T7 steel with good toughness and hardness, but less capable of cutting; usually used to manufacture the same time the need for greater toughness and a certain hardness, but not very high capacity requirements of cutting tools such as chisels, red top, small size pneumatic tools , used wood saw, chisel, forging dies, die, locksmith tools, hammers, rivet die, etc., can also do a top hand with a large mallet hammer.
T7 chemical composition of steel chemical composition shown in Table 2-20-1.
T7 steel chemical composition GB/T1299-2000) w /%
| C | Si | Mn | Cr | W |
| 0.65~0.74 | ≤0.35 | ≤0.40 | ≤0.030 | ≤0.035 |
Physical properties of the physical properties of T7 steel are shown in Table 2-20-2 ~ Table 2-20-4, its density ask 7.83t/m3; magnetic permeability μ of about 0.94mH / m; coercivity Hc of 318 ~ 954A in / m (Hc of the lower limit for the ball of tissue, the upper limit for pearlite; saturation magnetic induction Bs of 2.01 ~ 2.05T; resistivity ρ of 0.13 × 10-6Ω · m.
Table 2-20-2 T7 critical temperature of steel
| Critical point | Ac1 | Ac3 | Ar1 |
| Temperature (approximate) / ℃ | 730 | 770 | 700 |
Table 2-20-3 T7 steel wire (swelling) expansion coefficient
| Temperature / ℃ | 20~100 | 20~200 | 20~300 | 20~400 |
| Line (swelling) expansion coefficient / ℃ -1 | 11.8×10-6 | 12.6×10-6 | 13.3×10-6 | 14.0×10-6 |
Table 2-20-4 T7 thermal conductivity of steel
| Temperature / ℃ | 20 | 100 | 300 |
| Thermal conductivity λ / W · (m · K) -1 | 44 | 44 | 41.9 |
T7 steel thermal processing thermal processing are shown in Table 2-20-4.
T7 steel thermal processing
| Item | Heating temperature / ℃ | Before forging temperature / ℃ | Final forging temperature / ℃ | Cooling |
| Steel ingot | 1100~1150 | 1080~1120 | 850~750 | Cold air |
| Steel billet | 1050~1100 | 1020~1080 | 850~750 | Cold air |
