- What Is Pot Metal?
- What Is Pot Metal Used For?
- Is It Worth Welding Pot Metal?
- What Are The Problems Of Welding Pot Metal?
- What Do You Need To Know Before Welding Pot Metal?
- The Right Welding Rods For Pot Metal
- Preparing Pot Metal For Welding
- The area to be welded must be abraded and cleaned using one of these methods:
- Welding Zinc-Based Pot Metal
- The Correct Welding Technique For Zinc-Based Pot Metal
- What About Rolled Zinc Alloys?
- Here is a step by step process for TIG welding pot metal:
- The Right Type Of TIG Welding Machine
If you need to repair an item made from pot metal, it’s important to know how to weld it properly. Even if you are an experienced welder, you may find it difficult to carry out this job properly since the task is quite challenging to get right. Some experts even believe that welding pot metal isn’t possible at all, however it can be done as long as the appropriate steps are taken.
What Is Pot Metal?
Pot metal is sometimes known as white metal, die-cast zinc or even monkey metal. The term refers to any metal alloys with a low melting point which are used by manufacturers to make an inexpensive, rapid casting. The colloquial term “pot metal” was coined thanks to the practice in car manufacturing factories during the early part of the 20th century of collecting non-ferrous scraps of metal from the manufacturing process and then melting them down in a single pot to create cast products. Although small amounts of iron often got into the castings, it was kept to an absolute minimum since iron raised the alloy’s melting point too high.
What Is Pot Metal Used For?
Pot metal is often find in use on parts which are not required to withstand a high stress or torque. Items which are frequently made from pot metal include tool parts, toys, electronic components, cheap jewelry, car parts and furniture fittings. It may even be used in budget musical instruments like electric guitars.
Pot metal has no specific formula as it is made of a combination of several cheap metals, and its low cost is one of the reasons why it is used so often and for so many different applications. As there is no need for any specialized tools in order to cast pot metal thanks to its low melting point, it is an affordable choice, however on the downside, it often breaks down for precisely these reasons, becoming more misshapen with time.
Pot metal can easily be damaged, and therefore many classic automotive parts and other pot metal items will require repairs. While sometimes those repairs can be carried out quickly and easily with a handful of materials and tools, other times welding will be necessary to carry out a thorough repair to rectify the damage.
Is It Worth Welding Pot Metal?
As many of the items made from pot metal are cheap trinkets, quite often it is pointless to carry out welding in order to repair them since they are very low value. However, there are a number of pot metal items which are certainly worth the effort. For example, a number of antique items and classic car parts such as ornaments and trims are all made from pot metal and can be very valuable when repaired to a high standard with welding.
What Are The Problems Of Welding Pot Metal?
The main problem involved with welding pot metal is that it can be very hard to determine the type of alloy that it is. While some pot metal items can be welded safely, other are primarily alloys of aluminum or zinc and this presents a greater difficulty. Zinc, for example, cannot be welded since it releases toxic and harmful fumes. It is also extremely difficult to weld since its melting point is exceptionally low. If the alloy is primarily aluminum, it may potentially be completely unweldable.
What Do You Need To Know Before Welding Pot Metal?
Although welding broken metals is hard, it’s certainly not impossible. However, it is still key for the welder to be properly trained in welding safety since it can be a hazardous activity.
Wearing the correct protective clothing is also essential to guard against burns and injuries. Knowing the correct temperature for the metals with which you are working is also vital. Most pot metals will have a melting point that ranges from 610 degrees Fahrenheit and 1600 degrees Fahrenheit.
This makes carrying out welding tricky since it could reach its melting point before you have completed the necessary repairs. This will be doubly true if you are working with an aluminum alloy pot metal.
The Right Welding Rods For Pot Metal
The three main types of welding rods include:
- Alladin 3 in 1
All of these rods are actually advertised for the purpose of welding using small hand-held propane torches, which is not actually welding, but brazing, however they can also be used for the purpose of Tig welding pot metal.
Preparing Pot Metal For Welding
As pot metal parts usually are fairly clean, only a small about of minor grinding is often required before carrying out welding. However, the problem is often that the part has broken off completely.
If this has occurred, you will need to create a little groove of the crack as this will enable sufficient penetration to ensure a strong joint.
However, it is important to remember that, in the case of an ornamental item, if it has been broken due to a drop or fall, it will break again if it is dropped a second time, regardless of how deep the weld is penetrated, so there’s no need to go over the top on penetration.
The area to be welded must be abraded and cleaned using one of these methods:
- Using sandpaper
- Using an emery board
You may also need to degrease your work area for the best welding result.
Welding Zinc-Based Pot Metal
If the pot metal that you need to weld is zinc based, (which is most types of pot metal), it’s important to be aware that the melting point of this alloy is 725 degrees Fahrenheit. There are two kinds of zinc alloy used in welding – cast zinc and rolled zinc.
While these metals are brittle at room temperature, they require an elevated temperature for mechanical work. Zinc alloys also have two times the electric conductivity of steel as well as a lower melting range, around the same specific heats and higher thermal conductivity.
When welding zinc alloy pot metal, it’s important to adjust the welding flame to carburizing, however no soot should be deposit onto the joint. An oxyacetylene flame is a lot hotter than the flame required and therefore selecting a small tip is essential.
When welding a zinc-based pot metal, the welding rod can either be a die casting alloy of the same kind as the pot metal to be welded or made from pure zinc. Metal flux of 50% ammonium chloride and 50% zinc chloride can also be used, although this is not mandatory.
The Correct Welding Technique For Zinc-Based Pot Metal
When welding zinc-based pot metal, the following steps must be taken:
- The casting must be heated until the metal starts to flow.
- Once the metal is flowing, turn your flame so that it is parallel to the surface that you are welding. This will ensure that the side of the flame keeps the metal soft while the welding rod is heating to the same temperature.
- When the welding rod and base metal are at the same temperature, you should apply the rod to the walls of the joint and fuse with them thoroughly.
- Manipulate the rod to break up any surface oxides.
What About Rolled Zinc Alloys?
If the pot metal is made from a rolled zinc alloy, you will need to adopt resistance welding instead. This uses less heat input than arc welding or gas welding, but still ensures sound and professional looking welds. Spot or seam welding should be done on lap or flange joints, with the overlap size being dictated by how thick the metal sheet is.
The Application Of Resistance Welding
When resistance welding rolled zinc alloys, you will need to use a current which is equivalent to low electrode force and steel. Because of the softness of the metal, and its greater thickness, rolled zinc alloys will require a low inertia follow up to ensure control of your welding electrode. Although internal defects and cavities may be frequently seen, these can be reduced if you use a forging force.
What About Cast Zinc Alloys?
When welding a cast zinc alloy, you can adopt the same parameters that were established for use on rolled alloys. However, as an additional thing to look out for, cast zinc alloys frequently feature extra coatings, so you should remove those before you begin welding.
Using Super Alloy 1
One of the most recent developments in welding is a product which is called Super Alloy 1. This kind of rod has a melting point of 350 degrees Fahrenheit and it can bond at around half of the melting point of the majority of pot metals. It has a honey flux which turns brown when it has reached the right bonding temperature, ensuring that the welder knows when the time is right. When the product is finished, it can be polished or plated and will be just as strong as its base metal. This is an affordable yet very effective way of repairing zinc metals, even if you are a welder with very little experience.
TIG Welding For Pot Metal Repairs
If you are wondering how to weld pot metal, one of the options that sometimes work is TIG welding. This is a known technique for welding titanium, copper and two dissimilar metals and it perfect for tricky welds. It works by generating heat through an arc of electricity which jumps from a metal electrode onto the metal surface which is being welded. It works well on aluminum, so if you are using an aluminum-based pot metal, you will find that this form of welding works well.
TIG means Tungsten Inert Gas. It is named after its tungsten electrode as well as the inert argon gas sheath which surrounds it.
Here is a step by step process for TIG welding pot metal:
- Choose your electrode – often your TIG welder will have the correct electrode already installed. If you are welding an aluminum alloy pot metal, you will require a pure tungsten rod. There are several types of tungsten alloy rods too which are best suited to welding specific alloys, so you will need to determine which is the right one for your particular pot metal mix.
- Grind your electrode – you do this by grinding your tungsten rod into a point. This step must be completed especially if you are using a rod which has no rounded or pointed tip as it is brand new. As you weld, the tip will start to round due to the heat during welding. A pointed tip gives a directed, small arc whereas the arc dances around more with a round tip.
- Insert your electrode into the collect – you do this by unscrewing the rear of the electrode holder, inserting the rod and then replacing the back. You should ensure that the electrode’s tip is only around a quarter of an inch away from its protective sheath but no further.
- Choose your settings – an average TIG rig has 3 main options for electricity – DCEN, DCEP and AC. You will need AC for an aluminum alloy weld. You should then select one of the Penetrating options. Around a 7 on a 1-10 scale is the best option. Set your air setting to around 5 seconds if your machine enables you to do so. This refers to the length of time your gas will stay on following the arc stopping to prevent the weld from rusting or oxidizing. You should then adjust your Max Amps to a high setting of around 250.
- Turn on your gas – if you are welding an aluminum-based pot metal, you should use a pure argon gas. This is essential to prevent corrosion of the weld, since metal begins to rust or oxidize in the case of aluminum very rapidly at the very high temperatures which the metal can reach.
- Prepare the welding table and the metal – you will need a large metallic area to allow the electricity to flow properly through your metal surfaces. A welding table, specifically purchased for this purpose is ideal, however using a big piece of sheet metal is another suitable alternative as long as it is flat. Use a wire brush (kept purely for the purpose of cleaning aluminum) and scrub the metal’s surfaces. If you want the welds to look extra professional, you should also use acetone to wipe the welding rods down. However, if you aren’t really bothered about the way your welds look when they are done, there’s no need to worry about this step, but note that your welds will not only not be as attractive but they will also be a bit weaker. Clamp your metals in place so they will stay in the right place as you weld. Also, if you have some available, spray the welding table with some anti-spatter as this will prevent metal which has leaked off from sticking wherever it lands to maintain a flat surface.
- Wear the right clothing – TIG welding can burn your hands, damage your eyes or give you flash burns. You need to put on a pair of thick leather welding gloves as well as closed toed boots or shoes and a good quality welding helmet. You also need to wear a specialist welding coat or alternative a thick jacket or long sleeved shirt. You may want to invest in an auto darkening welding helmet, however a good one will be expensive as you need it to change quickly. If you want to be sure that it will darken rapidly, use an always-dark helmet instead and simply use a flashlight if you need to see what you’re doing without wanting to lift up your helmet.
- A final check – hold your electrode in your preferred hand and ensure it moves freely without the cord being tangled or hampered. You’re ready to start!
- Begin welding – hold your electrode around 1 inch from the metal’s surface. Never ever touch your metal with the electrode as the molten aluminum will then leap up onto your electrode. Should this happen accidentally, you should immediately stop, switch off your welder, take off the tungsten rod and grind it fully down before you begin again.
- Jam down in your foot pedal in order to quickly activate the current and transmit the heat to the metal. You need to heat the metal rapidly and begin your weld pool. You will recognize it as soon as it appears as the metal will become fluid.
- Begin welding at an edge. When your weld pool has formed, simply dip the rod in but only for a very tiny fraction of time since if the metal is heated for too long it begins to warp. The longer you heat the metal, you will notice that it warps more. This is known as a tack weld and it holds the piece of metal in place allowing you to remove the clamp and complete long bead welds.
- Once your weld pool has begun, you should ease off the foot pedal a little as this will control how much current and heat is being applied to the piece of metal. Remember that welds always shrink when they cool, so you should alternate sides if you want the welds to stay even.
- This will also help to keep one of the sides of metal from becoming too hot and then warping. Remember that hot metals warp considerably, and therefore if you fail to change sides, you could find that you are as much as quarter of an inch off where you metal needs to be.
- Draw a bead – once you have finished tacking, you should remove the clamps that you put in place earlier. Begin a weld pool by jamming your foot down onto the pedal rapidly. Once this is done, lighten the pressure on the pedal and regulate the current. If you find that the metal is beginning to melt or burn away, you are dumping in too much current, so back off with the foot pedal. On the other hand, if your metal surface is becoming flaky but not liquid, step harder on the foot pedal to exert more power. When welding aluminum alloy pot metals, move the electrode down towards the rod while you carefully feed the rod into the weld pool. The rod must be on the side of the electrode where the weld will form. This is called “leading” the electrode.
- Types of welds – the main problem in TIG welding is getting your weld pool to fool simultaneously on both of your pieces of metal. The fillet is the simplest form of weld – this is when two metals are joined at a right angle. The next easiest is a lap weld. This refers to two metals which rest flat, one against the other. A butt weld is a little harder to achieve. This is where 2 metals touch along their edges and it is hard to keep your electrode moving along the join in a straight line and it is also hard to keep your weld pool progressing well on both edges. Corners are tricky to deal with, since the heat will not dissipate evenly. Cosmetic welds are another possibility. These long more even over a longer length. You can create them by starting a weld pool then dipping the rod in before moving on to the next point. You should use them on any highly visible joint for a better finish. On the other hand, a strength welt does what it says, holds metal more tightly. These are ideal for areas that you are welding which are not visible. They are designed to be strong rather than attractive and are essential for use in anything that bears a load. You simply create these by drawing along the weld pool continuously while you constantly feed the rod in.
The Right Type Of TIG Welding Machine
You will need to choose the right TIG welding machine in order to effectively weld pot metal. An A/C TIG welder is what you are looking for and it must have a high frequency start. The majority of pot metal welding tasks are able to be welding using a small 1/16″ tungsten electrode with a blunt tapered tip.
Set your amps to around 80 max. When TIG welding pot metal, it’s advisable to only weld for up to 10 seconds at any one burst before stopping for a minute or so to allow the metal to cool. That means that just as the metal is flowing freely you should stop. Frequent cooling will ensure a professional finish.
Although welding pot metal has a reputation for being difficult, thanks to today’s modern technology it is much easier to handle. Although you may struggle to get it right the first few times, with a little practice you should be able to manage to repair your pot metal item and restore it to full strength and an attractive appearance.