Recently, the high-strength A500 + S31803 duplex stainless steel composite panel for chemical tanker, jointly developed by Shougang Research Institute of Technology and Shouqin Processing Company, has been certified by French BV and Chinese CCS, becoming the first domestic product to pass the certification of both BV and CCS. It marks the rolling composite technology of Shougang Group entering the international advanced ranks, which lays a good foundation for Shougang Group to promote its composite panel and other fields, such as chemical tanker.

BV is one of the world’s largest classification societies as well as a recognized leader in the industry; CCS is a domestic mainstream certification body. The certification of BV and CCS marks that the rolling composite panel of Shougang Group is recognized by authoritative bodies at home and abroad.

With developments in the chemical industry, especially the growth of the petrochemical industry, more raw materials are required and transportation demands for products are increasing. To meet the demands of long-distance transportation of these chemical materials, liquid chemical tankers came into being. The so-called chemical tanker refers to a liquid cargo ship created or adapted to carry a variety of toxic, flammable, volatile or corrosive chemicals. In most cases, liquid chemical tankers have a double bottom and a double side structure. The cargo hold is separated and equipped with dedicated cargo pumps and piping system to meet the needs of different chemicals.

As most cargos are strongly corrosive, a stainless steel or special anticorrosive coating is applied to the inner wall of the cargo hold and the piping system. Duplex stainless steel with good corrosion-resistant adaptability and higher strength is the first choice for such inner walls of the cargo hold. The high duplex stainless steel price makes the cost of a chemical tanker with this kind of material high. Due to the current international depression of the shipbuilding industry, all shipyards are hoping to reduce the construction cost. The duplex stainless steel composite panel, which boasts the corrosion-resistant performance of duplex stainless steel and the strength of carbon steel, can significantly reduce the construction cost, so it is becoming increasingly favored by shipyards.

Rolling stainless steel composite panels is based on traditional carbon steel, by using the method of rolling to composite a layer of stainless steel, so that the steel plate has the strong toughness of carbon steel and the corrosion resistant property of stainless steel. It is a new type of metal composite material. In light of the difference of material properties between carbon steel and stainless steel, it’s technically difficult to realize the strong metallurgical combination of different materials; In addition, the physical and chemical properties of carbon steel and stainless steel have to be considered, which imposes high demands on the rolling and heat treatment process. Facing strong demand for a new composite panel material, the scientific research personnel of Shougang Research Institute of Technology and the technicians of Qinghuangdao Shouqin Metal Materials Co., Ltd. and Shouqin Processing Company seized the opportunity and cooperated closely in carrying out EVI services quickly to deeply understand the needs of shipyards and shipowners. Learning that the original material for the inner wall of the cargo hold was duplex stainless steel and the shipyards didn’t want to change the original design (e.g., not thicken the walls) after the composite panel was used, the R&D team combined the high strength of duplex stainless steel, adopted the A500 + S31803 composite design and carried out targeted technical pre-research and reserves based on the strong matching principle. In light of the material property of duplex stainless steel, it was difficult to produce such a high-strength composite panel. Therefore, the R&D team carried out many pilot-scale tests to repeatedly explore and verify the technology, thus solving a series of problems like effective compound, strength and difficult shape control, and becoming successful at the very first try; after undergoing the rigorous certification process of classification societies, the performance of the steel plate met the demand of ship rules, allowing it to pass the certification of classification societies smoothly.