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U8A steel

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U8A steel

U8A Steel: Handbook of steels and alloys. 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 U8A.

General information on steel U8A

Substitute for the grade
Steel grade: У7А, У7, У10А, У10.
Type of delivery
U8a sheet, U8a strip, U8a circle, U8a tape, bars, including shaped: GOST 1435−74, GOST 2590−71, GOST 2591−71, GOST 2879−69. Calibrated rod GOST 1435−74, GOST 7417−75, GOST 8559−75, GOST 8560−78. Grinded rod and silversilver GOST 1435−74, GOST 14955−77. Tape GOST 2283−79, GOST 10234−77. Tape GOST 103−76, GOST 4405−75. Forgings and forged blanks GOST 1435−74, GOST 4405−75, GOST 1133−71.
Application
For tools working under conditions that do not cause heating of the working edge: milling cutters, hatchets, hatchets, chisels, circular and circular saws, rollers, punches, screwdrivers, combination pliers, side cutters.

Chemical composition of U8A steel

Chemical element %
Silicon (Si) 0.17−0.33
Manganese (Mn) 0.17−0.33
Copper (Cu), not more 0.20
Nickel (Ni), not more than 0.20
Sulfur (S), not more than 0.018
Carbon (C) 0.76−0.83
Phosphorus (P), not more than 0.030
Chromium (Cr), not more than 0.20

Mechanical properties of U8A steel

Mechanical properties depending on test temperature

t test,°C σ0, 2, MPa σB, MPa δ5, % ψ, % HB
Annealing or normalization
100   710 17 24 195
200   640 15 15 205
300     17 16 205
400     19 23 190
500   500 23 29 170
600   370 28 39 150
700   255 33 50 120
Tempering at 780 °C, oil. Tempering at 400 °C (smooth specimens 6.3 mm in diameter)
20 1230 1420 10 37  
-40 1270 1450 11 36  
-70 1300 1470 12 35  
Specimen 5 mm in diameter and 25 mm in length, deformed and annealed. Deformation rate of 10 mm/minute. Strain rate 0.007 1/s.
700   105 58 91  
800   91 58 100  
900   55 62 100  
1000   33 62 100  
1100   21 80 100  
1200   15 69 100  

Mechanical properties of the belt

Heat treatment, delivery condition Section, mm σB, MPa δ5, %
Strip annealed cold rolled
  0,1−1,5 650 15
  1,5−4,0 750 10
Cold-rolled bulk tape.
Strength class H1 0,1−4,0 750−900  
Strength class H2 0,1−4,0 900−1050  
Strength class H3 0,1−4,0 1050−1200  
Annealed strip of the highest quality category
  0,1−4,0 650 15

Technological properties of U8A steel

Forging temperature
The beginning 1180, the end 800. Cooling of blanks with a cross section of up to 100 mm in the air, 101−300 mm — in the pit.
Weldability
Not applicable for welded structures. The method of welding is CTS.
The machinability by cutting
At НВ 187−227 Kυ tv.spl. = 1.2, Kυ b.st. = 1.1.
Tendency to tempering ability
is not prone
Flockensitivity
not sensitive
Grindability
good

Temperature of U8A steel critical points

Critical point °С
Ac1 730
Ac3 765
Ar1 700
Mn 245

Hardness of steel U8A

Delivery condition, heat treatment regime HRCe surface HB
Heat-treated steel. Hardened 780−800 C, water. St. 63 187
Tempering 780−800 С, water. Tempering 160−200 C. 61−65  
Tempering at 780−800°C with water. Tempering at 200−300°C. 56−61  
Tempering at 780−800°C with water. Tempering 300−400 C. 47−56  
Tempering at 780−800°C with water. Tempering 400−500 C. 37−47  
Tempering at 780−800°C with water. Tempering at 500−600°C. 29−37  

Hardenability of U8A steel

Quenching at 790 °C.

Face-off distance, mm / HRCe
2 4 6 8 10 12 14 16 18
65,5−67 63−65 45,5−55 42−43,5 40,5−42,5 39,5−41,5 37−40,5 39−40 36−39,5
Crit. dia. in water, mm Size in oil, mm
15−20 4−6

Physical properties of U8A steel

Test temperature, °С 20 100 200 300 400 500 600 700 800 900
Modulus of normal elasticity, E, GPa 209 205 199 192 185 175 166      
Torsional shear modulus of elasticity G, GPa 81 80 77 74 71 67 62      
Steel density, pn, kg/m3 7839 7817 7786 7752 7714 7676 7638 7600 7852  
Thermal conductivity coefficient W/(m — °C)   49 46 42 38 35 33 30 24 25
Electrical resistivity (p, nominal value — m)   230 305 395 491 625 769 931 1129 1165
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) 11.4 12.2 13.0 13.7 14.3 14.8 15.2 14.5 15.2 15.7
Specific heat capacity (C, J/(kg -°C)) 477 511 528 548 565 594 624 724 724 703

Heat resistance, red resistance of steel U8A

Heat resistance

Temperature, °С Time, h Hardness, HRCэ
150−160 1 63
200−220 1 59