Value-added strip for the automotive market

Continuous galvanizing line supplied to JFE Steel Galvanizing Indonesia

The CGL at JSGI has performed reliably since its start-up in January 2016, 29 months after the contract signing. The facility is designed to produce a wide range of high-quality exposed automotive products in a combination line for annealed or galvanized strip (Figure 2). Strip thicknesses extend from 0.4 mm to 2.3 mm at widths between 800 mm and 1,850 mm. Processed strip grades include commercial quality (CQ), drawing quality (DQ), deep-drawing quality (DDQ), extra-deep-drawing quality (EDDQ), super-extra-deep-drawing quality (SEDDQ) and high-strength steels (HSS) for automotive applications. Table 1 shows the main technical specifications of the CGL. The features of the different sections, products and benefits are described in the following.

Entry section

Dual pay-off reels and associated equipment are installed in the entry section (Figure 3) of the galvanizing line to allow continuous strip feeding. The vertical entry looper after the entry section ensures sufficient strip storage in the tower so that continuous uninterrupted operations can take place in the process section while the strip is stopped for welding in the entry section. This is possible even at maximum process line speed. Removal of strip-surface impurities takes place in the cleaning section, which consists of a series of alkali dip-cleaning tanks, a brush scrubber, an electrolytic cleaning section, as well as auxiliary circulation systems to achieve superior cleaning results.

Entry section of the continuous galvanizing line

Center section

The advanced continuous annealing furnace is distinguished by its strip-heating and cooling system, thermal crown control of the furnace rolls, and stable strip speed. The vertical-type annealing furnace consists of a preheating zone, radiant tube heating, a soaking zone, rapid cooling and a turndown section. As the strip passes through the annealing furnace, defined heating and cooling steps (thermal cycles) are carried out depending on the strip grade to be produced.

Thermal crown control of the furnace rolls, accurate strip-tension control, optimum positioning of the steering and bridle rolls, and precise roll crown and surface roughness are the key factors to ensure fine strip quality, stable line operation and steady strip speed. In order to produce galvannealed strip, a coating pot with a channel-type induction-heating system, a galvannealing induction-heating furnace, as well as up- and down-leg cooling equipment is provided.

A vertical-type center looper is installed after the pot- cooling area and skin-pass mill to enable uninterrupted continuous operation in the process section. The 4-high wet-rolled skin-pass mill enhances the mechanical properties of the strip, ensures excellent strip flatness and imparts the required strip-surface roughness.

The continuous galvanizing line in operation at JSGI
Main technical specifications of the continuous galvanizing line

Strip thickness: 0.4 mm to 2.3 mm
Strip width: 800 mm to 1,850 mm
Coil weight: 30,000 kg
Welder type: Mash seam welder
Furnace type: Vertical
Coated material: Galvanized and galvannealed
Additional equipment: Skin-pass mill, side trimmer

Delivery and inspection sections

After passing through a chemical treatment section and delivery looper, the galvanized strip edges are trimmed by a highly accurate side trimmer. Together with fully automated parameter setup, high-yield side trimming is assured. The scrap baller winds trimmed scrap into a scrap ball, which is subsequently transferred to the scrap buckets by the scrap conveying system.

After inspection in the delivery inspection station, the strip is oiled, cut on the fly and then coiled by a tension reel. A quick sample gate is installed behind the flying shear. When a coil is wound completely, the reel mandrel collapses and a coil car takes the coil off the mandrel for placement onto the exit coil saddle. The coil is then picked up and transferred to the coil unloading position by the exit coil transfer car. Load cells on the skid measure the coil weight.

A promising outlook

The line was successfully started up in January 2016 following hot-run tuning of the annealing furnace and other equipment. The line now produces high-quality steel products for automotive customers in Southeast Asia.