Steel plate identification

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choprboy
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Steel plate identification

Post by choprboy »

Anybody familiar with common steel plate grades and how hardened/AR responds to machining?

I picked up a 2'x6' chunk of 1/2" steel plate from the scrap yard a while back to make plates for a transmission mount. There is usually a large supply of all different pieces, but little of it has original markings. The plate was hot-roll, rusting, and had been torch cut, so I expected it to standard A36 or similar. Occasionally the yard gets AR300/400/500, but they normally stack that to the side and charge a lot more for it.

The piece I picked up and started working is extremely hard to drill. It took me 3 sharpenings to drill a 1/4" hole thru the plate and my hole saw is barely scratching the surface. The chips start are very fine under light/moderate pressure, under heavy pressure they become large and sort of shattered, before the drill edge quickly dulls. Admittedly these are cheap HF drills, but in the middle of this they went thru a 1/4" thick piece of A36 (large channel) with standard stringy chips without any issues. Nothing remarkable on the grinder spark test and I can slowly cut thru with a cutoff blade. The bandsaw seems to cut thru it OK but it really likes to have cutting oil. With a file it is a bit harder than A36, but still cuts fine.

Anybody have any idea what steel this might be or have experience with how AR reacts to cutting/drilling with HSS? I'm working on cutting out a coupon to try carbide machining/drilling on my mill, but my big worry is that if I can't effectively drill it, then i doubt I'll be able to ream and tap the 2 dozen holes I will need.
choprboy
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Re: Steel plate identification

Post by choprboy »

Edit: With a small coupon on the mill, HSS endmills will barely touch it, though carbide would chug thru. My insert facemill threw glowing orange hot chips everywhere. HSS drills immediately crapped out, a cobalt steel drill did the job but wasn't happy. I broke the first and second tooth (the tooth tips) off a spiral flute HSS tap 1-1/2 thread in... My good HSS tap seems to cut, but its getting tough 2-3 threads in and I'm not going to risk it.

So this has got to be some sort of hardened steel plate.
whateg0
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Re: Steel plate identification

Post by whateg0 »

I don't know where my reply went, but you might try annealing it if you need to work with HSS. I had a chunk of 1/4" something that carbide would barely touch. Both I and a buddy went through a carbide endmills and inserts trying to put a hole in it. Finally put a chunk of it in his heat treat oven and it was workable. Never figured out what it was, though.

Dave
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warmstrong1955
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Re: Steel plate identification

Post by warmstrong1955 »

AR400 drills & taps well with HSS.
AR500 is at the upper end of hardness of what you can drill & tap with HSS.
Any AR plate, can work harden, like stainless steels can, when you drill. I use speeds closer to 304 & 316 rather than A36 speeds
when drilling. Flood cooling is the way to go too.

Never bothered to try a Horror Freight drill bit in any, and I don’t think I would. Same as stainless, if you heat up the plate, it will get hard. I would expect a HF bit to be on the bottom end of hardness as far as HSS goes, which could put it quite close to the plate hardness if you have AR500. You say you had to sharpen the bit 3 times, so you may have got there. Dullness will harden it up, and quick, just like stainless. This would explain the broken tap.

I always use USA made gun taps, and get better life with the coated ones. Lots of oil, and even though it’s a gun tap, in AR500, I will back it out of the hole, blow out any hips and oil it up and then go back in. Might do that a few times, depending on the depth of thread. AR400 I let her thread on through. I always go for a few thou over on hole diameter, especially with larger threads. You can be a bit larger than recommended for steels, and still maintain the strength.

All AR’s are not equal,ie; AR 500, the 500 is nominal. Most are closer to 450 bhn as received, and it varies among manufacturers. Put it on a loader bucket, and it can get beat up and work hardened to 550 in no time.

Might look here Too: http://www.chaski.org/homemachinist/vie ... hp?t=95237

Bill
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choprboy
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Re: Steel plate identification

Post by choprboy »

whateg0 wrote: Sun Oct 06, 2019 9:13 pm ... you might try annealing it if you need to work with HSS.
Unfortunately, the transmission adapter plates are about 18" across... My little oven will go to 2000F, but is only about 8"x8".
warmstrong1955 wrote: Sun Oct 06, 2019 10:00 pm AR400 drills & taps well with HSS.
AR500 is at the upper end of hardness of what you can drill & tap with HSS.
Any AR plate, can work harden, like stainless steels can, when you drill. I use speeds closer to 304 & 316 rather than A36 speeds
when drilling. Flood cooling is the way to go too.
Hmmm... interesting. I knew Hi-Roc/etc. straight flute carbide drills are used for hardened plate, but I didn't know HSS could be used on AR. I don't think it is work hardening as the chip flow is consistent (until the bit breaks down) and I tried high and low speeds drenched in cutting oil. Didn't seem anything like drilling 304 and the center ~1/8" of the plate seemed to drill much easier than the outer +3/8" to either side. Based on your description it sounds like it must be AR500 plate or something similar.

I don't expect much from my HF HSS drills, but they are cheap and abuse-able for use in the cordless drill and pilot holes. My good taps are YG (Korean). I love the spiral flute taps as I can power tap on the mill, or hand tap in a single go, thru 4140 and 304 without issue.
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liveaboard
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Re: Steel plate identification

Post by liveaboard »

I once made a compressor bracket for a diesel engine from some hard brittle scrapyard plate like that; it cracked. I welded and gusseted it, it cracked again.
I would suggest getting some other material for your transmission mounts.
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Harold_V
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Re: Steel plate identification

Post by Harold_V »

I'm assuming that the material in question is not precipitation hardening.

Heating, alone, does hot harden if the hardening process involves the carbon cycle (most common for alloy steels). The tool *not cutting* can work harden an area, however, assuming it is allowed to spin without generating a chip. Fact is, heating is what anneals. How fast an item cools is what determines hardness in the carbon cycle.

If one avoids excessive heating, it's entirely likely that the plate in question will serve perfectly fine as a transmission adapter. You just have to get past the less than friendly machining characteristics.

H
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choprboy
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Re: Steel plate identification

Post by choprboy »

Well.. there is a plate on the transmission side, another on the engine side, and about 4" of 12"dia pipe to be welded in between to form a bellhousing for the clutch. So heat will definitely be an issue.
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Harold_V
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Re: Steel plate identification

Post by Harold_V »

Yep! Unless you anneal the material well, you'll have issues with cracking. Even then, the procedure used would dictate success or failure. Carbon and welding tend to not go together well unless the carbon level is below .3%.

I think I'd seek different material in this instance.

H
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Rick
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Re: Steel plate identification

Post by Rick »

A few years back my Uncle gave me some 1/2" plate (hot rolled , rusting and flame cut edges) and he assumed it was just regular ole A36. After I got it home decided to look at it a bit closer and found some markings under the rust/dust and dirt. Turned out it was 4140, still have it as it wasn't suitable for what I was going to use it for. No idea where he got this from. He most likely bartered for it and has since passed so will never know.
Rick

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warmstrong1955
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Re: Steel plate identification

Post by warmstrong1955 »

choprboy wrote: Sun Oct 06, 2019 11:37 pm

Hmmm... interesting. I knew Hi-Roc/etc. straight flute carbide drills are used for hardened plate, but I didn't know HSS could be used on AR. I don't think it is work hardening as the chip flow is consistent (until the bit breaks down) and I tried high and low speeds drenched in cutting oil. Didn't seem anything like drilling 304 and the center ~1/8" of the plate seemed to drill much easier than the outer +3/8" to either side. Based on your description it sounds like it must be AR500 plate or something similar.

I don't expect much from my HF HSS drills, but they are cheap and abuse-able for use in the cordless drill and pilot holes. My good taps are YG (Korean). I love the spiral flute taps as I can power tap on the mill, or hand tap in a single go, thru 4140 and 304 without issue.
The way AR drills is nothing like stainless, it's only the way it can work harden, and yes, especially when the cutting edge breaks down. That is the only common characteristic I am talking about with AR & stainless.
And when you have AR500, which is about 450 bhn to begin with, it takes little to harden it up beyond the hardness of the HSS drill bit, and/or the tap. Same thing can happen with AR400 too.
And, like I mentioned, all AR's are not made equally, and some, has harder spots here & there, besides the edges and surface which is typical & normal. Depends on how well the material is rolled, and how they temper it after.
I had a dozen pieces of 1/2" AR500, that each needed (4) 17/32" holes in a year or so ago. Most went through without a hitch. One had a hole that was too hard for HSS. A couple others had (2) holes in each that HSS wouldn't drill. I finished those holes with carbide.

I would not use a spiral flute tap on any AR plate, not even with blind holes. I have used hand taps, talk about a pain, but have been using gun taps (spiral points) only, for years. They are a lot stronger, than both hand taps, and especially spiral flute, and with AR, you need as tough as you can get.

I can tell you from experience, it can be a real pain to work with. Mines & mills use a bunch of the stuff for wear plates.

Bill
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pete
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Re: Steel plate identification

Post by pete »

It's used in the haul truck boxes as well Bill and I suppose during a lot of large bucket rebuilding. I've got some plate cut offs that were used as OEM Cat haul truck box liners. Haven't quite dared to go past the thinking about machining it though. If it's AR 500 as I suspect it might be that material shouldn't be subject to cracking considering the impact forces the truck boxes and buckets see. Unfortunately sometimes even free material gets way too expensive if it starts eating tooling and buying something more suited to the job might end up being far cheaper.
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