Metal cleaners are used to wash steel sheets after rolling in order to cleanse the surface of rolling oil and fine iron particles that form when the steel is rolled thin. To facilitate thorough, rapid cleaning and quick drying in an industry that prizes high-speed and continuous processing, both the cleaner and rinse water are typically heated to more than 70°C. However, such heating adds substantially to the amount of fossil fuel consumed during production, a problem from the standpoint of energy efficiency and carbon dioxide emissions. Meanwhile, automakers have been relying more heavily on thin but strong high-tensile steel in order to boost fuel efficiency by reducing vehicle weight. High-tensile steel, due to its hardness leaves more iron particles on the surface after the rolling process. This in turn creates a need for even higher-performing cleaners.
To meet this challenge, Kao researchers analyzed the residue on steel sheets at the nanometer level (Figure 1) and applied Kao's core technological know-how in the field of interface science to develop a surfactant and iron-particle removing agent that quickly penetrate surface residue even at low temperatures. With these agents, we developed a low-temperature cleaner that demonstrates higher cleaning performance at 40°C than that of conventional products used at 80°C. Moreover, in an industry first, we applied surface modification technology to develop a rinse agent that quickly adsorbs on the surface of the steel sheet to enhance water repellency in the rinsing process and minimize the amount of water clinging to the sheet’s surface (Figure 2). This means quick drying, even with the use of room-temperature rinsing condition, reducing the environmental burden of the drying process. The annual energy savings realized by the average washing line through use of these low-temperature cleaner and rinsing agents is equivalent to an estimated 8,000 tons of CO2 emissions.
Kao is currently at work on technology to further lower cleaning temperatures as we work with customers to improve energy efficiency, part of our global commitment to the development of a low-carbon society.
Analysis of Surface Residue on Steel Sheet (SEM)
Analysis of Adsorption Behavior of Rinse Agent (dynamic high-speed AFM)