24 July 2021 Structural Steel Bar
DIN 1.5752 Structural Steel Bar
DIN 1.5725 is a widely used high quality carburizing structural steel that has high strength, ductility and hardenability compared to 15Cr and 20Cr steels. Quenching and tempering at low temperature or tempering at high temperature, have good mechanical properties, notched impact strength at low temperature, notch sensitivity, machinability and weldability is good, but the tempering brittleness, white point of high sensitivity After carburizing are required for secondary quenching, special circumstances also need cold treatment.
Chemical Composition:
| C(％) | Si(％) | Mn(％) | P(％) | S(％) | Cr(％) | Ni(％) | Mo(％) |
|---|---|---|---|---|---|---|---|
| 0.14～0.20 | ≤ 0.40 | 0.40 ~ 0.70 | ≤ 0.035 | ≤ 0.035 | 0.60～1.00 | 3.00 ~ 3.50 | - |
Physical properties (avarage values) at ambient temperature
- Modulus of elasticity [103 x N/mm2]: 210
- Density [g/cm3]: 7.83
- Thermal conductivity [W/m.K]: 34.0
- Electric resistivity [Ohm mm2/m]: 0.20
- Specific heat capacity[J/g.K]: 0.46
Mechanical Properties:
| Tensile Strength (MPA) | Yield Strength (MPA) | Reduction (%) | Elongation (10%) | Impact Strength (Aku2/J) | Hardness (HB) |
|---|---|---|---|---|---|
| 930 | 735 | 11 | 50 | 71 | 217 |
Equivalent Steel Grade :
| ASTM A29 | JIS G4105 | GB | DIN | EN | TOCT |
|---|---|---|---|---|---|
| 3415 | SNC815 | 20CrNi3 | 14NiCr14 | 15CrNi13 | 12XH3A |
Heat Treatment:
Coefficient of Linear Thermal Expansion 10-6 oC-1
| 20-100oC | 20-200oC | 20-300oC | 20-400oC | 20-500oC |
| 11.1 | 12.1 | 12.9 | 13.5 | 13.9 |
Continuous Cooling Transformation (CCT) Diagram:
Time-Temperature Transformation (TTT) Diagram:
Soft Annealing
Heat to 610-650oC, cool slowly. This will produce a maximum Brinell hardness of 229.
Hardening
Case-hardening: 880-980oC, oil (water), warm bath at 160-250oC. Carburising: Salt bath at 580-650oC, case-hardening box, air.
Direct hardening: 880-890oC, oil, hot bath at 160-250oC.
Core refining: 840-880oC, oil, hot bath at 160-250oC.
Case refining: 780-820oC, oil, hot bath at 160-250oC.
Normalizing
Normalizing temperature: 850 – 880oC.
Tempering
Tempering temperature: 150 – 200oC.
Hardenability in the end-quench test
| Hardness | 1.5 | 3 | 5 | 7 | 9 | 11 | 13 | 15 | 20 | 25 | 30 | 35 | 40 |
| H max. | 48 | 48 | 48 | 47 | 45 | 44 | 42 | 41 | 38 | 35 | 34 | 34 | 33 |
| H min. | 41 | 41 | 41 | 40 | 38 | 36 | 33 | 30 | 24 | 22 | 22 | 21 | 21 |
| HH max. | 48 | 48 | 48 | 47 | 45 | 44 | 42 | 41 | 38 | 35 | 34 | 34 | 33 |
| HH min. | 43 | 43 | 43 | 42 | 40 | 39 | 36 | 34 | 29 | 26 | 26 | 25 | 25 |
| HL max. | 46 | 46 | 46 | 45 | 43 | 41 | 38 | 37 | 33 | 31 | 30 | 30 | 29 |
| HL min. | 41 | 41 | 41 | 40 | 38 | 36 | 33 | 30 | 24 | 22 | 22 | 21 | 21 |
Forging
Hot forming temperature: 1050-850oC.