U7A steel
U7A steel
U7A 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 U7A.
General information on steel U7A
| Substitute for the grade |
| steel У8. |
| Type of delivery |
| Sections, 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, GOST 21997−76. Strip GOST 103−76, GOST 4405−75. Forgings and forged blanks GOST 1435−74, GOST 4405−75, GOST 1133−71. |
| Application |
| The tool, which operates in conditions that do not cause heating of the working edge: chisels, chisels, hammers, metal cutting scissor blades, axes, cleavers, chisels, combination pliers, sledgehammers. |
Chemical composition of steel U7A
| Chemical element |
% |
| Silicon (Si) |
0.17−0.33 |
| Manganese (Mn) |
0.17−0.28 |
| Copper (Cu), not more |
0.20 |
| Nickel (Ni), not more than |
0.20 |
| Sulfur (S), not more than |
0.028 |
| Carbon (C) |
0.66−0.73 |
| Phosphorus (P), not more than |
0.030 |
| Chromium (Cr), not more than |
0.20 |
Mechanical properties of U7A steel
Mechanical properties
| Heat treatment, delivery condition |
Section, mm |
σB, MPa |
δ4, % |
| Cold rolled annealed strip |
| |
0,1−1,5 |
650 |
15 |
| |
1,5−4,0 |
750 |
10 |
| Cold rolled clad strip. |
| 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 |
|
| Cold-rolled annealed strip of the highest quality category. |
| |
0,1−4,0 |
650 |
18 |
Mechanical properties depending on tempering temperature
| t tempering temperature, °C |
σ0, 2, MPa |
σB, MPa |
ψ, % |
KCU, J/m2 |
| Quenching for fine grain structure with cooling in water. |
| 300 |
1370 |
1590 |
8 |
31 |
| 400 |
1180 |
1270 |
11 |
44 |
| 500 |
970 |
1090 |
13 |
73 |
| 600 |
830 |
980 |
17 |
93 |
Mechanical properties depending on test temperature
| Heat treatment, delivery condition |
t test,°C |
σ0, 2, MPa |
σB, MPa |
δ5, % |
ψ, % |
KCU, J/m2 |
HB |
| Hardening at 860 °C, oil. Tempering at 450 °C. |
| |
-50 |
1760 |
1860 |
10 |
32 |
24 |
|
| Annealing or normalization |
| |
100 |
|
690 |
16 |
30 |
|
200 |
| |
200 |
|
660 |
13 |
22 |
|
200 |
| |
300 |
|
|
18 |
20 |
|
200 |
| |
400 |
|
620 |
22 |
26 |
|
180 |
| |
500 |
|
460 |
27 |
34 |
|
155 |
| |
600 |
|
330 |
33 |
45 |
|
135 |
| |
700 |
|
205 |
38 |
60 |
|
110 |
| Sample with diameter of 5 mm and length of 25 mm deformed and annealed. Strain rate 10 mm/minute. The strain rate is 0.007 1/s. |
| |
700 |
|
105 |
64 |
90 |
|
|
| |
800 |
|
94 |
65 |
100 |
|
|
| |
900 |
|
63 |
60 |
100 |
|
|
| |
1000 |
|
36 |
62 |
100 |
|
|
| |
1100 |
|
22 |
65 |
100 |
|
|
| |
1200 |
|
17 |
92 |
100 |
|
|
| Annealing. |
| Vizg=195 MPa |
600 |
|
|
26 |
71 |
|
|
| Vizg=85 MPa |
700 |
|
|
45 |
88 |
|
|
| Vizg=52 MPa |
800 |
|
|
38 |
71 |
|
|
| Vizg=27 MPa |
900 |
|
|
59 |
92 |
|
|
| Vizg=25 MPa |
1000 |
|
|
58 |
98 |
|
|
| Vizg=20 MPa |
1100 |
|
|
65 |
99 |
|
|
Technological properties of U7A 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. |
| Machinability |
| In the annealed state at HB 187 and σB = 620 MPa Kυ tv.spl. = 1.2, K υ b.st. = 1.1. |
| Tendency to tempering capacity |
| is not inclined |
| Floc-sensitivity |
| not sensitive |
| Grindability |
| good |
Temperature of U7A steel critical points
| Critical point |
°С |
| Ac1 |
730 |
| Ac3 |
770 |
| Ar1 |
700 |
| Mn |
280 |
U7A steel hardness
| Delivery condition, heat treatment regime |
HRCe surface |
HB |
| Heat-treated steel. Hardened 800−820 C, water. |
St. 63 |
187 |
| Tempering 820 C, water. Tempering 160−200 C. |
60−63 |
|
| Tempering at 820 °C with water. Tempering 200−300 C. |
54−60 |
|
| Tempering at 820 °C with water. Tempering 300−400 C. |
43−54 |
|
| Tempering at 820 °C with water. Tempering 400−500 C. |
35−43 |
|
Hardenability of steel U7A
Hardening at 800 °C.
| Distance from end face, mm / HRCe |
| 2.5 |
5 |
7.5 |
10 |
15 |
20 |
25 |
30 |
| 43,5 |
37 |
35 |
34 |
32 |
28,5 |
22 |
20 |
| Crit. dia. in water, mm |
Crit. dia. in oil, mm |
| 15−20 |
4−6 |
Physical properties of U7A steel
| Test temperature, °С |
20 |
100 |
200 |
300 |
400 |
500 |
600 |
700 |
800 |
900 |
| Steel density, pn, kg/m3 |
7830 |
|
|
|
|
|
|
|
|
|
| Thermal conductivity coefficient W/(m — °C) |
46 |
46 |
|
41 |
|
|
33 |
|
|
29 |
| Electrical resistivity (p, nominal value — m) |
130 |
|
|
|
|
|
|
|
|
|
| Test temperature,°C |
20−100 |
20−200 |
20−300 |
20−400 |
20−500 |
20−600 |
20−700 |
20−800 |
20−900 |
20−1000 |
| Specific heat capacity (C, J/(kg -°C)) |
|
|
580 |
664 |
819 |
970 |
710 |
706 |
685 |
|
Heat resistance, red resistance of steel U7A
Heat resistance
| Temperature, °С |
Time, h |
Hardness, HRCэ |
| 150−160 |
1 |
63 |
| 20−220 |
1 |
59 |
