TW201414884A - Method for removing rust scale of steel material - Google Patents

Abstract

The present invention provides a method for removing rust scale of steel material, in which a steel whose surface has rust scale is subjected to rust-removing treatment at least two times. The rust-removing treatment consists of a step (a) and a step (b). The step (a) includes: placing a steel material into a treatment reagent, and using chemical impregnation method or chemical electrolysis method to make the rust loose but not release from the surface of the steel material. The step (b) includes: removing said steel material from the treatment reagent, and using a mechanical method to make said loosened rust scale release from the surface of the steel material. The present invention can completely remove the rust scale from the surface of the steel material by using the step (a) and the step (b) to carry out rust-removing treatment at least two times.

Description

Method for removing steel scale

The present invention relates to a method for removing scale of steel materials, and more particularly to a method for removing scale of steel materials which can prolong the service life of the treatment reagent.

Annealing, quenching, welding, forging and heat treatment processes involved in the production of steel produce an undesired black oxidizing material on the surface of the steel, which is commonly referred to as "rust". The presence of scale not only affects the quality of the steel surface, but also adversely affects subsequent processing effects and finished product quality, so it must be removed.

At present, steels such as carbon steel, stainless steel and high-alloy steel are generally pickled to remove scale, and acid is used to dissolve the scale on the surface of the stainless steel to separate the scale from the steel. The specific method is 60 to 75 ° C. The mixture was washed with a mixture of nitric acid (HNO ₃ ) and hydrofluoric acid (HF) as an acid wash for about 15 to 30 minutes.

However, the hydrofluoric acid contained in the pickling solution is a tube product. After pickling, the scale falls into the pickling solution and gradually dissolves, so that the pickling solution must be replaced due to the high concentration of heavy metal ions such as iron, chromium and nickel. . The pickling waste liquid needs special treatment to remove heavy metal ions, but even the treated pickling waste liquid can no longer be used; currently, the acid-base neutralization method is used to sediment the sludge containing metal ions in the pickling waste liquid. It is separated, solidified and dried before being treated by landfill, but the area available for burial is limited and soil contamination is bound to occur.

In addition, nitric acid-containing pickling liquids produce nitrogen oxides (NO _x ) such as nitrogen monoxide (NO) and nitrogen dioxide (NO ₂ ) during use. Although the addition of an oxidizing agent such as hydrogen peroxide (H ₂ O ₂ ) to the pickling solution helps to reduce the amount of nitric acid used and reduce the formation of nitrogen oxides, the problem of contamination caused by the pickling waste liquid cannot be solved.

It can be seen from the above that the pickling liquid itself and its waste liquid cause great harm to the environment and human health. Therefore, it is necessary to develop a method for reducing the scale of the pickling liquid by using environmentally-friendly green technology as a target.

Accordingly, it is an object of the present invention to provide a method of removing scale from steel.

Therefore, the method for removing the scale of the steel material according to the present invention comprises: performing a rust removal treatment on the steel material having a surface containing at least two times, the rust removal treatment consisting of the steps (a) and (b): (a) placing the steel material in a treatment reagent and using a chemical impregnation method or a chemical electrolysis method to loosen the scale from the surface of the steel material without departing from the steel material; and step (b) the steel material from the treatment reagent The medium is removed and the loosened scale is detached from the surface of the steel by mechanical means.

The method of the invention mainly removes the scale on the surface of the steel through the steps (a) and (b), and the step (a) does not cause the scale to fall into or dissolve in the treatment reagent, thereby prolonging the treatment reagent. The service life does reduce the amount of processing reagents.

The method for removing scale of steel material comprises: making a surface contain The steel of the scale is subjected to at least two rust removal treatments, the rust removal treatment consisting of steps (a) and (b): step (a) placing the steel in a treatment reagent and using chemical impregnation Or chemical electrolysis, the scale is loosened from the surface of the steel without leaving the steel; and step (b) the steel is removed from the treatment reagent, and the loosened scale is separated from the surface of the steel by mechanical means. .

When the step (a) causes the scale structure to be damaged and a defect such as a perforation or a crack is generated, the treatment agent can penetrate into the scale tissue and act on the scale, and even penetrate the scale and the surface of the scale and the scale adjacent to the scale. A very small amount of steel reacts, causing the scale to loosen from the surface of the steel without leaving the steel.

The mechanical descaling of the step (b) is not limited to any method or apparatus, as long as the mechanical force which provides direct contact or contact with the loosened surface of the steel surface by the medium is applicable. Preferably, the mechanical force is brushing or grinding.

The prior art has enabled the ultrasonic wave to remove the scale while the steel reacts with the treatment reagent, but this will cause the scale to fall off and gradually dissolve in the treatment reagent, resulting in an increase in the metal ion concentration of the treatment reagent. reuse. The mechanical treatment of the present invention is not in the treatment reagent, but causes the scale to fall off from the surface of the steel in a separate area to prevent the scale from falling off contaminating the treatment reagent and prolonging the service life of the treatment reagent.

Since the composition of the steel itself and the manufacturing conditions thereof cause the composition and structure of the scale, and the bonding strength between the scale and the steel material is greatly different, the number of times and the processing conditions of the method for removing the rust on the surface of the steel containing the scale are required by the method of the present invention. Depending on the type of steel, manufacturing conditions, and the condition of the scale In order to prevent the steel from being worn out due to excessive rust removal treatment, and to achieve the desired effect of completely removing the scale without damaging the steel.

In addition, since the step (a) causes the scale to loosen from the surface of the steel material without departing from the steel material, the present invention does not cause the metal ion concentration in the treatment reagent to be increased due to repeated rust removal treatment. It can still have good effect of loosening the scale after repeated use; therefore, it is recommended to repeat the use of the treatment reagent in step (a), without replacing each time, which will help to greatly reduce the amount of treatment reagent and improve the efficiency of descaling. And save costs.

Preferably, the steel is selected from the group consisting of carbon steel, stainless steel or high alloy steel.

Although the main component of the surface of the carbon steel is iron oxide, if the rust is removed only by mechanical descaling, most of the scale can be removed, but the scale root cannot be completely removed. Therefore, the pickling method is generally used. Handling, but it is easy to cause excessive pickling. The scale of the stainless steel surface includes NIO ₂ , Cr ₂ O ₃ , FeO. Cr ₂ O ₃ , FeO. Cr ₂ O ₃ . A dense spinel oxide such as 3Fe ₂ O ₃ is very strong in combination with steel. It is not suitable for carbon steel rust removal method to remove stainless steel scale; high alloy steel contains a higher proportion of nickel and chromium. The combination of the scale and the steel is closer. However, after the steel material has been subjected to at least two descaling treatments by the method of the present invention, the scale can be effectively removed by using a small amount of the treatment reagent.

Preferably, the chemical electrolysis method is a conductive method selected from direct contact with the steel material or a non-direct contact with the steel material.

Preferably, the treatment reagent comprises an aqueous solution selected from the group consisting of aqueous sulfuric acid solution, aqueous sodium sulfate solution, aqueous sodium phosphate solution, aqueous solution of trisodium phosphate, aqueous sodium chloride solution, aqueous chloric acid solution, and aqueous solution of ammonium sulfate. Liquid, and aqueous ammonium phosphate solution. The aqueous solution selected for use in the present invention does not contain nitric acid and hydrofluoric acid, and does not cause nitrogen oxides which cause work safety and environmental problems.

Further preferably, the aqueous solution is selected from the group consisting of an aqueous solution of sodium sulfate, an aqueous solution of sodium phosphate, an aqueous solution of trisodium phosphate, an aqueous solution of sodium chloride, an aqueous solution of chloric acid, an aqueous solution of ammonium sulfate, and an aqueous solution of ammonium phosphate. Since the oil may be attached to the surface of the steel during the processing of the steel, the rust removal effect is affected, and the scale is difficult to remove or even completely removed. The aqueous solution described above has the effect of cleaning the surface of the steel material, and helps to remove grease or lubricant adhering to the surface of the steel material, thereby making the rust removing effect more desirable.

More preferably, the aqueous solution is selected from the group consisting of 0.5-10 M sulfuric acid aqueous solution, 0.1-2 M sodium sulfate aqueous solution, 0.1-2 M sodium phosphate aqueous solution, 0.1-2 M sodium trisodium phosphate aqueous solution, 0.1-5 M sodium chloride solution. Aqueous solution, 0.1~2 M aqueous chloric acid solution, 0.1~2 M ammonium sulfate aqueous solution, and 0.1~2 M ammonium phosphate aqueous solution. Although the upper limit of the concentration of the aqueous solution is related to the solubility of the chemical contained in the aqueous solution, when the concentration of the aqueous solution is too low, the conductivity is insufficient and the treatment efficiency is poor; and if the concentration is too high, the chemical cannot be made. The product is dissolved or crystallized at low temperatures.

The time during which the steel is placed in the treatment reagent depends on the actual conditions. Generally, the time does not need to be too long, as long as the scale structure has been initially damaged and the surface of the steel is loosened. The present invention makes it possible to control the degree of loosening of the scale by repeatedly performing and adjusting the operating parameters of the steps (a) and (b). If the rust removal treatment is carried out for the first time, it is recommended to carry out the step (a) treatment to select a neutral or alkaline treatment agent which has a surface effect of cleaning the steel, And to avoid excessive loosening of the scale, the step (b) can be carried out; if the second or second time is used for the rust removal treatment, it is recommended that the treatment agent for the step (a) is selected to be easily penetrated into the lower layer of the scale ( Specifically, for example, a surfactant may be added to reduce the surface tension of the treatment agent, but the excessive loosening of the scale must be avoided, and then step (b) is performed.

Preferably, the chemical impregnation method has a treatment time of 10 to 30 minutes.

Preferably, the chemical electrolysis has a treatment time of from 1 to 120 seconds and a current density of from 10 to 400 amps/cm 2 . If the current density is too low, the scale removal effect is not good; if the current density is too high, the electrode will generate too much hydrogen and oxygen, which is inconvenient in operation and causes unnecessary power consumption.

Preferably, the cathode material of the chemical electrolysis method is any metal material that can conduct electricity, or a conductive non-metal material (such as graphite); the anode material is a metal material or a conductive non-metal material that does not generate an insulating oxide layer on the surface, for example, Lead, graphite, platinum, platinum oxides, or other noble metal families or their oxides.

Preferably, step (a) is carried out at 0 to 90 °C. This temperature range considers that the treatment reagent contains an aqueous solution, and it is necessary to ensure that step (a) can be carried out without the ice solution being frozen.

Preferably, the treatment reagent further comprises an oxidizing agent.

More preferably, the oxidizing agent has a concentration of 0.1 to 2 M and is selected from the group consisting of hydrogen peroxide, chloric acid, hypochlorous acid, perchloric acid, or a salt thereof.

The present invention will be further illustrated by the following examples, but it should be understood that this embodiment is intended to be illustrative only and not to be construed as limiting.

<Chemicals and Materials>

Steel: Stainless steel hot-rolled wire with stainless steel surface, purchased from Huaxin Stainless Steel Co., Ltd., model "304 J3", diameter 6.5 mm, thickness of rust is about 5 μm.

Brushing material: produced by 3M company, the surface contains gold steel sand.

<Examples 1 to 6 and Comparative Example 1> [Example 1] Rust removal treatment

The rust removal treatment of Example 1 was carried out in the following two rust removal treatments:

First descaling treatment

Step (a)-Preparation of a 0.5 M aqueous solution of sodium sulfate as a treatment reagent, by chemical electrolysis, that is, the steel containing the surface of the scale is immersed in the aqueous sulfuric acid solution at 30 ° C for anodic electrolysis for 24 seconds, the current density is 50 Ampere / square metric.

Step (b) - removing the steel material from the treatment reagent and removing excess sulfuric acid aqueous solution on the surface, and then brushing the steel material with the brush material to disengage the loose scale from the surface of the steel material.

Second descaling treatment

Step (a) - preparing a 0.5 M aqueous solution of sodium sulfate as a treatment reagent, using a chemical electrolysis method, that is, immersing the steel material having a scale on the surface in the sulfuric acid aqueous solution at 50 ° C for anodic electrolysis for 12 seconds, and having a current density of 200 Ampere / square metric.

Step (b) - taking out the steel material from the treatment reagent and removing excess sulfuric acid aqueous solution on the surface, and then brushing the steel material with the brush material to make The loose scale peels off the surface of the steel.

The rust removal treatment conditions and various operation parameters of Example 1 are described in detail in Table 1.

Rust removal evaluation

The surface of the steel material after the rust removal treatment of Example 1 was observed, and the degree of scale removal was judged, and the evaluation results are described in detail in Table 1 below.

◎: Indicates that the surface of the steel surface is completely removed by 30 times magnification.

○: indicates that the surface of the steel surface is completely removed by visual observation.

△: indicates that there is still residue on the surface of the steel.

[Examples 2 to 4]

Examples 2 to 4 are similar to the embodiment 1 to remove the scale of the steel material, and the difference is that the number of times of the rust removal treatment, the type and concentration of the treatment reagent, the operating parameters of the chemical electrolysis method, and the rust removal treatment are changed. The number of times of treatment, the processing parameters, and the number of treatments are shown in Table 1.

The surface of the steel body which had been subjected to the removal of the scale was subjected to the same rust removal effect evaluation as in Example 1, and the results are shown in Table 1.

[Example 5]

The rust removal treatment of Example 5 is carried out in the following steps (a) and (b) in sequence, and the rust removal treatment is repeated twice, wherein the treatment reagent of the step (a) does not need to be replaced.

Step (a) - A 0.5 M aqueous solution of sulfuric acid was prepared as a treatment reagent, and the treatment reagent further contained 0.5 M of hydrogen peroxide. The steel containing the surface of the scale is immersed in the treatment reagent at 50 ° C by chemical impregnation method. Minutes, loosening the scale.

Step (b) - taking out the steel material from the treatment reagent and removing the excess treatment agent on the surface, and then brushing the steel material with the brush material to disengage the loose scale from the surface of the steel material.

The rust-removing treatment conditions and various operation parameters of Example 5 are described in detail in Table 1, and the surface of the steel material having the scale-removed steel was evaluated for the same rust-preventing effect as in Example 1, and the results are shown in Table 1.

[Embodiment 6]

In the sixth embodiment, the scale of the steel material is removed in the same manner as in the fifth embodiment, that is, the rust removal treatment is repeated twice, and the treatment reagent of the step (a) does not need to be replaced; the difference is that the type of the treatment reagent is changed. And the operating parameters of the concentration and chemical impregnation method, the processing reagents, operating parameters and the number of treatments are shown in Table 1.

The surface of the steel material having the scale-removed Example 6 was subjected to the same descaling effect evaluation as in Example 1, and the results are shown in Table 1.

[Comparative Example 1]

The rust removal treatment of Comparative Example 1 was carried out only once, as follows:

First descaling treatment

Step (a) - preparing a 0.5 M aqueous solution of sodium sulfate as a treatment reagent, immersing the steel material containing the scale on the surface of the sulfuric acid aqueous solution by chemical electrolysis at 30 ° C for anodic electrolysis for 60 seconds, and having a current density of 100 amps / Square metric.

Step (b) - taking out the steel material from the processing reagent and removing excess processing reagent on the surface, and then brushing the steel material with the brushing material to make it loose The moving scale peels off the surface of the steel.

The rust-removing treatment conditions and various operation parameters of Comparative Example 1 are described in detail in Table 1, and the surface of the steel material having the scale-removed steel was evaluated for the same rust-preventing effect as in Example 1, and the results are shown in Table 1.

It can be seen from Table 1 that each of Examples 1 to 6 is subjected to at least two rust removal treatments, and the scale is loosened from the surface of the steel by chemical electrolysis or chemical immersion, and then the rust is completely removed by mechanical rust removal. In addition, the rust removal effect is good. Among them, the treatment reagents used in the first and second descaling treatments of Examples 5 and 6 were the same treatment reagents, and were not replaced, and the amount of the treatment reagents was greatly reduced.

In contrast, Comparative Example 1 in which only one rust removal treatment was performed was performed by chemical electrolysis and mechanical rust removal, even though the chemical electrolysis time was significantly longer than the total time of the two chemical electrolysis of Example 1, and the current density was the same as in Example 1. Twice, it is still impossible to completely remove the scale from the steel surface.

From the above, it can be seen that the single descaling treatment and the treatment time of the step (a) are long [Comparative Example 1], the effect is shorter than the multiple descaling treatment and the processing time of the step (a) is shorter [Example 1] In addition, the longer the treatment time of the step (a), the greater the chance that the scale may fall off or dissolve in the treatment reagent, and the treatment reagent may not be reused and must be replaced, and therefore, the treatment of the step (a) is shortened. Time and increase the number of rust removal treatments can effectively maintain the effectiveness of the treatment reagent.

In summary, the present invention can perform the rust removal treatment at least twice by the chemical electrolysis method or the chemical immersion method of the step (a) and the mechanical rust removal of the step (b), and the scale can be self-destructed without damaging the steel material. The steel surface is completely removed and the service life of the treatment reagent can be extended, which greatly reduces the production of treatment reagent waste liquid which will seriously pollute the environment.

However, the above is only the preferred embodiment of the present invention, and the scope of the present invention cannot be limited thereto, that is, the patent application according to the present invention The scope of the invention and the equivalent equivalents and modifications of the invention are still within the scope of the invention.

Claims (10)

A method for removing scale of steel material, comprising: subjecting a steel material having a surface to a scale to at least two rust removal treatments, wherein the rust removal treatment is composed of steps (a) and (b): step (a) Putting the steel material into a treatment reagent, and using the chemical impregnation method or the chemical electrolysis method, the scale is loosened from the surface of the steel material without leaving the steel material; and the step (b) removing the steel material from the treatment reagent, The loosened scale is detached from the surface of the steel by mechanical means. The method for removing scale of steel according to the first aspect of the invention, wherein the steel is selected from the group consisting of carbon steel, stainless steel or high alloy steel. The method for removing scale of a steel material according to the first aspect of the invention, wherein the chemical electrolysis method is a conductive method selected from direct contact with the steel material or a non-direct contact with the steel material. The method for removing scale of a steel material according to the first aspect of the invention, wherein the treatment reagent comprises an aqueous solution selected from the group consisting of an aqueous solution of sulfuric acid, an aqueous solution of sodium sulfate, an aqueous solution of sodium phosphate, and an aqueous solution of trisodium phosphate. An aqueous solution of sodium chloride, an aqueous solution of chloric acid, an aqueous solution of ammonium sulfate, and an aqueous solution of ammonium phosphate. The method for removing scale of a steel material according to claim 4, wherein the aqueous solution is selected from the group consisting of 0.5 to 10 M aqueous sulfuric acid solution, 0.1 to 2 M aqueous sodium sulfate solution, and 0.1 to 2 M sodium phosphate aqueous solution. 0.1~2 M trisodium phosphate aqueous solution, 0.1~5 M sodium chloride aqueous solution, 0.1~2 M chloric acid aqueous solution, 0.1~2 M ammonium sulfate aqueous solution, and 0.1~2 M phosphorus Aqueous ammonium acid solution. The method for removing scale of a steel material according to the first aspect of the invention, wherein the chemical impregnation method has a treatment time of 10 to 30 minutes. The method for removing scale of steel according to claim 1, wherein the chemical treatment has a treatment time of 1 to 120 seconds and a current density of 10 to 400 amps/cm 2 . A method of removing scale of a steel material according to claim 1, wherein the step (a) is carried out at 0 to 90 °C. A method of removing scale of a steel material according to claim 4, wherein the treatment reagent further comprises an oxidizing agent. The method for removing scale of steel according to claim 9, wherein the oxidant has a concentration of 0.1 to 2 M and is selected from hydrogen peroxide, chloric acid, hypochlorous acid, perchloric acid, or Its salts.