24 July 2021 Structural Steel Bar
CK22 Structural Steel Bar
CK22 structural steel is a slightly higher carbon and manganese content plain carbon steel than 1020. It is used for its somewhat greater strength while still having good ductility. CK22 equivalent to Chinese Steel Grade 20#, belongs to high quality low carbon carbon steel, cold extrusion, carburizing and hardened steel. The steel has low strength, good toughness, plasticity and weldability. The tensile strength is 253-500 MPa and the elongation is ≥24%.
Chemical Composition:
| Steel Grade | C | Si | Mn | S | other |
|---|---|---|---|---|---|
| C22E | 0,20 | 0,25 | 0,50 | 0,030 | (Pb) |
| C22R | 0,20 | 0,25 | 0,50 | 0,020 0,035 | (Pb) |
Forging or hot rolling: Normalising:
Soft annealing: Hardening: Tempering:
Treated for cold shearability +S:
Soft annealed +A:
Quenched and tempered, +QT:
1100 - 850°C
880 - 920°C/air
680 - 710°C/furnace 860 - 900°C/water 550 - 660°C
Shearable in as rolled condition
-
< 16 | >16 – 40 | >40 – 100 | >100 – 160 | >160 – 250 |
<8 | 8<t<20 | 20<t<60 | 60<t<100 | 100<t<160 |
min. 340 | min. 290 | - | - | - |
500 - 650 | 470 - 620 | - | - | - |
min. 20 | min. 22 | - | - | - |
min. 50 | min. 50 | - | - | - |
min. 50 | min. 50 | - | - | - |
Mechanical properties:
Phase transition temperature (approximate) Ac1=735°C, Ac3=855°C, Ar3=835°C, Ar1=680°C
Normalizing specification The temperature is 920~950°C and it is air cooled. Hardness 131~156HBS.
Specification for Softening of Cold Pressed Blanks Temperature 700~720°C, holding time 8~15h, and then cooling rate of 50~100°C/h, with the furnace down to the temperature ≤550~600°C, baked and cooled.
Hardness before treatment ≤ 143HBS, hardness after softening ≤ 131HBS.
Quenching specification Temperature 910°C ± 10°C, 10% NaCl brine cooling.
Measured yield strength fy = 245 MPa, elastic modulus E = 206 Gpa, Poisson's ratio ν = 0.3.
Shear strength 275-392 MPa, tensile strength 253-500 MPa, yield strength 275 MPa, elongation 25%.
As long as the annealing temperature is 600-650 degrees, the holding time is 1-2 hours.