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Steel 18KHGT

Description

Steel 18KHGT

Steel 18KhGT: a brand of steels and alloys. Below is the systematized information on the purpose, chemical composition, types of supplies, substitutes, temperature of critical points, physical, mechanical, technological and casting properties for the grade — Steel 18HGT.

General information about steel 18HGT

Substitute brand
Steel: 30KHGT, 25KHGT, 12KHN3A, 12KHN2N4A, 20KHN2N, 14KHGSN2MA, 20KHGR.
Delivery type
Sheet 18khgt, circle 18khgt, long products, including shaped: GOST 4543−71, GOST 259071, GOST 2591−71, GOST 2879−69. Calibrated bar GOST 7417−75, GOST 8559−75, GOST 8560−78, GOST 1051−73. Polished bar and silver bar GOST 4543−71, GOST 14955−77. Strip GOST 103−76. Forgings and forged billets GOST 1133−71.
Application
Critical refining or case-hardening parts that require increased core strength and toughness and high surface hardness when exposed to impact loads.

Chemical composition of steel 18HGT

Chemical element %
Silicon (Si) 0.17−0.37
Manganese (Mn) 0.80−1.10
Copper (Cu), no more 0.30
Nickel (Ni), no more 0.30
Sulfur (S), no more 0.035
Titanium (Ti) 0.03−0.09
Carbon (C) 0.17−0.23
Phosphorus (P), no more 0.035
Chromium (Cr) 1.00−1.30

Mechanical properties of steel 18HGT

Section, mm σ 0.2, MPa σ B, MPa δ 5 ,% ψ,% KCU, J / m 2 HB HRC e
Normalization 880−950 ° C. Hardening 870 ° С, oil. Vacation 200 ° C, air or water.
Samples 880 980 nine 50 78    
Normalization 930−960 ° C. Cementation 930−950 ° C. Hardening 825−840 ° С, oil. Vacation 180−200 ° C.
  360 640       157−207  
50 800 1000 nine     285 57−63
Cementation 920−950 ° С, air. Hardening 820−860 ° С, oil. Vacation 180−200 ° C, air.
20 930 1180 ten 50 78 341 53−63
60 780 980 nine 50 78 240−300 57−63

Mechanical properties at elevated temperatures

test t, ° C σ 0.2, MPa σ B, MPa δ 5 ,% δ 4 ,% ψ,% HB
Normalization
20 420 520   26 77 156
200 360 460   24 78  
300 310 465   24 68  
400 300 470   29 75  
500 300 410   27 76  
600 240 325   45 86  
Sample 6 mm in diameter, 30 mm long, forged and normalized. Deformation rate 50 mm / min. Strain rate 0.03 1 / s
700 205 235 46   88  
800 76 135 51   94  
900 54 95 55   96  
1000 50 78 58   100  
1100 25 43 61   100  
1200 thirteen 25 56   100  

Mechanical properties depending on the tempering temperature

vacation t, ° С σ 0.2, MPa σ B, MPa δ 5 ,% ψ,% KCU, J / m 2 HRC e
Hardening 880 ° С, oil.
200 1150 1370 eleven 57 98 41
300 1150 1330 ten 57 78 41
400 1150 1210 nine 57 78 40
500 950 940 fifteen 66 144 32
600 720 780 20 73 216 22

Mechanical properties depending on the section

Section, mm σ 0.2, MPa σ B, MPa δ 5 ,% ψ,% KCU, J / m 2 HRC e
Hardening 850 ° С, oil. Vacation 200 ° C, air.
five 1320 1520 12 50 72  
fifteen 930 1180 thirteen 50 78 38
20 730 980 fifteen 55 113 thirty
25 690 980 19 50 93 28

Technological properties of steel 18HGT

Forging temperature
Beginning 1200, end 800. Sections up to 250 mm are cooled in air, 251−350 mm — in a pit.
Weldability
welded without restrictions (except for chemically-thermally treated parts). Welding methods: RDS, KTS.
Machinability by cutting
After normalization at HB 156−159 σ B = 530 MPa K υ tv.spl. = 1.1, K υ b.st. = 1.0.
Tendency to release ability
not inclined
Flock sensitivity
not sensitive

Temperature of critical points of steel 18HGT

Critical point ° C
Ac1 740
Ac3 825
Ar3 730
Ar1 650
Mn 360

Impact strength of steel 18HGT

Impact strength, KCU, J / cm 2

Delivery status, heat treatment +20 -20 -40 -60
  114 101 93 85

Endurance limit of steel 18HGT

σ -1, MPa τ -1, MPa n σ B, MPa σ 0.2, MPa Heat treatment, steel condition
490 294   980 780 Sample with a cross section of 50 mm, HB 240−300
637   1E + 6     Cementation 960 C, hardening 840 C, oil, tempering 180−200 C, HB 240−300.
  480 5E + 6     Normalization 1100 C, cooling up to 870 C, quenching in oil, tempering 200 C, HB 415.

Hardenability of steel 18HGT

Hardening 900 C. Hardness for strips of hardenability HRCe.

Distance from the end, mm / HRC e
1.5 3 4.5 6 7.5 nine 12 fifteen eighteen 21
41.5−50.5 39.5−49.5 36.5−47.5 33−46 30−44.5 27.5−42.5 24.5−42.5 23−37.5 35.5 34
Amount of martensite,% Crit. Diam. in water, mm Crit. Diam. in oil, mm Crete. hardness, HRCэ
50 33−82 12−52 32−36
90 23−48 6−24 38−43

Physical properties of steel 18HGT

Test temperature, ° С 20 100 200 300 400 500 600 700 800 900
Normal elastic modulus, E, GPa 211 205 197 191 176 168 155 136 129  
Torsional shear elastic modulus G, GPa 84 80 77 75 68 66 59 52 49  
Density of steel, pn, kg / m 3 7800                  
Thermal conductivity coefficient W / (m ° С) 37 38 38 37 35 34 31 thirty 29  
Test temperature, ° С 20−100 20−200 20−300 20−400 20−500 20−600 20−700 20−800 20−900 20−1000
Linear expansion coefficient (a, 10−6 1 / ° С) 10.0 11.5 12.3 12.8 13.3 13.6        
Specific heat (C, J / (kg ° C)) 495 508 525 537 567 588 626 705    

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