Stainless Steel - Martensitic - 1.4125 (440C) Bar

1.4125 (440C) Bar

Grade 440C is capable of attaining, after heat treatment, the highest strength, hardness and wear resistance of all the stainless alloys. Its very high carbon content is responsible for these characteristics, which make 440C particularly suited to such applications as ball bearings and valve parts.

Grades 440A and 440B are identical except for slightly lower carbon contents (0.60 - 0.75% and 0.75 - 0.95% respectively); these have lower attainable hardnesses but slightly higher corrosion resistances. Although all three versions of this grade are standard grades, in practice 440C is more available than the A or B variants.

A free-machining variant 440F (UNS S44020) also exists, with the same high carbon content as 440C. Again this grade is not readily available in Australia.

Martensitic stainless steels are optimised for high hardness, and other properties are to some degree compromised. Fabrication must be by methods that allow for poor weldability and usually also allow for a final harden and temper heat treatment. Corrosion resistance is lower than the common austenitic grades, and their useful operating temperature range is limited by their loss of ductility at sub-zero temperatures and loss of strength by over-tempering at elevated temperatures.

Chemical Composition

Spec: EN 10088-3:2005

1.4125 Steel

Chemical Element % Present
Carbon (C) 0.95 - 1.20
Chromium (Cr) 16.00 - 18.00
Manganese (Mn) 0.0 - 1.00
Silicon (Si) 0.0 - 1.00
Phosphorous (P) 0.0 - 0.04
Sulphur (S) 0.0 - 0.03
Molybdenum (Mo) 0.40 - 0.80
Iron (Fe) Balance


Physical PropertyValue
Density 7.65 g/cm³
Thermal Expansion 10.1 x10^-6 /K
Modulus of Elasticity 200 GPa
Thermal Conductivity 24.2 W/m.K
Electrical Resistivity 0.6 x10^-6 Ω .m

Spec: EN 10088-3:2005

Bar - Up To 100mm Dia or Thickness

Mechanical PropertyValue
Proof Stress 448-1900 MPa
Tensile Strength 758-2030 MPa
Elongation A50 mm 4-14 %

Alloy Designations






Supplied Forms

  • Bar


Typical applications include:

Rolling element bearings

Valve seats

High quality knife blades

Surgical instruments


Corrosion Resistance

Good resistance to the atmosphere, fresh water, foods,  alkalies and mild acids. Best resistance in the hardened and tempered and  passivated condition. A smooth polished surface also assists.


The corrosion resistance of grade 440C approximates that  of grade 304 in many environments.

Heat Resistance

Not recommended for use in temperatures above the relevant  tempering temperature, because of reduction in mechanical properties by  over-tempering.


In the annealed condition this grade is relatively easily  machined; approximately the same as for high speed steel. Chips are tough and  stringy so chip breakers are important. If these grades are hardened  machining becomes more difficult and probably impossible.

Heat Treatment

Annealing - Full  anneal - 850-900°C, slow furnace cool to about 600°C and then air cool.  Sub-critical Annealing - 735-785°C and slow furnace cool.

Hardening - Heat  to 1010-1065°C, followed by quenching in warm oil or air. Oil quenching is  necessary for heavy sections. Immediately temper at 150-370°C to obtain a  wide variety of hardness values and mechanical properties as indicated in the  accompanying table.

Tempering in the  range 425-565°C is to be avoided because of reduced impact resistance and  corrosion resistance. Tempering in the range 590-675°C results in lower  hardness (the product become machinable) and high impact resistance.


If welding is necessary pre-heat at 250°C and follow welding  with a full anneal. Grade 420 filler will give a high hardness weld (although  not as high as the 440C), but 309 or 310 will produce soft welds with higher  ductility.

Datasheet Search

Last Datasheet Revision

13 March 2020


This Data is indicative only and as such is not to be relied upon in place of the full specification. In particular, mechanical property requirements vary widely with temper, product and product dimensions. All information is based on our present knowledge and is given in good faith. No liability will be accepted by the Company in respect of any action taken by any third party in reliance thereon.

Please note that the 'Datasheet Update' date shown above is no guarantee of accuracy or whether the datasheet is up to date.

The information provided in this datasheet has been drawn from various recognised sources, including EN Standards, recognised industry references (printed & online) and manufacturers’ data. No guarantee is given that the information is from the latest issue of those sources or about the accuracy of those sources.

Material supplied by the Company may vary significantly from this data, but will conform to all relevant and applicable standards.

As the products detailed may be used for a wide variety of purposes and as the Company has no control over their use; the Company specifically excludes all conditions or warranties expressed or implied by statute or otherwise as to dimensions, properties and/or fitness for any particular purpose, whether expressed or implied.

Advice given by the Company to any third party is given for that party’s assistance only and without liability on the part of the Company. All transactions are subject to the Company’s current Conditions of Sale. The extent of the Company’s liabilities to any customer is clearly set out in those Conditions; a copy of which is available on request.