JPS6213082B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention has put into practical use a new method of directly cold rolling hot rolled steel sheets with scales attached, by omitting the pickling process of the conventional method of manufacturing cold rolled steel sheets, in which hot rolled steel sheets are pickled and then cold rolled. The present invention relates to a method for manufacturing cold-rolled steel sheets. In most conventional production of cold-rolled steel sheets, hot-rolled steel sheets are pickled with sulfuric acid or hydrochloric acid to almost completely remove scale generated during hot finishing and coiling, and then cold rolling is performed. This method has a long history in steel manufacturing, and it has become common knowledge to remove black scale from hot-rolled steel sheets before cold rolling. However, recently, a new method of directly cold rolling hot-rolled steel sheets with scales still attached has been proposed and researched. For example, JP-A-52-21245, JP-A-Sho.
No. 52-21246, JP-A No. 52-52157, JP-A No. 52-
The method proposed in Publication No. 52158 and the like corresponds to this. This new method (hereinafter referred to as the direct cold rolling method), in which the scale is directly cold rolled with no pickling, shortens the manufacturing equipment for steel sheets by omitting pickling.
It has great advantages such as saving labor and energy, improving the working environment, and eliminating the need for waste acid equipment. On the other hand, regarding the direct cold rolling method, there are problems such as the contamination of the rolling oil during rolling is significant, how to easily remove scale during cold rolling or in the process after rolling, and compared to the case where scale is removed by pickling. However, there remain problems such as an increase in the load during rolling, an increase in the amount of wear on the rolling rolls, and the tendency for flaws to occur. The present invention aims to solve the above-mentioned problems by reducing rolling load, roll wear, and roll flaws. As mentioned above, in the direct cold rolling method, cold rolling is performed with scale still attached, but since this scale layer has a higher wear coefficient than the base steel of the steel sheet, the rolling load is higher than when rolling a pickled steel sheet. do.
Furthermore, since the hardness of the scale is higher than that of the steel sheet base, the amount of roll wear increases and roll flaws are likely to occur. In order to solve these problems, the present inventors conducted research on rolling lubrication methods and found a method to solve these problems all at once. The rolling lubrication method will be explained. Conventionally, in the case of cold rolling pickled steel sheets, when rolling ultra-thin steel sheets that generally require a high degree of lubricity, oils such as animal and vegetable oils were forcibly stirred with hot water and emulsified10.
Direct application is often done by spraying a high concentration emulsion oil of ~20%. On the other hand, for rolling when the plate thickness is relatively thick and does not require a very high level of lubricity, a low concentration of 5% or less is made by emulsifying a mixture of mineral oil and oil as the main component with an emulsifier in hot water. Many methods use recirculating emulsion rolling oil. Therefore, when rolling was carried out using the conventional lubrication method for the direct cold rolling method, the following problems were found. That is, when recirculating rolling is performed using a low-concentration emulsion rolling oil containing an emulsifier, the rolling load increases significantly compared to the rolling of pickled steel sheets, and the surface of the rolling rolls becomes rough and wear increases. It became clear that the rolls were large and that scratches were likely to occur on the roll surface. Furthermore, even when direct rolling is performed using high-concentration emulsion rolling oil containing animal and vegetable oils, it is clear that the rolling load increases, although not as much as with low-concentration emulsion oil containing emulsifiers, and that roughness and flaws occur on the roll surface. Summer. As a result of research into rolling lubrication methods to solve these problems, we supplied a composition containing an organic polar compound as a main component and no emulsifier to the surface of hot rolled steel sheets before or during cold rolling. However, rolling with conventional emulsion rolling oil greatly improves rolling lubricity compared to rolling with emulsion rolling oil alone, and is also effective in reducing roll wear and roll flaws. I realized something. Furthermore, it has been found that by supplying the organic polar compound as described above, rolling is possible using water alone or a lubricating liquid dissolved or dispersed in water. An example of these effects is shown in FIG. 1 with respect to rolling load measurement results. From the results shown in FIG. 1, it is clear that rolling lubricity is improved by applying an organic polar compound. The reason why the lubricity is improved by applying an organic polar compound that does not contain an emulsifier is considered to be as follows. First, the organic polar compound itself has a strong adsorption force on the surface of the steel sheet and has good lubricity, and since it does not contain an emulsifier, there is no need to worry about the emulsification being removed during rolling. Therefore, as long as the amount necessary for rolling lubrication is present on the steel plate surface, rolling can be carried out using water alone or a lubricating liquid dissolved or dispersed in water, which has inferior lubricity compared to conventional emulsion oil.
Thus, the composition containing the organic polar compound must be applied to the steel strip surface prior to applying the rolling lubricant, such as emulsion rolling oil. Next, in the case of rolling using emulsion oil, the following can be considered. When using a low-concentration emulsion rolling oil containing an emulsifier, the rolling oil concentration is low and the emulsion is relatively stable, so it is difficult to be destroyed even if it hits the steel plate surface by spray during rolling. Since the amount of rolling oil attached to the steel plate is small, the lubricity is slightly inferior. Therefore, even a stable emulsion is easily adsorbed to the surface where the polar compound according to the present invention is present, so the rolling lubricity is improved due to the synergistic effect of increasing the amount of rolling oil attached and the good lubricity of the polar compound itself. It is considered that On the other hand, when using a high-concentration emulsion rolling oil such as animal or vegetable oil that does not contain an emulsifier, the concentration of the rolling oil is high and the emulsion is relatively unstable, so it is easily destroyed when it hits a steel plate by spraying. Therefore, the amount of rolling oil attached is large and the lubricity is relatively excellent. However, in this case, the lubricity tends to become unstable because the amount of adhesion changes due to non-uniform application due to the spray pattern on the steel plate, and the emulsifying property changes in a fraction of a second due to fluctuations in the raw material oil and fat components. is also not sufficient. Therefore, since the presence of the polar compound according to the present invention improves lubricity, it is thought that the influence of fluctuations in emulsifying property will be reduced. As explained above, the main requirement of the present invention is to supply a composition containing a water-insoluble organic polar compound as a main component that does not contain an emulsifier before or during rolling. The organic polar compound used in the present invention will be specifically explained. (b) Fatty acids: fatty acids of animal and vegetable oils such as beef tallow, rapeseed oil, etc. and their hydrogenated fatty acids; lauric acid and other straight chain saturated fatty acids; oleic acid and other unsaturated fatty acids, such as dimer acid and trimer acid. Polybasic fatty acids; oxyfatty acids; amino fatty acids; isofatty acids; synthetic fatty acids; etc. are suitable. (b) Amine: laurylamine, oleylamine, and other saturated or unsaturated aliphatic amines; aromatic amines and cyclic amines such as benzylamine and dicyclohexylamine can also be used. Furthermore, fatty acid salts of amines produced by the reaction of these amines and fatty acids can also be used. (c) Alcohol: Lauryl alcohol, oleyl alcohol, and other saturated or unsaturated aliphatic alcohols; and aromatic alcohols such as benzyl alcohol can also be used. In addition, aliphatic or cyclic polyhydric alcohols can also be used. (d) Monool fatty acid ester: Beeswax and other natural waxes are suitable.
Waxes synthesized from higher primary alcohols and fatty acids can also be used. (e) Fatty acid ester of polyalkylene glycol: Polyethylene glycol fatty acid ester and polypropylene glycol fatty acid ester are suitable. (f) Fatty acid esters of polyols having a neopentyl nucleus: Suitable are single fatty acid partial esters or fatty acid saturated esters such as pentaerythritol, dipentaerythritol, neopentyl glycol, trimethylolethane, trimethylolpropane, and mixtures of two or more. It is. As the fatty acid used for esterification, those explained in (a) are suitable. (g) Fatty acid esters of polyols having three or more OH groups in one molecule and not having a neopentyl nucleus: glycerin, polyglycerin, mannitol,
Single or mixtures of two or more fatty acid partial esters or fatty acid saturated esters such as anhydrosorbitol are suitable. As the fatty acid used for esterification, those explained in (a) are suitable. (H) Phosphate esters: Alkyl phosphates, alkylaryl phosphates, polyoxyethylene alkyl allyl ether phosphates, polyoxyethylene alkyl ether phosphoric esters, polyoxyethylene fatty acid phosphoric esters, and the like are suitable. (li) Boric acid ester: Boric acid partial esters produced from boric acid and monoalcohols or polyhydric alcohols, saturated esters, and mixtures thereof are suitable. Although the organic polar compounds are broadly classified into the above nine types, organic polar compounds other than these can be used in the same manner as long as they have excellent lubricity. Polar compounds have the best lubricity when used at a purity close to 100%, but to reduce costs,
It can also be diluted with other non-polar compounds. For example, mineral oil is the most practical diluent.
As for the coating amount, as a polar compound, if it is 0.05 g/m ² or more, it is effective in improving lubricity, and the larger the coating amount is, the more preferable it is, but economically, it is 0.05 g/m 2 to 3 g/m ²
is appropriate. In addition, when supplying the polar compound before rolling, spray coating, electrostatic spray coating, roll coater coating, coating during skin pass before rolling, etc. may be used. It is sufficient if the coating is applied to the steel plate. On the other hand, when supplying during cold rolling, there are two methods: transfer to the steel plate by spraying or other methods on the rolling rolls, and directly applying the material to the steel sheet between stands during rolling. You can also do it. When feeding during rolling, it may be applied in all passes or in a specific pass, but in terms of lubricity and workability, it is best to feed it to the rolls in front of the first pass or to the surface of the steel plate after the first pass. Most preferably, it is supplied. The present invention will be described with reference to examples. The test conditions are explained below. (b) Test steel plate A hot-rolled steel plate for manufacturing SPCC cold-rolled steel plates specified in JIS was sampled at a production factory, and dimensions of 2.3 mm (thickness) x 50 mm (width) x 100 mm (length) were used for rolling tests. I used it after shearing it. The pickled steel plates were made from factory-collected material and were pickled in the laboratory to remove scale. (b) Rolling conditions 1 Rolling machine: 11 stands, levering mill 2 Roll dimensions: 460 mm (diameter) x 100 mm (body length) 3. Rolling speed: 250 m/min 4. Method of supplying polar compounds The method of supplying polar compounds before rolling is It was sprayed directly onto the surface of the steel plate using a paint spray gun. On the other hand, as a method of supplying it during rolling, it was applied to the roll surface using a spray gun on the front side of the first pass and was transferred to the steel plate surface by rolling. Among the polar compounds, those that are solid at room temperature were heated and melted before being sprayed. 5 Rolling Lubricant (a) Water alone Industrial water was used at 20-25°C and sprayed onto the material suction port of the rolling roll. (b) Water-soluble or water-dispersible lubricant The lubricant was dissolved or dispersed in industrial water and used at 20 to 25°C, and then sprayed onto the material suction port of a rolling roll. (c) Low concentration emulsion oil A commercially available emulsion type rolling oil containing 60% mineral oil and an emulsifier is made into a 3% emulsion.
Used at ℃. The emulsion oil was sprayed onto the material suction port of the rolling roll while being circulated. (d) Highly concentrated emulsion Commercially available beef tallow is vigorously stirred to make a 20% emulsion oil and used at 80℃. Emulsion oil was sprayed onto the steel plate at the front of the rolling mill and used in a non-circulating manner. (c) Measurement of rolling load The rolling reduction rate in one pass is 30 depending on each lubrication condition.
%, and the total load during rolling was measured using a load cell. Next, this load was divided by the width of the rolled test piece of 50 mm and expressed as Kg/mm. (d) Measurement of roll wear After rolling 100 test pieces under each lubrication condition according to the rolling schedule shown in Table 1 below, a replica of the roll surface was taken and observed under a microscope to determine the surface roughness and wear conditions. I judged it.

[Table] (e) Measurement of the degree of flaw occurrence on the roll surface The degree of flaw occurrence on the roll surface after rolling by the above-mentioned abrasion measuring method was determined by observing with the naked eye. The results of experiments conducted under the above conditions are shown in Table 2 as examples. As can be seen from Table 2, according to the present invention, even if the scaled hot-rolled steel sheet is directly rolled, it can be rolled in the same way as a pickled steel sheet, and there are almost no problems with roll wear and roll flaws.

【table】

【table】 [Brief explanation of the drawing]

Figure 1 shows a scaled hot-rolled steel plate (2.3 mm (thickness) x 50 mm (width) x 100 mm) coated with the polar compound according to the present invention.
(Long)) is pre-coated and then cold-rolled using water or emulsion rolling oil, and the rolling load at that time was measured. This is compared with the case of a steel plate that has undergone a conventional pickling process. This is what I did. Rolling conditions Roll dimensions: 460φ x 100mm (body length) Rolling speed: 250 m/min Scaled hot-rolled steel sheet: Rolling with 3% emulsion oil...Reference number 1 in the diagram Brewing hot-rolled steel sheet: Rolling with 3% emulsion oil
...Number 2 in the figure Hot rolled steel sheet with scales: Rolled with water after applying lauric acid 0.5g/ ^m2 ...Number 3 in the figure Hot rolled steel sheet with scales: Rolling with 3% emulsion oil after applying lauric acid 0.5g/ ^m2 rolling
...Number 4 in the diagram

Claims (1)

[Claims] 1. When cold rolling a hot rolled steel sheet with scale still attached, a water-insoluble composition containing an organic polar compound as a main component and containing no emulsifier is applied prior to cold rolling, and then emulsion rolling is performed. A method for producing a cold-rolled steel sheet, which comprises cold rolling by supplying at least one of oil, a water-soluble or water-dispersible lubricant, and water.