Wednesday, November 30, 2022

How to weld stainless steel to make craft beer kegs?

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It is very much in vogue craft beer brewing; the existence of wikiguides like Instructables, Wikihow and others allowed many people to decide to make beer production a profitable hobby – or just a fun hobby. However, since there is not much information on how to weld stainless steel, many people end up going into debt to buy the barrels for fermentation.

Is it possible to weld stainless steel to make craft beer kegs? Fortunately, the answer is positive: not only can it be done, it’s very simple! It is only necessary to learn some secrets and read the necessary advice to carry out this operation successfully.

Welding stainless steel: secrets and tips

The first thing you need to know is that it is possible weld stainless steel using TIG or MIG techniques. It is advisable to work with these —preferably TIG welding— and not with welding manual, since they produce a neater and firmer weld than those that can be obtained with arc welding.

The second: the recommended steel for this type of application is AISI 304: a very common austenitic steel on the market. As filler material use AISI 308L (or ER316L) steel.

Third: it is not necessary to preheat the parts, since the AISI 304 steel It is austenitic in nature. It is essential to apply heat after the welding, since, as the coefficient of expansion of this metal is 50% higher than that of other carbon steels, rapid cooling could cause cracking. Take care that the temperature does not exceed 400°C, as at higher temperatures the chromium will begin to diffuse and change the metallographic structure.

Other important factors

Note also that this steel has a lower coefficient of electrical conductivity than other carbon steels; this implies that you will need more electric current in the electrode to achieve the same welding than in other steels. try weld stainless steel of discard before doing it on the final pieces.

Finally, for MIG welding, if your machine does not have a table for stainless steels, try the parameters for carbon steel and increase the voltage and current by approximately 15%. Those new values ​​should be a good starting point to compensate for the increased strength of this material. Remember to use AISI 308LSi or ER316L steel wire.

Welding the stainless steel barrel

Assuming that you already have the cut and stuffed pieces ready for the welding—, the welding equipment is prepared with the following parameters.

welding method thickness (mm) Voltage (V) Current (A) Filler material Argon gas flow (m³/min) Welding speed (cm/min) Feed (cm/min)
TIG 1.15 or 2.3 12 or 14 30/70 (normal polarity) ER316L 0.34 5 or 10 as necessary
MIG 1.6 twenty-one 85 (reversed polarity) ER316L 0.425 48.25 467.35

Barrel body (central cylinder)

If you have a plate of stainless steel and not a tube, you must first weld this, thus making a tube with a seam. To do this, cut the sheet metal taking it to the size of the developed cylinder and generate the ribs (the radial reinforcements that will give resistance to the cylinder). Then carefully bend the sheet metal and clamp the free ends with a vise.

Barrel welding – stainless steel

try the welding as one with square ends, although in practice there will be a slight V-angle. welding to hold the sheet in place, and start welding from right to left, always taking care that the temperature does not exceed 400 °C, to avoid the diffusion of chrome in the crystalline structure of the metal. Every four inches stop and heat the heat-affected area with a torch flame to avoid stress and breakage. Remember, do not exceed 400°C. If you have a helper, you can make the cord welding continuously, while the other person heats the metal with the flame.

After the seam is done, examine it carefully. This joint is key for the barrel: if there is a defect, try to fix it now: later it will be a cumbersome task and will jeopardize the success of the project.

taps

If the faucet is stainless steel you can solder it without problems using the same technique (TIG or MIG). If, on the other hand, it is made of bronze or copper, it will be advisable to make a soft soldering with torch. Prepare the surfaces by brushing, cleaning and applying the necessary fluxes and eutectics.

The best flux for joining copper or bronze parts is AWS type 3A, and the best filler material is silver.

silver content tin content Temperature (°C)
3 97 220
two 98 230

Finally you need to weld the bottom and top. These pieces must be convex, to give the beer Barrel the necessary resistance when they contain the beer under pressure. Weld the base first, taking the same care as when making the side seam. Then weld the cap. Next, you need to weld the handle or handle. This piece can be recycled from an old barrel. Always remember: After welding, heat the welding area with a torch. welding, to avoid cracks due to sudden cooling.

Lid - stainless steel weld on barrel

Lid – stainless steel weld on barrel

hydraulic tests

Before it is put into service, a series of hydraulic tests should be performed to rule out any leakage and weld failure that could result in fluid leakage or leakage. To do this, immerse the barrel in a tub, connect a compressor to the faucet and apply compressed air until reaching 50% more than the maximum service pressure. Being submerged, any leaks will be immediately apparent through the bubbles.

Once this test has been passed, all that remains is to carry out an interior and exterior cleaning.

Additional Recommendations

The beer Barrel It is designed to store the beer after the fermentation process. Do not use the container stainless steel to carry out the cooking process, since it is not designed for that purpose. Instead, build an open, copper cooking pot capable of withstanding the temperature of the flame without weakening its crystalline structure.

This barrel is designed to receive the beer before the gasification process (when the extra sugar is added for this process). Always take into account the maximum pressure that this container must withstand, calculating a safety margin of at least 50% at that value, for the maximum service pressure of the barrel.

Adapt a stainless steel pot

It is also possible to modify a commercial pot of stainless steel for our purpose: to cook the must. For this we need a cooking pot capable of withstanding the heat of the fire without welding there.

It is possible to modify a large pot—the kind commonly used for stewing—for our purpose. It is only necessary that it be a new pot or a pot that has been perfectly washed, so that no food remains between the folds of the upper edge.

It is necessary to make a hole in the pot on one of the sides and below, to weld the necessary nipple there for the subsequent pouring. It is convenient weld stainless steel here, to prevent galvanic corrosion from occurring over time.

The nipple can have a thread at the outer end, to attach any necessary fittings there. On the inner side it is only necessary to remove the burrs.

Once the hole has been made to the size of the tube (it should be made a few hundredths or tenths smaller, so that both surfaces fit well), the latter is placed and welding is carried out, taking care to apply heat after welding. welding with a flame to avoid any cracking.

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