How dependent was Nazi Germany on iron ore from Sweden?

Question

From the wikipedia article on Swedish iron mining during WW2, there are a lot of uncited claims. I'll quote the most outstanding of them here:

In the year before the war, Germany received 22 million tons of iron ore from various foreign sources. Although it was able to produce around 10m tons of its own iron ore each year, it was of low grade quality and needed to be mixed with high grade material from other countries such as Sweden, which annually supplied it with 9 million tons

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Grand Admiral Raeder, head of the German navy, declared that it would be "utterly impossible to make war should the navy not be able to secure the supplies of iron-ore from Sweden".

Any truth to these?

Apparently the British thought it critical enough to try to interdict it, but never got much of a chance after Germany controlled Norway (1940 May onwards). Still, if it was this critical, you'd think there be sources. Just how dependent was Nazi Germany on Swedish iron ore? Would the Wehrmacht really grind to a halt without it?

I'm looking for documented numbers regarding this.

Answer 1

The Plan R 4 article lists the following source:

Ziemke, Earl F. (2000) [1960]. "Chapter 2, The German Decision to Invade Norway and Denmark"., Command Decisions, United States Army Center of Military History. CMH Pub 70-7.

Quoting from the source, emphasis mine:

With due allowance for Hitler's tendency to play by ear, it can be said that the German interest in Norwegian neutrality at the beginning of the war was sincere. For Germany the advantages were substantial. Of the approximately six million tons of Swedish magnetite iron ore which Germany imported annually, about half passed through the Norwegian ice-free port of Narvik.

So while the numbers don't really match up (6 vs. 9 millions), the overall claim that Swedish ore was a significant ressource for Germany is legit.

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Extending regarding the comment on total numbers:

This site lists 1937 worldwide iron ore production. It doesn't list its sources, but it looks far too detailed and matches with my knowledge of these matters at a glance, so I doubt the numbers are made up.

Copying the numbers (in per cent of global production) for iron ore, sorted:

• USA, 38.0
• USSR, 14.3
• France, 11.7
• Sweden, 9.3
• Rest of British Empire, 5.9
• UK, 4.4
• Greater Germany (incl. Austria, Czech Protectorate), 4.1
• Japan (incl. occupied territories), 2.2
• Rest of French Empire, 1.8
• Latin America, 1.4
• Norway, 0.7
• Italy, 0.5
• Yugoslavia, 0.3
• China, 0.2
• Hungary, 0.1
• Rumania, 0.1
• Greece, 0.1

The overall global production for 1937 is given as 98.0 million metric tons.

In light of those numbers, I'd say six million tons of annual imports are pretty significant, especially since France is not yet conquered.

Answer 2

It is not the number of tonnes that matter it is the quality of the iron ore. Wiki notes that the Swedish iron ore was of very high quality whereas German iron or was not. This matters for the following reasons:

1. You can't build good tanks, ships etc with low quality iron ore. Without Sweden's high quality iron ore Germany's own iron ore was of limited use
2. Mixing the iron ore's also made the steel making more efficient
3. high quality iron ore actually contains a lot more iron per tonne

Answer 3

Iron ore comes as Hematite, Goethite, Limonite, etc, and Magnetite.

Basically Fe2O3 for the others and Fe3O4 for Magnetite. Plus contaminants.

Fe3O4 contains more iron per molecule than Fe2O3. Purified it comes to about 67% iron and 33% oxygen. Fe2O3 comes in at around 63% iron.

But, as dug out of the ground, Hematite etc. can be pretty close, with little contaminants, while Magnetite can be anything from 20% valuable mineral to 40% valuable mineral.

Removing the waste from Magnetite involves grinding fine, to around 30-40 micron, consuming huge quantities of energy, plus very costly separation equipment. In many cases Hematite/Goethite can be dug out of the ground, crushed these days to -1.25 inch +1/4 inch (lump), and -1/4 inch (fines), and shipped.

Saying how much ore has come out of the ground is misleading if you have to separate out and throw away two thirds of it. Typically, you ship ore fit for the furnace, i.e. refined (Magnetite), or high grade (other).

You can't put fine ground Magnetite into a furnace. It has to be turned into pellets, which is another energy intensive process. Sometimes the fine ground refined ore is shipped to somewhere with low energy costs for pelletising.