Rizhao Steel's pickling and galvanizing line
In 2003, construction work began at Rizhao Steel – a private enterprise – on a stretch of seashore in the Chinese province of Shandong. Ten years later, Rizhao Steel had become an integrated group of companies with a combination of agglomerate production (sinter, pellets), production of iron and steel, rolling mills, power generation, and more.
In 2014, Rizhao Steel took the next step by going further downstream in its product chain. ANDRITZ Metals was chosen to supply a complete pickling and galvanizing line (PGL), including the mechanical, process engineering, and electrical equipment. The efficient and eco-friendly ANDRITZ pickling and furnace technology as well as experience with related processes in complex production lines were the key factors for the customer to award us this order. The investment in a PGL for thin, hot-rolled strip represents a further commitment to customers to provide galvanized sheet material for the competitive construction applications and metal processing industry markets. Our PGL, a multi-process line, produces 700,000 tons of galvanized steel annually. By combining the pickling and galvanizing processes in a single system, this integrated line provides high added value for the customer in terms of profitability and environmental benefits. The incoming material is hot-rolled, low-carbon steel strip coming from the adjacent endless strip production line.
In the first step, the scale breaker cracks the scale on the strip surface. The subsequent chemical pickling with hydrochloric acid and an additional spray pickling section at the entry and exit of the pickling tank deliver scale-free hot strip to the first skin pass mill (SPM1). Strip flatness is improved by skin passing, and strip roughness for the subsequent coating process is defined at this stage.
Following heating, the strip then enters the zinc pot and air knife. A wide range of coating layers can be achieved using closed loop control between air knife and coating gauge measurement system. After-pot cooling (APC) and water quenching cool the strip sufficiently for downstream processing. A second skin pass mill (SPM2) is located after the APC tower in order to control strip thickness tolerances and surface texturing. Final surface finishing for enhanced corrosion protection, deep drawing ability and visual appearance of the product are defined in the chemical coating section.
Combining high-efficiency pickling, specific skin passing, and the optimized heat-to-coat treatment within a single process line gives the customer a competitive advantage in terms of investment as well as operational cost and minimized environmental impact. This process set-up enables production of a final galvanized hot strip with specific cold mill tolerances. The market is demanding high-quality products with most economical and environmentally friendly technology. The answer from Metals in the field of galvanized steel sheet for numerous mass-market applications was the introduction of combined pickling and galvanizing lines for hot strip. Extensive expertise and experience from all major ANDRITZ manufacturing companies, such as Sundwig, Selas, Bricmont, as well as the ANDRITZ China and Vienna offices, successfully created this complex line tailored to the customer’s needs.
This project was awarded to ANDRITZ in July 2014, and the line went into commercial operation for pickling and coiling in April 2016. In October 2016, the first galvanized product was produced on the line. In the subsequent months, production was ramped up and product quality improved continuously. At the final acceptance tests, the plant production capacity and all other technical guarantee figures were successfully demonstrated and the Final Acceptance Certificate was signed by Rizhao Steel and ANDRITZ in September 2018.
At Rizhao Steel, the next ESP line is currently being installed, and the raw material available for further processing will thus be further increased. Additional investments in downstream processing lines will be a consequence. As Metals has always strived to challenge traditional processes, this will be the next opportunity for new developments and appropriate technologies customized to customer requirements. Metals will certainly seek out this new opportunity.
Hot-rolled, low-carbon steel strip
SPHC, SPHD, SPHE, HSLA 330–440
35 tons max.
|Coil outer diameter|
Entry/exit section 210 m/minute max.
Process section 170 m/minute max.
|Coating mass range|
Scale breaker ≤ 2%
Skin pass mill 1 ≤ 3%
Skin pass mill 1 ≤ 8%
Tension leveler ≤ 2%