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AR 360 Question

Greetings all,

I am having to bend some 5/8" AR 360 Plate, approximately 1 1/4" wide. I am using a 200 ton Haco-Atlantic press brake, but we are still having to heat the parts to get them to bend without breaking. Let me tell you, THAT was not fun. The first piece I broke had already bent my bottom die and after fixing it I needed to get a few more degrees of break into it. I was just at the bottom of the stroke when it BANGS! I immediately let off and start looking at my dies to see what broke this time. To my surprise it was the part that had cracked, 3/4 of the way threw from the bottom/outside of the break and very jaggedly. I have been sure to be standing at an angle to the part, neither directly in front or to the side in case something decides to make a quick exit. :)

Anywho, here's my question. I am heating this AR plate (with an O/A rosebud torch) to a dull red, about 1" to each side of the break point, mostly on the bottom/outside of the break where it cracked before. My concern is am I going to hurt its abrasion resistance doing this? Could I be taking out some of its temper in the area that I am heating? Is the resistance due to the alloying of the metal or a tempering process I could be screwing up?

I will thank all repliers now for your time and consideration, and I also hope this makes enough sense to be repliable to.

Regards, Jim C Roberts

Reply to
Jim C Roberts
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People have been killed forming AR plate. As a general rule it is not wise to form AR thicker than 1/4 inch. You are very wise to stand aside. The one case that I was told about many years ago invoved an operator who was decapitated by the half sheet flying out from the die. Commercial forming dies are not made for bending hot material. You cannot be using the eight times rule. Your bottom die should be at least eight times as wide as the thickness for bending mild steel. ( five inches for 5/8 inch) As soon as you bend hot you have changed the hardness of the material. You are entering an unknown area. Randy

Reply to
Randy Zimmerman

We don't usually attempt to break it. Normally we plasma cut it and weld it into parts. These pieces are to be scrapers going on a roller chain.

You are very wise to stand aside.

Scared is more like it.

The one case that I was told about many years ago invoved an operator who was

And Ernie thought he had a bad day. Thankfully the only thing I have ever had to shatter in a break is some plexiglass. Fortunately the break was an old Chicago hand break so we were off to the sides when it occured.

I am using a "home made" set of dies consisting of a piece of 1" round and a piece of 1/2" plate welded together to form the top die. The bottom die is a piece of 3x3x3/8" angle iron turned with the V up, mounted on a base plate with gussets to help the outside of the V stay relatively straight. It is probably not 5" wide, more like 4 1/4" I believe.

Thanks for your reply Randy, this has become a mute point now that I finished the parts up this morning, but I do appreciate the post.

Regards, Jim

Reply to
Jim C Roberts

As an afterthought... it is not a bad idea to anneal and then send out for heat treat. During my apprenticeship I had one "European " style employer who had me straighten scraper bars that were heat treated. I had to set them up between two raised bars then hit them with a sledge with everything I had. When I was finished the face of the hammer was all ridged from striking the bars on their edge. I realize that I was chosen for the job, being most expendable. All through the stack I was expecting one to shatter in front of me. Randy

Reply to
Randy Zimmerman

From a point of almost total ignorance, is it possible that some of the problem could be caused by your tooling creating unequal stress points during the bending cycle?

Reply to
Ace

I have no idea Ace. I attributed the cracking to the material being brittle because of the hardness of it. I have broken heavier material, including round bars, in this same set up with little to no cracking. I have wondered how a set of dies with "swivels" on the two outside points would work for heavier materials. I'll put that on my to do list...................

Regards, Jim

Reply to
Jim C Roberts

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