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sleeping-wood
17th Mar 2008, 09:45 PM
I am about to start putting togther a steel staircase for a house I am building. The staircase has been engineered and is what is known as a "spine beam" staircase. The design has a central stringer with steel treads welded to the stringer. The spine is 200x100x4 RHS, the treads and associated supports are 10mm plate welded to the spine beam. On top of the steel treads a timber tread is bolted from underneath.
I am contemplating using a 3 phase stick welder (old tranny type) I have available.
After reading several posts here about inverter welders that are available am I going to get a better job if I shell out and purchase an inverter welder for the job? Next question is what rods would anyone care to reccomend to give best results for this thichness of material?

Claw Hama
17th Mar 2008, 10:04 PM
Nothing wrong with an old skool 3ph welder, should do just fine with that thickness of steel and as I just posted a while ago you still can't beet CIG rods for ease of welding 3 - 3.5mm rods satincraft (they may have a new name now)

DJ’s Timber
17th Mar 2008, 10:14 PM
:whs: use either 3.2mm or 4mm Satincraft rods.

Claw Hama
17th Mar 2008, 10:22 PM
:whs: use either 3.2mm or 4mm Satincraft rods.
Sorry DJ, I'm still old skool and think of them in gauges (10#) not up with exact mm sizes of rods unless I'm looking at the packet.:B

Vernonv
18th Mar 2008, 11:09 AM
I agree with the guys above :2tsup: ... unless of course you need an excuse to buy an inverter, in which case they don't know what they are talking about and an inverter is the ONLY way to go:D.

patty
18th Mar 2008, 11:42 AM
Yep totally agree you dont have to shell out huge $$$$ to get a nice job the 3 phase welder will be fine obviously you do have 3 phase on site?

I am interested in the design of the Staircase Sleeping Wood as I have an old spiral staircase I want to get rid of do you have any plans or pics so I can have a squizz it might give me some ideas

sleeping-wood
18th Mar 2008, 04:38 PM
There are lots of pictures on the net, but it may take a bit of searching.
The important thing to do with this type of staircase is to get it "Engineered" as you don't want a footy team standing on it and have the thing collapse.:no: It also has to comply with the BCA.

If you want to have a look at some (great) designs go here, there are so many different designs you may find something you like http://www.pushpullbar.com/forums/showthread.php?t=2358&highlight=staircase

The link is to an architecture and design forum. Search for staircase if the link don't work http://www.pushpullbar.com/forums/index.php thread is called stairs, stairs, stairs

Sorry but I don't have my plans in digital format, but I can post some photos when I start construction if you wish. Here are a few pictures I have collected.

Grahame Collins
18th Mar 2008, 08:15 PM
Hi,
Your 3 phase will be more than adequate for the job.

I could think of better electrodes than Satincraft.I say this as many new to welding fellas have problem with slag inclusions

There are other electrodes more tolerant of long arc lengths and welding over their own slag.However when used competently they produce a good finish.

grahame

sleeping-wood
18th Mar 2008, 09:09 PM
Hi Grahame,

Would you care to nominate a suitable electrode?
I was thinking of using a 4mm rod so I have to purchase as I only have 3.2mm in my rod stock.
I would prefer one that has limited splatter (if one exists) Are the cheap electrodes any good? I have never used them and must confess that lately all I have used are satincraft.

Fossil
18th Mar 2008, 09:49 PM
Cheap Chinese electrodes are crap IMO.


I have several boxes of Liquid Arc 6012, 6013 and 7018 and they are a decent electrode. I have a large stock at hand, which were given to me by a retired boilermaker. For your application, 6010 or 6012 would probably be ok depending on your welding and prep skills.

Grahame Collins
18th Mar 2008, 10:16 PM
My choice would be

Kobe Rb 26

Wia Aust Arc 12 P

Cig Weld 12 Xp

Fossils Liquid Arc can would be alright too.

If you have Satincraft and have no trouble with them, use them by all means .I try to steer new guys away from Satincraft as slag problems can put them right off welding.

Grahame

sleeping-wood
18th Mar 2008, 10:45 PM
Who stock these rods?

Grahame Collins
18th Mar 2008, 10:51 PM
Welding supply shops.

Engineering supply shops

Google (Australia )them for suppliers that may be close to you.
Grahame

thesupervisor
22nd Mar 2008, 08:21 PM
for this purpose i would use a low hydrogen type rod a 16 or 18 in 3.2mm even if you just do the root run in the low hydrogen and the top run in a gp 6013 i tend to go over board on strenght on structual stuff as i would feel not too good if your stairs fail and some one gets hurt so the price of some rods shouldnt matter either

Grahame Collins
23rd Mar 2008, 09:18 PM
A point needs to made about using low hydrogen electrodes.
People assume that because an electrode has a high tensile strength,it is an automatic choice.

Yes they have a substantially higher yield ie 70KPa as against 60 KPa.
The parent metal in this case is structural steel which has a tensile a bit less than the 60KPa electrode tensile.The same load applied that would make the 60KPa electrode fail will also make the LH bead fail.

If an excessive load is applied, the weakest area shall fail and that would be the structural steel.

The low hydrogen bead will pull out of the steel virtually intact.
I have done thousands of welding cert tests and can assure you this is what happens.

Grahame

thesupervisor
23rd Mar 2008, 10:36 PM
thats intresting graham but if a weld was stressed onto its self it would not fall out?
lets say a stair tread and its attached to the stringer on the top and the underside if execisive load was applied would the metal bend first or would the weld fail ?
im no expert but i like to learn so if you could tell us how most of the failures occur in the tests you have done would be intresting

Grahame Collins
28th Mar 2008, 10:50 PM
Sorry guys ,its been a real busy week.

The spine beam design is one I would have an engineer calculate some loading specs for you and specify a particular minimum safety load limit.

From the pictures I can see is a horizontal tee welded to a vertical plate standing vertically (and welded to ) on the incline beam.

If the plates are 10mm plates are welded to the incline beam which is 6mm wall thickness,then say a max load applies at the outer edge of the stair tread.

The stair treads being say 900mm wide would have a leverage of 450mm on the vertical plate.

Its a matter of working out the maximum conceivable load that could possibly to be applied at that area. So not being trained to work out loads in Newton/ metres, I will not even try.
The longer the leverage and difference in the load changes calcs considerably. Its one of those crazy things where you might calculate for,say,several large drunken footballers lifting an 4cwt anvil up those particular stairs for a prank. Would it bend the plate or fracture the metal? I suspect it would only bend the metal ,least ways until the drunks got a fright then dropped the anvil down the stairs. Anyway serve you right for letting those drunken idiots like that in your place anyway.

The testing I did was mainly on 225 x 100 x 12m MS plate.
which was welded with LH 3.25mm 7016 electrodes. the plates were set up as a tee section on the center line of the plate.
The weld was a 3 pass fillet welded between 10mm min and 12mm max leg lengths on 1 side of the tee joint.
The break test was conducted so that the weld bead was placed uppermost in the press. The load was applied to to top edge of the highest plate.

The resulting fracture usually removed the LH bead pretty much as an entire piece, displaying the coarse m/steel grain structure. From memory I think they used to go between 17 and 20 tonne pressure loading before fracture occured. Steel tensile is around 30 something ton per PSI ,but this was a leverage induced fracture so its something different.Below is an illustration of the fracture testing arrangement.


I am ready for bed,
Cheers have a great week end
Grahame

sleeping-wood
9th Apr 2008, 07:22 PM
Finally have started on the stringer and landing beams for the staircase. The stringer and beam are 200x100x4 RHS with 10mm end plate to the landing beam. This lot goes to the grit blaster next week for cleanup before fitting into the house, tread welding and painting.

I am waiting for the tread material to come back from the laser cutter to do the tread work.

The plan drawing is an early drawing given to the engineer to work with to provide steel sizes etc.

spooled
14th Apr 2008, 10:29 PM
Looking good sleeping wood. Keep us posted on it. What rod did you end up using? I would have recommended a WIA 13S or Kobe 6013 if you can rotate the job around so all the welds are done in the flat position. If any of the welds are positional then I'd always go with WIA 12P.

Some info on lo-hy's. As you said Grahame many people use them where they are not really necessary. The advantages of these rods are that they have a higher tensile weld metal (to suit the high tensile steels they are designed for), and tend to avoid cracking under the weld bead caused by hydrogen from moisture. If you're not welding high tensile or crack sensitive steels then they are only going to be harder to weld with and more expensive. The only mild steel applications they are used in are high fatigue situations, eg high pressure steam pipe that is repeatedly heating and cooling, or a vehicle chassis such as a truck or train that is constantly flexing.

Grahame I know you know what you're on about, but the tensile strength ratings are not in kpa. In the AWS standard the 60 and 70 in 6013 etc is one hundredth of the tensile strength in psi. So they are 6000 and 7000 psi respectively. In the metric standard they would be 41 and 48 which is one tenth of the tensile strength in mpa, or 410 and 480mpa.

Oh and btw for a weld to be classed as hydrogen controlled both the electrodes and the work need to be preheated.