KR20000032100A - Method for removing fat from cold rolled steel sheet at a low temperature - Google Patents

Abstract

PURPOSE: A method for producing a cleansing solution for removing fat from a cold rolled steel sheet at a low temperature is provided to promote emulsification action between the surface of the steel plate formed by cold rolling and the alkaline solution by adding surface active agents into the solution for removing fat from the steel sheet, thereby removing the fat from the steel plate relatively at a low temperature. CONSTITUTION: A method for producing a cleansing solution for removing fat from a steel sheet at a low temperature includes the steps of adding dodecyl alcohol ethoxylate and sodium gloconate to a caustic soda solution in the range of 0.25-0.45 weight percent with reference to the whole weight of the cleansing composition solution and immersing the cold rolled steel sheet into the caustic soda solution at a temperature in the range of 45-60°C, wherein if the amount of the dodecyl alcohol ethoxylate and the sodium gloconate is less than 0.25 weight percent, the effect of the removing fat is deficient while if the amount exceeds 0.45 weight percent, economical effect can not be obtained since the effect of the removing fat is almost same and not proportionally increased.

Description

Low Temperature Degreasing Method of Cold Rolled Steel Sheet

The present invention relates to a low temperature degreasing method of a cold rolled steel sheet, and more particularly, to a method in which the cold rolled steel sheet can be degreased at a lower temperature than when using caustic soda as a conventional degreasing liquid.

Generally, foreign materials such as rolling oil, dust, and machine oil are attached to the surface of cold rolled steel sheet at about 200mg per square meter.These materials form carbides due to incomplete combustion during annealing, causing defects in the post-annealing process. In addition, since the surface aesthetics are harmed, the surface is cleaned by chemical and mechanical methods during degreasing. The allowable amount of residual oil after degreasing depends on the type of rolled oil and the processing after degreasing.

In this degreasing process, the steel sheet is passed through an alkali tank degreased by depositing the steel sheet in an alkaline solution (for example, sodium hydroxide or ortho-sodium silicate) in the range of 80 to 85 ° C, and then oxygen generated by electrolysis of water. And an electrolytic cleaning tank for removing foreign substances on the surface of the steel sheet using hydrogen gas.

The strip of cold rolled steel sheet which has been degreased in the electrolytic cleaning tank passes through a hot water cleaning tank that cleans the residue on the surface of the steel sheet with water, and then is sprayed with hot air to the surface to remove moisture from the surface, and then completely dried. Let's do it.

In this degreasing process, degreasing at a temperature of 80 to 85 ° C. has a problem in that a considerable amount of energy is consumed to perform the degreasing process at a relatively high temperature.

Accordingly, an object of the present invention is to provide a method for degreasing foreign substances in cold rolled steel sheet at a lower temperature in an effort to reduce energy consumption during cold rolled steel sheet degreasing process.

According to the invention,

In degreasing the cold rolled steel sheet by immersing it in a cleaning solution containing a caustic soda solution,

The cleaning solution is made by adding dodecyl alcohol ethoxylate and sodium gluconate to the caustic soda solution within the range of 0.25 to 0.45% by weight, respectively, based on the total weight of the degreasing cleaning composition. Provided is a low temperature degreasing method of a cold rolled steel sheet comprising immersing in a caustic soda cleaning solution containing silalcohol ethoxylate and sodium gluconate.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The present inventors have found that by adding an appropriate surfactant to the cold rolled steel sheet degreasing solution, the alkali solution can be brought into good contact with the surface of the cold rolled steel sheet, and the emulsification reaction can be accelerated to be degreased at a low temperature.

In the present invention, an alkaline degreasing washing liquid is prepared by adding dodecyl alcohol ethoxylate and sodium gluconate to a caustic soda solution. The dodecyl alcohol ethoxylate and sodium gluconate are both water-soluble compounds having a high affinity with water and have a property of lowering the surface tension and are well in contact with the rolling oil on the surface of a cold rolled steel sheet to promote emulsification, as well as to promote emulsification. The saponification reaction also takes place so that the degreasing of the cold rolled steel sheet can be performed smoothly even at low temperatures.

The amount of dodecyl alcohol ethoxylate and sodium gluconate added to the alkaline solution is preferably in the range of 0.25 to 0.45% by weight based on the degreasing cleaning liquid. If the amount of these added is less than 0.25% by weight it was shown that the degreasing effect is not very good, if it exceeds 0.45% by weight degreasing effect reaches a nearly constant level is economically undesirable.

By adding such surfactants to the alkaline solution, the cold rolled steel sheet can be degreased at a temperature range of 45 to 60 ° C., which is much lower than the temperature range currently used for cold rolled steel sheet degreasing. If the temperature range is less than about 45 ° C., the rate at which the surfactant reacts with the rolled oil is slowed to increase the reaction time, and if it exceeds 60 ° C., the energy consumption increases, which is not appropriate.

Hereinafter, the present invention will be described in more detail with reference to Examples.

<Example 1>

First, a degreasing solution was prepared by adding 0.25% by weight of dodecyl alcohol ethoxylate and 0.25% by weight of sodium gluconate to a 3% by weight solution of caustic soda.

The temperature of the alkali solution thus prepared was increased and maintained at 50 ° C., and the cold rolled steel sheet sample cut into a size of 10 cm × 10 cm was immersed in the solution for 20 seconds to be degreased, washed immediately with distilled water, and then hot air dried. The weight loss of the cold rolled steel sheet sample thus degreased was measured and the results are shown in Table 1 below.

<Example 2>

Example 1 was repeated except that 0.30% by weight of dodecyl alcohol ethoxylate and 0.25% by weight of sodium gluconate were added and the temperature of the alkaline solution was maintained at 45 ° C. The weight loss value was measured as in Example 1, and the results are shown in Table 1 below.

<Example 3>

The method of Example 2 was repeated except that the temperature of the prepared alkaline solution was maintained at 50 ° C. The weight loss of the cold rolled steel sheet sample thus degreased was measured and the results are shown in Table 1 below.

<Example 4>

The method of Example 2 was repeated except that the temperature of the prepared alkaline solution was maintained at 55 ° C. The weight loss of the cold rolled steel sheet sample thus degreased was measured and the results are shown in Table 1 below.

Example 5

The procedure of Example 1 was repeated except that dodecyl alcohol ethoxylate and sodium gluconate were each added by 0.35% by weight. The weight loss value was measured as in Example 1, and the results are shown in Table 1 below.

<Example 6>

The procedure of Example 1 was repeated except that dodecyl alcohol ethoxylate and sodium gluconate were each added by 0.45% by weight. The weight loss value was measured as in Example 1, and the results are shown in Table 1 below.

Comparative Example 1

A degreasing solution was prepared using only 3% by weight caustic soda solution without adding the surfactant used in the present invention, and the temperature was maintained at 80 ° C. Cold rolled steel sheet samples cut to a size of 10 cm x 10 cm were immersed in this solution for 20 seconds, degreased, washed with distilled water, and dried by hot air. The weight change of the cold rolled steel sheet sample thus degreased was measured, and the results are shown in Table 1 below.

Comparative Example 2

The procedure of Comparative Example 1 was repeated except that 0.15% by weight of dodecyl alcohol ethoxylate and 0.15% by weight of sodium gluconate were added to the caustic soda solution and the temperature of the degreasing solution was maintained at 50 ° C. The weight change of the cold rolled steel sheet sample thus degreased was measured, and the results are shown in Table 1 below.

Comparative Example 3

The procedure of Comparative Example 1 was repeated except that 0.20% by weight of dodecyl alcohol ethoxylate and sodium gluconate were added to the caustic soda solution and the temperature of the degreasing solution was maintained at 50 ° C. The weight change of the cold rolled steel sheet sample thus degreased was measured, and the results are shown in Table 1 below.

division Dodecyl Alcohol Ethoxylate (wt%) Sodium Gluconate (% by weight) Degreasing temperature (℃) Weight loss (g) Example 1 0.25 0.25 50 0.0044 Example 2 0.30 0.25 45 0.0045 Example 3 0.30 0.25 50 0.0045 Example 4 0.30 0.25 55 0.0047 Example 5 0.35 0.35 50 0.0046 Example 6 0.45 0.45 50 0.0046 Comparative Example 1 - - 80 0.0036 Comparative Example 2 0.15 0.15 50 0.0038 Comparative Example 3 0.20 0.20 50 0.0039

As shown in the table, when dodecyl alcohol ethoxylate and sodium gluconate were added less than 0.25% by weight, the cold rolled steel sheet was not effectively degreased, and when they were added within the range of 0.25 to 0.45% by weight, low degreasing It can be seen that it shows an excellent degreasing effect even at temperature.

According to the present invention, by adding dodecyl alcohol ethoxylate and sodium gluconate to a caustic soda solution which is a conventional degreasing solution, the cold rolled steel sheet can be effectively degreased at a lower temperature.

Claims (1)

In degreasing the cold rolled steel sheet by immersing it in a cleaning solution containing a caustic soda solution, The cleaning solution is made by adding dodecyl alcohol ethoxylate and sodium gluconate to the caustic soda solution within the range of 0.25 to 0.45% by weight, respectively, based on the total weight of the degreasing cleaning composition. Immersed in a caustic soda cleaning solution containing silalcohol ethoxylate and sodium gluconate Low Temperature Degreasing Method of Cold Rolled Steel Sheet