Fracture While Braking

Bending along the grian wil induce this,

I do not know what W44 is, must be hard which increases the fracturbility.

My stint at the shipyard I had to specfy and watch the setup to make sure the fabricators did not bend with the grain, esspecially critical components such as lifting lugs, that had a shallow bump in it (approx. 10-15 degrees).

these lugs where 1" to 2" thick material, but 12 ga. the outer fibers breaking, what size upper die must had a sharp nose, and the lower die how wide was the VEE.

As long as I'm asking, how many tons was the brake press?

phoenix911

W44 is equivalent to A36, supposed to be soft, 25% elongation.

material was 3/8" x 12" HR flat

upper die 1" with ~3/16 radius

Lower die 3"

tonnage unknown, another departments castoff Chicago mechanical press.

Rick

with a mechanical BP, there isn't much control to the speed. There may be a shock load to the material. May be bending with the grain.....and have be lucky in the past.

We controlled the speed with the clutch, and broke it in 4 steps. Hard to see how we could have been more gentle.

We sort of understand the grain issue, but we were trying to use less material. What we really don't understand is the catastrophic failure during the hot bend.

Cheers

Rick

HOT BEND!, I'm sorry I missed that, Sorry I can't help hope you find a solution.

I'm watching this thread, your problem is becoming interesting.

toughness of steel has a low point at a given temperature it is possible that you heated not enough and had in the bending region the critical teperature. In forging this is well known.

Hi All:

When I was taught die design they recommended the form die have a radius of one times the metal thickness. Your die is only 1/2 the stock thickness. I think this could be causing you a problem. God's blessings Bill

Hello RickZillman

Nearly 50 years ago we first ran into that problem, and it was caused by steel sourced at that time from Japan. We had previously been supplied steel from the UK steel works.

We then asked our steel suppliers to ensure that they supplied us in future from steel works in the UK, and there was no further problem.

You do not list your Location or Country (easy for you to do that in your Profile, and it auto-updates through all your Topics and Posts, including this one).

I would be carefully checking the source Country of that steel, and perhaps go back to your earlier source, where you had no problems, as we did all those years ago.

As an aside, after some 6 years from that first trouble we again sourced steel from Japan, and no further troubles ensued - it appeared they had solved the problem.

Bending along the grain does generally result in early fracture.

Steel which has been allowed to cool to far before being rolled also has the early fracturing problem.

Kind Regards....

Apologies for incorrect spelling in the final sentence of my above Post.

<"....Steel which has been allowed to cool to too far before being rolled also has the early fracturing problem.....">

Kind Regards....

Apologies for incorrect spelling in the final sentence of my above Post.

<"....Steel which has been allowed to cool to too far before being rolled also has the early fracturing problem.....">

Congratulations for using correct spelling and English. I'm happy to see there are others who pay attention to proper spelling and grammar.

We first assumed it MUST be Chinese steel, but the documentation shows it was cast and rolled in the U.S. On the right is a piece that we broke, with some backside fracturing, on the left, the piece(s) that fractured with a bang. As can be seen, we were only on the second bump when it let go.

Regards,

Rick

Interesting observation Sparkstation,

In college, in a course I had taken physical metallurgy 101 per say.

The professor that taught, said that the Japanese visited our steel works (U.S.), and were appalled be how dirty the facilities were, and said that they could make cleaner and more efficient steel, and they did.

in the late 60's and 70's the cars, such as Honda's had such pure steel that in the northern winter climates, the bodies were rusted out within 2 years.

They learned the hard way, what they thought were impurities, was needed in the steel to make them more durable.

phoenix911

are there no quality control, material certification, or procurement specifications?

do we buy what is the cheapest and hope for the best?

Thanks to all who responded!

We have spoken to several other shops, and each report similar problems! One shop had cracking while forming 1/8" sheet!

I guess we just can't take the material being infinitely malleable for granted anymore.

Rick

We see it all the time, not only with Steel but Aluminum also. And occassionally the outer surface with Galvanized material will peel off. We are able to ask for material from our vendor to come from certain mills which we have found the material is much better than others. When it comes to buying materials cheaper is really not better and in the end is much more costly between rejects in house and rework need to repair and replace. And more importantly the chance of sending bad product to your customer.