Advances in tinning line using tension multi roll leveler

With the expectation of replacing aluminium packaging gradually, the prospects of this new material is very high.

From the view of the development trend of the technology, both tin plate products and tin coating are getting thinner. As a result, the production technology is becoming more complex and difficult and has become the high-level production line in the manufacturing field of thin electrolytic tinplate in metallurgical industry.

In addition, canning and printing processes using tinplate sheets as raw material are extremely sensitive to strip shape. The cold rolling process of black steel also produces a considerable amount of internal stress in strip steel, causing tinplate flexures easily when such stress is released during downstream deep processing of shearing.

The use of REDEX Tension Multi Roll Leveler eliminate the flatness defects of strip steel in metallurgy and improve the shape of strip. Therefore, it has become one of the benchmarks that measure the technical level of the electrolytic tinplate production line.

Breakthrough in mass production

Through the development of tinplate applications, many domestic steel mills have begun to construct electrolytic tinplating units. Some have even introduced large advanced continuous tinplating units with high output. Baoshan Iron & Steel Co. Ltd (Baosteel) is one of them.

Currently, the company has become one of the leading domestic companies in the field of tinplates and double cold reduction (DCR) technology. In order to better meet the production requirement on the flatness of DCR tinplates (the product after rolling process/annealing/single or double reduction skinpass), Baosteel planned to upgrade its 1420 cold rolling No. 2 tinplating unit (C217) to one that can produce both SR (Single Reduction) and DR (Double Reduction) tinplated products.

The C217 unit of Baosteel is reported to have a total production capacity of 180,000 t/a. The unit uses continuous annealing (CA) black steel strip and DCR black steel strip. While the original design of C217 unit did not include a tension leveler, it was unable to run mass production. As such, there was an urgent need to add a tension multi roll leveler to the production line. Due to tight schedule and the production line having the necessity of running continuously, Baosteel set the bar high in open tendering.

First of all, the vendor needed to provide the tension leveler and supporting equipment that are advanced, reliable, easy to maintain (including front and back tension bridle rollers) to ensure the continuous and stable operation of the units and provide good performance in the cold rolling production line. Next, it must upgrade the motors, drives, and other electrical equipment at the same time. It was also required to upgrade the entire cleaning section to eventually realise fully automated operation and avoid noise pollution. Finally, since the tinnings lines of Baosteel were required to run around the clock, the time for equipment delivery, installation and commissioning must be kept as short as possible.

This created a great challenge for many vendors. Thanks to its compact REDEX tension multi-roll leveler and experiences of successful applications at large steel mills abroad, the perfect evaluation scores on technology and business practices set REDEX apart from other outstanding vendors.

Proven applications worldwide
The PMR 1300 used by REDEX on Baosteel's tinning line production tension multi roll leveler jointly developed by ARCELOR PACKAGING International, IRSID, and REDEX, following the RDI development standards of CECA.

PMR 1300 tension multi roll leveler can apply force on both tensile and bending deformation of the strip at the same time to achieve precise elongation control. Thus, all fibres in the strip are stretched to the same length to obtain excellent flatness of the strip and effectively eliminate the internal stress of steel strip.

Mr. Jiang Ling, general manager of REDEX (Shanghai) Co. Ltd, said, "This tension multi roll leveler is specially designed for very thin and hard steel strip with very limited residual elongation. It integrates our proprietary mechanical drive system and strip steel elongation control system, offering higher precision of strip steel elongation and tension without the risk of breaking the strip steel. In addition to modernising an existing tinning line, it can be integrated into a new tinning line, ideal for materials in DWI, SR, and DR material grades with better effect on wave, coil set, crossbow, bending, micro buckle, and internal stress, etc.”

He added, “It is worth to mention that the unit adopts the high quality innovative multi-roller compact design. The overall assembly and installation precision is below 0.02 mm. It also provides closed-loop intermesh gap control and closed-loop crown adjustment control, applicable to any strip steel. It can carry out reliable permanent setting of various thickness to ensure an advanced flexible tension multi roll leveler process with high efficiency and low energy consumption. The tension multi roll leveler effect can be increased by 50 %.”

Easy and fast installation
Since the tinning’s lines are required to run around the clock, the time for equipment delivery, installation and commissioning must be minimised.

"At this point, our strengths were fully reflected. Under normal circumstances, the installation and commissioning would take two to three weeks. Our product was pre-assembled in the factory prior to delivery, requiring no on-site assembly. To ensure a successful acceptance, we also sent three French engineers to the work site.

As the result, it took only eight days to complete the entire process of installation, commissioning and production nearly half a month ahead of the schedule, Mr. Jiang Ling added.

According to Mr. Jiang, for the past 5 years, REDEX tension multi roll leveler has dominated the tinplating application market with No. 1 market share. The cooperation with Baosteel allows REDEX tension multi roll leveler to be used on the tinplating production line in China for the first time.