you get the properties. I am sure you are aware of these.

Casting parts are likely to have internal casting defects,you must be able to identify and locate these defects . Determining the critical flaw size is important for your application alternately, a steel has to be chosen that has a large critical flaw size,so that it can be measured more accurately.

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"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[Asteryx]

The parts are arms on a device that will be subjected to both tensile and lateral loading.

The incentive is just design and weight efficiency; we want to design in geometry that does much more for strength and performance of the part than we can do with plate.

The competition does something similar with a good track record, although we're trying for slightly higher mechanical properties.

We've been casting ~G50 parts and are happy, and initial prototypes to that grade are good; we're just unfamiliar with casting the higher mechanical properties and what's going to be involved in getting there.

The parts range from about 2 kg up to 30 kg, and we will go much higher if feasible - up to about 150 kg. Lost wax investment for the small ones and sand for the big guys.

 

[arunmrao]

Lost wax for the smaller ones is a good selection maybe up to 5 kgs.Chemistry wise,it is not difficult,you could adapt similar chemistries with some grain refining,which the foundry I am sure will know. Oil quench and temper the steel appropriately You should be good,but please look for manufacturing defects in the castings.

Will the foundry accept to do small batches or is the alloy regularly being processed by the foundry.

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[swall]

In general, steel castings are spec'd to min mechanical properties and the chemistry, within a certain range, is left to the discretion of the foundry. Addition of a weldability requirement adds a further restriction to chemistry, mainly on carbon content. The heat treat process will be at the discretion of the foundry to conform to the mechanical property requirements.

 

[Guest102023]

I doubt you can make a cast equivalent to these steels, since they depend on thermomechanical processing for their properties, foremost of which is very fine grain structure. It may be possible to obtain the same yield and tensile properties using conventional alloys, but not the excellent low-temperature impact properties of HSlA steels.

 

[swall]

Brimstoner--good point about the low temperature service requirement. What I took from Asteryx is that he wants equivalent strength to the HSLA material and he also needs weldability and, as you pointed out, low temperature performance. Castings can be made to do these things; it just gets more expensive than meeting just the strength level.

 

[Asteryx]

Thanks for the replies.

The requirement for Charpy CVN average is ? 34 J at -20 deg C.

Operating temps are as above no lower than freezing; will be used underwater.

Microalloy is on the notepad here too, but I understand elongation will suffer. Bending is a preferable failure mode for us than breaking... even if it has to be at a lower yield.

Swall we will talk to the foundries but just wanted to know what we're talking about to a limited degree before doing so.

 

[Guest102023]

That Charpy requirement is not onerous; I'm sure the foundry has a recipe for you.

 

[JamesCKelly]

Just curious - that cast HSLA isn't a grade that would embrittle, is it, at the nominal 850F/454C temperature used for hot dip galvanizing?
In any event, the weldment should be stress relieved before hot dip to avoid cracking from molten zinc.