HK, HT, or HU material in annealing application 1

[jjdavis]

We are looking at changing the material of grid plates that we use in an annealing oven. The max temp is around 1550 deg F. We currently use HT material. One person has recommended HU or HX (increased Nickel content) to increase ductility while another has recommended HK (increased Chrome content) to increase heat strength. Which is better for our application more Nickel or more Chrome?

Thanks.

 

[arunmrao]

The person recommending HU or HX has perhaps no concern what it might cost you. HK or HN is good enough for annealing furnace charge grids. If you could redesign the grid by providing stiffeners at frequently failed region it should help extending the life. If possible ask the foundry to add Nb ,it helps.

 

[macmet]

We are currently using HH material in our furnace. Our performance is fairly good although we were considering a switch to HK. But as arunmrao pointed out the cost of nickel these days is incredible.

Check out this link,

http://www.infomine.com/Investment/HistoricalCharts/ShowCharts.asp?c=Nickel

 

[EdStainless]

The first question is 'how are the current grids failing?'
You have to be careful. If these see rapid heating and/or cooling then making them stronger may result in them failing faster.
If you need more ductility and long term metallurgical stability then paying for more Ni is not a problem.

Let's identify the problem first.

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Rust never sleeps
Neither should your protection

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[jjdavis]

The grids are round and are made up of 3 sections, with 2 sections being half circles. Basically, divided in 3 by 2 parallel lines. The sections are bolted and welded together. The half circle sections end up pulling away from the center section, distorting more at the thinnest cross sectional area, the points of the half circle. Also, the edges recieve a bit of breakage. Probably due to age and lifting the grids by the edges.

 

[EdStainless]

Have you looked at the microstructure? What is the camage mechanism?
Are these run at temperature in air?

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[jjdavis]

No, we really haven't done failure analysis of the grid plates. Since we are a manufacturing facility, we really don't have the equipment to do that sort of thing.

Yes, air only.

 

[arunmrao]

I am familiar with the kind of fixture you described as I make those kind. Most of the damages in your kind of operations occurs from rough handling. Also in an attempt to bring all the members together to form a circle,thin members are designed and these get broken . Try working around these and you may be able to extend the useful life.