premmington
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BOC Argoshield & Air Products bottles are expensive to hire/exchange, due to bottle rental agreement. Linde *removed for legal reasons* will sell you a welding shielding bottle, but outlets are few and far between, unless you live in the midlands, and they cost the earth
You can use CO2 as a shielding gas for Mig welding mild steel but not for stainless steel due to carbon contamination from carbon dioxide, carbon monoxide is created from the heat in the weld pool. Using CO2 as a shielding gas converts MIG welding (metal inert gas) to MAG welding (metal active gas). Active, being the absorption of carbon into weld pool from the carbon monoxide expelled from the heated shielding gas.
Ready source's of bottled CO2 are pub gassing bottles cellar gas, tavern gas & sureflow. Do not use bottles with nitrogen in them (grey bottles for cream flow beers, Guinness, sureflow mixes). Pub bottles weight 17.25kg when full, 11kg when empty, dimensions are 94cm high x 14cm Ø diameter and they are black in colour, any black bottles marked CO2 with a white stripe down them are for liquid with-drawel and thus no use for welding. £20 is about the going rate for a full pub bottle at the time of writing. Another source of CO2 are 4.7kg fire extinguishers. Most fire extinguisher suppliers will refill bottles. Some pubs now use full size CO2 bottles! The size of industrial W-size oxygen, argon/argoshield welding bottles, 230bar pressure, weighing 85kg gross, dimensions 146cm high x 23cm Ø diameter.
CO2 pub bottles show about 50bar (750psi) at 15°C when full and have a 5/8 bsp male threaded fitting. Standard argon bottles have 5/8bsp female fitting designed for a male bullnose fitting. So an adapter or dedicated CO2 regulator is needed, adapter/regulators available from http://weldability.com/. Machine Mart sell the cheapest industrial type CO2 regulators.*
CO2 when compressed turns into liquid-ish fluid, thus low bottle pressure, propane/butane & LPG acts very much the same. When contents of the bottle turns from liquid to a gas it lowers in temperature, due to process of gas transfer from a liquid state. Thus you may experience some weld splatter as the cold shielding gas hits the red hot weld pool. You can overcome this by fitting a CO2 heater directly threaded to the bottle before the regulator. I use a Murex Sirocco heater but a cheaper version from http://weldability.com/ is available. At very high flow rates i.e. building ships/bridges, CO2 will have to be heated as the low temperatures cause vapor locks and damage to regulators/gas lines. Splatter is also caused by the Arc voltage increasing in CO2, a different type of Mig welding, takes place above <200A in CO2, spray transfer, this has some good side effects i.e. improving weld penetration in really thick plate. If you, can't live with a bit of splatter on thin plate when using 0.6mm wire, you will need Argoshield Lite from BOC, Argoshield Lite also leaves the weld bead with a flatter profile than CO2, which is handy when welding repair patches on cars, saving time on post weld grinding.
Most low amperage (>150A) Mig/Mag welding will need shielding gas supplied to torch at a pressure of1.5-2.0bar (20-30psi) and a volume of 5-7 litres a minute, when welding outside in windy conditions will require more gas, about 10 litres a minute and/or physically shielding your welding with a jury rigged windshield, plywood or sheet metal. A Bobbin Type Flowmeter to set the flow rate between regulator and mig torch is a must for economical usage of gas. It will pay for itself very quickly.
More expensive MIG welders have spot welding timers, one of ours is fitted with this function, I have never used it and consider it to be a total waste of money. You will need a special nozzle shroud with slots in the side of it, to use it anyway. We have two MIG welding sets, a Murex autolynx4 inverter & Miller compact 151 (The Miller being the best of the two, its actually the best portable MIG I have ever used & they cost less than half of the price of a Lincoln, Murex or professional Cebora). Welders with reverse polarity function are handy for using different types of wire i.e. gasless (flux cored). Solid*wire sizes 0.6mm to 0.8mm are needed for all auto repair work. Spools come in 0.5kg 5kg 15kg sizes, 5-15kg size far cheaper if you are going to do any amount of welding.
Alumininium, stainless steel and mig brazing must be done in pure argon.**Helium (balloon gas) can be used for MIG/TIG welding really thick alloys, its messy with lots of splatter, but the weld penetration is very good.
Do not be tempted to transfer gas from one bottle to another, CO2 is a fluid and its very difficult to achieve gas transfer and Argon bottles are pressurized to 230bar (3450psi) when full. Which would cause a oblivious safety hazard for the connection pipe! Connecting/gas transfer pipes are available from scuba diving kit outlets thou. Pressure bottles need to be secured/chained upright or stored lying down, if one falls over and knocks the valve off, you will get a torpedo bouncing about your garage! A point of interest is: in Europe adapters are available to refill 13kg 19kg 49kg propane bottles via auto-gas-pumps, its a cheaper way of buying the gas than exchanging them.
The new Vectra-C model from Vauxhall has been built using galvanised steel plate. By using galvanised steel plate, Vauxhall are offering a longer body life through improved corrosion resistance. This in turn demands the application of new welding techniques, materials and processes in body repair and MIG brazing is a process that is used to braze together galvanised plates using a copper based MIG brazing filler wire (CuSi3) with a low melting temperature >500°C. Thus not removing the original galvanised coating. Spray on, weld thru nickel primer is now available for MIG welding galvanised panels with normal mild steel wire, which improves the rust prevention somewhat at higher temperatures. MIG brazing wire is availible from Machine Mart in 0.5kg or 5kg rolls.
Don't be tempted for "no gas welding wire" all though its improving all the while, its not very good on thin plate & car body work, due to the slag it creates. Its very good for heavy plate (spray transfer <200amps) & when welding outside, the use it was designed for, plus you will need welder that has reverse polarity, gas mig torches are positive, no gas torches are negative. Real high amperage flux cored wire Mig welding above <400amps still use CO2 shielding gas to achieve higher arc voltage & thus deeper weld penatration.
Alumininium MIG repairs to automotive type castings. If its broken you have nothing to lose by trying to fix it! Some types of alloy are not weldable i.e. high heat treated 7075 and some others. MIG welding alloy will need to be done in pure argon, back gassed if the item has a hole in it. The trick is finding a matching wire to the base metal (not easy as only two types of wire available in 0.5kg spools 5% Silicon for cast alloy and 5% Magnesium for extruded alloy) plus getting the item for welding very clean by removing the outside layer of oxide. Alloy MIG welding will need more amps as alloy transfers heat at a greater rate. A higher flow of shielding gas will be needed due to the oxidizing properties of aluminum. Preheating in an oven or a propane torch (not oxy/propane or oxy/acetylene) can save cracking when cooling. Most low spec MIG welders, work by dip transfer i.e. short circuiting the feed wire into the weld pool, which causes the DC voltage to act like AC, thus burning the oxides out of the weld pool. We have in the past welded cracks in cylinder heads, alternator bodies, motorcycle crankcases, with more success using a MIG welder with argon/alumininium wire than the other option of using our more expensive AC TIG inverter/welder. If your going to do a lot of alloy MIG welding, a teflon torch liner will make wire feeding a lot easier, most wire feeding problems are caused by having the feed rollers adjusted to tight, the wire needs to slip between them if the arc does not ignite. Alloy 0.8mm wire will need 1.0mm contact tip as the alloy wire expands so much with heat from welding, causing torch jam-ups & feed motor birds nests. The big problem with welding alumininium is it does not change colour when hot, so you can't see the weld pool/bead very well. More expensive Mig welders are constant voltage, which works better for dip transfer at low amp settings!
You can use CO2 as a shielding gas for Mig welding mild steel but not for stainless steel due to carbon contamination from carbon dioxide, carbon monoxide is created from the heat in the weld pool. Using CO2 as a shielding gas converts MIG welding (metal inert gas) to MAG welding (metal active gas). Active, being the absorption of carbon into weld pool from the carbon monoxide expelled from the heated shielding gas.
Ready source's of bottled CO2 are pub gassing bottles cellar gas, tavern gas & sureflow. Do not use bottles with nitrogen in them (grey bottles for cream flow beers, Guinness, sureflow mixes). Pub bottles weight 17.25kg when full, 11kg when empty, dimensions are 94cm high x 14cm Ø diameter and they are black in colour, any black bottles marked CO2 with a white stripe down them are for liquid with-drawel and thus no use for welding. £20 is about the going rate for a full pub bottle at the time of writing. Another source of CO2 are 4.7kg fire extinguishers. Most fire extinguisher suppliers will refill bottles. Some pubs now use full size CO2 bottles! The size of industrial W-size oxygen, argon/argoshield welding bottles, 230bar pressure, weighing 85kg gross, dimensions 146cm high x 23cm Ø diameter.
CO2 pub bottles show about 50bar (750psi) at 15°C when full and have a 5/8 bsp male threaded fitting. Standard argon bottles have 5/8bsp female fitting designed for a male bullnose fitting. So an adapter or dedicated CO2 regulator is needed, adapter/regulators available from http://weldability.com/. Machine Mart sell the cheapest industrial type CO2 regulators.*
CO2 when compressed turns into liquid-ish fluid, thus low bottle pressure, propane/butane & LPG acts very much the same. When contents of the bottle turns from liquid to a gas it lowers in temperature, due to process of gas transfer from a liquid state. Thus you may experience some weld splatter as the cold shielding gas hits the red hot weld pool. You can overcome this by fitting a CO2 heater directly threaded to the bottle before the regulator. I use a Murex Sirocco heater but a cheaper version from http://weldability.com/ is available. At very high flow rates i.e. building ships/bridges, CO2 will have to be heated as the low temperatures cause vapor locks and damage to regulators/gas lines. Splatter is also caused by the Arc voltage increasing in CO2, a different type of Mig welding, takes place above <200A in CO2, spray transfer, this has some good side effects i.e. improving weld penetration in really thick plate. If you, can't live with a bit of splatter on thin plate when using 0.6mm wire, you will need Argoshield Lite from BOC, Argoshield Lite also leaves the weld bead with a flatter profile than CO2, which is handy when welding repair patches on cars, saving time on post weld grinding.
Most low amperage (>150A) Mig/Mag welding will need shielding gas supplied to torch at a pressure of1.5-2.0bar (20-30psi) and a volume of 5-7 litres a minute, when welding outside in windy conditions will require more gas, about 10 litres a minute and/or physically shielding your welding with a jury rigged windshield, plywood or sheet metal. A Bobbin Type Flowmeter to set the flow rate between regulator and mig torch is a must for economical usage of gas. It will pay for itself very quickly.
More expensive MIG welders have spot welding timers, one of ours is fitted with this function, I have never used it and consider it to be a total waste of money. You will need a special nozzle shroud with slots in the side of it, to use it anyway. We have two MIG welding sets, a Murex autolynx4 inverter & Miller compact 151 (The Miller being the best of the two, its actually the best portable MIG I have ever used & they cost less than half of the price of a Lincoln, Murex or professional Cebora). Welders with reverse polarity function are handy for using different types of wire i.e. gasless (flux cored). Solid*wire sizes 0.6mm to 0.8mm are needed for all auto repair work. Spools come in 0.5kg 5kg 15kg sizes, 5-15kg size far cheaper if you are going to do any amount of welding.
Alumininium, stainless steel and mig brazing must be done in pure argon.**Helium (balloon gas) can be used for MIG/TIG welding really thick alloys, its messy with lots of splatter, but the weld penetration is very good.
Do not be tempted to transfer gas from one bottle to another, CO2 is a fluid and its very difficult to achieve gas transfer and Argon bottles are pressurized to 230bar (3450psi) when full. Which would cause a oblivious safety hazard for the connection pipe! Connecting/gas transfer pipes are available from scuba diving kit outlets thou. Pressure bottles need to be secured/chained upright or stored lying down, if one falls over and knocks the valve off, you will get a torpedo bouncing about your garage! A point of interest is: in Europe adapters are available to refill 13kg 19kg 49kg propane bottles via auto-gas-pumps, its a cheaper way of buying the gas than exchanging them.
The new Vectra-C model from Vauxhall has been built using galvanised steel plate. By using galvanised steel plate, Vauxhall are offering a longer body life through improved corrosion resistance. This in turn demands the application of new welding techniques, materials and processes in body repair and MIG brazing is a process that is used to braze together galvanised plates using a copper based MIG brazing filler wire (CuSi3) with a low melting temperature >500°C. Thus not removing the original galvanised coating. Spray on, weld thru nickel primer is now available for MIG welding galvanised panels with normal mild steel wire, which improves the rust prevention somewhat at higher temperatures. MIG brazing wire is availible from Machine Mart in 0.5kg or 5kg rolls.
Don't be tempted for "no gas welding wire" all though its improving all the while, its not very good on thin plate & car body work, due to the slag it creates. Its very good for heavy plate (spray transfer <200amps) & when welding outside, the use it was designed for, plus you will need welder that has reverse polarity, gas mig torches are positive, no gas torches are negative. Real high amperage flux cored wire Mig welding above <400amps still use CO2 shielding gas to achieve higher arc voltage & thus deeper weld penatration.
Alumininium MIG repairs to automotive type castings. If its broken you have nothing to lose by trying to fix it! Some types of alloy are not weldable i.e. high heat treated 7075 and some others. MIG welding alloy will need to be done in pure argon, back gassed if the item has a hole in it. The trick is finding a matching wire to the base metal (not easy as only two types of wire available in 0.5kg spools 5% Silicon for cast alloy and 5% Magnesium for extruded alloy) plus getting the item for welding very clean by removing the outside layer of oxide. Alloy MIG welding will need more amps as alloy transfers heat at a greater rate. A higher flow of shielding gas will be needed due to the oxidizing properties of aluminum. Preheating in an oven or a propane torch (not oxy/propane or oxy/acetylene) can save cracking when cooling. Most low spec MIG welders, work by dip transfer i.e. short circuiting the feed wire into the weld pool, which causes the DC voltage to act like AC, thus burning the oxides out of the weld pool. We have in the past welded cracks in cylinder heads, alternator bodies, motorcycle crankcases, with more success using a MIG welder with argon/alumininium wire than the other option of using our more expensive AC TIG inverter/welder. If your going to do a lot of alloy MIG welding, a teflon torch liner will make wire feeding a lot easier, most wire feeding problems are caused by having the feed rollers adjusted to tight, the wire needs to slip between them if the arc does not ignite. Alloy 0.8mm wire will need 1.0mm contact tip as the alloy wire expands so much with heat from welding, causing torch jam-ups & feed motor birds nests. The big problem with welding alumininium is it does not change colour when hot, so you can't see the weld pool/bead very well. More expensive Mig welders are constant voltage, which works better for dip transfer at low amp settings!