JP3033411B2 - Method of peeling Zn plating from Zn plated steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing a Zn plating for reuse of a steel sheet having a Zn-containing plating layer formed thereon.

[0002]

2. Description of the Related Art In Japan, scrap is reused from the viewpoint of effective use of resources. Until now, scraps that are easy to reuse or have low costs for reuse are very small. It is only being reused,
At present, it is not enough to cope with the increasing supply of scrap. In addition, since the proportion of waste scrap with a large amount of impurities in the supplied scrap is increasing, the quality of recycled products is degraded, and the recycling of scrap is not as advanced as shouting. For this reason, there is a concern that in the future, there will be no choice but to discard a large amount of non-reusable waste iron scrap.

Under such a background, it is necessary to efficiently remove impurities such as Zn from iron scrap in order to prevent the Zn-plated steel material from being discarded simply as waste scrap. Have been proposed. Methods for removing impurities Zn are roughly classified into a method in which scrap is treated in a solid state without melting and a method in which scrap is treated in a liquid state.

As a method of treating in a solid state, there are an alkaline electrolysis method in which a potential is applied in an alkaline aqueous solution to passivate Fe and promote the dissolution of Zn, and an ammonia leaching method in which complex ions are formed to separate and remove Zn. There are laws. On the other hand, as a method of processing in a molten liquid state,
There is a method of decomposing Zn and iron by evaporating under vacuum or high temperature.

[0005]

However, all of the above conventional methods have the following problems and cannot be satisfied. First, there is a problem that the removal efficiency is low and the cost is high. The other method has a problem that white smoke of Zn is generated and the working environment is deteriorated. Therefore, it has not been put to practical use at present. The present invention has been made in view of the above problems, and is a method capable of efficiently removing Zn plating from iron scrap in a solid state without deteriorating a working environment and at a low cost. The purpose is to provide.

[0006]

According to the method of the present invention for stripping Zn plating from a Zn-plated steel material, a plated steel material mainly containing Zn is heated to a temperature exceeding 800 ° C. and 1100 ° C. or less in an oxidizing atmosphere. This is to heat and oxidize to peel off Zn as an oxide, and to mechanically perform the above-mentioned peeling and removing while heating and oxidizing.

[0007]

In the present invention, by heating a Zn-plated steel material in an oxidizing atmosphere, Zn in the plating layer becomes an oxide and is easily removed from the base material. Examples of the oxidizing atmosphere include air, oxygen-rich air, and pure oxygen. Hereinafter, the operation and effect of the present invention will be described with reference to details and results of a basic experiment that led to the completion of the present invention.

<Experiment 1> Effect of Heating Temperature A small piece of Zn-plated steel sheet of 7 cm × 4 cm was used as a sample, and an oxidizing atmosphere was selected under an air atmosphere, and each was heated to a predetermined temperature for a predetermined time. After cooling, the plating layer was peeled off with a ball mill, and the Zn concentration in the steel sheet was analyzed. The result is shown in FIG. As can be seen from FIG. 1, generally, the higher the temperature, the better the Zn removal efficiency.
Approximately 75% of Zn is removed by heating for 0 minutes. 80
At a heating temperature of 0 ° C. or lower, Zn removal was not confirmed.

<Experiment 2> Influence of Oxygen Concentration in Atmosphere In order to examine the effect of oxygen concentration in an oxidizing atmosphere, various oxygen concentrations, that is, air atmosphere, pure oxygen atmosphere, and 4% were used.
In an oxygen atmosphere, the Zn-plated small pieces were treated in the same manner as in Experiment 1 described above. The heating temperature was 950 ° C., and the treatment was performed for various times. After cooling, the plating layer was peeled off with a ball mill, and the Zn concentration in the steel sheet was analyzed. The result is shown in FIG. As can be seen from FIG. 2, there is no significant difference depending on the difference between the atmosphere, pure oxygen, and 4% oxygen atmosphere. If the atmosphere is an oxidizing atmosphere, Zn removal proceeds, and the effect of the oxygen concentration in the atmosphere is not recognized. <Experiment 3> Analysis of peeled material Table 1 below shows the chemical analysis values of the peeled material, and Table 2 below shows the results of X-ray diffraction of the peeled material.

[0010]

[Table 1]

[0011]

[Table 2]

According to the analysis results in Tables 1 and 2, 60 to 70% of Zn is contained in the peeled material, and the composition is Zn.
It can be seen that they are O and ZnFe ₂ O ₄ . When the heat oxidation is performed for 30 minutes, FeO is further included in the peeled material. From these results, it can be seen that if the heating oxidation is performed for a long time, the base material is oxidized to Fe.

As can be seen from Experiments 1 to 3, by heating to a temperature higher than 800 ° C. and lower than 1100 ° C. in an oxidizing atmosphere, the Zn-plated portion is reliably oxidized and easily peeled off. Easy removal and removal can be easily performed. If the time of thermal oxidation is too long, the base material is oxidized, but on the other hand, the removal of Zn further progresses. Further, it has been concluded that the heating temperature in the treatment method of the present invention must exceed 800 ° C., preferably 850 ° C. or higher, more preferably 900 ° C. or higher, and most preferably 950 ° C. or higher.

<Experiment 4> De-Zn Treatment Using a Linda Furnace In Experiments 1 and 2, the sample was cooled after heating and oxidation, and mechanical peeling and removal were performed by a ball mill. If so, we experimented with its effectiveness. 7cm x 4cm Zn for the experiment
Approximately 7 kg of a small piece of plated steel sheet was charged into a Linda furnace and heated and rotated at 950 ° C. for 30 minutes in an air atmosphere. The rotation speed of the Linda furnace was 13 times / min. In Test 1, the balls were placed in the furnace during heating, and oxidation and mechanical stimulation were performed in parallel. In Test 2, the balls were not placed in the furnace. In Test 1, the Zn concentration of a sample sampled from the furnace during heating and rotation was measured. In Test 2, after heating, cooling and treatment with a ball mill, the Zn concentration was measured. FIG. 3 shows the change over time.

According to the results shown in FIG. 3, when a method of giving an impact by a ball or the like during heating (test 1) is also used.
It can be seen that the Zn plating layer was effectively peeled off. Then, as compared with the case of cooling once and performing separation and removal with a ball mill or the like as in Experiments 1 and 2 (Test 2), the result is rather improved, and mechanically while oxidizing the Zn plating layer proceeds. It turns out that peeling is very effective. Next, in an experiment using this Linda furnace, a heating temperature higher than 1100 ° C., for example, 1200 ° C.
When the sample was heated and oxidized at ℃, the sample was fused and could not be taken out of the furnace. The temperature at which fusing begins depends on the thickness (heat capacity) of the steel sheet, but considering general use,
The heating temperature is desirably 1100 ° C. or less in consideration of fusion.

Example 1 A Zn-plated steel sheet was cut into small pieces by a shredder, and 25 kg of the small pieces were put into a rotary kiln, and heated at 950 ° C. for 30 minutes in an air atmosphere while applying impact by rotation. Thereafter, the treated steel sheet was taken out, and the Zn concentration in the steel sheet was analyzed. Table 3 shows the results.

[0017]

[Table 3]

In the batch processing in this rotary kiln, the Zn removal rate calculated from Table 3 was about 75%. <Example 2> Unlike Example 1, in Example 2, a sample steel sheet was continuously treated using a rotary kiln. The heat oxidation conditions were the same as in Example 1 above, and a sample steel plate was continuously added at a rate of 1 kg / min to perform a heat oxidation treatment. After the heating, the Zn concentration of the sample continuously taken out was measured. Table 4 shows the results.

[0019]

[Table 4]

Calculating from Table 4, in Example 2 of the continuous treatment, the Zn removal rate was about 70%.

[0021]

As described above, in the method for stripping Zn plating from Zn-plated steel according to the present invention, the steel is kept in a solid state in an oxidizing atmosphere at a temperature higher than 800 ° C.
Because it is made to heat and oxidize at a temperature of 0 ° C or less, mainly Z
There is an effect that the stripping and removal of the plating layer (impurity) containing n can be performed easily, efficiently, and at a low cost. Accordingly, a useful means for promoting the reuse of inexpensive iron scrap is provided. In addition, it is evaluated as a highly practical technology because it does not degrade the working environment and does not involve ancillary treatment such as wastewater treatment.

[Brief description of the drawings]

FIG. 1 is a diagram showing the effects of heating temperature and time in a processing method according to the present invention.

FIG. 2 is a view showing the influence of the oxygen concentration in the atmosphere in the processing method according to the present invention.

FIG. 3 is a view showing a result when the processing method of the present invention is performed using a Linda furnace.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Isao Kobayashi 2222-1, Ikeda Pioneer, Ikeda-cho, Onoe-cho, Kakogawa-shi, Hyogo Pref. 2222-1, Ikeda, Ikeda Cultivation Kakogawa Research Area, Kobe Steel, Ltd. References JP-A-63-96224 (JP, A) JP-A-2-298225 (JP, A) JP-A-5-279755 (JP, A) JP-A-5-125459 (JP, A) −5212 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22B 19/30 C22B 1/00 C22B 7/00

Claims (1)

(57) [Claims] 1. A method for stripping and removing Zn plating from a steel material on which a plating layer mainly containing Zn is formed, wherein the Zn plating is mechanically heated and oxidized in an oxidizing atmosphere to a temperature exceeding 800 ° C. and 1100 ° C. or less. A method for stripping Zn plating from a Zn-plated steel material, wherein the Zn plating is stripped and removed.