| Galvanizing Lines | | | | efficiency of the lines can be improved by using |
| Galvanizing lines can include machinery for coil joining | | | | larger coils or by inserting a step to join the end of |
| before the galvanizing procedure. While steel can be | | | | one coil to the beginning of the next, therefore |
| welded after galvanizing, it requires special | | | | providing the machine with a continuous feed that |
| precautions such as ventilation due to fumes. | | | | cuts downtime significantly. |
| Galvanizing is the process of coating steel with zinc. | | | | A sequence of machinery that includes a coil joining |
| "Coating" is somewhat of a misnomer, however, | | | | operation before hot dip galvanizing might go like this: |
| because the zinc actually becomes part of the steel. | | | | - pay-off reel |
| The reason steel is galvanized is to prevent rust and | | | | - leveller |
| corrosion. When steel is dipped in zinc and exposed | | | | - cropping shear |
| to air, the pure zinc undergoes a reaction with | | | | - welding machine |
| oxygen to make zinc oxide. The zinc oxide reacts | | | | - entry loop accumulator |
| with carbon dioxide to form zinc carbonate. Zinc | | | | Typically a welding machine, whether portable or |
| carbonate is a dull gray, strong material that usually | | | | fixed, will include a TIG end welder. TIG stands for |
| stops further corrosion. | | | | tungsten inert gas. This type of welder generates |
| | | | heat with an arc of electricity going from a tungsten |
| Applications for galvanized steel include use in safety | | | | electrode to the metal welding surface. A sheath of |
| barriers, appliances, car body parts, handrails, walling, | | | | argon gas mixed with carbon dioxide surrounding the |
| and roofing. Metal buckets are often galvanized, and | | | | electrode keeps the weld as clean and free from |
| galvanized steel is used in ductwork for heating and | | | | debris as possible. The trailing coil end is first sheared |
| cooling systems. Besides hot dip galvanizing, metal | | | | and positioned inside the weld station. Then the |
| can be galvanized by electroplating, which deposits a | | | | leading end of the next coil is sheared and positioned. |
| layer of zinc from an aqueous electrolyte. This forms | | | | The welding is automatic. |
| a very thin, strong bond. | | | | TIG welding is great for coil joining but it can be |
| Thermal diffusion galvanizing creates a zinc coating | | | | dangerous done by hand. There are TIG machines |
| similar to that produced by hot dip galvanizing. With | | | | for coil joining where the coil ends to be joined are |
| thermal diffusion galvanizing, zinc is applied in the form | | | | fed in, automatically welded by the machine, and the |
| of a powder combined with accelerator chemicals. | | | | newly continuous line of steel then flows onto an |
| The metal and zinc compound are sealed up in a | | | | entry accumulator. |
| drum, and the drum is rotated in an oven. The | | | | Processing plants like those with galvanizing lines that |
| accelerator chemicals cause the iron-zinc diffusion, or | | | | use cold rolled steel can experience productivity |
| alloying, takes place at a lower temperature than | | | | drops of 20 to 30% when they have to stop |
| does hot dip type galvanizing. Thermal diffusion | | | | production lines so that a new coil of steel can be |
| galvanizing results in a more uniform coating that is | | | | threaded in when the old coil runs out. A coil joining |
| more wear-resistant. The process also eliminates | | | | machine included in the production process can cut |
| need for caustic, acid, and flux baths to prepare the | | | | productivity losses drastically by allowing continuous |
| parts for hot dipping. | | | | feeding of coiled steel into the production machinery. |
| Since hot dip galvanizing lines use coiled steel, the | | | | |