Fins- Most Important Component For Tube Making
After strip is formed into round shape, inner fibres of tube come closer and outer fibres fall apart. if such a tube is welded then it will be a very weak welding, as both surfaces of open tube will not be matching. For this reason round shape is made to pass through fin pass rolls. There are 2 to 3 stands depending upon tube size, gauge and mill design. Fin conditions the strip edges for proper welding. Its functions are -
- Guiding the edges of strip
- Squaring the edges for butt welding
- Directing the tube to squeeze rolls for perfect welding
Fin should be wear resistanr & tough. Best raw material for Fin is AISI-D2.
| C = 1.50 |
Si = 0.40 | Mn = 0.40 |
| Cr = 12.0 | Mo = 0.90 | V = 0.70 |
Edges of strip strike and rub fin on both sides.
Recommended hardness is 56/58 HRC.
Next best Raw Materials for Fin are Cr-V / Ni-Cr Steel with hardness 56/58 HRC.
In India Fins are also made from AISI-D3 & SAE-52100 having hardness 56/58 HRC.
Recommended tolerances on Fin are -
| Outer diameter |
= |
± 0.1 mm |
| I.D. |
= | G-7 |
| Keyway Width | = | + .1 / + .4 |
| Keyway Depth | = | + .2 / + .5 |
| Keyway corner radius |
= | 2.0 R |
| Thickness |
= | ± 0.02 mm |
| Bevel |
= | ± 30’ |
| Bevel Diameter |
= | ± 0.5 mm |
| P.C.D. on holes |
= | ± 1.0 mm |
| = | ||
| = |
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