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Steel 20X12VNMF

20X12VNMF steel

20Cr12VNMF steel: steel and alloys classifier. Below is systematized information on the purpose, chemical composition, types of supply, substitutes, critical point temperatures, physical, mechanical, technological and foundry properties for the grade — Steel 20X12VNMF.

General information about 20X12VNMF steel

The substitute for the following steel grade
of steel grades: 15Х12ВНМФ, 18Х11МНФБ.
Delivery type
Round 20х12ВНМФ, bar stock, including shaped: GOST 5949−75, GOST 2590−71, GOST 2591−71, GOST 2879−69, GOST 18968−73, GOST 19442−74. Calibrated bar GOST 7417−75, GOST 8559−75, GOST 8560−78. Grinded rod and silver GOST 14955−77. Strip GOST 4405−75, GOST 103−76, GOST 18968−73. Forged and forged blanks GOST 1133−71.
Application
Bands, diaphragms, bolts, nuts, pins and other heavy-duty parts operating at 600 ° C. Steel heat-resistant martensitic class.

Chemical composition of steel 20X12VNMF

Chemical element %
Vanadium (V) 0.15−0.30
Tungsten (W) 0.7−1.1
Silicon (Si), max. 0.6
Manganese (Mn) 0.5−0.9
Copper (Cu), not more than 0.30
Molybdenum (Mo) 0.5−0.7
Nickel (Ni) 0.5−0.9
Sulfur (S), max. 0.025
Carbon (C) 0.17−0.23
Phosphorus (P), not more than 0.030
Chromium (Cr) 10.5−12.5

Mechanical properties of steel 20X12VNMF

Heat treatment, delivery condition Section, mm σ0.2, MPa σB, MPa δ5, % ψ, % KCU, J/m2
Isothermal annealing at 830−860°C, isothermal holding at 630−660°C
Tempering 1010−1060°C, oil. Tempering 660−770°C, air. 60 590 740 15 50 59

Mechanical properties at elevated temperatures

t test,°C σ0, 2, MPa σB, MPa δ5, % ψ, % KCU, J/m2
Bar thickness 40−120 mm. Hardening at 1050 °C, oil. Tempering at 700 °C. At 20 °C NV 255−271.
20 700−730 830−870 15−18 55−59 93−118
300 600−620 720−730 14−15 59−63 127−147
400 570−590 670−680 13−14 55−62 137−147
500 520−570 550−570 14−15 59−78 118−147
550 450−470 500−520 18−19 70−79 127−137
600 355−370 370−395 20−23 79−88 132−147
650 275−315 295−340 26 87 152
Disc diameter 750−1020 mm, height 300 mm. Quenching at 1050 °C, oil. Tempering at 720 °C (tangential samples). At 20 °C NV 228−248.
20 600−650 750−810 14−23 41−55  
100 580−610 720−760 16−18 45−53 78−137
200 540−570 690−710 13−17 37−54 88−147
300 520−540 640−680 13−17 46−51  
400 500−510 610−670 12−14 45−51  
500 440−460 510−530 15−19 52−61  
600 335−355 345−365 21−31 83−85  

Mechanical properties depending on tempering temperature

Heat treatment, delivery condition t tempering temperature, °C σ0, 2, MPa σB, MPa δ5, % ψ, % KCU, J/m2 HB
Rods. Tempering at 1000 °C, oil.
Curing time at tempering 2 h 650 830 950 15 60 78 290
Curing time at tempering 2 h 700 780 900 16 59 98 255
Curing time at tempering 2 h 750 660 800 17 63 166 240
Curing time at tempering 10 h 650 880 1030 14 58 49 300
Curing time at tempering 10 h 700 780 930 15 59 78 280
Curing time at tempering 10 h 750 710 830 17 63 117 240

Mechanical properties in the long term strength test

Creep limit, MPa Creep rate, %/h t test,°C Ultimate long-term strength, MPa Test duration, h t test, h
274 1/100000 450 382 10000 500
98−118 1/100000 550 103 10000 600
78 1/100000 580 343 100000 500
54 1/100000 600 88 100000 600

Technological properties of 20X12VNMF steel

Forging temperature
The beginning 1230, the end 900. Sections up to 250 mm are subjected to annealing with one supercooling. Sections from 250 to 400 mm — annealing and two supercooling.
Weldability
Steel is hardly weldable. Welding method — РДС, preheating and subsequent heat treatment are required.
machinability
In the annealed state at HB 187 and σB = 610 MPa, K υ b.st. = 0.6.

Temperature of critical points of 20X12VNMF steel

Critical point °С
Ac1 805
Ac3 870

Endurance limit of 20X12VNMF steel

σ-1, MPa n
314−412 1Е+7

Physical properties of 20X12VNMF steel

Test temperature, °С 20 100 200 300 400 500 600 700 800 900
Modulus of normal elasticity, E, GPa 212 207 202 196 190 181 167      
Steel density, pn, kg/m3 7850 7830 7800 7780 7760 7730 7700 7670    
Thermal conductivity coefficient W/(m — °C)   25 25 26 26 27 27      
Test temperature,°C 20−100 20−200 20−300 20−400 20−500 20−600 20−700 20−800 20−900 20−1000
Coefficient of linear expansion (a, 10−6 1/°C) 10.6 10.9 11.2 11.4 11.7 11.9 12.0 12.1 10.7 11.7