Durabor® 22MnB5

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Description

Quenchable boron steel represent a breakthrough in heat treatment technology. This steel uses boron as a hardening agent. The melting and refining process, together with thermomechanical treatment by controlled hot rolling, allow ArcelorMittal quenchable boron steel to attain a remarkable degree of hardness and a very uniform microstructure, resulting in excellent mechanical loading performance after heat treatment of the finished part.

Related Standards

Equivalent Materials

Los datos sobre este material han sido proporcionados por ArcelorMittal.

A menos que se indique lo contrario, todas las medidas corresponden a condiciones de temperatura ambiente. A menos que se indique lo contrario, se utilizan las unidades del SI.
Las normas armonizadas son similares a uno o varios estándares del proveedor. Es posible que algunas normas armonizadas se ajusten al estándar original, mientras que otras pueden quedar fuera de su alcance.

Ashby charts

Propiedades

Medidas

PropertyValue

Dimensions

Please feel free to check the figure on the right side of the material page for more details.

Mecánica

PropertyValueComment

Dureza Rockwell C

45 [-]

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Quenched | 6 mm specimen in the rolling direction

Elongación

10 %

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Quenched | 6 mm specimen in the rolling direction

27 %

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Delivery condition | 6 mm specimen in the rolling direction

Límite elástico

350 MPa

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Delivery condition | 6 mm specimen in the rolling direction

1100 MPa

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Quenched | 6 mm specimen in the rolling direction

Resistencia a la tracción

520 MPa

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Delivery condition | 6 mm specimen in the rolling direction

1500 MPa

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Quenched | 6 mm specimen in the rolling direction

Chemical properties

PropertyValueComment

Aluminio

0.02 %

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min.

Azufre

0.008 %

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max.

Boro

0.002 - 0.005 %

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Carbono

0.2 - 0.25 %

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Fósforo

0.025 %

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max.

Manganeso

1.1 - 1.4 %

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Silicona

0.15 - 0.35 %

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Titanio

0.02 - 0.06 %

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Technological properties

Property
Application areas

Quenchable boron steel is used in applications requiring good wear resistant properties. The main applications for these steel grades after heat treatment are agricultural machinery (discs, plough shares), machinery for public works and mining, cutting equipment, tubes for automotive safety parts etc. A popular application for untreated steel is concrete mixer drums.

Chemical composition

This grade receives a globularisation treatment of the manganese sulphides. The efficiency of boron is ensured by the addition of elements that bind nitrogen.

Delivery condtion

In spite of their moderate hardness and mechanical properties, boron grades exhibit remarkably good abrasion resistance in their delivery condition, thanks to their composite microstructure consisting of a hard pearlite phase embedded in ferrite. They are therefore very cost-effective solutions for applications requiring good abrasion resistance.

Heat Treatment

The recommended austenitising temperature is 880°C. The temperature at the beginning of the quenching process (i.e. at the maximum cooling rate) is 750°C. Ac3 temperature is 860°C, for a heating rate of 5°C/s. Ac1 temperature is 750°C, and Ms (Martensitic Start) starting temperature is 400°C.

In a tensile test, after austenitisation for 5 minutes at 850°C followed by water quenching, the structure of the sample obtained is entirely of the martensite type. In the same test performed at 840°C, a few islands of residual ferrite can be observed, regularly distributed.


After heat treatment


Its extreme hardness after heat treatment makes this grade particularly suitable for applications requiring high wear/abrasion resistance. Its use allows significant weight saving (up to 50% compared with an HSLA grade) in structural and automotive components. The specific advantage of ArcelorMittal quenchable boron steels is their suitability for water quenching, making the process more environmentally friendly (less effluent treatment) than that used for conventional carbon steels. Their hardening performance is excellent with both liquid and gas quenching.


  • The choice of grade will depend on:
  • The required hardness of the finished part
  • The abrasion resistance required
  • The severity of the forming process envisaged

  • Other

    Fatigue resistance is determined after heat treatment and quenching. Durabor® 22MnB5 steel 2.65 mm thick has been fatigue-tested by cyclical tensile loading with a load ratio of Rs = 0.1 after different heat treatments. Specimens were austenitised at 950°C for 5 minutes.


    Specimen heated for 5 minutes at 950°C followed by:Endurance limit sD (MPa)Spread (sigma) (MPa)Maximum stress sD (MPa)
    Water quenching2535562
    Oil quenching2606578
    Water quenching + heat treatment at 200°C for 20 minutes29326651


    *sD = (smax - smin)/2

    The fatigue resistance of ArcelorMittal's boron quenchable steels is between 40 and 60% higher than S355MC AM FCE low alloy grade. It can be reduced by over 30% if total decarburisation is carried out.

    Processing methods

    Forming

    This grade can be hot or cold formed.

    Surface condition

    This boron grade is available in A unexposed surface quality only.