UGI® 4121

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UGI® 4121 is a martensitic grade which, thanks to the addition of Molybdenum combined with a high sulphur content, provides a good compromise between corrosion resistance and machinability that is better than that of other resulphurised martensitic stainless steel grades.

Related Standards

This material data has been provided by Ugitech SA.

All metrics apply to room temperature unless otherwise stated. SI units used unless otherwise stated.
Equivalent standards are similar to one or more standards provided by the supplier. Some equivalent standards may be stricter whereas others may be outside the bounds of the original standard.

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7.7 g/cm³

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Elastic modulus

215 GPa

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25 %

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Hardness, Rockwell C

47.0 - 50.0 [-]

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After quenching + tempering 100-300°C

Tensile strength

776 MPa

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Coefficient of thermal expansion

0.0000115 1/K

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20 to 300°C

Thermal conductivity

30 W/(m·K)

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Electrical resistivity

5.5e-07 Ω·m

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Chemical properties



0.2 - 0.26 %

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12.5 - 14.0 %

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1.1 - 1.5 %

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0.75 - 1.5 %

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0.15 - 0.27 %

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Technological properties

Application areas

  • Rotary axes in the watch industries and automotive industries
  • Cutting tools (drills) in the medical and the dental industries
  • Corrosion properties

    The best corrosion resistance properties are obtained in the quenched and tempered condition. Polishing increases the corrosion resistance even further and a passivation treatment is recommended. Under such conditions, this grade will be water and vapour resistant. If the grade was tempered at too high a temperature, the corrosion resistance will be impaired by carbide segregation precipitation at the grain boundaries. Annealing must not be carried out at temperatures between 400°C and 580°C as this will affect corrosion resistance.

    General machinability

    Best machinability is obtained in the skin-passed condition (Rm: 800 – 950 MPa). Grinding and polishing are recommended to obtain a finer surface finish for optimum corrosion resistance. Localised overheating during grinding must be avoided, as this could affect the corrosion resistance.

    Heat Treatment

    UGI® 4121 can be hardened by a quenching treatment from 1030°C to 1070°C and by tempering.

    Softening: soft annealing between 780°C and 830°C, slow cooling 30°C/h down to 600°C followed by air cooling.

    Softening annealing (subcritical): between 650°C and 760°C, followed by air cooling

    Intermediate annealing during cold deformation: preferably between 650°C and 680°C, followed by air cooling

    Quenching: oil quenching between 980°C and 1050°C, fast air or gas quenching

    Tempering: tempering is used to adjust the mechanical characteristics of the products, as shown on the right side of the material page.

    The tempering temperature range from 100°C to 300°C enables an optimum compromise between mechanical strength and corrosion resistance to be obtained. The temperature range between 400°C and 580°C must be avoided to prevent embrittlement and the associated reduction in corrosion resistance. Tempering must be carried out as soon as possible after quenching. The tempering temperature must rise slowly to avoid any distortion and cracking of sophisticated geometry parts.


    Available products:

    ProductShapeFinishToleranceDimensions (mm)
    Bright barRoundTurned and polishedISO 9-10 22-115
    DrawnISO 9-10 1.8-30
    GroundISO 6-7-8-9 1.5-70
    HexagonalDrawn 3.0-60
    Wire rodRoundPickled 5.5-32
    Drawn wireRoundUnpolishedISO 6-7-8-9 1.0-14

    Other formats: contact the supplier

    Surface polishing

    The presence of a large number of manganese sulphide inclusions (MnS) can reduce the quality of the polishing and its productivity. That is why optimal polishing is obtained on products in the quenched and tempered condition at low temperature < 200°C.


    This grade cannot be welded. Soft soldering is still possible.