How to demagnetize metal for welding? – Beginner welding guide

To perform welding, it is important to know how to demagnetize metal, since a magnetic field may cause several welding defects or even extinguish an electric arc. Moreover, those magnetic fields can be harmful to electrical appliances. Magnetized metallic tools are likely to induce electric current with a higher voltage than the voltage in appliances.

In addition, knowing how to demagnetize metal is important because a magnetized metal object still saves magnetic properties during the heating process.

There are several techniques that will help you to demagnetize metal. In what follows, we will discuss each of them and provide some tips to make the process easier.

Magnetized metal. Causes and consequences

Before we start, we need to discuss the reason metals can get magnetized.

Such metals as nickel, cobalt, and iron create a spontaneous magnetic field which is called magnetization. How can an object be magnetized?

For example, a workpiece or a welding table can be magnetized under the influence of external magnetic fields in their creation, transportation, storage, and work environment.

If you work with metals, using any kind of magnet can be the reason of appearing of a magnetic field. For example, when you use an electromagnet to remove metals. Another reason is power sources or live cables which are located close to metals. Plasma cutting may as well create a strong magnetic field when it is close to a metal object.

Magnetism can appear when you heat treat the metal or forge it. Pipes also tend to cause strong residual magnetism.

Moreover, if you have performed any magnetic non-destructive testing, this may also result in developing magnetism.

Don’t use DC current to weld because in that case, you always use the same polarity, which is likely to result in residual magnetism on your welding table.

And of course, we should mention that the earth’s magnetic field can also be the reason for the magnetized metal in case it was held in a North-South direction for a while.

If the working surface is magnetized it is likely to interfere with the arc and cause blow defects, so it is essential to detect residual magnetism before it will lead to serious consequences.

How to detect magnetism?

Usually, it is recommended to use a gauss meter for detecting and measuring magnetism. You can use either an analog or digital gauss meter. These devices will help you to determine how strong the effect of the magnetic field on the object is put.

Digital gauss meter

This device will help you to determine a numerical readout of the magnetic field’s strength. It is likely to give a more accurate measurement in comparison with an analog gaussmeter.

If you want to use a digital gaussmeter you need to make sure that the probe is close enough, otherwise, the results of measurement can be inaccurate. It is recommended to try several measurements before testing the device.

Analogue gauss meter

This device is also very helpful, but it can’t give you a numerical readout as the digital one does.

It is equipped with a needle that moves up and down and indicates the amount of magnetic force.

When you use this gauss meter, make sure that the needle is on zero, and it is better to perform several measurements to get a more accurate result.

Alternative methods

If you don’t have a gauss meter but still need to measure residual magnetism, you can use a compass, which also can detect magnetism properly. Or you can throw metal shavings on the metal and check where they will stick.

In addition, for safe welding, you need your gauss level to be lower than 5 gausses within a joint. During the welding, you need to control this level, not increase it to 20 gausses. During TIG welding, a lower arc voltage is used, so the level mustn’t increase to 10 gausses.

Demagnetizing metal. Required tools and performance

First of all, the natural demagnetizing process takes a lot of time, but it can be performed quickly if you place the strong magnet near the metal object. But there are some other methods to demagnetize metal and reduce residual magnetism.

Use a commercial demagnetizer

The right tool for the demagnetization process is a demagnetizer, which consists of a coil powered by alternating current. These tools come in different forms. They may come as handheld, pen style, and table type.

To demagnetize metal and reduce residual magnetism, you can also try a degausser coil, but the process will take more time and effort.

Use a battery

The first way to remove magnetism is to use a battery. For this, you will require a suitable metal object from stainless steel or other material, a battery, and a cable without insulating characteristics.

You start with establishing a connection between the battery and the metal piece with the help of the cable. Then you twist one of the ends of the cables (use pliers) and wrap each wire together. Twisted parts mustn’t be touched. Use tape on the connecting point of the cable to prevent the metal magnet from having access to both ends.

Then the wires are to be connected to the metals. Avoid touchpoints while wrapping the wires around. Connect them with the help of tape and turn on the battery. Now you can start demagnetizing metals.

Demagnetizing metal with the help of electricity

For this, you will require such primary materials as a copper cable, and a circuit.

Start with making a long coil of insulated copper wire connected to the circuit. Then you need to put the metal bar inside the wire so that it will face the east-west direction. Connect the cable to a source of alternating current. Switch on the circuit and when magnetism disappears, reduce the current.

Use an electromagnet

This type of magnet is used to create magnetic fields. To demagnetize metal using the electromagnet, wrap the object in insulated wires and connect the wires to the terminals. Put an electromagnet on the magnetized area and then turn on the power. When you have reached 2 feet away from the metal, turn the magnet off.

Reduce the magnetic field with the help of a degausser

This tool uses magnets to demagnetize metal. Usually, it is used for hard drives and other electronic devices. If you are taking advantage of this method, make sure that the object is placed in the center of the magnet.

Heat-treating the metal

This method means heating the object to the necessary temperature that removes magnetism. This temperature is called the Curie point and may vary from metal to metal.

Using this method, you allow the energy free the magnetic dipole from an ordered orientation.

The time you need for heating and magnetic properties also may vary depending on the thickness of your metal. For example, ferromagnetic metals have spontaneous internal magnetic fields.

Heat the metal slowly, and use a gaussmeter to control the level of the residual magnetism. When you have reached the necessary temperature, the demagnetization process starts. Let it cool to room temperature. Heat treatment will help you to completely remove residual magnetism.

If you don’t have access to a blowtorch, you can perform the heating process by leaving the metal in direct sunlight for a few hours.

Remember that extensive heat can damage protective coatings. Heating may not only change the magnetic properties of the metal but add some qualities that you don’t require, such as elasticity and strength.

DC and AC current

You can use AC for demagnetizing metal. Start with wrapping a welding cable around the workpiece. Magnetic fields take the strength from the amperage and the number of times you wrap the cable around the metal. Connect the cables so that they close the circuit and join them.

Switch on the welding machine and use the highest level of amperage. Switch the welding machine off and decrease the amperage to a steady rate. Ten seconds will be fine. This is how you demagnetize metal by applying the AC current.

If you’ve decided to use DC, then you need to create the field with the opposite direction to the residual magnetism. You also must be careful not to create a reverse field that will be stronger than is necessary. You must reduce the amperage in 10 to 15-ampere increments, and reverse the polarity to allow the remaining magnetism to reduce to a safe level.

Hammer

A hammer can be used for demagnetizing metal. Put the object on a hard surface and hit it. The impact will demagnetize metal by causing the magnetism to dissipate.

Other things you need to know about magnetization

You have to know the magnetic properties of different metals before you perform the demagnetization.

Manganese and iron can be magnets. For this, you need to level off the magnetic dipoles. There are also materials called permanent magnets, which you still can demagnetize. These materials involve neodymium iron boron, ceramic (ferrite) magnets, samarium cobalt, and aluminum nickel cobalt magnets.

You may be wondering what happens when a metal loses its properties. When you demagnetize metals, they tend to have little or no strong strength. This can influence ductility and malleability without affecting tensile strength or percent elongation.

Useful tips

Demagnetizing metal can be a difficult task, so here are some tips to make the process easier for you.

First of all, always remember to exercise caution, since magnets can be rather dangerous if you don’t handle them properly.

As we said before, you need to clarify which type of metal you are working with since they all have different properties. This may cause different problems during demagnetization because the response of the metal can be different from what you expected.

FAQ

To conclude. How to demagnetize metal?

The natural process of demagnetization is pretty slow, so you need to know how to demagnetize metal yourself. Moreover, this is very useful for welding, since the workpiece and the welding table can easily be magnetized. So if you can demagnetize metal, you can prevent several welding defects.

You can take advantage of a demagnetizer, a hammer, battery, or demagnetize your welding table or workpiece by applying AC and DC. Choose the most suitable tool for your specific case. You can also heat the metal, and it doesn’t always require a blowtorch, since you can heat it by placing it in direct sunlight.

To add, if you are not successful with one method, you can always try another one. Try until you find the solution to your particular case.

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