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Steel 20K

Description

Steel 20K

Steel 20K: brand of steels and alloys. Below is a 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 20K.

General information of steel 20K

Substitute brand
steel 15K
Delivery type
Thick sheet 20k GOST 5520−79, GOST 19903−74.
Application
Flanges, bottoms, solid-forged and welded drums of steam boilers, half-couplings, apparatus bodies and other parts of boiler construction and vessels, operating under pressure and at temperatures up to 450 ° C.

Chemical composition of steel 20K

Chemical element %
Silicon (Si) 0.15−0.30
Manganese (Mn) 0.35−0.65
Copper (Cu), no more 0.30
Arsenic (As), no more 0.08
Nickel (Ni), no more 0.30
Sulfur (S), no more 0.040
Carbon (C) 0.16−0.24
Phosphorus (P), no more 0.040
Chromium (Cr), no more 0.30

Mechanical properties of steel 20K

Fur. properties
Fur. properties versus test temperature
Fur. properties depending on heat treatment
Fur. properties when tested for long-term strength

Mechanical properties

Heat treatment, delivery condition Section, mm σ 0.2, MPa σ B, MPa δ 5 ,% KCU, J / m 2
KCU — as delivered / after mechanical aging
Category sheets: 2−5, 10, 11, 16, 18 <20 245 400−510 59 59/29
Category sheets: 2−5, 10, 11, 16, 18 21−40 235 400−510 54 54/24
Category sheets: 2−5, 10, 11, 16, 18 41−60 225 400−510 49 49/24

Mechanical properties versus test temperature

test t, ° C σ 0.2, MPa σ B, MPa δ 5 ,% ψ,% KCU, J / m 2
Sheets 37−40 mm thick, hot rolled
20 215−245 400−440 thirty 56 62−103
100 195 390 20 47−55 88−167
200 195   15−17 39 73−137
300 165   23 44−51 64−113
400 165 370 24 61 54−78
500 155 250 23 61 44−73
600 59 110 31−37 73−81 59−225
Lmsta 37−40 mm thick after annealing at 880−900 ° C.
20 245 400−430 thirty 55−60 73−98
200 180−225 350−500 17−28 43−62 83−117
300 145−185 350−510 24 52−60 78−93
400 135−175 320−400 22−33 60−73 59−73
500 120−150 200−270 24−43 71−83 49−64
600 69−98 110−150 36−48 84−91 113

Mechanical properties depending on heat treatment

Heat treatment, delivery condition σ 0.2, MPa σ B, MPa δ 5 ,% ψ,% KCU, J / m 2
Hot rolled condition, heat exposure 10,000 h, 450 ° С. 235−245 425 30−32 59−83 55−83
Hot rolled condition, heat exposure 30,000 h, 450 ° C. 235 395 32 62 82−125
Hot rolled condition, heat exposure 40,000 h, 450 ° С. 210 395 29−31 60−62 81−104
Hot rolled condition, heat exposure 10,000 h, 500 ° C. 185−215 350−360 27−31 65−68 75−137
Hot rolled condition, heat exposure 30,000 h, 500 ° C. 175−195 360 30−33 62−64 88−125

Mechanical properties when tested for long-term strength

Creep limit, MPa Creep rate,% / h t test, ° С Long-term strength, MPa Duration tests, h t test, h
108 1/100000 400 127 10000 450
94 1/10000 450 93 100,000 450
63 1/100000 450 76 10000 500
      54 100,000 500

Technological properties of steel 20K

Forging temperature
Beginning 1260, end 750.
Weldability
Can be welded without restrictions. Methods of welding RDS, ADS submerged arc and gas shielded, EShS.
Tendency to release ability
Not inclined.
Flock sensitivity
Not sensitive.

Temperature of critical points of steel 20K

Critical point ° C
Ac1 724
Ac3 845
Ar3 815
Ar1 682

Yield strength of steel 20K

Test temperature, ° C / s 0.2
200 250 300 350 400 450
215 195 175 155 135 120

Physical properties of steel 20K

Test temperature, ° С 20 100 200 300 400 500 600 700 800 900
Normal elastic modulus, E, GPa 207 204 201 196 187 176 162      
Density of steel, pn, kg / m 3 7850                  
Thermal conductivity coefficient W / (m ° С)   51 49 46 42 39 36      
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)   11.9 12.8 13.2 13.6 13.9        
Specific heat (C, J / (kg ° C)) 470 483   538 571          

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