Is Slag Magnetic? 7 Facts You Should Know!

Slag is produced during the metallurgical process of ores. In this article, we shall discuss whether the slag possesses magnetic properties or not in detail.

Slag can be magnetic or nonmagnetic depending upon the by-product of the ore. The slag consists of by-products like silicon dioxide, ferrous matter, and other metal oxides. The magnetic characteristic of slag is due to the presence of this matter generated.

The slag is used for coating, cleaning, and producing different substances. The other metals are exacted from the ore slag. We shall discuss in detail which type of slag is magnetic and which is not, and also the magnetic behavior of a different type of slag with detailed reasons and facts further this topic.

Is all slag magnetic?

The magnetic slag responds to the magnetic matter and attracts easily to the magnet. Let us discuss whether all slag is magnetic or not.

All slag is not magnetic. The slag is a remnant of the extracted metals from the ore, and the slag composition differs based on the variant of the ore and remaining unextracted metals. Only the slag, which consists of magnetic metals, shows magnetic behavior.

The examples of magnetic slag are listed below in the table:-

Type of SlagMagnetic or Nonmagnetic
Iron slagMagnetic due to iron
Ferrochrome slagMagnetic due to ferromagnetic iron and chromium
Steel slagMagnetic because steel consists of Fe.
Wollastonite slagWeakly magnetic due to the presence of garnet, Mg, Mn, and Fe substituting Ca.
Thomas slagWeakly magnetic due to the paramagnetic behavior of the calcium.
Cement SlagWeakly magnetic and lower magnetic permeability.
Glass slagMagnetic as the glass slag attracts towards the magnet.
Welding slagMagnetic due to the paramagnetic behavior.
Magnetic Slags

Non Magnetic Slag

The nonmagnetic slag does not attract toward the magnet and does not show a response in the presence of the magnetic field. Here is a table listing the nonmagnetic slag below.

Type of SlagMagnetic or Nonmagnetic
Silica slagNonmagnetic due to the presence of diamagnetic silica.
Coal slagNonmagnetic due to the presence of carbon.
Lead oxide slagNonmagnetic as it is diamagnetic.
Silicon dioxide slagNonmagnetic due to diamagnetic behavior.
Nonmagnetic Slags

Is coal slag magnetic?

Coal slag is produced by burning organic matter and when the coal is melting at 2500 degrees. Let us discuss whether a coal slag is magnetic or nonmagnetic.

Coal slag is weakly magnetic and shows paramagnetic behavior. Coal is entirely composed of carbon, which consists of two unpaired electrons in its outer orbital that pair up with other carbon elements to form metallic bonds. The paramagnetic characteristic of coal slag is due to the presence of carbon.

Is iron slag magnetic?

The iron slag is produced while manufacturing of iron and steel with traces of limestone (CaO) and silica matter (SiO2). Let us ponder on the magnetic behavior of iron slag.

Iron slag is magnetic and shows ferromagnetic characteristics due to the presence of iron. Iron has four unpaired electrons in its 3d orbital, which makes it magnetic. The limestone is paramagnetic, and silicon dioxide is diamagnetic and responsible for the reduction of the magnetic permeability of the iron slag.

Is welding slag magnetic?

The slag formed on the metal during welding is due to the reaction with the oxygen to form the metal oxides. Let us illuminate whether a welding slag is magnetic or not.

The welding slag is nonmagnetic and shows diamagnetic behavior. It is in the form of oxides. It composes of calcium fluoride, calcium carbonate, and silicates. The oxides are mostly diamagnetic in characteristics. The welding slag having traces of Fe is magnetic, and its silicates and carbonates are paramagnetic.

Slag Image by Rosser1954 (CC BY-SA 3.0) from Wikimedia Commons

Is copper slag magnetic?

Copper slag is produced during the extraction of copper by the process called smelting. Let us discuss whether a copper slag is magnetic or nonmagnetic.

Copper slag is magnetic and polar magnetized because it contains a huge amount of ferromagnetic iron. Iron oxide is reduced to give iron during the smelting of copper in the furnaces. Also, copper shows a paramagnetic behavior due to the presence of a single electron in its valence orbital.


We can conclude with this article that the slag can be magnetic and nonmagnetic based on the types of matter it constitutes. The slag is strongly magnetic if it consists of ferromagnetic particles and nonmagnetic if the combination of metals leads to the absence of free electrons.

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