Geology, Geology Talk

Steel: A global product for the US market

In 2018 the USA imposed steel tariffs on all but four countries outside North America (including Australia). Bill Langer explains the importance of the ingredients that make up US steel production – and why tariffs on imported resources don’t perhaps promise the jobs boom that the Trump administration is hoping for …

Unless you have been hiding under a rock (there are worse ways to spend your time!), you probably have heard about tariffs on steel as one way to boost the American economy and bring jobs back home. But is steel really being made in America?

Well, yes, but many of the ingredients that go into steel are mined elsewhere and still have to be imported.

The three raw materials used in making pig iron (the material needed to make steel) are iron ore, coke (residue left after heating coal in the absence of air) and limestone (CaCO3) or burnt lime (CaO). About two tonnes of ore, one tonne of coke and half a tonne of limestone are required to produce one tonne of iron.

The US has plenty of those three basic ingredients to make all the iron it needs. But there are other mineral elements that are sometimes used to manufacture steel from pig iron. One of those elements is silica (Si – quartz). The silica dissolves in the iron and increases the strength and toughness of the steel without greatly reducing ductility. Generally, the silica gravel (also known as metallurgical gravel) has to be of high purity, free of specific deleterious elements and of a proper size and strength. Fortunately, we also have plenty of silica to make steel.

There are a number of other basic mineral elements that are required to manufacture different types of steel. Unfortunately, the United States is not self-sufficient for most of those elements.

Take a look at the map (Figure 1). It shows some of the elements that are imported for use in steel and their sources. The abbreviations for the elements shown on the map, and their uses in steel, are shown below:

  • Co (cobalt) is used in making cutting tools. Sixty-one per cent of the cobalt used in the US is imported.
  • Cr (chromium) is added to steel to increase tensile strength, hardness, toughness, resistance to wear and abrasion, and resistance to corrosion. The US produces some chromium through recycling, but imports all of the chromium ore it uses.
  • Mn (manganese) removes unwanted oxygen and control sulphurs, which makes steel brittle. The US has not produced high-quality manganese ore since 1970.
  • Ni (nickel) increases the strength and hardness of steel as well as increasing resistance to corrosion and scaling at elevated temperatures. The US imports 52 per cent of the nickel it consumes.
  • P (phosphorus) increases the strength and hardness of steel and improves machinability. The US has a large a phosphate reserve base. Nevertheless, it imports 10 per cent of what it uses.
  • Ti (titanium) makes steel lighter and stronger. Seventy-five per cent of the titanium the US uses is imported.
  • V (vanadium) increases strength, hardness, wear resistance and resistance to the shock impact of steel as well as improving the properties of high-speed metal cutting tools. The US previously produced vanadium as a by-product of uranium processing but no longer does so.
  • W (tungsten) increases the strength, wear resistance, hardness, and toughness of steel, and imparts superior hot-working and greater cutting efficiency at elevated temperatures. There has been no tungsten production in the US since 2016.

So, if there is steel supporting that rock you have been hiding under, remember the steel was made with resources from all over the world.

Bill Langer is a consultant geologist. Email bill_langer@hotmail.com or visit researchgeologist.com 

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