Background Information
Molybdenum is a kind of transition element, and its oxidation state is easy to change. It plays the role of electron transfer in oxidation reduction-reactions. In the form of oxidation, molybdenum is likely to be in the +6-Valence state, although it can revert to a +5-price status during electronic transfer. Molybdenum is not only a trace element necessary for humans, animals and plants, but also an important element in steel and alloy. Metal molybdenum and molybdenum iron are the commonly used molybdenum-containing furnace materials. At times, molybdenum oxide concentrates can also be used for direct smelting reduction of molybdenum-containing steel grades. Molybdenum reserves are estimated to be19 million tons in the Earth's crust with 8.6 million tons recoverable.
- Item Name: Molybdenum
- Element Symbol: Mo
- Atomic Number: 42
- Atomic Volume: 95.94
The Role Molybdenum Plays in Stainless Steel Microstructure and Heat Treatment
1. Molybdenum is soluble in ferrite, austenite and carbide, also an element that reduces the austenite phase region.
2. When the molybdenum is low, it forms a cementite with iron and carbon; when it is high, special carbide of molybdenum can be formed.
3. Molybdenum improves steel hardenability better than chromium but slightly less than manganese.
4. Molybdenum improves steel tempering stability. As a single alloying element, molybdenum increases temper brittleness of the steel; when coexisting with chromium, manganese, etc., molybdenum reduces or inhibits temper brittleness caused by other compositions.
The Role Molybdenum Plays in Stainless Steel Mechanical Properties
1. Molybdenum exerts solid solution strengthening effect on ferrite, meanwhile, it improves the carbides stability. As a result, it enhances steel strength.
2. Molybdenum is conducive to improving ductility, toughness and wear resistance of the steel.
3. Molybdenum increases the softening and recovery temperature as well as the recrystallization temperature after deformation strengthening, improves the creep resistance of ferrite tremendously, effectively inhibits the aggregation of cementite underneath and promotes the precipitation of special carbides, thus it becomes the most effective alloying element to improve steel creep strength.
The Role Molybdenum Plays in Stainless Steel Physical and Chemical Properties
1. In magnetic steel containing 1.5% carbon, 2%-3% molybdenum improves residual magnetic induction and coercivity.
2. Molybdenum can passivate steel surface in both reducing acid and strong oxidizing salt solution. Therefore, molybdenum can generally improve steel corrosion resistance and prevent pitting corrosion in the chloride solution.
3. The steel corrosion resistance deteriorates when the molybdenum is high above 3%.
4. Steel with less than 8% molybdenum can still be forged and rolled, but when the molybdenum is higher than that, the steel deformation resistance to hot working will be increased.
Molybdenum Applications in Stainless Steel
1. Molybdenum is widely used in quenched and tempered structural steel, spring steel, bearing steel, tool steel, stainless acid-resistant steel, heat-resistant steel and magnetic steel.
2. Chromium-molybdenum steel can be a replacement to chrome-nickel steel to manufacture important parts in many applications.
3. China abounds with molybdenum, but molybdenum reserves are not abundant worldwide. Molybdenum-containing steel is properly developed in China.
Related
- Functions of Microalloy Elements Nb, V and Ti in Steel
- The Role Manganese Plays in Stainless Steel
- The Role Chromium Plays in Stainless Steel
- The Role Nickel Plays in Stainless Steel
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