Method for eliminating residual magnetism in pipe-blank for welded steel pipe longitudinally seam-welded from inside
US4107503A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 10, 1977 |
| Grant date | Aug 15, 1978 |
| Priority date | — |
| Expiry date | Mar 10, 1997 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB23K9/0253
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
After longitudinally seam-welding a pipe-blank for welded steel pipe from the inside along a groove by the arc welding process which comprises using direct electric current supplied to a consumable electrode through a cable as the welding current, the polarity of said consumable electrode applied for said longitudinal seam-welding is switched over to the opposite polarity, an arc from said consumable electrode is ignited again on a tab plate attached to the end of said pipe-blank on the completion side of said longitudinal seam-welding to cause a direct electric current for eliminating magnetism to flow through said cable in the opposite direction to that of said direct electric current for welding, thereby eliminating residual magnetism in said pipe-blank produced by said direct electric current for welding flowing through said cable introduced into said pipe-blank during said longitudinal seam-welding.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.