Welding colours

[CRS51]

Hello all, have been practicing welding with the tig and some stainless pipe and angle and have started to get some colours in the welds, is this good/bad/needs to be rectified ?
1.6 tungston, 6lpm, 3mm wall stainless and 40-45 amps.

Also is stainless VERY expensive in general ?
I visited my local steel stockists and explained I was learning to tig weld and asked if they had any unsaleable offcuts that I could have in return for tea bags/coffee/a few quid for the lads and they gave me a quote for £20+vat for 2 pieces of 4" dia pipe 6" long and 1/8" wall thickness.
Seems very dear to me ?
Cheers Chris

 

[Sub-arc]

Colours look pretty normal to me. Some nice welds there too (bead width a bit inconsistent)

And s/s is expensive, along with all other metals. Just ask the pikemiesters.

 

[julieanncharters]

if you want stainless to practice on, go and visit a good scrap yard that deals in non- ferrous.
otherwise expect to pay a fortune for new stuff.

 

[cumbriasteve]

I think where stainless is concerned there is no such thing as unsaleable offcuts, offcuts even as small as a cig packet are sold on ebay simply because there are that many people using the material for hobby work, etc etc.

 

[backpurge]

Where you have the colours, the material has lost its corrosion properties so will corrode unless rectified, don't worry it is perfectly normal. Apart from that the welds look quite respectable, well done

 

[Shox Dr]

They look fine, if I was to be pedantic the last picture shows too much heat, the RHS half of the weld, you can see the weld is dark and the HAZ is wider than the rest.

 

[CRS51]

Ok thanks for the comments, more practice for me !

Chris.

 

[Goodwelder]

Use a 2.4 needle and 120amps and a 1.6 rod if you find one of them tig bits that go between the torch and the pink outside bit that has mesh in they work well. I was told if it goes any darker than gold colour it's f***** because there's too much heat in it.
But I'm self taught by trial and error I could be wrong

 

[Welderpaul]

needle

*Tungsten*

 

[Paul.]

one of them tig bits that go between the torch and the pink outside bit that has mesh in

Gas lens

But I'm self taught by trial and error I could be wrong

Really? !

 

[langy]

Gas lens



Really? !

Troll alert !!!

 

[backpurge]

[QUOTE I was told if it goes any darker than gold colour it's f***** because there's too much heat in it.
But I'm self taught by trial and error I could be wrong[/QUOTE]

You're wrong fella

 

[Lawnmowerboy]

I thought gold was the right balance between power feed arc gap ect...

 

[Alfaman]

Shox Dr and Backpurge are both spot on. Not a whole lot wrong with those SS welds, good work there!

[QUOTE I was told if it goes any darker than gold colour it's f***** because there's too much heat in it.
But I'm self taught by trial and error I could be wrong

You're wrong fella

You're wrong, troll (Edited for accuracy)

 

[ChrisJohnsSculpture]

Well look at it this way....

The colours are caused by thin layers of oxide on the surface of the metal. The colour of oxide formed depends on the highest temperature that the surface of the metal reached. The precise mechanism of the colour formation eventually comes down to quantum physics but suffice to say that there is a general relationship between the maximum temperature and the colour . The colour/temperature ranges from a light gold (around 170degC through bronze to purple then blue (300 odd deg C) and then finally a matt grey.

Clearly when you are welding you are melting metal so the weld bead itself must, by definition get much hotter then this range, however the shielding gas, should prevent any oxides from forming until it has cooled somewhat.

So...the actual oxide colouration you get depends on several factors...
how much heat actually goes into the weld in the first place, the gas coverage, how quickly the weld cools vs the travel rate .

Some materials eg titanium alloys are extremely sensitive to atmospheric contamination at temperatures well below their melting point and as such need special precautions (trailing gas shields, inert gas filled welding cabinets etc) so any colouration may be an indication of a problem.

But for steels which don't have this sensitivity oxide colours aren't a particularly reliable indication of any one factor. The extent of the colouration outside of the shielding gas coverage will give an indication of the size of the heat affected zone so if the oxidised area is very wide or very uneven that may indicate a problem.

 

[langy]

Well look at it this way....

The colours are caused by thin layers of oxide on the surface of the metal. The colour of oxide formed depends on the highest temperature that the surface of the metal reached. The precise mechanism of the colour formation eventually comes down to quantum physics but suffice to say that there is a general relationship between the maximum temperature and the colour . The colour/temperature ranges from a light gold (around 170degC through bronze to purple then blue (300 odd deg C) and then finally a matt grey.

Clearly when you are welding you are melting metal so the weld bead itself must, by definition get much hotter then this range, however the shielding gas, should prevent any oxides from forming until it has cooled somewhat.

So...the actual oxide colouration you get depends on several factors...
how much heat actually goes into the weld in the first place, the gas coverage, how quickly the weld cools vs the travel rate .

Some materials eg titanium alloys are extremely sensitive to atmospheric contamination at temperatures well below their melting point and as such need special precautions (trailing gas shields, inert gas filled welding cabinets etc) so any colouration may be an indication of a problem.

But for steels which don't have this sensitivity oxide colours aren't a particularly reliable indication of any one factor. The extent of the colouration outside of the shielding gas coverage will give an indication of the size of the heat affected zone so if the oxidised area is very wide or very uneven that may indicate a problem.

I bet he already knew that

 

[Seano]

Use a 2.4 needle and 120amps and a 1.6 rod if you find one of them tig bits that go between the torch and the pink outside bit that has mesh in they work well. I was told if it goes any darker than gold colour it's f***** because there's too much heat in it.
But I'm self taught by trial and error I could be wrong

Dude you are ..................................................................................................

 

[Drains]

Dude you are ..................................................................................................

View attachment 29116

In so many ways

 

[Goodwelder]

Clearly colour is a good indication of the heat input and thus the mechanical properties of the stainless! Hence like you said trailing shields with Ti etc.... With dairyfab anything beyond gold will have you packing!

 

[ChrisJohnsSculpture]

Clearly colour is a good indication of the heat input and thus the mechanical properties of the stainless! Hence like you said trailing shields with Ti etc.... With dairyfab anything beyond gold will have you packing!

Not really, it's a rough indicator of the temperature of the metal after it's been exposed to atmosphere but as I said that is a combination of various factors.

The point is that a weld seam must have been exposed to temperatures far in excess of 'gold coloured' otherwise it would never have got anywhere near fusion temperatures.

The idea that no part of the weld ever gets hotter that 200degC is plainly ridiculous.

It also depends whether your taking about the bead itself or the wider HAZ.

Excessive oxidation in the zone which shoud be covered by shielding gas may indicate a problem but then again it may not. A slow travel rate will tend to reduce the oxidation of the weld bead but that doesn't mean that it wan;t excessively heated.

To take an extreme example you could weld something in an inert gas booth and it would never show any oxidation colours no matter how much heat you put into the weld. By the same token you might deliberately weld something like chrome moly tube with a high current and fast travel speed and get a lot of surface oxidation and produce better welds than if you did it more slowly and ended up with a nice shiny weld.

It's also worth bearing in mind that after about 300degC the oxide colour is grey so as long as it's not very heavy it can appear to be colourless so if you are using a wide cup on thin metal its perfecter possible to have no visible oxide colours at all.