JPH11100652A - Colored hot-dip galvanizing using manganese in carbon steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve problems in a method of adding Mn in colored hot-dip galvanizing using Mn in a carbon steel, i.e., the problems that unevenness in color is easy to occur on the surface and a uniformly colored product is difficult to produce and to obtain a uniform colored layer free from uneveness in color. SOLUTION: A carbon steel is immersed into a Zn-Mn-Ca melting bath contg. Mn whose amt. to be added is regulated to the range of 0.1 to 2.0% and Ca whose amt. to be added is regulated to the range of 0.01 to 1.2% and heated to the range of the bath temp. of 425 to 445 deg.C for at least >=1 min, within 60 sec after zinc oxide coating on the surface of the Zn bath is removed, the carbon steel is taken up from the Zn bath, and after the passage of >=20 sec in the air, water cooling is executed to color uniform and stable light yellow on the surface of the carbon steel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a Mn in carbon steel capable of obtaining a uniform and stable colored oxide film by eliminating color unevenness which tends to occur when hot-dip galvanizing using Mn on carbon steel. The present invention relates to a colored hot-dip galvanizing method using the method.

[0002]

2. Description of the Related Art Although a method of forming a colored layer by an oxide film on a metal surface is well known in other metal fields, even in hot-dip galvanizing, Zn containing Mn, Ti or the like is used.
After immersing a steel material or the like in the bath and raising it, the oxide film is colored by holding it in the air or in a high-temperature atmosphere for a certain period of time, and then cooled to stop the color development to a desired degree to obtain a colored oxide film. It is known.

[0003]

However, in the above-mentioned method in which Mn is added to a Zn bath, color unevenness is easily generated on the metal surface, and it is difficult to obtain a uniformly colored product. For example, when Mn is added to a Zn bath, it changes to light blue, yellow, light red, magenta, and blue-green depending on the time from when the sample is pulled out of the bath until it is cooled. Also, bath temperature, M
It is difficult to obtain a constant color depending on the amount of n added.

The present invention has been made in view of the above problems, and has been made in order to solve the problems. An object of the present invention is to provide a method of coloring hot-dip galvanizing using Mn in carbon steel. Color melting which can solve the problem in the above-mentioned method of adding Mn, that is, the problem that color unevenness is easily generated on the surface and it is difficult to obtain a uniformly colored product, and a uniform colored layer without color unevenness can be obtained. It is to provide a galvanizing method.

[0005]

In order to achieve the above object, the invention of claim 1 is directed to an Mn having an additive amount in the range of 0.1% to 2.0% and an additive amount of 0.01 to 2.0%. % Of Ca in the range of not less than 1.2% to not more than 1.2%, and a bath temperature of 42%.
The carbon steel is immersed in a Zn-Mn-Ca dissolving bath at a temperature in the range of 5 ° C to 445 ° C for at least 1 minute, and the carbon steel is removed within 60 seconds after the zinc oxide film on the surface of the Zn bath is removed.
After withdrawing from the n bath and elapse of 20 seconds or more in the air,
It is a method in which the surface of the carbon steel is colored with a uniform and stable light yellow color by water cooling.

[0006] In the invention of claim 2, the amount of addition is 0.1%.
% Of Mn metal in the range of not less than 2.0% and not more than 2.0% and 0.5% to 2.0% of misch metal, and at a bath temperature of 425 ° C to 475 ° C.
After immersing the carbon steel in the misch metal dissolving bath for at least 1 minute and removing the zinc oxide film on the surface of the Zn bath,
Within 0 seconds, pull the carbon steel out of the Zn bath,
After a lapse of 0 seconds or more, the carbon steel surface is cooled with water and a uniform and stable light blue color is obtained.

Further, in the invention of claim 2, the amount of addition is 0.1
% To 2.0% or less of Mn and the amount of addition is 0.1%.
5% to 2.0% of misch metal and Ca of 0.01% to 0.3%
60 seconds after immersing carbon steel in a Zn-Mn-Mischmetal-Ca dissolving bath at a bath temperature of 425 ° C to 475 ° C for at least 1 minute to remove a zinc oxide film on the surface of the Zn bath. The carbon steel is pulled out of the Zn bath within 20 seconds, and after elapse of 20 seconds or more in the air, it is cooled with water, and the surface of the carbon steel is colored in a uniform and stable light blue color.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described more specifically. Hot-dip galvanizing of carbon steel is performed as follows. First, oil or the like adhering to the surface of the carbon steel is removed using, for example, an alkali degreasing method. For example, carbon steel is immersed in a bath containing caustic soda for about 10 to 20 minutes.

Next, the carbon steel is pickled. Pickling is performed to remove rust and scale on the surface of carbon steel. It is usually performed using hydrochloric acid, and the carbon steel is immersed in a solution of 5% to 15% hydrochloric acid for 20 minutes to 60 minutes. After that, acid and rust on the surface of the carbon steel are washed away by washing with water.

Subsequently, a flux treatment is performed. The purpose of flux treatment after pickling is to smooth the reaction between iron and zinc on the iron surface and improve the adhesion of zinc. The role of the flux is that all deposits, dirt, and pickling occur from the iron surface. The purpose is to remove the slight rust and to eliminate zinc oxide on the surface of the Zn bath when the material to be plated is immersed in the Zn bath. For flux treatment of carbon steel, for example, Z
Carbon steel in mixed aqueous solution of nCl ₂ and NH ₄ Cl for 20 minutes
Soak for about 60 minutes.

After passing through such a pretreatment step, a hot dip galvanizing step is started. At a temperature of 420 ° C. or less in the temperature of the Zn bath, zinc cannot be dissolved. At a temperature of 480 ° C. or higher, the problem of the cost of the heat source occurs and the service life of the zinc pot is shortened. Therefore, the operating temperature range of normal zinc plating is 425 ° C. to 475 ° C.

In the hot-dip galvanizing step, for example, the bath temperature and M
There are the following three methods for the amount of n added. At a bath temperature of 425 ° C. to 445 ° C., the amount of Mn in the range of 0.1% or more to 2.0% or less and the amount of addition of 0.01% or more to 1% or less with respect to the weight ratio of the molten zinc. Ca in the range of ≦ 2% and 425 ° C. to 475 ° C. Mn and the amount of addition in the range of 0.1% to 2.0% with respect to the weight ratio of molten zinc in the range of 425 ° C. to 475 ° C. Is 0.5% or more and 2.0% or less in the range of 425 ° C. to 475 ° C., and the amount of addition is 0.1% to 2.0% with respect to the weight ratio of molten zinc. % Of Mn metal and Mish metal whose addition amount is 0.5% or more and 2.0% or less and Ca whose addition amount is 0.01% or more and 0.3% or less.

In the above case, the amount of Mn added is 0.1
%, Coloring is difficult. When the amount of Mn added is 2
%, It is difficult to dissolve.

If the amount of Ca is less than 0.01%, a uniform pale yellow color cannot be obtained. If the amount of Ca exceeds 1.2%, the fluidity of the coating on the Zn surface deteriorates, so that a part of the coating adheres to the plated surface when the plated carbon steel is pulled out of the bath. Easy to do.

In the case of (1), the amount of misch metal added is 0.5
%, A uniform pale blue color cannot be obtained. If the amount of misch metal added exceeds 2.0%, no coloring occurs.

In the case of (1), if the Ca content exceeds 0.3%, no coloring occurs. Furthermore, the addition amount is 0.01%
By adding Ca in the range from the above to 0.3% or less, Zn
The fluidity of the surface coating is better than that of the case, so that when the plated carbon steel is pulled out of the bath, a part of the coating is easily prevented from adhering to the surface of the plated carbon steel. be able to.

The conditions for obtaining a uniform color are (1) bath temperature, (2) amount of added Mn, and (3) elapsed time from dipping the sample into the bath, pulling up the sample from the bath surface, and cooling with water. (Hereinafter referred to as cooling time), (4) Since the zinc oxide film formed on the bath surface was removed to reveal a clean Zn surface,
The elapsed time until the oxide film is formed on the surface (hereinafter referred to as elapsed time) is an important condition. However, on a clean Zn surface, a zinc oxide film is formed as time passes, and after 60 seconds or more, a large amount of zinc oxide is present on the bath surface. When the sample is pulled out of the bath, a large amount of zinc oxide adheres to the sample surface, and it is difficult to form a zinc oxide film having a uniform color. Elapsed time 60
Within seconds, a large amount of zinc oxide does not adhere to the surface of the sample, and a uniform-colored zinc oxide film can be formed. In actual operation, the zinc oxide on the Zn surface is removed, and the sample is pulled up within a maximum of 90 seconds in elapsed time.

The bath temperature, the amount of Mn added,
In the Zn bath containing the added amount of Ca and the added amount of misch metal, the carbon steel subjected to the above-described pretreatment is quickly immersed, and for an appropriate time, for example, about 1 minute to 10 minutes, in a normal plating operation. After soaking for 3 minutes, pull up. In the case of lifting, the zinc oxide film on the surface of the Zn bath is removed and 6
Raise within 0 seconds. Before cooling with water, the surface of the galvanized sample should be made as uniform as possible.
Allow to cool in the atmosphere for 0 seconds or more, then cool in water. The actual cooling time is up to 3 minutes.

After cooling, the process proceeds to the finishing step of the galvanized carbon steel. In the finishing step, zinc dripping and zinc adhering to the portion to be non-plated are removed by a grinder or the like. Through this finishing step, the plating operation of the carbon steel is completed.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments.
The size of the carbon steel used in the examples is 35 mm in length x 2 in width.
5 mm × 1.5 mm thickness was used. Table 1 shows the composition of carbon steel. A graphite crucible was used as a container for the plating bath, and its size was 85 mm in inner diameter × 120 mm in depth. Table 2 shows the composition of zinc used in the experiment. The temperature has a measurement error of ± 5 ° C.

[0021]

[Table 1]

[0022]

[Table 2]

[When adding Mn and Ca]
n is 0.1%, 1.0%, 2.0% by weight,
The amount of Ca added is 0.01%, 0.6%, 1.2% by weight.
%. Mn having a purity of 99.9% was used. The impurity is unknown. Ca with a purity of 99% was used. The impurities contain a small amount of Ti. Zn is as shown in Table 2 above.
The following was used. The bath temperature is 430 ° C, 44
Performed at 0 ° C.

The test results are shown in Tables 3 to 20. Of these, Tables 3 to 11 show bath temperatures of 430 ° C. and Tables 12 to 20
Has a bath temperature of 440 ° C. Regarding the uniformity of coloring, “×” indicates that color unevenness occurred, and “○” indicates uniform coloring.
The evaluation was made as follows. "Elapsed" in the table indicates elapsed time,
“S” indicates seconds and “cooling” indicates cooling time.

[0025]

[Table 3]

[0026]

[Table 4]

[0027]

[Table 5]

[0028]

[Table 6]

[0029]

[Table 7]

[0030]

[Table 8]

[0031]

[Table 9]

[0032]

[Table 10]

[0033]

[Table 11]

[0034]

[Table 12]

[0035]

[Table 13]

[0036]

[Table 14]

[0037]

[Table 15]

[0038]

[Table 16]

[0039]

[Table 17]

[0040]

[Table 18]

[0041]

[Table 19]

[0042]

[Table 20]

[When adding Mn and misch metal]
In the test, the addition amount of Mn was 0.1%, 1.0%,
2.0%, the amount of misch metal added is 0.5 by weight
%, 1.0%, and 2.0%. Mn has a purity of 99.
A 9% one was used. The impurity is unknown. In the misch metal, La: 25.6%, Ce: 51.1%, Pr:
4.8%, Nd: 15.5%, Sm: <0.2%, F
e: 0.4%, Ca <0.05%, Mg: 0.1%, A
l: What consisted of <0.1% of components was used. Zn
Used those shown in Table 2 above. The bath temperature is
The test was performed at 430 ° C, 450 ° C, and 470 ° C.

The test results are shown in Tables 21 to 47. Of these, the bath temperature is 430 ° C in Tables 21 to 29, the bath temperature is 450 ° C in Tables 30 to 38, and the bath temperature is 470 in Tables 39 to 47.
° C. The uniformity of the coloring was evaluated as "x" when color unevenness occurred, and "〇" when uniform coloring was observed. In the table, “elapsed” indicates elapsed time, “s” indicates second, and “cooling” indicates cooling time.

[0045]

[Table 21]

[0046]

[Table 22]

[0047]

[Table 23]

[0048]

[Table 24]

[0049]

[Table 25]

[0050]

[Table 26]

[0051]

[Table 27]

[0052]

[Table 28]

[0053]

[Table 29]

[0054]

[Table 30]

[0055]

[Table 31]

[0056]

[Table 32]

[0057]

[Table 33]

[0058]

[Table 34]

[0059]

[Table 35]

[0060]

[Table 36]

[0061]

[Table 37]

[0062]

[Table 38]

[0063]

[Table 39]

[0064]

[Table 40]

[0065]

[Table 41]

[0066]

[Table 42]

[0067]

[Table 43]

[0068]

[Table 44]

[0069]

[Table 45]

[0070]

[Table 46]

[0071]

[Table 47]

[When Mn, Misch Metal, and Ca are Added] In the test, the amount of Mn added was 0.1% by weight,
0%, the amount of misch metal added is 0.5% by weight,
2.0%, Ca content 0.01%, 0.3% by weight
I went in. Mn having a purity of 99.9% was used.
The impurity is unknown. For misch metal, La: 25.6
%, Ce: 51.1%, Pr: 4.8%, Nd: 15.
5%, Sm: <0.2%, Fe: 0.4%, Ca: <
What consisted of components of 0.05%, Mg: 0.1%, and Al: <0.1% was used. Ca with a purity of 99% was used. The impurities contain a small amount of Ti. The Zn shown in Table 2 was used. The bath temperature is 430
C., 450.degree. C. and 470.degree.

Tables 48 to 71 show the test results. Tables 48 to 55 have a bath temperature of 430 ° C, Tables 56 to 63 have a bath temperature of 450 ° C, and Tables 64 to 71 have a bath temperature of 470 ° C.
° C. The uniformity of the coloring was evaluated as "x" when color unevenness occurred, and "〇" when uniform coloring was observed. In the table, “elapsed” indicates elapsed time, “s” indicates second, and “cooling” indicates cooling time.

[0074]

[Table 48]

[0075]

[Table 49]

[0076]

[Table 50]

[0077]

[Table 51]

[0078]

[Table 52]

[0079]

[Table 53]

[0080]

[Table 54]

[0081]

[Table 55]

[0082]

[Table 56]

[0083]

[Table 57]

[0084]

[Table 58]

[0085]

[Table 59]

[0086]

[Table 60]

[0087]

[Table 61]

[0088]

[Table 62]

[0089]

[Table 63]

[0090]

[Table 64]

[0091]

[Table 65]

[0092]

[Table 66]

[0093]

[Table 67]

[0094]

[Table 68]

[0095]

[Table 69]

[0096]

[Table 70]

[0097]

[Table 71]

[0098]

As is apparent from the above description, according to the colored hot-dip galvanizing method using Mn in the carbon steel according to the first aspect of the present invention, the addition amount is from 0.1% or more to 2.0% or more.
% Of Mn and Ca in an amount of 0.01% or more to 1.2% or less, and a bath temperature of 425 ° C.
Carbon steel is immersed in a Zn-Mn-Ca dissolving bath at a temperature in the range of -445 ° C for at least 1 minute, and the carbon steel is pulled out of the Zn bath within 60 seconds after removing the zinc oxide film on the surface of the Zn bath. After elapse of 20 seconds or more in the inside, water-cooling can be performed to obtain a carbon steel surface that is uniformly and stably colored in pale yellow without color unevenness.

Further, according to the colored hot-dip galvanizing method using Mn in the carbon steel according to the second aspect of the present invention, the amount of Mn and the amount of Mn in the range of 0.1% to 2.0% are set.
Zn containing a misch metal in a range of 5% or more to 2.0% or less and a bath temperature in a range of 425 ° C. to 475 ° C.
-Mn- Carbon steel is immersed in a misch metal dissolving bath for at least 1 minute, and after removing the zinc oxide film on the surface of the Zn bath, the carbon steel is pulled out of the Zn bath within 60 seconds and passed in the air for at least 20 seconds. After that, by cooling with water, it is possible to obtain a carbon steel surface uniformly and stably colored in pale blue without color unevenness.

According to the colored hot-dip galvanizing method using Mn in the carbon steel according to the third aspect of the present invention, the amount of Mn in the range of 0.1% or more and 2.0% or less and the amount of Mn are not limited. It contains a misch metal in the range of 0.5% to 2.0% and Ca in the range of 0.01% to 0.3%, and a bath temperature of 425 ° C to 475 ° C. The carbon steel is immersed in the Zn-Mn-Mischmetal-Ca dissolving bath for at least one minute or more, and within 60 seconds after the zinc oxide film on the surface of the Zn bath is removed, the carbon steel is pulled out of the Zn bath, and the carbon steel is removed in air for 20 minutes. After a lapse of at least two seconds, water-cooling can provide a carbon steel surface uniformly and stably colored in pale blue without color unevenness. Moreover, since the fluidity of the coating on the surface of Zn is better than in the case of the invention of claim 2, when the plated carbon steel is pulled out of the bath, a part of the coating is It can be easily prevented from adhering to the surface.

Claims (3)

[Claims] 1. An Mn having an addition amount of 0.1% or more and 2.0% or less and an addition amount of 0.01% or more and 1.2% or less.
It contains Ca in the following range, and has a bath temperature of 425 ° C to 445.
Carbon steel is immersed in a Zn-Mn-Ca dissolving bath at a temperature of at least 1 minute for at least one minute, and within 60 seconds after the zinc oxide coating on the surface of the Zn bath is removed, the carbon steel is pulled out of the Zn bath and is then removed in air. A colored hot-dip galvanizing method using Mn in carbon steel, characterized in that the carbon steel surface is uniformly and stably colored pale yellow by cooling with water after elapse of 20 seconds or more. 2. A method according to claim 1, wherein said additive contains Mn in a range of 0.1% to 2.0% and misch metal in a range of 0.5% to 2.0%, and a bath temperature of 425 ° C. 475
The carbon steel was immersed in the Zn-Mn-mish metal dissolving bath at a temperature of at least 1 minute for at least 1 minute, and the carbon steel was immersed within 60 seconds after the zinc oxide coating on the surface of the Zn bath was removed.
A colored hot-dip galvanizing method using Mn in carbon steel, wherein the carbon steel surface is pulled out of the bath, and after elapse of 20 seconds or more in air, and then water-cooled to color the surface of the carbon steel uniform and stable light blue. 3. A Mn having an addition amount of 0.1% or more and 2.0% or less, a misch metal having an addition amount of 0.5% or more and 2.0% or less, and an addition amount of 0.01% or less. % Of Ca in a range of not less than 0.3% to not more than 0.3% and a bath temperature of 42%.
The carbon steel is immersed in the Zn-Mn-Mischmetal-Ca dissolving bath at a temperature in the range of 5 ° C to 475 ° C for at least one minute, and the carbon steel is immersed in the Zn bath within 60 seconds after removing the zinc oxide film on the Zn bath surface. M is a carbon steel characterized in that the carbon steel surface is pulled up from the inside, and after elapse of 20 seconds or more in the air, is water-cooled and the surface of the carbon steel is colored uniformly and stably light blue.
a hot-dip galvanizing method using n.