33MnCrB5-2, 1.7185, 27MnCrB5-2, 1.7182 – boron steel

33MnCrB5-2, 1.7185, 27MnCrB5-2, 1.7182 – boron steel according to EN 10083-3.

33MnCrB5-2, 1.7185 – description

Machine steel boron toughening steel. Used on machine parts tempered or isothermally hardened. Cuttable with a shear if supplied in a condition with increased shearability (+S), with hardness below 255 HB. The tempering temperature must be selected in such a way as to obtain the desired properties. The higher the tempering temperature, the lower the mechanical properties, but the higher the ductility and resistance to cracking.

An alloying addition that distinguishes this alloy from other toughening steels is boron. Even a small amount of boron significantly increases the hardenability. Its effectiveness is 50 times stronger than molybdenum, 75 times stronger than chromium and about 400 times stronger than a nickel (calculations for steel with carbon content 0.4%), although it is effective only in small quantities, and above a certain limit begins to negatively affect the mechanical properties and hardenability. Boron also reduces the weldability.

Alloy 33MnCrB5-2 contains more carbon than 27MnCrB5-2, and consequently has higher tensile strength and yield strength, but at the expense of ductility and impact strength.

Physical and mechanical properties

Mechanical properties of 27MnCrB5-2 alloy when quenched and tempered (+QT):

• Round bars:
  • Diameter D: < 16 mm
    • Yield strength Re: > 800 MPa
    • Tensile strength Rm: 100-1250 MPa
    • Elongation A: > 14 %
    • Percent reduction of area Z: > 55 %
  • Diameter D: 16-40 mm
    • Yield strength Re: > 750 MPa
    • Tensile strength Rm: 900-1150 MPa
    • Elongation A: > 14 %
    • Percent reduction of area Z: > 55 %
    • Impact energy KV: 60 J
  • Diameter D: 40-60 mm
    • Yield strength Re: > 700 MPa
    • Tensile strength Rm: 800-1000 MPa
    • Elongation A: > 14 %
    • Percent reduction of area Z: > 55 %
• Flat products:
  • Thickness: < 8 mm
    • Yield strength Re: > 800 MPa
    • Tensile strength Rm: 1000-1250 MPa
    • Elongation A: > 14 %
    • Percent reduction of area Z: > 55 %
  • Thickness: 8-20 mm
    • Yield strength Re: > 750 MPa
    • Tensile strength Rm: 900-1150 MPa
    • Elongation A: > 14 %
    • Percent reduction of area Z: > 55 %
    • Impact energy KV: > 60 J
  • Thickness: 20-40 mm
    • Yield strength Re: > 700 MPa
    • Tensile strength Rm: 800-1000 MPa
    • Elongation A: > 15 %
    • Percent reduction of area Z: > 55 %
    • Impact energy KV: > 65 J

Mechanical properties of 33MnCrB5-2 alloy when quenched and tempered (+QT):

• Round bars:
  • Diameter D: < 16 mm
    • Yield strength Re: > 850 MPa
    • Tensile strength Rm: 1050-1300 MPa
    • Elongation A: > 13 %
    • Percent reduction of area Z: > 50 %
  • Diameter D: 16-40 mm
    • Yield strength Re: > 800 MPa
    • Tensile strength Rm: 950-1200 MPa
    • Elongation A: > 13 %
    • Percent reduction of area Z: > 50 %
  • Diameter D: 40-60 mm
    • Yield strength Re: > 750 MPa
    • Tensile strength Rm: 900-1100 MPa
    • Elongation A: > 13 %
    • Percent reduction of area Z: > 50 %
• Flat products:
  • Thickness: < 8 mm
    • Yield strength Re: > 850 MPa
    • Tensile strength Rm: 1050-1300 MPa
    • Elongation A: > 13 %
    • Percent reduction of area Z: > 50 %
  • Thickness: 8-20 mm
    • Yield strength Re: > 800 MPa
    • Tensile strength Rm: 950-1200 MPa
    • Elongation A: > 13 %
    • Percent reduction of area Z: > 50 %
    • Impact energy KV: > 50 J
  • Thickness: 20-40 mm
    • Yield strength Re: > 750 MPa
    • Tensile strength Rm: 900-1100 MPa
    • Elongation A: > 13 %
    • Percent reduction of area Z: > 50 %
    • Impact energy KV: > 50 J

Hardness of steel with required hardenability:

• For 33MnCrB5-2:
  • Distance from front 1,5 mm: 48-57 HRC
  • Distance from front 3 mm: 47-57 HRC
  • Distance from front 5 mm: 47-57 HRC
  • Distance from front 7 mm: 46-57 HRC
  • Distance from front 9 mm: 45-57 HRC
  • Distance from front 11 mm: 44-56 HRC
  • Distance from front 13 mm: 53-55 HRC
  • Distance from front 15 mm: 51-54 HRC
  • Distance from front 20 mm: 36-53 HRC
  • Distance from front 25 mm: 31-50 HRC
  • Distance from front 30 mm: 25-47 HRC
  • Distance from front 35 mm: 20-45 HRC
• For 27MnCrB5-2:
  • Distance from front 1,5 mm: 47-55 HRC
  • Distance from front 3 mm: 46-55 HRC
  • Distance from front 5 mm: 45-55 HRC
  • Distance from front 7 mm: 44-54 HRC
  • Distance from front 9 mm: 43-54 HRC
  • Distance from front 11 mm: 51-53 HRC
  • Distance from front 13 mm: 39-52 HRC
  • Distance from front 15 mm: 36-51 HRC
  • Distance from front 20 mm: 30-47 HRC
  • Distance from front 25 mm: 34-44 HRC
  • Distance from front 30 mm: 20-40 HRC
  • Distance from front 35 mm: max 37 HRC

Heat treatment and plastic working

Following parameters are recommended for working and heat treatment as for 27MnCrB5-2:

• Temperature of austenitization: 880-920°C
• Tempering temperature: 400-600 °C
• Maximum critical diameter:
  • Hardening temperature: 900°C, Hardness of core 38 HRC, water cooling: 52 mm
  • Hardening temperature: 900°C, Hardness of core 38 HRC, oil cooling: 43 mm

Following parameters are recommended for working and heat treatment as for 33MnCrB5-2:

• Temperature of austenitization: 860-900 °C
• Tempering temperature: 400-600 °C
• Maximum critical diameter:
  • Hardening temperature: 880°C, Hardness of core 42 HRC, water cooling: 55 mm
  • Hardening temperature: 880°C, Hardness of core 42 HRC, oil cooling: 45 mm

We deliver this steel alloy as:

• Round bars, flat bars and square bars

Replacements, equivalents and other designations:

33MnCrB5-2, 1.7185, 27MnCrB5-2, 1.7182, 28MnCrB5, 28MCB5, 32MCB5, SB28M13CB