Table 1. Chemical Composition
| Unit:% | |||||
| Symbol of grade | C | Si | Mn | P | S |
| STK290 | - | - | - | 0.050 max. | 0.050 max. |
| STK400 | 0.25 max. | - | - | 0.040 max. | 0.040 max. |
| STK490 | 0.18 max. | 0.55 max. | 1.65 max. | 0.035 max. | 0.035 max. |
| STK500 | 0.24 max. | 0.35 max. | 0.30 to 1.30 | 0.040 max. | 0.040 max. |
| STK540 | 0.23 max. | 0.55 max. | 1.50 max. | 0.040 max. | 0.040 max. |
| Notes a) If necessary,alloying elements other than specified in this table may be added. b) For the tube of grade STK540 exceeding 12.5 mm in wall thickness,the chemical composition may be subject to the aggreement between the purchaser and the manufacturer. | |||||
Table 2. Mechanical Properties
| Symbol of grade | Tensile strength N/mm² | Yield point of proof stress N/mm² | Tensile strength in weld zone N/mm² | Flattening | Bendability | |
| Distance between plates(H) | Bend angle | Inside radius | ||||
| Applied outside diameter | ||||||
| All outside diameters | All outside diameters | All outside diameters | All outside diameters | 50 mm max. | ||
| STK290 | 290 min. | - | 290 min. | 2/3 D | 90° | 6 D |
| STK400 | 400 min. | 235 min. | 400 min. | 2/3 D | 90° | 6 D |
| STK490 | 490 min. | 315 min. | 490 min. | 7/8 D | 90° | 6 D |
| STK800 | 500 min. | 355 min. | 500 min. | 7/8 D | 90° | 6 D |
| STK540 | 540 min. | 390 min. | 540 min. | 7/8 D | 90° | 6 D |
| NOTE 1 D of this table is the outside diameter of the tubes. NOTE 2 1 Nmm²=1MPa | ||||||