Last Updated: August 13, 2026
Ferromolybdenum (FeMo) is an iron-molybdenum ferroalloy used mainly to introduce molybdenum into steel, cast iron and other alloy systems. Commercial FeMo grades commonly contain a high proportion of molybdenum, with FeMo55, FeMo60 and FeMo70 among the grade designations used in industrial supply.
The correct grade should be selected according to the required Mo content, impurity limits, particle size and downstream steelmaking process. Carbon, silicon, phosphorus, sulfur and copper may also need to be controlled according to the applicable specification and customer requirements.
What Is Ferromolybdenum?
Ferromolybdenum is a ferroalloy containing molybdenum and iron, produced for use as a concentrated molybdenum addition in metallurgy.
Instead of adding pure molybdenum metal directly, steelmakers can use FeMo to introduce a controlled amount of molybdenum into the melt. Molybdenum is used in many alloy systems because it can influence hardenability, strength, wear resistance and elevated-temperature performance depending on the steel composition and heat-treatment route.
Commercial grades should not be identified by Mo percentage alone. The limits for C, Si, P, S, Cu and other controlled elements can also determine whether a particular FeMo specification is suitable.
For current product specifications, see our ferromolybdenum grades and supply sizes.
Typical Ferromolybdenum Grades and Composition
Ferromolybdenum is available in different grades according to molybdenum content and impurity requirements. Commercial designations such as FeMo55, FeMo60 and FeMo70 indicate different molybdenum-content positions, but the complete chemical specification should always be checked before ordering.
| Item | What Buyers Should Confirm | Why It Matters |
|---|---|---|
| Mo | Required FeMo grade and contractual Mo range | Determines the amount of molybdenum delivered to the melt |
| C | Maximum carbon limit | Important for steels with restricted carbon chemistry |
| Si | Maximum silicon limit | Additional silicon must fit the steel chemistry allowance |
| P / S | Maximum impurity limits | Should remain within the final steel impurity budget |
| Cu | Check when required by the applicable specification | May be restricted in specific alloy and steel grades |
Specification Note: The original product sample shown on this page is labeled Mo = 71.41%. This should be treated as an individual analysis result rather than a universal composition for all FeMo70 material. Final acceptance should be based on the agreed grade and batch COA.
How Can Ferromolybdenum Quality Be Checked?
Chemical analysis is the primary method for confirming ferromolybdenum quality, while fracture appearance can provide a useful preliminary visual check.
A qualified FeMo lump commonly shows a relatively fine and uniform crystalline structure on a fresh fracture surface. A matte or finely crystalline cross-section is generally preferred for visual screening.
In traditional visual inspection, obvious bright star-like points on the fracture may be treated as a warning sign of abnormal sulfur-related inclusions, while a strongly shiny or mirror-like fracture can indicate unusually high silicon or a different solidification structure.
However, fracture appearance cannot replace laboratory analysis. A material should not be accepted or rejected for sulfur or silicon content solely from visual appearance. The actual Mo, C, Si, P, S and other required values should be confirmed by chemical testing and the batch COA.
What Is Ferromolybdenum Used For?
Ferromolybdenum is mainly used as a molybdenum alloying addition in steelmaking and cast-iron production. The amount added depends on the target Mo content and the performance requirements of the final alloy.
Alloy and Structural Steels
Molybdenum is added to alloy steels where improved hardenability, strength or resistance to softening at elevated temperatures is required.
The required FeMo addition depends on the base chemistry, heat treatment and target mechanical properties rather than simply on the steel application name.
Tool and Mold Steels
Tool steels and mold steels may contain molybdenum to support hardness, hardenability and resistance to tempering or thermal exposure.
Because these alloys often have tightly controlled chemistry, FeMo impurity limits and actual batch composition become particularly important.
Stainless and Heat-Resistant Steels
Molybdenum is used in selected stainless and heat-resistant steel grades where it contributes to the required corrosion, strength or elevated-temperature performance.
The exact benefit depends on the complete alloy system. FeMo should therefore be selected according to the specified steel grade rather than assuming that every stainless steel requires the same molybdenum addition.
Wear-Resistant and Heat-Resistant Cast Iron
Ferromolybdenum can also be used to introduce molybdenum into specialized cast irons where wear resistance, strength or high-temperature behavior needs to be modified.
The required dosage depends on the casting composition, section thickness, cooling conditions and required microstructure.
How Is Ferromolybdenum Produced?
Ferromolybdenum is generally produced from molybdenum-bearing raw materials through roasting and metallurgical reduction.
A conventional production route starts from molybdenite concentrate. The concentrate is oxidized to produce a molybdenum oxide-rich material, which can then be reduced together with iron-bearing material to form ferromolybdenum.
Metallothermic and silicothermic reduction routes can be used depending on the plant design. Ferrosilicon and aluminum may be used as reducing materials in some conventional production processes.
After the reduction reaction, the FeMo alloy is separated from the slag, cooled and then crushed and classified into the required commercial size.
For a more detailed process description, see our guide to ferromolybdenum production and use.
Molybdenum Concentrate → Roasting → Molybdenum Oxide Feed → Reduction → FeMo Alloy → Crushing and Sizing
Ferromolybdenum Product Appearance
What Particle Sizes Are Available for Ferromolybdenum?
Ferromolybdenum is normally supplied in lump form, with particle size selected according to the customer's charging and melting practice.
Common size ranges used on this page include:
| Particle Size | Typical Purchasing Consideration |
|---|---|
| 10–30 mm | Smaller lump range where controlled charging or faster assimilation may be preferred |
| 10–50 mm | Common industrial lump size for steelmaking and alloy addition |
| 30–50 mm | More concentrated coarse-lump range for specified charging systems |
| Customized Size | Can be agreed according to furnace, ladle and feeding requirements |
Particle size can influence handling and dissolution behavior. Excessive fines may increase material loss and oxidation exposure, while oversized pieces may require different melting conditions.
The size range should therefore be included in the purchasing specification rather than treated only as a packaging detail.
What Standards Apply to Ferromolybdenum?
Ferromolybdenum can be supplied according to national, international or customer-specific chemical requirements.
GB/T 3649-2008 is China's current national standard for ferromolybdenum. It covers technical requirements, inspection, testing, packaging, storage, marking and quality certification for FeMo used in steelmaking, casting and alloy production.
ASTM A132 is another specification used for ferromolybdenum in international procurement. It covers ferromolybdenum grades and size requirements and includes chemical controls for molybdenum, carbon, phosphorus, sulfur, silicon and copper.
Commercial labels such as FeMo55, FeMo60 or FeMo70 should therefore not replace the full purchase specification when strict chemistry control is required.
What Should Buyers Check Before Ordering Ferromolybdenum?
A FeMo purchase specification should define chemical composition, particle size, inspection requirements and packing.
| Purchase Item | What to Confirm |
|---|---|
| FeMo Grade | FeMo55, FeMo60, FeMo70 or another agreed specification |
| Mo Content | Required minimum and/or permitted molybdenum range |
| Impurity Limits | C, Si, P, S, Cu and other elements required by the steel grade |
| Particle Size | 10–30 mm, 10–50 mm, 30–50 mm or another agreed range |
| Fracture Appearance | Visual screening for abnormal inclusions or structure, followed by chemical verification where required |
| Batch COA | Actual chemical analysis corresponding to the supplied batch |
| Packing and Storage | Packing, moisture protection and transportation requirements |
Where waterproof or moisture-resistant transport is required, the requirement should be agreed before shipment and included in the order specification.
FAQ About Ferromolybdenum
What is ferromolybdenum used for?
Ferromolybdenum is mainly used to introduce molybdenum into alloy steel, tool steel, stainless steel, mold steel and selected cast irons. The required Mo addition depends on the target alloy composition and performance requirements.
What is FeMo70?
FeMo70 is a commercial ferromolybdenum grade designation associated with a high molybdenum-content specification. The exact permitted chemistry should be checked against the applicable standard, supplier specification and batch COA.
Is Mo 71.41% normal for FeMo70?
A measured Mo value such as 71.41% can represent the analysis of an individual FeMo sample. It should not be treated as the fixed composition of every FeMo70 shipment. The contractual grade limits determine whether the batch is acceptable.
What does a good ferromolybdenum fracture look like?
A relatively fine and uniform crystalline fracture is commonly used as a preliminary visual quality indicator. Unusual bright points or strongly mirror-like areas may justify further inspection, but chemical analysis is required to confirm sulfur, silicon and other impurity levels.
What ferromolybdenum particle size is commonly supplied?
Common commercial sizes include 10–30 mm, 10–50 mm and 30–50 mm, while customized ranges can be agreed according to furnace and charging requirements.
What should a FeMo COA include?
A batch COA should identify the material and batch and report the chemical parameters agreed in the purchase specification, typically including Mo and relevant impurities such as C, Si, P, S and Cu.
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