What grade steel for general purpose "better than mild" fabrication?

[FridgeFreezer]

Per the title really - almost everything people DIY fabricate uses mild steel and that's mostly fine, but from time to time I have the feeling that I could/should be using something a little better for some parts that will see a bit of actual stress.

However, there's a ton of different grades out there all with varying properties and tradeoffs - and of course price & availability varies too.

I'm aware of tool steels and the like but a lot of that stuff is somewhat specific to one particular application.

I guess I'm fishing for what's the next step up from mild - something commonly used / easily available & still general purpose but a bit tougher all round, possibly something easily DIY heat-treatable as that seems to be a common factor with the stronger stuff.

[Stellaghost]

22 minutes ago, FridgeFreezer said:

 

I guess I'm fishing for what's the next step up from mild 

Thicker mild.........

I'll get my coat...........

regards Stephen

[elbekko]

I used some S355 for the winch cradle in my bumper, the numbers made it look very much worth it. And I noticed the difference drilling it...

[sean f]

Cheep steel is often EN1 or EN3 both soft easily welded and easily formed, easily forms pretty much says easily bent.

Next common step is up to EN8 which is general engineering grade after that it becomes more specific, I use EN24 for higher strength stuff. As a general rule the higher the EN number the stronger it is (and more expensive!). Also the higher numbers will mostly heat treat well to make them very hard, weld EN24 with no special treatment and you will struggle to scratch it with a file, down side is it is then more brittle, there are ways of welding it so it doesn't become brittle but that's more specialist stuff. I believe standard halfshafts are EN18 and heat treated but don't have any proof of that.

Since I can often acquire marine bar ends and scrap I often use 316 stainless for machining odds and sods but also get Duplex which is engineering stainless and difficult to beat when strength is required but the prices are high if buying new from a dealer (I get corroded or worn shafts as scrap).

[FridgeFreezer]

@Stellaghost I don't know what I expected but you delivered

@sean f thanks, the heat-treating thing is the double-edged sword I am trying to walk along as I don't want something that becomes significantly brittle after being welded / actively requires treatment to correct, although being able to harden stuff by heating would be nice sometimes it would be nice not to have to.

Just found a useful table here: https://www.hillfoot.com/steel-grade-equivalent

I notice EN8 is ~SAE 1040, EN9 is ~SAE1050, EN19 is ~SAE 4140 which gets thrown around a lot on the US side of the internet for everything, and EN24 is ~SAE 4340, that at least helps line up EN specs to the majority of stuff you see on the internet which is US-based.

[steve b]

EN9 is a good higher grade and can be heat treated for added hardness once machined/formed etc.

Steve

[FridgeFreezer]

2 hours ago, elbekko said:

I used some S355 for the winch cradle in my bumper, the numbers made it look very much worth it. And I noticed the difference drilling it...

Looking at the table, S355 ~= EN14 (150M19) "A medium tensile, low carbon manganese steel which is readily weldable and possesses good impact resistance." sounds ideal for a bumper!

https://www.hillfoot.com/products/150m19-non-alloyed-019-carbon-ndash-manganese-steel

[Daan]

EN24 is technically not weldable, but I am sure people managed at home. En36 is for case hardening. En14 is generally used for machined parts which need welding.

S355 should do for most fabrication jobs.

If you want to go fancy with T45 roll cage tube, the appropriate grade of sheet steel is S515:

 Largest stockist of S514/ S515 sheet steel - Proformance Metals

This bunch sells anything you like and don't reply with annoying things like 'trade account only' or 'minimum quantity'. Phill mats is a lovely chap too, here is the ebay store for groovey metals:

Commercial Materials (proformancemetals.co.uk)

[Snagger]

Are the prefix letters denoting the form of the steel, like S for sheet, T for tube and EN for a block or ingot (enlarged nugget 😉)?

[Daan]

6 minutes ago, Snagger said:

Are the prefix letters denoting the form of the steel, like S for sheet, T for tube and EN for a block or ingot (enlarged nugget 😉)?

S means structural steel. T45 means 45 Ton/sq inch tensile strength. 

EN stand for Emergency Number, created pre-WW2 and is still used today.

[Ed Poore]

I wouldn't forget the main thing is to think carefully about the design first. I know you didn't ask about aluminium but I'm using it as an easy example.

People often replace bits with aluminium thinking it'll be lighter but in a like for like situation the aluminium quite often ends up weighing the same and costing twice as much because it's not as strong and work hardens / is more brittle. Where aluminium wins is if you start being clever with the design such that you can make stronger structures with less materials.

I think the same is true of the more "exotic" steels. They have their place but there's a lot to be said for "mild" steels flexibility. For example yes you could make steering rods out of EN24 that's massively strong etc., but what happens when you push things - you'll probably break something more difficult to replace. A soft flexible steering rod, perhaps a little thicker, that can be bent back into shape more easily if the worse were to happen in the middle of nowhere would probably be preferable to some unobtanium steering rod. Particularly if it's not swappable for a standard one reasonably quickly.

PS not directing it at you @FridgeFreezer but more for completeness of the thread.

[Ed Poore]

A cracking example of what I was getting at was I went on a site visit where they were experimenting with 3d printing artillery shells. The director who was giving me the tour had got royally peed off with the team because they basically remade a shell that was made on a lathe. So it took longer, wasn't as good and offered no benefit in performance.

What he had expected them to do was print the shell with a honeycomb structure inside. The explosives were liquid so would have flowed around the structure but then they could have made the shell lighter with the same strength and got more explosive in.

[miketomcat]

9 hours ago, Ed Poore said:

A cracking example of what I was getting at was I went on a site visit where they were experimenting with 3d printing artillery shells. The director who was giving me the tour had got royally peed off with the team because they basically remade a shell that was made on a lathe. So it took longer, wasn't as good and offered no benefit in performance.

What he had expected them to do was print the shell with a honeycomb structure inside. The explosives were liquid so would have flowed around the structure but then they could have made the shell lighter with the same strength and got more explosive in.

That's a classic example of 'that's the way we've always done it' I used to come up against this often. I'd get shouted down when I asked "why?" Fortunately my boss now is much more open to different ideas as long as they get the job done.

Mike