IRON ORE

One of the most abundant metals on the planet, iron makes up five percent of the earth’s crust and most of the outer core and inner core, which by mass makes it the most common element on Earth. It is also a common element found in the universe, as it has been discovered both in meteorites that come to earth as well as supernovas. No matter where it comes from, iron has a variety of purposes, whether it’s for maintaining human health or for its use in steelmaking. It is vital not only for industry, but for the continued existence of the world.

 

With an atomic number of 26 and the symbol Fe (for ferrum, or the Latin word for iron), this metal is a part of group eight on the periodic table, or transition metals located in the d-block. Like its fellow group members ruthenium and osmium, iron has a silvery color and high melting and boiling points, although in its natural state iron ore is filled with iron oxides that can make it appear to be a variety of colors ranging from rusty red to deep purple, which makes it a material also commonly used for pigments in paints and colored coatings. In its purest form, iron is a relatively soft element, but most of the time it is found with other elements that give it a harder texture, especially when it is mined. In its natural state, iron is often found bound in silicate or carbonate materials.

 

Iron has a long, extensive history of being melted down and used in a variety of ancient tools that can be traced as far back as 2.6 million years ago, ranging from wrought iron in 3000 B.C. Egypt to cast iron in China in the 5th century B.C.  Although the welding of copper tools predate the use of iron in history, it became much more desirable than the precious reddish metal due to its abundance. Iron was particularly desirable due to it being much easier to manipulate and shape into desired forms than other natural elements such as aluminum, which requires electricity in order to mold. In recent years, iron has been replaced by other materials such as plastic and glass fibers, but it still maintains an important place in modern society with a variety of uses across the world and remains vital as a part of commerce.

 

As an individual element, iron has a vital role in the maintaining of life in plants and animals, as it works with hemoglobin and myoglobin in order to facilitate oxygen transference in the blood stream for humans and animals. It also plays an important part in the cellular respiration in plant life. It can additionally be used for a variety of chemical compounds, whether it’s for purifying welding for other types of ore or forming binary compounds. It is sometimes used for scientific purposes as a measuring gauge, since iron tends to react the same way every time in experiments as opposed to other elements that lack reproducibility and stability, making it much more desirable for testing. However, for most of its practical purposes, iron is used mainly for industry and manufacturing.

 

IRON OXIDES

Iron ore is typically found combined with oxygen, which is commonly known as iron oxide. During processing,  the oxygen will typically be removed from the iron, along with other impurities, in order to obtain the pure metal.

There are sixteen iron oxides in different colors that have been identified, but there are several particular iron oxides that are the most commonly found:

  • Magnetite (Fe3O4), which is approximately 72 percent iron
  • Hematite (Fe2O3), which is around 70 percent iron
  • Goethite (FeO(OH)), which is approximately 63 percent iron
  • Limonite (FeO(OH).n(H2O)), which is up to 60 percent iron
  • Siderite (FeCO3), which is around 48.2 percent iron

Any of the materials above that contain over 60 percent iron, usually magnetite and hematite, are considered to be ready for blast furnaces used to make iron in its usable forms, such as pig iron. In the past, particularly during the American Revolutionary War and Napoleonic times, it was usually goethite that was used for iron weapons and tools.

As the industrial revolution set in during the mid-1800s, hematite was the preferred source of iron, which is referred to in the industry as “natural ore,” as it can go directly from the ground into a blast furnace for smelting with very few impurities. However, in recent years, particularly since World War II, this has changed dramatically, as magnetite has a higher concentration of iron ore to other iron oxides and is now being utilized more often in smelting.

Magnetite can be found mainly in banded iron formations, which is sedimentary rock that has ore combined with quartz, and is commonly known as taconite. It is also found in magmatic deposits originating from volcanic activity as well as in some river areas. If you look very carefully, magnetite can also be found on sandy beaches in parts of California and New Zealand.

 

IRON TO STEEL

The most common industrial use of iron in modern times is steel. Approximately 98 percent of all iron ore that is mined in the world is used in the production of steel. This alloy, which is made up of mainly iron and carbon, has been used almost as long as pure iron has been used over the centuries. Today, it is utilized for a variety of purposes, ranging from building infrastructure to railways to appliances in the home.

Smelting, or melting material to obtain ore, has been used for centuries in the pursuit of making and casting steel. The most common technique for creating useable iron today is through the use of a blast furnace, which combines iron ore with charcoal and limestone which causes many of the impure materials, such as oxygen, in iron ore to burn off.

 

This helps make what is known as pig iron, which is the basis of all irons used in industry and includes about four to five percent carbon. As a result, pig iron is rather brittle and needs to be refined further in order to be utilized for steel or any other type of iron welding. From pig iron, there are several options when it comes to usage:

  • The majority of carbon is reduced from the pig iron to about 0.3 percent creating wrought iron, which is rarely used today but was once utilized in gates, rails and nails.
  • Two to four percent carbon in iron combined with silicon, manganese and other trace elements creates cast iron for various tools.
  • When the carbon in pig iron is reduced to between 0.5 and 1.5 percent, with some other trace elements added, the ending result is low carbon steel. This is the preferred material in industries using steel where weldability, formability and additional strength are required.

 

When steel is created, other elements can be brought in to add other desired qualities; for example, if you add 10 to 30 percent chromium, it will result in stainless steel, which allows it to resist rust. However, in order to make sure the steel being forged is strong enough to withstand demanding applications, the iron has to have as many impurities as possible eliminated, such as phosphorus, silica and sulfur. These elements in particular will weaken the forged steel and possibly cause future breakage.

 

There is no way to actually determine between types of steel visually. Industries that require specific grades of steel use instrumentation to analyze the material to be able to confirm the exact type of alloy in order to make certain the wrong alloy is not used for a job that requires a specific alloy. Still gaining popularity in the testing/analysis arena is the handheld XRF which can provide instantaneous non-destructive elemental results and grade identification of carbon steel.

 

What Can the Bruker S1 TITAN do for Your Iron Ore Mining?

Mining for iron ore is considered to be one of the most important industries in the world, as its use is connected to a variety of different commerce through steelmaking. The majority of mining takes place in China, Australia and Brazil, but it can be found on almost every continent. The price of iron is considered to be one of the most important numbers to track in the stock market and can say more about the world economy than most any other element that is mined.

The mining of iron ore is considered to be easier than other metals, as the most desirable iron oxides tend to have magnetic properties, particularly magnetite and hematite. These ores have a higher concentration of iron to other elements, which means the grade of magnetite and hematite increases as well as their price points when they’re eventually sold on the market. Since magnetite is lower in aluminum, phosphorus and titanium and has a higher concentration of pure iron than other classifications, it often commands a higher price than other types of iron ore.

No matter the type of iron ore that is being mined, the most important thing reflecting the price of that specific iron ore is the ratio of pure iron to other elements. If they are below an atomic number of 18, they are often referred to as light elements, and in the case of iron ore, they are usually referring to aluminum, magnesium, silicon, phosphorus, chlorine and sulfur. Other elements found in iron ore above the atomic number of 18, such as titanium, are categorized as heavy elements. No matter how valuable the other elements are, when it comes to iron ore and smelting, they are all considered to be impure elements, as they will affect the final quality of the iron. XRF instruments or elemental analyzers are more and more used today at mines site, in the refining process and in the factory to be able to determine the concentration of elements in the ore through the various stages of mining, processing, manufacturing and distribution.

No matter the atomic number of an element, large amounts of impure elements in iron ore can incur smelting penalties, as these elements can slow the operations at any plant that is preparing the ore for use. Impurities such as silicon can be valuable on its own, but it has to be highly controlled when iron ore is being smelted for a specific purpose. The biggest problem with light elements found in raw iron ore is that they’re trickier to find and need a very sensitive analysis system. This is where XRF analysis comes in. XRF can provide results and find impure elements to help manage cost and get the most out of a mine.

Lab analysis has been used in the past with iron ore, with atomic absorption, ICP and fire assay being the most commonly employed. However, these methods often take more time and preparation to create appropriate samples, which, along with submission to a lab, means that results are often delayed. This is why many labs have utilized XRF technology in recent years allowing for more efficiency in producing usable results. Find out How XRF Works.

Sample preparation for XRF requires iron ore to be pulverized in order to properly map out the atomic structure on a flat surface, which is a relatively easy preparation method. Another way to test is by creating fusion beads, which grinds the iron ore into a pulp and is then combined with a flux such as lithium and occasionally an oxidant to create a molten glass bead. Although these fusion beads can make the material homogenous on an atomic level and can make iron ore easier to analyze than in its original state, there are many analysts who don’t like it due to the dilution of the natural ore.

Field Portable XRF (FPXRF), however, has taken the next step in the mining market. It has the ability to be used with very little to no sample preparation, although it is recommended that a pulp specimen be prepared for the most accurate results, particularly for the reading of penalty elements. FPXRF can be used at all stages of the mining process, from exploration to ore grade determination to final product analysis. Incredibly easy to use, almost anyone on the site can use it. It also provides immediate results, whereas a lab takes time to analyze the results that a portable machine can give you in seconds, allowing important decisions to be made by geologists in the field in real-time.

Both systems have vital uses, and one doesn’t necessarily replace the other, as there are certain things only a laboratory can determine. While a lab might offer an extremely precise measurement with lower limits of detection, a portable XRF offers real-time results that allow on-site technicians to create geochemical data sets at a rapid pace and be able to make more time-sensitive decisions if necessary. Combining these two techniques allows a more precise form of measurement when it comes to mining operations. Contact Bruker to find out how the S1 TITAN can expedite your Iron Ore Mining efforts!