Metal Casting Zone Info Blog

Posts Tagged ‘Guidelines’

Welding cast iron calls for some special procedure. Welding cast iron is a challenging task and there can be no two opinions about that. Cast iron, unlike most other steels, has much greater carbon content at 2 to 4 percent. This causes most cast iron to be brittle making it difficult to weld. If the following procedure is followed, cast iron can be welded with relative ease:

Use either cooling or heating while welding cast iron as it is important to keep cast iron out of the 150- to 500-degree F range. Preheating is widely preferred, but there are times when cooling are also done. But stick to either cooling or heating and do not attempt to change in the middle of a weld.

Though preheating the cast iron part should suffice, it is preferable to preheat the entire casting slowly and uniformly in the 500- to 1,200-degree Frange. Be very careful to heat within the stated range as overheating may cause cast iron to crack. The casting should get hot just to the extent you can to touch it comfortably with your bare hand. If need be, make short welds intermittently to avoid overheating.

Occurrences of small cracks when welding cast iron, is inevitable. You can apply some sealing compound to prevent leakages. If there are major cracks you must repair with studding. Studding is a complex process calling for a lot of skills. The first step is to drill and tap holes on the surface that has beveled. The next step is to put in steel studs and the studs should come out 5 to 6 mm above the surface and the studs should then be welded to remain in place.

Preheated welding can be easily done – particularly for small and manageable objects. While welding the cast iron without preheating, it is extremely essential the operator has good control over the welding gun and make the welds as small as possible.

Welding cast iron with an arc welder calls for different procedure. As a matter of fact, persons capable of welding cast iron with arc welder are few in number and there is a great demand for such skilled persons.

You may have to either purchase or hire a SMAW (shielded metal arc welding or stick electrode) welder depending how often you do cast iron welding with arc welder. Plug your welder into a 220V outlet and then plug in your ground cord and welder electrode holder cord into the welder. Please know that to weld cast iron, you need a special electrode. You may buy a 770 stick electrode to weld cast iron.

First of all, clean the surface area to be welded with a wire brush. Clamp the grounding clamp cord from the welder onto the piece of cast iron that has to be welded. Thereafter, place an electrode into the welder electrode holder and position the electrode near where the weld has to begin.

Continue to tap the electrode on the cast iron till an arc is created and begin to weave the electrode stick from side to side. Make it a point to keep the arc slightly away from the piece of steel you are welding. Wait for a few minutes for the weld to cool off gradually. Use the welding hammer to chip off the slag from the top of the weld.

Guidelines of making Plaster craft

Plaster craft is a complex process unless you are aware of its ins and outs. Given below are a few guidelines of making plaster craft.

Step – 1:

Cover your work surface with an old newspaper or a vinyl peace. As you may see from this photo plaster casting is a bit messy, so it is essential to protect your countertops.

Step – 2:

Check the mould to ensure it is clean and dry. Any dirt might show on the finished casting.

Step – 3:

Many moulds cannot sit flat on the counter, therefore, it is important to give them support while using. The most simple process is a zip lock bag filled with a few pounds of rice. Rice bags are convenient to pack and store when not being used and are made of common materials most people find handy. A box of sand will also work well but it is more difficult to store it when not being used.

Step – 4:

The surface tension of the water tends to trap air leading to pinholes in the finished casting. Airid is a product meant to break that surface tension, reducing the chances of trapped air. Spray or wipe a thin coat of Airid into the mould.

Step – 5:

Wiggle the mould down onto your rice/sand bag till it looks level. You are now ready to mix plaster.

Step – 6:

To find out how much plaster will it hold fill the mould with water. It is the exact amount of water you will need. Add a bit more and weigh it on scale.

Step – 7:

Plaster should always be added to water and never vice versa. Sprinkle it in slowly to allow it to absorb water.

Step – 8:

Let the mixture remain undisturbed for 2 minutes so the plaster absorbs all water.

Step – 9:

For coloring, pigments should be added now.

Step – 10:

Utilize a potato masher to mix thoroughly for about a minute. Small amounts can be mixed with a stick.

Step – 11:

Pour the plaster in a corner of mould and let it flow across the complete mould. On deeper moulds, pour it down the side of corner to avoid entrapped air.

Step – 12:

Once the mould is poured, wiggle it to dislodge any air which may have remained in the mould.

Step – 13:

Periodically feel the mould. When the mould is warm to touch, the plaster casting may be removed.

Step – 14:

Gently flex the edges of mould to break sides of casting loose.

Step – 15:

Hold the mould just above the rice/sand bag. Use pressure gently to take out the casting.

Step – 16:

After casting is out, set the mould to be cleaned.

Step – 17:

Utilize a knife to cut the sharp edges off the back of the casting. For fast drying it should be put where it gets air from all angles.

Step – 18:

When fully hardened, most of the plaster will flake off or breakout the plaster.

Step – 19:

Flex the blade of the plaster blender to flake the dried plaster off.

Step – 20:

Wipe off tools and moulds for final cleaning up.

Step – 21:

If you utilize a rice bag any drips may be removed by flexing the bag. For sand box, just pick out any plaster that has fallen on sand.

Step – 22:

Pack up your moulds, tools and plaster. Throw away the old newspaper with which you had covered the working area. If you had used vinyl piece, dust it and wipe with wet cloth.