| Steel tube starts out as flat steel strip that has been | | | | takes from entering into the mill to the time it passes |
| slit to the correct width for the end tube size. It is | | | | through the cutoff is only a few seconds. |
| then passed through a series of rolls that form it into | | | | After the tube is manufactured there are a number |
| a round tube. After the steel has been formed it | | | | of secondary processes that are performed |
| passes through a weld box. The weld box for ERW | | | | depending on the end use. Some of the common |
| tube uses electrical resistance of the steel tube to | | | | items are Deburring, Dedimpling, & Coating. |
| create heat. This heat is what welds the two steel | | | | Deburring is a process where the tube passes |
| edges together. Using this method will produce a | | | | through a machine with spinning wire brushes. These |
| strong weld that is just as strong as or stronger than | | | | wire brushes smooth out and remove the jagged |
| the original steel. | | | | edges normally left after the tube is cut. This is done |
| After welding the surface left behind, known as flash | | | | when the ends of the tube will be exposed in the |
| is removed if there is a requirement to do so. After | | | | end product. |
| the flash control process the tube travels through a | | | | Dedimpling can be done at the same time as cutting |
| cooling box that is filled with special coolant. Once the | | | | but also may be a secondary process. When certain |
| tube leaves the cooling box it now goes through a | | | | shapes are cut the knife dents in the tube slightly. |
| group of finishing rolls. These finishing rolls are used to | | | | The dedimple process is done by a machine that |
| change the shape of the tube and make the final | | | | inserts plugs into the end of each tube to remove |
| dimensions. Common shapes include: round, square, | | | | the dent. |
| rectangle, oval, & octagonal. Following the | | | | The material used to coat the tube depends on the |
| finishing process the tube is generally coated with an | | | | end application. A tube may be coated with a metallic |
| anti-rust liquid to protect the steel tube. | | | | material such as zinc to protect it, or chrome to give |
| Finally the tube passes through a cutoff that cuts the | | | | it a gleaming finish. The tube may also be powder |
| tube to the required lengths. The steel tube generally | | | | coated or painted. |
| moves through the mill at fast speeds. The time it | | | | |