JPH0465885B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention provides a steel strip with uniform and good surface appearance without uneven gloss even when annealed without degreasing the rolling oil adhering to the austenitic stainless steel strip after cold rolling. The present invention relates to a continuous annealing method that allows for finishing. (Prior art) Conventionally, austenitic stainless steel strips that have finished cold rolling are generally annealed by passing them through a continuous annealing and pickling line. The surface of the obi is finished in a pattern. This is because the steel strip is annealed with rolling oil, rolling wear powder, etc. non-uniformly adhered to the surface of the steel strip, so the surface oxidation reaction during annealing progresses unevenly in response to the adhesion of these particles, causing the surface of the steel strip to deteriorate. This is because a patterned oxide scale is formed on the surface of the material, and this pattern remains as a pattern that cannot be erased even by pickling. This pattern remaining on the surface of the steel strip is confirmed as uneven gloss or, in severe cases, as uneven color, and is difficult to completely erase. This has been an obstacle in manufacturing the resulting steel sheet products. This kind of pattern is caused by the difference in the formation of oxide scale between areas with a lot of rolling oil and rolling wear powder and areas with less adhesion, especially when the heating method of the annealing furnace is a rapid heating method, because the rate of oxide scale formation is fast. As a result, the difference in gloss after pickling increased and became more noticeable. Furthermore, in the case of rapid heating using a rigid annealing furnace, the direction of the heat flow is in the direction of progress of the steel strip, which spreads the rolling oil and rolling wear debris upward, making the pattern larger and more noticeable. It was something like that. For this reason, conventionally, when an austenitic stainless steel strip is cold rolled and then continuously annealed in a continuous dull pickling line, it is necessary to degrease it before annealing to remove rolling oil and rolling wear powder, and then perform annealing. Ta. (Problem to be solved by the invention) However, the degreasing equipment is not necessarily installed in the annealing equipment or the continuous annealing pickling line, but is often a separate equipment, making the process complicated. There was a drawback. Therefore, several methods have been developed in which continuous annealing is performed without degreasing and with rolling oil and rolling wear debris still attached. For example, inserting paper into the steel strip after cold rolling, absorbing and adhering rolling oil and rolling wear particles, and removing them; increasing the acid concentration during pickling;
This method includes strengthening the pickling process and reducing the contrast of uneven gloss. However, in the former method, the pattern of the difference in the thickness of the interleaving paper and the wrinkle pattern that occurred when the interleaving paper was inserted were transferred and did not disappear even after acid washing, and the cost of the interleaving paper was high. Furthermore, even with the latter method, the uneven gloss could not be completely eliminated, and the amount of acid consumed increased, resulting in a high acid consumption rate. (Means for Solving the Problems) In view of the problems described above in the conventional method of continuous annealing with rolling oil and rolling wear debris attached, the present invention has been developed by Continuous annealing with powder attached does not cause uneven gloss after pickling; in other words, a steel strip with the same surface appearance as degreasing before annealing is obtained, and continuous annealing does not increase costs. The present invention provides a method. The continuous annealing method of the present invention removes rolling oil and rolling wear particles attached to the steel strip, unlike conventional methods.
While it is based on the idea of reducing the amount of electricity, it is based on the opposite idea. In other words, the present inventor focused on the fact that gloss unevenness occurs in a pattern because rolling oil and rolling wear particles are non-uniformly adhered to the steel strip, and applied oil on the contrary to check the adhesion state. Based on the idea that if it was uniform, uneven gloss would not occur, we applied oil to the surface of the steel strip to make the oil adhesion uniform, and it was confirmed that uneven gloss did not occur. be. Thus, the present invention provides a method for continuously annealing an austenitic stainless steel strip after cold rolling in a state where rolling oil is adhered to the strip, in which JIS-K-2283 is used before annealing.
(Petroleum Products Kinematic Viscosity and Viscosity Test Methods, 1974)
The oil having a viscosity of 4 to 80 cSt at 40° C. is uniformly applied to the surface of the steel strip in an amount ranging from 0.2 to 20 g/m ² . The reason why the oil applied to the stainless steel strip in the present invention is as described above is because if the oil is less than 4 cSt, it will be much more volatile than the rolling oil attached to the stainless steel strip. It volatilizes quickly and has a strong tendency to prevent oxide scale from forming uniformly.If it exceeds 80 cSt, the viscosity is too high and it becomes difficult to apply it thinly and uniformly.
This may lead to increased costs due to increased oil usage,
This is because uneven coating may cause uneven gloss. Also, the application amount was 0.2g/
If it is less than 20g ^/m2 , the amount applied is too small to fill in uneven adhesion of rolling oil and cover the entire surface uniformly.On the other hand, if it exceeds 20g/ ^m2 , dripping or flowing may occur. This is because the coating becomes uneven and the amount of oil used increases. The oil may be applied by a known method such as spraying, roll coating, roll squeezing, or electrostatic coating. Further, it is preferable to apply the coating near the entrance of the annealing furnace while passing the stainless steel strip through the annealing furnace. This is to prevent the oil that has been evenly applied to the surface of the steel strip from being carried away by the various rollers and other items placed in front of the furnace, and to prevent the line containing these rollers from being contaminated. However, in this case, depending on the application method, a highly flammable oil mist is generated, which poses a risk of fire. Therefore, in areas where oil mist is generated by the application method, a less flammable oil containing 5 to 40% water should be used as the oil. Here the moisture content of the oil is 5%
If it is less than 40%, the decrease in flammability will be small, and if it exceeds 40%, it will reduce the thermal efficiency during annealing, which is not preferable. In addition, in the present invention, the stainless steel strip is limited to austenitic stainless steel strips, but this is because the effect is remarkable when the present invention is applied to austenitic stainless steel strips, and other ferrite or martensitic stainless steel strips are used. There is no problem in applying it to stainless steel strips, but the effect is weak. Next, the present invention will be explained with reference to Examples. (Example) Example 1 After cold rolling, a SUS304 stainless steel strip with a thickness of 1.0 mm was passed directly through a continuous annealing pickling line without degreasing, and minerals were adjusted to various viscosities near the entrance of the annealing furnace. Apply oil by spraying and annealing (1100
℃ for 40 seconds) and pickled. Figure 1 shows the viscosity and coating amount of mineral oil and the surface appearance after pickling.
Good results were obtained when the concentration was 0.2 to 20 g/m ² . Example 2 In the same manner as in Example 1, a SUS304 stainless steel strip was passed through a continuous annealing and pickling line, and oil (100% oil or water-containing) was applied to the steel strip at the entrance of the annealing furnace. Then, it was annealed and pickled. On the other hand, as comparative examples, a method of degreasing after cold rolling, followed by annealing and pickling, a method of inserting interleaf paper after cold rolling to absorb rolling oil, then annealing and pickling, and a method of directly annealing after cold rolling. , I used the pickling method. Table 1 shows the results, and according to the present invention, it was possible to obtain a good appearance similar to that obtained by annealing and pickling after degreasing.

[Table] We also investigated the fire safety of mineral oil with a viscosity of 15 cSt (flash point 180°C) and found that when water was added, the fire safety decreased as shown in Figure 2. It was confirmed that there was an improvement. In addition, fire safety was investigated by turning water-containing oil into oil mist with a concentration of 50 g/min using a compressor, placing an ignition source 1 meter in front of the oil mist outlet, and measuring the flame area when ignited by that ignition source using a photography method. The flammability test was conducted using the following flammability test method. Note that the oil mist flame area index in Figure 2 indicates that the water content of oil is 0%.
The flame area at that time is 100. (Effects) As described above, the present invention uniformly applies oil to the surface of the austenitic stainless steel strip after cold rolling and annealing it without degreasing, but this method is different from the conventional method of degreasing and annealing. The surface appearance can be made the same as the case. In addition, in terms of work and cost, since it only involves applying oil, it is simpler and cheaper than the conventional methods of inserting interleaf paper or strengthening pickling.

[Brief explanation of the drawing]

FIG. 1 shows the viscosity and application amount of mineral oil and the surface appearance after pickling when annealing and pickling were performed by the method of the present invention in Example 1. FIG. 2 is a graph showing oil mist fire safety of water-containing oil.

Claims (1)

[Claims] 1. In a method of continuously annealing an austenitic stainless steel strip after cold rolling with rolling oil attached, the viscosity at 40°C according to JIS-K-2283 is 4 to 80 cSt before annealing. Apply a certain amount of oil to the surface of the steel strip from 0.2 to 20
A continuous annealing method for austenitic cold-rolled stainless steel strip, characterized in that the coating is uniformly applied in an amount in the range of g/m ² . 2. The continuous annealing method for an austenitic cold-rolled stainless steel strip according to claim 1, characterized in that an oil containing 5 to 40% water is applied as the oil.