Difference Between Down Hill & Up Hill Welding

http://www.ehow.com/video_4428025_uphill-welding-wrought-iron-fence.html

http://www.weldingtipsandtricks.com/mig-welding-techniques.html

http://www.google.co.uk/search?q=up+hill+welding&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-GB:official&client=firefox-a

hope the links help

GA for the good explanation.

We just do not know what sort of material he's trying to weld in his down hill (vertical down) method.

Furthermore, I would personally offer him either GP type rutile or the cellular type for good deep penetration that can be further controlled by polarity when it comes to doing root runs on pipes.

What are you welding and how thick is it? And what is the use for it? From 1/8 and thicker you should leave a opening between - (approx. 1/32 to 1/16) the bigger the rod the more opening. The rod should be pointed upwards under an angle of 35 a 55 degrees and then sliding downwards. If your rod has a substantial mantle, you can rest the rod against the material in the sleeve. Make sure to have the gap filled in. Use a slightly darker glass #10 or #11, because you will look into the arc from above. Once you see what you are doing, welding is a temptation and an addiction.....Enjoy.

I'm not welding anything mate!

What I said was due to not knowing the OP's intentions....he might be welding a pipe in 45 degree or a pressure vessel.

In any case he wants to know the difference between the two methods.

I would also add that in vert down there can be a greater chance for slag inclusions and poor penetration. In vert up the problem is heat build up. Heat rises so as you travel up so is the preheat in the base metal. That helps in the penetration area but too much can cause problems at the top of the weldment. There the heat has no place to go so the tendency is to have a blow out at the end of the weld. A way around that is to use a run off tab.

Simply speaking, vertical up-hill welding, is welding from bottom to top of a weld joint on a plate. Since the movement is against the gravity the weld travel speed is slower (say 300 mm/min. with 3.20mm size electrode for SMAW process) and results in more heat flow during the welding in the joint.

vertical down-hill welding, is welding from top to bottom of a sheet. Since the movement is towards gravity the weld travel speed is (say1 1/2 times faster in downhill - 450 mm/min. and with higher current) and results in lesser heat flow in the joint.

This reduced heat flow during vertical down is good up to 3 to 4.00 mm thick sheet metals and with a sq. butt joint. You will have less distortion /warping apart from achieving required penetration and fusion at the root.

For plate metals beyond 4.00 mm & for unlimited thicknesses the heat flow will not be sufficient due to thickness factor and invariably you have to opt for vertical up position and with a bevel opening.

To understand the heat in put during welding operation.i.e., Heat in put (or) arc energy is calculated by basic formula (say in SMAW process)

Arc voltage*Arc amperage*60= V*A*60 kilo joules per mm length of weld.

1000 * weld travel speed in mm S*1000

26 V *130A*60 = 0.676 kj / mm.

1000*300 mm/min.

27 V *140 A*60 = 0.504 Kj / mm.

1000*450 mm/min.

Generally light coated rutile type electrodes are used for V-Down and medium heavy coated for V-Up positions.

Similarly in cross country pipe line welding beyond 20 inches size and above, E 6010 / E7010 etc., (light coated) electrodes are used in V- Down welding for root welding to achieve a faster travel speed and higher productivity followed by E 7013 for filler cap in V-Up positions. Off late GMAW process welding is being used in place of SMAW in cross country pipe welding.

On the other hand, in plant piping, where, 100% Radiographic Quality welds are required we use same E 6010 electrodes in V-Up position.

Sridhar

"For plate metals beyond 4.00 mm & for unlimited thicknesses the heat flow will not be sufficient due to thickness factor and invariably you have to opt for vertical up position and with a bevel opening."

It is not unlikely that you would opt for using a vert. up method under 1/4 (6.35mm) plate if you are welding a tank for instance, unless you're using a home workshop method because then any goes.

You'd use vert. up on pipes for root runs though, even if they are about 4mm, it also depends on the position of the pipe though.

If you work for a constructing firm they would always supply the right kind of welding rods for the job. And if you weld a tank they would likely to give you a cellulose type welding rod to use on a 1/4 plate to do vert down with good penetration, even if you weld for x-ray. Naturally, you'd need to gauge the back side and again repeat the process. Of course you would need to use run out plates (finger bars) to give you a defect free fillet on both ends. If you do a good job your fillet should not protrude >1mm on each side.

it is not unlikely that you would opt for using a vert. up method under 1/4 (6.35mm) plate if you are welding a tank for instance, unless you're using a home workshop method because then any goes.

On production line, it is common to use vertical down for thickness beyond 2.0 mm and up to 4.00 mm including tanks made of sheet metal. It is easy to weld in vertical down than in vertical up. Of course you have to provide a root gap (where required) depending upon the size of the electrode and travel speed. It will help to to reduce the distortion during the welding, than in Vert. up..

You'd use vert. up on pipes for root runs though, even if they are about 4mm, it also depends on the position of the pipe though.

Since the discussion is on Vertical up / down, any welding up to 4.00 mm thick pipes/tubes in vertical up will puncture (burn through) the joint due to slow maneuverability of electrode in overhead and inclined segments.

a cellulose type welding rod to use on a 1/4 plate to do vert down with good penetration, even if you weld for x-ray. Naturally, you'd need to gauge the back side and again repeat the process.

Using a rutile coated electrode in place of a cellulose type electrode for vertical down is more economical and in both cases the results will be good. It may not be necessary to back gouge if proper weld parameters including current and travel speeds are selected. Back gouging and re-welding on a thin sheet is a costlier proposal.

Sridhar.