JP2016089222A - Glass lining method for cast iron product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glass lining cast iron product, and a glass lining method for a cast iron product for producing the cast iron product.SOLUTION: Provided is a glass lining cast iron product having a structure where the surface of a cast iron product is covered with a glaze, the surface of the cast iron product is decarburized by heating treatment for the cast iron product, and a glaze component is filled in a gap produced by the decarburization.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a glass lining cast iron product and a glass lining method for a cast iron product for producing the cast iron product. Glass lining is also referred to as glass lining.

  In the drainage piping system of buildings, pipe joints are used to join pipes together. There are various types of pipe joints such as elbows and joints that bend at right angles and y-shaped branch joints in addition to those that are connected in a straight line. However, it is obvious that the one used for the portion that changes the flow of drainage is likely to be subjected to a large resistance as compared with the joint used for the straight portion. In addition, the drainage pipe system has various conditions, and in particular, there are many reports of kitchen drainage pipes in which holes are opened in the joint body in a short period of time, resulting in a water leakage accident.

Analyzing the cause of the water leakage accident can point out the following problems.
1) The maintenance and management of the grease trap is inappropriate, so that a large amount of oil and fat flows into the drain pipe, causing a load on the drain pipe.
2) Dirt adheres to the inner surface of the drainage pipe, and unreasonable cleaning means are used to remove it, resulting in damage to the drainage pipe.
3) There is no cleaning port for cleaning the inside of the drain pipe, and proper cleaning cannot be performed. As a result, dirt accumulates and a vicious cycle of unreasonable cleaning occurs.
4) For example, if sufficient water washing is not performed after disinfection with sodium hypochlorite, it may cause corrosion.
5) If sufficient water does not flow in the disposer system, organic matter is deposited in the drain pipe.

  Due to the above-mentioned causes, hydrogen sulfide is generated by the action of sulfate-reducing bacteria on organic matter and fats and oils, and when sulfuric acid is generated by sulfur-oxidizing bacteria, the inside of the drainage pipe becomes a serious corrosive environment. Although a protective coating such as epoxy resin is formed on the inner surface of the drainage pipe, it cannot withstand corrosive environments, so rust is generated in the joints that are cast iron products, and rust is cleaned by contact with a cleaning hose, etc. It is cut every time. If pipe cleaning and rust generation are repeated in this way, it is thought that a hole will open in a short period of time, leading to a water leak accident.

The following methods can be considered as countermeasures that can be taken for the cast iron products as described above.
A: For example, when the current protective film is an epoxy resin coating and the film thickness is about 50 μm, the film thickness is increased several times to about 300 μm.
B: The protective film is changed to a resin other than an epoxy resin, for example, a resin such as nylon or vinyl chloride, and is formed to have a film thickness of about 300 μm by baking coating of the powder resin.
C: A protective film having a thickness of about 1000 μm is molded on the inner surface of the cast iron product using an arbitrary resin.
D: A protective coating having a required thickness is formed by plating on the inner surface of the cast iron product using zinc, aluminum, nickel or the like.

However, the above measures have the following problems.
A: As a general matter, resin coating is excellent in chemical resistance, but the coating surface is soft and has a problem in wear resistance.
B: Although there is the above problem, it is effective as a measure against a mere corrosive environment, but it is not suitable for a drain pipe such as an elbow where contact with a cleaning tool occurs.
C: Although it can be said that molding has higher durability than coating, the linear expansion coefficient of resin and cast iron is greatly different, so that there is a high possibility that the molded film peels off on the adhesive surface due to repeated heating and cooling. In addition, there is a limit to the shape that can be molded by injection molding, and it is difficult to deal with cast iron products that are rich in shape changes such as joints of drain pipes.
D: Metal plating is harder and better in adhesion than a resin protective film, but has a problem in chemical resistance. Chemical resistance is important because chlorinated chemicals also flow into the kitchen drain piping.

Moreover, although the prior art was investigated about the precedent which gives glass lining to cast iron products, the example was not found. However, there is an invention referred to as a glass lining construction method disclosed in JP-A-2002-167680, which is the same stainless steel material as the base material, Ni metal, Cr metal, Fe metal, Co metal Ni—Cr alloy on the surface of the stainless steel base material. And a thermal spraying treatment of a thermal spray material selected from Fe-Cr alloy to form a thermal spray treatment layer, and a glass lining layer is formed on the lower layer by heat treatment of the glass lining by the upper side and the upper side. A method is disclosed. This construction method makes it possible to apply a stable and uniform glass lining layer to large-sized glass lining devices made of a stainless steel base material, and there is nothing related to the glazing technique on the cast iron product surface.
JP 2002-167680 A

  This invention is made | formed in view of the said point, The subject is providing the glass lining method of the cast iron product for manufacturing a glass lining cast iron product and the cast iron product. Another object of the present invention is to provide a glass-lined cast iron product that can reliably protect the cast iron product used in the drainage piping system from corrosion of the inner surface.

  In order to solve the above-described problems, the present invention provides a method in which the surface of a cast iron product is coated with glaze, and the cast iron product surface is decarburized by the heat treatment of the cast iron product, and the glaze is generated in the voids generated by decarburization. The realization of a glass-lined cast iron product characterized by having a structure filled with components.

  The cast iron product according to the present invention is, for example, a cast iron product that is exposed to a corrosive environment or high heat, and has a glass lining layer on the surface exposed to the corrosive environment or high heat.

  Such a glass-lined cast iron product can be applied to, for example, a pipe joint. In this case, as for the pipe joint used for a drainage piping system, it is desirable that the thickness of the glass lining layer on the inner surface is 300 μm or more as described above. The glass lining layer having a thickness of about 300 μm or more is formed, for example, by repeating the glazing and firing step a plurality of times as described above on cast iron products.

  The glass-lined cast iron product according to the present invention covers the surface of the cast iron product with glaze, decarburizes the cast iron product surface, and fills the voids generated by decarburization with the glaze component in the furnace. It can be manufactured by a method of charging and baking at a temperature of 973 to 1223K for 10 to 80 minutes. In this method, decarburization and glaze filling are performed simultaneously.

  In the method of the present invention, the cast iron product is put into a furnace as a pretreatment step, whereby the graphite on the surface of the cast iron product is decarburized in advance at a temperature of 873 to 1223 K for 10 to 120 minutes, and then the cast iron product The surface is coated with glaze, the cast iron product is put into a furnace, the cast iron product surface is decarburized, and the voids generated by decarburization are filled with glaze components at a temperature of 973-1223 K at 10-80. You may implement by the means of baking for a minute. This method precedes only a decarburization process, and performs the glaze filling by subsequent baking. Therefore, the present invention can be implemented by either a method in which decarburization is performed prior to filling of the glaze or a method in which decarburization and filling are performed simultaneously.

  The reason why the lower limit of the temperature in the decarburization process is set to 873 K is that the decarburization depth is proportional to time. The reason why the upper limit of the temperature is set to 1223 K is that it is not preferable because it approaches the melting point of gray cast iron. Thus, the decarburization treatment as the pretreatment step can be performed by a combination of temperature and time suitable for the necessary decarburization depth.

  An object of the present invention is to provide a glass lining on the surface of a cast iron product, thereby forming a protective coating that can withstand even a corrosive environment such as a kitchen drainage pipe. The cast iron products and glass linings handled in the present invention are not special per se. However, there is almost no precedent in the technology of applying glass lining to the surface of cast iron products. For this reason, in order to complete the present invention, it was necessary to obtain a certain knowledge by repeating many trials and errors. As a result, according to the present invention obtained, it is possible to extend the life of the cast iron product while suppressing the cost.

  What is revolutionary in the present invention is that the surface of the cast iron product is decarburized and filled with a glaze component mainly composed of a silicon compound substituted in the voids generated by the decarburization so that it is replaced with carbon. It is to become. As a result, a kind of anchor effect can be obtained by the glaze component. The feature of the present invention is that the glass lining layer can be firmly fixed to the surface of the cast iron product in this way and has been completed as a glass lining method. Therefore, in the glass lining method according to the present invention, a firing step is an important requirement in order to obtain a kind of anchor effect by the decarburization.

  The firing step required in the glass lining method according to the present invention is performed at a temperature of 973 to 1223K for 10 to 80 minutes. As the furnace, an electric furnace generally used for the glass lining method is used. The cast iron product to be treated is, for example, gray cast iron (FC150), and the glaze component is a general component composed of a component used for a glaze product or the like. However, other than the above, for example, all steel types included in JIS G 5501 gray cast iron products, and further cast iron products made of materials such as all steel types included in JIS G 5502 spheroidal graphite cast iron; Etc. can be applied to the present invention without problems. The condition of 973-1122 K at the above baking step for 10-80 minutes is necessary so that the glaze used in the present invention is completely melted and does not cause foaming or scorching.

  As the glass lining method of the present invention, a configuration in which a firing process in which a cast iron product whose surface is covered with glaze is put into a furnace is repeated a plurality of times is preferable. It is desirable that the firing step performed by putting the cast iron product whose surface is covered with glaze into the furnace is repeated at least twice at a temperature of 1073 K and a time of 40 minutes. Repeating the firing process a plurality of times means that a plurality of glass lining layers are formed, whereby a lining layer having a thickness of more than about 300 μm can be obtained, which is sufficient as an inner surface treatment layer of the joint. Is the thickness.

In addition, the linear expansion coefficient of cast iron (FC) is close to 11 to 13.5 × 10 ⁻⁶ , and the linear expansion coefficient of the glass lining part is close to 8 to 13 × 10 ^−6. Can be used. Further, the hardness of the surface of the glass lining portion is measured as Hv ≧ 500, which is a mechanical strength that can sufficiently withstand an external force expected to be applied by a washing machine.

  Since the present invention is constructed and operates as described above, a glass lining method can be suitably applied to cast iron products, and a glass having good corrosion resistance and wear resistance can be obtained by the method of the present invention. There is an effect that a lining cast iron product can be manufactured. The present invention also provides a glass-lined cast iron product that can reliably protect its inner surface from corrosion as a cast iron product used in a drainage pipe system that is exposed to harsh conditions such as a kitchen drainage pipe. be able to.

Hereinafter, the present invention will be described in more detail with reference to the drawings.
<Cast iron products>
First, the cast iron product which is the subject of the invention will be described. 1 and 2 show a joint 10 called an elbow as an example of a cast iron product according to the present invention. This elbow joint 10 has a bent portion 13 in the form of changing the flow path at right angles between the open ends 11 and 12. The cast iron product in this embodiment is gray cast iron (FC150). Glass lining layers 14 and 15 are formed on the inner and outer surfaces of the joint 10 according to the present invention. Since the drainage pipe for kitchen is assumed, the inner lining layer 14 that is easily exposed to a corrosive environment is formed on the outer surface. It is formed thicker than the lining layer 15 (see FIG. 2). The glass lining layer 14 on the inner surface is formed to be about three times as thick as the glass lining layer 15 on the outer surface.

  If an example of the connection structure of the drain pipe 16 using the said coupling 10 is shown concretely, it will become like FIG. This structure has a separation preventing structure in which a steel ball-containing packing 17 is disposed on the outer surface of the end portion of the drain pipe 16, and the connection ring 18 and the flange portion 19 of the joint 10 are tightened using bolts and nuts 26. . In the drawing, the steel ball 17a is used to obtain the biting action, but the joint capable of carrying out the present invention is not limited to this example, and other methods can be taken.

  As another example of the cast iron product according to the present invention, a case where it is carried out on the two-handed pan 20 will be described with reference to FIGS. The pan 20 is composed of a container 21 and a lid 22, and the container 21 is an embodiment of the present invention, but either the embodiment is attached to the lid 22 or, for example, is made of glass. But it ’s okay. Ductile cast iron (FCD) is used for the material of the pan 20 and is formed thin by precision casting.

  Since the container 21 is made of ductile cast iron (FCD), spheroidal graphite 23 exists independently (see FIG. 4), but the spheroidal graphite 23 also appears on the surface of the ductile cast iron. For this reason, since the spherical graphite 23 existing on the surface is decarburized, a void 24 is generated on the surface, so that the glaze component 25 is filled in the void 24. Accordingly, for the container 21 made of ductile cast iron (FCD), the glass lining layer is casted by casting the glaze component in the same manner as in the case of using cast iron products made of gray cast iron (FC), which will be described later. It can be firmly fixed to the product surface, and a kind of anchor effect can be obtained.

Next, the means and method of the present invention relating to the glass lining applied to the cast iron product will be described.
<Glue>
The ingredients and composition of the glaze are as follows.
Component _{A: SiO 2 + TiO 2 + ZrO} 2 = 40~75 wt%
However, the ratio of each element in A component is as follows.
SiO _2: 40~75 mass%
TiO _2: 0 to 15 wt%
ZrO ₂ : 0 to 10% by mass
If the component A is less than 40% by mass, the strength of the frit itself is lowered, and it is not preferable. If it exceeds 75% by mass, the frit viscosity of the frit is increased and the melting point of the frit composition is increased.

Component _{B: Na 2 O + K 2 O} + Li 2 O = 0.5~20 wt%
However, the ratio of each element in B component is as follows.
Na ₂ O: 0.5 to 20 wt%
K ₂ O: 0 to 15% by mass
Li ₂ O: 0 to 10% by mass
If the B component is less than 0.5% by mass, the frit meltability is deteriorated, and it is not preferable. If it exceeds 20% by mass, the linear expansion coefficient is increased and the balance of physical properties is lost.

C component: CaO + BaO + ZnO + MgO = 1-15 mass%
However, the ratio of each element in C component is as follows.
CaO: 1 to 15% by mass
BaO: 0 to 10% by mass
ZnO: 0 to 6% by mass
MgO: 0 to 5% by mass
If the C component is less than 1% by mass, it is insufficient for improving the alkali resistance of the frit. If it exceeds 15% by mass, the frit viscosity of the frit increases and the melting point of the frit composition increases. It is not preferable.

Component _{D: B 2 O 3 + Al 2} O 3 + Cr 2 O 3 + Fe 2 O 3 = 1~20 wt%
However, the ratio of each element in D component is as follows.
B ₂ O ₃ : 1 to 20% by mass
Al ₂ O ₃ : 0 to 10% by mass
Cr ₂ O ₃ : 0 to 10% by mass
Fe ₂ O ₃ : 0 to 10% by mass
If the D component is less than 1% by mass, the frit meltability is lowered, and the devitrification preventing effect is remarkably reduced. .

E component: CoO + MnO + NiO + CuO = 0 to 5 mass%
However, the ratio of each element in E component is as follows.
CoO: 0 to 5% by mass:
MnO: 0 to 5% by mass
NiO: 0 to 5% by mass
CuO: 0 to 5% by mass
The component E contributes to improving the adhesion of the frit. However, if it exceeds 5% by mass, the foaming phenomenon during firing becomes remarkable, which is not preferable.

In addition, although the component described as 0 is not essential for vitrification, it has a relationship with auxiliary roles, such as viscosity, adjustment of a calcination temperature, and adhesiveness.

Firing process Glass lining method In the glass lining method, cast iron products are put into a furnace, whereby the graphite on the surface of the cast iron products is pre-decarburized, but this step can be performed as a pretreatment step. In addition, after the pretreatment step, a glazing step using a glaze composed of the components A to E can be performed. However, it is possible to perform a direct coating method in which the pretreatment step is omitted and the glaze composed of the components A to E is applied to the surface of the joint 10 which is a cast iron product. In order to obtain a glaze, it is produced as a fluidized glass lining liquid by treating with water as a dispersion medium by a conventional method of glaze production. Hereinafter, the glass lining method of the present invention will be described separately.
<Part 1>
The surface of the joint 10 which is a cast iron product is coated with the glaze composed of the components A to E, the cast iron product is put into an electric furnace, the cast iron product surface is decarburized, and the void generated by the decarburization is formed. Bake for 40 minutes at a temperature of about 1073 K to fill the glaze ingredients. The glazing and firing process is repeated three times for the joint to produce a glass-lined cast iron product.
<Part 2>
As a pretreatment step, the joint 10 which is a cast iron product is put into a furnace, whereby the graphite on the surface of the joint 10 is decarburized in advance at a temperature of 873 to 1223 K for 10 to 120 minutes, and then the surface of the cast iron product is glazed. The cast iron product is put into a furnace, and the cast iron product surface is decarburized, and fired at a temperature of 973 to 1223K for 10 to 80 minutes in order to fill the voids generated by the decarburization with the glaze component. The above glazing and firing steps are performed at least once on the inside of the joint to produce a glass-lined cast iron product.

The joint 10 which is a glass-lined cast iron product obtained by the method 1 has a smooth glass-lining layer. When the surface hardness was measured, a value of Hv ≧ 500 was obtained in terms of Wuckers hardness. The surface hardness equivalent to that of the joint 10 by the method 2 was also obtained. Since the performance test 1 regarding hardness was performed about the glass-lined cast iron product which concerns on this invention, here, a hardness test and its result are demonstrated as follows.
Evaluation purpose: To evaluate the hardness of the glass lining layer obtained by the present invention.
Evaluation method: JIS Z 2244 Vickers hardness test-According to the test method.
-Criteria: Hardness of 500Hv or more.
The test results are shown in Table 1 below. According to Table 1, an average value of 609 HV is obtained.
Table 1

＊一時間を二分して３０分間を冷却、３０分間を加熱する工程を１サイクルとし、低温・冷却と高温・加熱の変化に要する時間は３分以内とした。 The performance test 2 revealed that the glass-lined cast iron product according to the present invention had the glass-lined layer adhered to the cast iron product surface very firmly. In the performance test, rapid cooling and rapid heating were evaluated by applying thermal stress to the specimen, and the method is as follows.
・ Temperature profile: High temperature 100 ℃, Low temperature-10 ℃
・ Time required for low temperature to high temperature change: within 3 minutes ・ Movement cycle: 3, 5, 10, 20
Table 2 below shows the test results of the judgment criteria: no cracks reaching the casting substrate in the glass lining layer, and no peeling reaching the casting substrate in the glass lining layer.
Table 2

* One hour was divided into two, 30 minutes was cooled and 30 minutes was heated, and one cycle was taken as one cycle, and the time required to change between low temperature / cooling and high temperature / heating was within 3 minutes.

  From the facts shown by such performance tests 1 and 2, the inventors have inferred that the glass lining layer is fixed to the cast iron surface by a special mechanism. Therefore, in order to clarify the phenomenon that would have occurred at the interface between the glass lining layer and the cast iron product surface, an analysis by EPMA (Electron Probe Micro Analyzer) was attempted. As a result of the analysis, the facts supporting the novelty of the present invention were found, and the contents thereof will be mentioned next.

  The above analytical test was conducted by requesting the Saitama Industrial Technology Center. The requested product is the joint 10 of the glass-lined cast iron product obtained by the first method, and the requested items are analysis and mapping by an X-ray microanalyzer. FIG. 5 and FIG. 6 show reflected electron images as one of the test results. In FIG. 5, L1 represents a glass lining layer, L2 represents a decarburized layer, and L3 represents a cast iron layer. The layer of L2 is a surface layer of the cast iron layer, but the layer having a thickness of about 100 μm shown in the lower column as a scale is different from the cast iron layer L3 having a black streak pattern, and the glass lining layer L1 and I guess that it is decarburized from the relationship.

  FIG. 6 shows a backscattered electron image magnified to × 2000 while the magnification of FIG. 5 is × 100. When the magnified image of FIG. 6 is seen, it can be seen that the decarburized layer L2 that appears bright enters a dark or dotted line-like pattern from the surface layer. This dark-looking pattern extends from the surface layer, that is, the glass lining layer L1, and its end reaches a depth of about 100 μm as described above.

  Further, FIG. 7 shows a color map (the original figure is color drawing since it is color drawing, but color drawing is not permitted in the bylaws of the Patent Law, and is shown by tone drawing). FIG. 7 is a color map relating to Si, and the red color of the original drawing showing a high concentration is the glass lining layer L1 at the top of FIG. The majority of FIG. 7 occupies the blue decarburized layer L2 in the original drawing, and the decarburized layer L2 has a streak or dotted line pattern appearing from the surface layer, which is a silicon compound and is from the glass lining layer L1. It is what is growing.

  From the above analysis results and the facts shown in the color map, the silicon compound enters the decarburized surface layer of the cast iron layer L3 and is entangled with the cast iron layer L3, so that it exhibits the state like the anchor effect described above. It can be inferred with sufficient certainty.

It is a section explanatory view showing an example of the cast iron product concerning the present invention. It is sectional explanatory drawing which expands a part same as the above and shows a connection ring added. It is a section explanatory view showing other examples of cast iron products concerning the present invention. It is an expanded sectional explanatory view showing a part of the above typically. It is a 100-times-magnification backscattered electron image which shows the glass-lined cast iron product obtained by the method of this invention. It is a reflected-electron image of 2000 times magnification in the principal part same as the above. Similarly, a color map of Si (silicon compound).

DESCRIPTION OF SYMBOLS 10 Joint 11, 12 Both ends of joint 13 Bending part of joint 14 Glass lining layer of inner surface 15 Glass lining layer of outer surface 16 Drain pipe 17 Packing 18 Connection ring 19 Flange part 20 Pot 21 Container 22 Lid 23 Spherical graphite 24 Gap 25 glaze ingredients

  The present invention relates to a glass lining method for cast iron products for producing cast iron products. Glass lining is also referred to as glass lining.

  In the drainage piping system of buildings, pipe joints are used to join pipes together. There are various types of pipe joints such as elbows and joints that bend at right angles and y-shaped branch joints in addition to those that are connected in a straight line. However, it is obvious that the one used for the portion that changes the flow of drainage is likely to be subjected to a large resistance as compared with the joint used for the straight portion. In addition, the drainage pipe system has various conditions, and in particular, there are many reports of kitchen drainage pipes in which holes are opened in the joint body in a short period of time, resulting in a water leakage accident.

Analyzing the cause of the water leakage accident can point out the following problems.
1) The maintenance and management of the grease trap is inappropriate, so that a large amount of oil and fat flows into the drain pipe, causing a load on the drain pipe.
2) Dirt adheres to the inner surface of the drainage pipe, and unreasonable cleaning means are used to remove it, resulting in damage to the drainage pipe.
3) There is no cleaning port for cleaning the inside of the drain pipe, and proper cleaning cannot be performed. As a result, dirt accumulates and a vicious cycle of unreasonable cleaning occurs.
4) For example, if sufficient water washing is not performed after disinfection with sodium hypochlorite, it may cause corrosion.
5) If sufficient water does not flow in the disposer system, organic matter is deposited in the drain pipe.

  Due to the above-mentioned causes, hydrogen sulfide is generated by the action of sulfate-reducing bacteria on organic matter and fats and oils, and when sulfuric acid is generated by sulfur-oxidizing bacteria, the inside of the drainage pipe becomes a serious corrosive environment. Although a protective coating such as epoxy resin is formed on the inner surface of the drainage pipe, it cannot withstand corrosive environments, so rust is generated in the joints that are cast iron products, and rust is cleaned by contact with a cleaning hose, etc. It is cut every time. If pipe cleaning and rust generation are repeated in this way, it is thought that a hole will open in a short period of time, leading to a water leak accident.

The following methods can be considered as countermeasures that can be taken for the cast iron products as described above.
A: For example, when the current protective film is an epoxy resin coating and the film thickness is about 50 μm, the film thickness is increased several times to about 300 μm.
B: The protective film is changed to a resin other than an epoxy resin, for example, a resin such as nylon or vinyl chloride, and is formed to have a film thickness of about 300 μm by baking coating of the powder resin.
C: A protective film having a thickness of about 1000 μm is molded on the inner surface of the cast iron product using an arbitrary resin.
D: A protective coating having a required thickness is formed by plating on the inner surface of the cast iron product using zinc, aluminum, nickel or the like.

However, the above measures have the following problems.
A: As a general matter, resin coating is excellent in chemical resistance, but the coating surface is soft and has a problem in wear resistance.
B: Although there is the above problem, it is effective as a measure against a mere corrosive environment, but it is not suitable for a drain pipe such as an elbow where contact with a cleaning tool occurs.
C: Although it can be said that molding has higher durability than coating, the linear expansion coefficient of resin and cast iron is greatly different, so that there is a high possibility that the molded film peels off on the adhesive surface due to repeated heating and cooling. In addition, there is a limit to the shape that can be molded by injection molding, and it is difficult to deal with cast iron products that are rich in shape changes such as joints of drain pipes.
D: Metal plating is harder and better in adhesion than a resin protective film, but has a problem in chemical resistance. Chemical resistance is important because chlorinated chemicals also flow into the kitchen drain piping.

Moreover, although the prior art was investigated about the precedent which gives glass lining to cast iron products, the example was not found. However, there is an invention referred to as a glass lining construction method disclosed in JP-A-2002-167680, which is the same stainless steel material as the base material, Ni metal, Cr metal, Fe metal, Co metal Ni—Cr alloy on the surface of the stainless steel base material. And a thermal spraying treatment of a thermal spray material selected from Fe-Cr alloy to form a thermal spray treatment layer, and a glass lining layer is formed on the lower layer by heat treatment of the glass lining by the upper side and the upper side. A method is disclosed. This construction method makes it possible to apply a stable and uniform glass lining layer to large-sized glass lining devices made of a stainless steel base material, and there is nothing related to the glazing technique on the cast iron product surface.
JP 2002-167680 A

This invention is made | formed in view of the said point, The subject is providing the glass lining method of cast iron products. Another object of the present invention is to provide a glass lining method capable of reliably protecting cast iron products used in drainage piping systems from corrosion on the inner surface.

In order to solve the above-mentioned problems, the present invention introduces a cast iron product into a furnace as a pretreatment step, whereby the graphite on the surface of the cast iron product is previously decarburized at a temperature of 873-1223K for 10 to 120 minutes, Thereafter, the surface of the cast iron product is coated with glaze, the cast iron product is put into a furnace, the surface of the cast iron product is decarburized, and a temperature of 973 to 1223K is filled to fill the voids generated by decarburization. For 10 to 80 minutes .

The glass-lined cast iron product manufactured according to the present invention is, for example, a cast iron product that is exposed to a corrosive environment or high heat, and has a glass lining layer on the surface exposed to the corrosive environment or high heat. It is desirable to be.

  Such a glass-lined cast iron product can be applied to, for example, a pipe joint. In this case, as for the pipe joint used for a drainage piping system, it is desirable that the thickness of the glass lining layer on the inner surface is 300 μm or more as described above. The glass lining layer having a thickness of about 300 μm or more is formed, for example, by repeating the glazing and firing step a plurality of times as described above on cast iron products.

  The glass-lined cast iron product according to the present invention covers the surface of the cast iron product with glaze, decarburizes the cast iron product surface, and fills the voids generated by decarburization with the glaze component in the furnace. It can be manufactured by a method of charging and baking at a temperature of 973 to 1223K for 10 to 80 minutes. In this method, decarburization and glaze filling are performed simultaneously.

  In the method of the present invention, the cast iron product is put into a furnace as a pretreatment step, whereby the graphite on the surface of the cast iron product is decarburized in advance at a temperature of 873 to 1223 K for 10 to 120 minutes, and then the cast iron product The surface is coated with glaze, the cast iron product is put into a furnace, the cast iron product surface is decarburized, and the voids generated by decarburization are filled with glaze components at a temperature of 973-1223 K at 10-80. You may implement by the means of baking for a minute. This method precedes only a decarburization process, and performs the glaze filling by subsequent baking. Therefore, the present invention can be implemented by either a method in which decarburization is performed prior to filling of the glaze or a method in which decarburization and filling are performed simultaneously.

  The reason why the lower limit of the temperature in the decarburization process is set to 873 K is that the decarburization depth is proportional to time. The reason why the upper limit of the temperature is set to 1223 K is that it is not preferable because it approaches the melting point of gray cast iron. Thus, the decarburization treatment as the pretreatment step can be performed by a combination of temperature and time suitable for the necessary decarburization depth.

  An object of the present invention is to provide a glass lining on the surface of a cast iron product, thereby forming a protective coating that can withstand even a corrosive environment such as a kitchen drainage pipe. The cast iron products and glass linings handled in the present invention are not special per se. However, there is almost no precedent in the technology of applying glass lining to the surface of cast iron products. For this reason, in order to complete the present invention, it was necessary to obtain a certain knowledge by repeating many trials and errors. As a result, according to the present invention obtained, it is possible to extend the life of the cast iron product while suppressing the cost.

  What is revolutionary in the present invention is that the surface of the cast iron product is decarburized and filled with a glaze component mainly composed of a silicon compound substituted in the voids generated by the decarburization so that it is replaced with carbon. It is to become. As a result, a kind of anchor effect can be obtained by the glaze component. The feature of the present invention is that the glass lining layer can be firmly fixed to the surface of the cast iron product in this way and has been completed as a glass lining method. Therefore, in the glass lining method according to the present invention, a firing step is an important requirement in order to obtain a kind of anchor effect by the decarburization.

  The firing step required in the glass lining method according to the present invention is performed at a temperature of 973 to 1223K for 10 to 80 minutes. As the furnace, an electric furnace generally used for the glass lining method is used. The cast iron product to be treated is, for example, gray cast iron (FC150), and the glaze component is a general component composed of a component used for a glaze product or the like. However, other than the above, for example, all steel types included in JIS G 5501 gray cast iron products, and further cast iron products made of materials such as all steel types included in JIS G 5502 spheroidal graphite cast iron; Etc. can be applied to the present invention without problems. The condition of 973-1122 K at the above baking step for 10-80 minutes is necessary so that the glaze used in the present invention is completely melted and does not cause foaming or scorching.

  As the glass lining method of the present invention, a configuration in which a firing process in which a cast iron product whose surface is covered with glaze is put into a furnace is repeated a plurality of times is preferable. It is desirable that the firing step performed by putting the cast iron product whose surface is covered with glaze into the furnace is repeated at least twice at a temperature of 1073 K and a time of 40 minutes. Repeating the firing process a plurality of times means that a plurality of glass lining layers are formed, whereby a lining layer having a thickness of more than about 300 μm can be obtained, which is sufficient as an inner surface treatment layer of the joint. Is the thickness.

In addition, the linear expansion coefficient of cast iron (FC) is close to 11 to 13.5 × 10 ⁻⁶ , and the linear expansion coefficient of the glass lining part is close to 8 to 13 × 10 ^−6. Can be used. Further, the hardness of the surface of the glass lining portion is measured as Hv ≧ 500, which is a mechanical strength that can sufficiently withstand an external force expected to be applied by a washing machine.

  Since the present invention is constructed and operates as described above, a glass lining method can be suitably applied to cast iron products, and a glass having good corrosion resistance and wear resistance can be obtained by the method of the present invention. There is an effect that a lining cast iron product can be manufactured. The present invention also provides a glass-lined cast iron product that can reliably protect its inner surface from corrosion as a cast iron product used in a drainage pipe system that is exposed to harsh conditions such as a kitchen drainage pipe. be able to.

Hereinafter, the present invention will be described in more detail with reference to the drawings.
<Cast iron products>
First, the cast iron product which is the subject of the invention will be described. 1 and 2 show a joint 10 called an elbow as an example of a cast iron product according to the present invention. This elbow joint 10 has a bent portion 13 in the form of changing the flow path at right angles between the open ends 11 and 12. The cast iron product in this embodiment is gray cast iron (FC150). Glass lining layers 14 and 15 are formed on the inner and outer surfaces of the joint 10 according to the present invention. Since the drainage pipe for kitchen is assumed, the inner lining layer 14 that is easily exposed to a corrosive environment is formed on the outer surface. It is formed thicker than the lining layer 15 (see FIG. 2). The glass lining layer 14 on the inner surface is formed to be about three times as thick as the glass lining layer 15 on the outer surface.

  If an example of the connection structure of the drain pipe 16 using the said coupling 10 is shown concretely, it will become like FIG. This structure has a separation preventing structure in which a steel ball-containing packing 17 is disposed on the outer surface of the end portion of the drain pipe 16, and the connection ring 18 and the flange portion 19 of the joint 10 are tightened using bolts and nuts 26. . In the drawing, the steel ball 17a is used to obtain the biting action, but the joint capable of carrying out the present invention is not limited to this example, and other methods can be taken.

  As another example of the cast iron product according to the present invention, a case where it is carried out on the two-handed pan 20 will be described with reference to FIGS. The pan 20 is composed of a container 21 and a lid 22, and the container 21 is an embodiment of the present invention, but either the embodiment is attached to the lid 22 or, for example, is made of glass. But it ’s okay. Ductile cast iron (FCD) is used for the material of the pan 20 and is formed thin by precision casting.

  Since the container 21 is made of ductile cast iron (FCD), spheroidal graphite 23 exists independently (see FIG. 4), but the spheroidal graphite 23 also appears on the surface of the ductile cast iron. For this reason, since the spherical graphite 23 existing on the surface is decarburized, a void 24 is generated on the surface, so that the glaze component 25 is filled in the void 24. Accordingly, for the container 21 made of ductile cast iron (FCD), the glass lining layer is casted by casting the glaze component in the same manner as in the case of using cast iron products made of gray cast iron (FC), which will be described later. It can be firmly fixed to the product surface, and a kind of anchor effect can be obtained.

Next, the means and method of the present invention relating to the glass lining applied to the cast iron product will be described.
<Glue>
The ingredients and composition of the glaze are as follows.
Component _{A: SiO 2 + TiO 2 + ZrO} 2 = 40~75 wt%
However, the ratio of each element in A component is as follows.
SiO _2: 40~75 mass%
TiO _2: 0 to 15 wt%
ZrO ₂ : 0 to 10% by mass
If the component A is less than 40% by mass, the strength of the frit itself is lowered, and it is not preferable. If it exceeds 75% by mass, the frit viscosity of the frit is increased and the melting point of the frit composition is increased.

Component _{B: Na 2 O + K 2 O} + Li 2 O = 0.5~20 wt%
However, the ratio of each element in B component is as follows.
Na ₂ O: 0.5 to 20 wt%
K ₂ O: 0 to 15% by mass
Li ₂ O: 0 to 10% by mass
If the B component is less than 0.5% by mass, the frit meltability is deteriorated, and it is not preferable. If it exceeds 20% by mass, the linear expansion coefficient is increased and the balance of physical properties is lost.

C component: CaO + BaO + ZnO + MgO = 1-15 mass%
However, the ratio of each element in C component is as follows.
CaO: 1 to 15% by mass
BaO: 0 to 10% by mass
ZnO: 0 to 6% by mass
MgO: 0 to 5% by mass
If the C component is less than 1% by mass, it is insufficient for improving the alkali resistance of the frit. If it exceeds 15% by mass, the frit viscosity of the frit increases and the melting point of the frit composition increases. It is not preferable.

Component _{D: B 2 O 3 + Al 2} O 3 + Cr 2 O 3 + Fe 2 O 3 = 1~20 wt%
However, the ratio of each element in D component is as follows.
B ₂ O ₃ : 1 to 20% by mass
Al ₂ O ₃ : 0 to 10% by mass
Cr ₂ O ₃ : 0 to 10% by mass
Fe ₂ O ₃ : 0 to 10% by mass
If the D component is less than 1% by mass, the frit meltability is lowered, and the devitrification preventing effect is remarkably reduced. .

E component: CoO + MnO + NiO + CuO = 0 to 5 mass%
However, the ratio of each element in E component is as follows.
CoO: 0 to 5% by mass
MnO: 0 to 5% by mass
NiO: 0 to 5% by mass
CuO: 0 to 5% by mass
The component E contributes to improving the adhesion of the frit. However, if it exceeds 5% by mass, the foaming phenomenon during firing becomes remarkable, which is not preferable.

In addition, although the component described as 0 is not essential for vitrification, it has a relationship with auxiliary roles, such as viscosity, adjustment of a calcination temperature, and adhesiveness.

Firing process Glass lining method In the glass lining method, cast iron products are put into a furnace, whereby the graphite on the surface of the cast iron products is pre-decarburized, but this step can be performed as a pretreatment step. In addition, after the pretreatment step, a glazing step using a glaze composed of the components A to E can be performed. However, it is possible to perform a direct coating method in which the pretreatment step is omitted and the glaze composed of the components A to E is applied to the surface of the joint 10 which is a cast iron product. In order to obtain a glaze, it is produced as a fluidized glass lining liquid by treating with water as a dispersion medium by a conventional method of glaze production. Hereinafter, the glass lining method of the present invention will be described separately.
<Part 1>
The surface of the joint 10 which is a cast iron product is coated with the glaze composed of the components A to E, the cast iron product is put into an electric furnace, the cast iron product surface is decarburized, and the void generated by the decarburization is formed. Bake for 40 minutes at a temperature of about 1073 K to fill the glaze ingredients. The glazing and firing process is repeated three times for the joint to produce a glass-lined cast iron product.
<Part 2>
As a pretreatment step, the joint 10 which is a cast iron product is put into a furnace, whereby the graphite on the surface of the joint 10 is decarburized in advance at a temperature of 873 to 1223 K for 10 to 120 minutes, and then the surface of the cast iron product is glazed. The cast iron product is put into a furnace, and the cast iron product surface is decarburized, and fired at a temperature of 973 to 1223K for 10 to 80 minutes in order to fill the voids generated by the decarburization with the glaze component. The above glazing and firing steps are performed at least once on the inside of the joint to produce a glass-lined cast iron product.

The joint 10 which is a glass-lined cast iron product obtained by the method 1 has a smooth glass-lining layer. When the surface hardness was measured, a value of Hv ≧ 500 was obtained in terms of Wuckers hardness. The surface hardness equivalent to that of the joint 10 by the method 2 was also obtained. Since the performance test 1 regarding hardness was performed about the glass-lined cast iron product which concerns on this invention, here, a hardness test and its result are demonstrated as follows.
Evaluation purpose: To evaluate the hardness of the glass lining layer obtained by the present invention.
Evaluation method: JIS Z 2244 Vickers hardness test-According to the test method.
-Criteria: Hardness of 500Hv or more.
The test results are shown in Table 1 below. According to Table 1, an average value of 609 HV is obtained.
Table 1

＊一時間を二分して３０分間を冷却、３０分間を加熱する工程を１サイクルとし、低温・冷却と高温・加熱の変化に要する時間は３分以内とした。 The performance test 2 revealed that the cast iron product manufactured by the glass lining method according to the present invention has the glass lining layer firmly fixed to the cast iron product surface. In the performance test, rapid cooling and rapid heating were evaluated by applying thermal stress to the specimen, and the method is as follows.
・ Temperature profile: High temperature 100 ℃, Low temperature-10 ℃
・ Time required for low temperature to high temperature change: within 3 minutes ・ Movement cycle: 3, 5, 10, 20
Table 2 below shows the test results of the judgment criteria: no cracks reaching the casting substrate in the glass lining layer, and no peeling reaching the casting substrate in the glass lining layer.
Table 2

* One hour was divided into two, 30 minutes was cooled and 30 minutes was heated, and one cycle was taken as one cycle, and the time required to change between low temperature / cooling and high temperature / heating was within 3 minutes.

  From the facts shown by such performance tests 1 and 2, the inventors have inferred that the glass lining layer is fixed to the cast iron surface by a special mechanism. Therefore, in order to clarify the phenomenon that would have occurred at the interface between the glass lining layer and the cast iron product surface, an analysis by EPMA (Electron Probe Micro Analyzer) was attempted. As a result of the analysis, the facts supporting the novelty of the present invention were found, and the contents thereof will be mentioned next.

  The above analytical test was conducted by requesting the Saitama Industrial Technology Center. The requested product is the joint 10 of the glass-lined cast iron product obtained by the first method, and the requested items are analysis and mapping by an X-ray microanalyzer. FIG. 5 and FIG. 6 show reflected electron images as one of the test results. In FIG. 5, L1 represents a glass lining layer, L2 represents a decarburized layer, and L3 represents a cast iron layer. The layer of L2 is a surface layer of the cast iron layer, but the layer having a thickness of about 100 μm shown in the lower column as a scale is different from the cast iron layer L3 having a black streak pattern, and the glass lining layer L1 and I guess that it is decarburized from the relationship.

  FIG. 6 shows a backscattered electron image magnified to × 2000 while the magnification of FIG. 5 is × 100. When the magnified image of FIG. 6 is seen, it can be seen that the decarburized layer L2 that appears bright enters a dark or dotted line-like pattern from the surface layer. This dark-looking pattern extends from the surface layer, that is, the glass lining layer L1, and its end reaches a depth of about 100 μm as described above.

  Further, FIG. 7 shows a color map (the original figure is color drawing since it is color drawing, but color drawing is not permitted in the bylaws of the Patent Law, and is shown by tone drawing). FIG. 7 is a color map relating to Si, and the red color of the original drawing showing a high concentration is the glass lining layer L1 at the top of FIG. The majority of FIG. 7 occupies the blue decarburized layer L2 in the original drawing, and the decarburized layer L2 has a streak or dotted line pattern appearing from the surface layer, which is a silicon compound and is from the glass lining layer L1. It is what is growing.

  From the above analysis results and the facts shown in the color map, the silicon compound enters the decarburized surface layer of the cast iron layer L3 and is entangled with the cast iron layer L3, so that it exhibits the state like the anchor effect described above. It can be inferred with sufficient certainty.

It is a section explanatory view showing an example of the cast iron product manufactured by the glass lining method concerning the present invention. It is sectional explanatory drawing which expands and shows a part of the same as the above. It is a section explanatory view showing other examples of cast iron products concerning the present invention. It is sectional explanatory drawing which shows a part of the same typically. It is a 100-times-magnification backscattered electron image which shows the glass-lined cast iron product manufactured by the method of this invention. It is a reflected-electron image of 2000 times magnification in the principal part same as the above. Similarly, a color map of Si (silicon compound).

DESCRIPTION OF SYMBOLS 10 Joint 11, 12 Both ends of joint 13 Bending part of joint 14 Glass lining layer of inner surface 15 Glass lining layer of outer surface 16 Drain pipe 17 Packing 18 Connection ring 19 Flange part 20 Pot 21 Container 22 Lid 23 Spherical graphite 24 Gap 25 glaze ingredients

Claims (7)

The surface of the cast iron product is coated with a glaze, and the cast iron product surface is decarburized by the heat treatment of the cast iron product, and the void formed by the decarburization is filled with a glaze component. Glass lining cast iron products. 2. The glass lining cast iron product according to claim 1, wherein the cast iron product is exposed to a corrosive environment or high heat, and has a glass lining layer on at least a surface exposed to the corrosive environment or high heat. 6. The glass-lined cast iron product according to claim 5, wherein the cast-iron product is a pipe joint used in a drainage piping system, and the thickness of the glass lining layer on the inner surface is 300 [mu] m or more. In order to coat the surface of the cast iron product with glaze, decarburize the cast iron product surface, and fill the voids generated by decarburization with the glaze component, the cast iron product is put into a furnace, and the temperature is 973-1223K. A glass lining method for cast iron products, characterized by firing for 10 to 80 minutes. As a pretreatment step, the cast iron product is put into a furnace, whereby the graphite on the surface of the cast iron product is decarburized in advance for 10 to 120 minutes at a temperature of 873 to 1223K, and then the surface of the cast iron product is coated with glaze, The cast iron product is put into a furnace, the surface of the cast iron product is decarburized, and fired at a temperature of 973 to 1223K for 10 to 80 minutes in order to fill the voids generated by the decarburization with a glaze component. The glass lining method of the cast iron product according to claim 4. The glass lining method for a cast iron product according to claim 4 or 5, wherein a firing step in which a cast iron product whose surface is covered with glaze is put into a furnace is repeated a plurality of times. The glass lining of a cast iron product according to claim 4 or 5, wherein the firing step performed by putting the cast iron product whose surface is coated with glaze into the furnace is repeated at least three times at a temperature of 1073K and a time of 40 minutes. Method.

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