In modern cold-rolling mill production, a complex emulsion system is generally used to spray a specified quantity of emulsion into the roll gap and onto the strip surface. After entering the rolling deformation zone, the emulsion first adheres to the roll and strip surfaces, forming a thin lubricating oil film. The water carries away the heat of deformation and friction generated during rolling, providing cooling. Cold-rolling emulsion is a chemical product made by mixing 1–3% rolling oil with 97–99% water by mass.
Generation of odor
Large quantities of cold-rolling emulsion are sprayed during production, usually >20m3/h. The substantial heat from the strip vaporizes the rolling oil and water in the emulsion into fine particles, which are discharged through the chimney by the extraction equipment above the rolling mill. During prolonged use, the rolling oil undergoes slow chemical changes under the combined effects of water, high temperature and catalysis by iron and steel constituents. Together with the oil's own odor, these changes produce a distinctive pungent smell, which the mill's overhead exhaust chimney releases into the surrounding area during production.
Detection of odor
The relevant dimensionless value of the "odor" concentration can be measured using the "three-point comparative odor method" in GB/T 14675-93. Usually the "odor" concentration emitted by cold rolling emulsion is between 500-1500. The government's standard value for the odor of such cold rolling emulsion is usually below 1000. Since the odor of the emulsion will flow to the surroundings with the airflow near the chimney, causing unpleasant sensations in the human body, the odor of the emulsion should be effectively controlled.
Measures to control emulsion odor
An apparatus and method for purifying odorous gases from cold-rolling emulsions. This method filters or centrifugally collects odor-rich rolling oil and other substances from the emulsion to obtain gas with less odor. A catalyst rich in iron and manganese then further decomposes the odorous chemicals in the gas. The technology has the advantages of broad applicability to many types of emulsions and good treatment performance. However, this complex treatment requires specialized catalysts, making its overall technical and economic performance relatively poor and unsuitable for widespread adoption.
A water-based metalworking lubricant containing nanoscale molybdenum disulfide and its preparation method. The formulation mainly uses various water-soluble lubricating compounds, including triethanolamine, aqueous sodium polyacrylate, a silane coupling agent, and sodium diacetate, followed by the addition of nanoscale molybdenum disulfide powder as a cold-rolling lubricant. Because this technology uses entirely water-soluble substances, it can avoid the odor problems of traditional cold-rolling emulsions. However, the nanoscale molybdenum disulfide particles in the formulation can remain on the strip and affect subsequent coating performance, making widespread application difficult.
A synthetic compound that effectively masks odors. Mainly 1-(2-hydroxyphenyl)-3-(pyridine-4-yl)propyl-1-ketone/salt, etc. Although these substances have a good odor masking effect, they are more expensive. When used in cold rolling oil, they will also significantly affect the lubricity of the rolling oil, so they are not practical.
A low-odor rolling oil for cold rolling of iron and steel and its method of use. The low-odor cold-rolling oil contains, by mass: 0–30% natural fats and oils, 50–90% synthetic lubricating esters, 0.8–4.5% surfactants, 2.0–6.5% extreme-pressure antiwear agents, and 0.5–1.5% antioxidant additives. The emulsion temperature is controlled at 48–53°C, its concentration below 2.5%, and its iron-powder content <250 ppm.
(Source: Steel Rolling Home)