Charpy Tests

[Welderpaul]

We need to Charpy test some 40mm thick ms transition plates (Posh base plates)as well as ultra sonic. (BS 5996 Grade LC2)
I understand these tests are to ensure that laminations are not present.
How do laminations get included in the plate - presumably from the rolling process? Would these cause the plate to tear apart (Delaminate) under load if they were present?

We get cast certs from the profilers, would these be sufficient?

 

[Paul.]

Not base plates for robots are they?. Charpy testing is done on a specimen of the material not the actual job, not something you can do yourself. when we did something similar a few years ago we bought certified material. bounce the problem over to your supplier and keep a solid paper trail is the best way to do it.

 

[Welderpaul]

Not robots no. Theres lots on the internet about the method of testing but i dont see how the test method translates into finding laminations in the plate. Or is it the ultra sonic thats better at finding delaminations?
'Pre certified' material seems the way to go - presumably its not done as part of the standard manufacturing process of plates though.
Theres going to be some tremendous loads on these plates.

 

[Paul.]

i dont see how the test method translates into finding laminations in the plate. Or is it the ultra sonic thats better at finding delaminations?
'

Ultra sonic and x ray would find laminations, charpy is an impact test (destructive) to determine toughness and brittleness.
I used Pegasus profiles for my plates, all nicely cut to size, surface ground, certified and stamped with matching Id numbers, they're probably a bit far away for you though.

 

[TechnicAl]

Laminations are very very rare, almost non existent these days. Way back when they could be a problem but unless its coming from some outpost of the civilised world its highly unlikely that the plate is laminated.
It can be directional just the same as wood ie with or across the grain and you can get segregation.

As someone has already said, the Charpy test is done to determine brittleness, usually done at sub zero temeprature. Its a small piece 55mm long, 10mm square with a 2mm deep V notch cut into one side. This is hit by a hammer from a specified height at a certain speed (a british standard hammer blow). You then measure the amount of energy the piece has absorbed.

Sometimes they specify the direction of the test piece (along or across the rolling direction) so you can find the weakest link.

Usually you buy plate already tested but sometimes its not available so you need to test it, or you can upgrade it (or try to) by testing it at a lower temperature than they did originally.

 

[Welderpaul]

What is segregation Al?

 

[Dune]

Paul, if you could give some details on what the plates are going to be used for and in what conditions I may be able to help you. As a structural engineer I have to have similar tests done on bridge bearings. The pre cert is often the way to go and if you need a full destruction test, you would use the bakers dozen principle.

 

[TechnicAl]

What is segregation Al?

Usually in MS plate its Carbon that tends to concentrate along the centre line. Its basically due to the carbon migrating from the outside of the plate leaving the centre with higher carbon (like a line of people where instead of taking a step forward they all take a step back except one). The heat of rolling does the job.

This results in the centre being harder, higher strength and more brittle than the rest. If you acid etch the plate (through thickness) you can see a dark line.

 

[Hitch]

The LC, stands for low carbon doesn't it?

 

[TechnicAl]

The LC, stands for low carbon doesn't it?

I dont know but the BS is the old standard for Non Destructive testing not the plate chemistry spec, so I doubt it. But Ive been wrong before (dont tell her indoors)

 

[cookie munsta]

use only british, american or skippy/ kiwi steel depending on where you are, occacionally you will need to test welds for defects but testing steel is a new one isn't it?, maybe it gets them around having to specify uk steel, as some asian brands have quality fluctuations, and it wouldn't be really fair trade friendly to exempt them. I'd use local steel and use thier garentee and pass on the price. reputation is everything in competetive markets

 

[Welderpaul]

After a bit of arm twisting, it looks like our profiler can supply the stamped plates c/w all the test certs we need. Saves a lot of messing about.
Cheers all.