A ceramic composite pipe for desulfurization and its manufacturing process

Abstract

A ceramic composite pipe for desulfurization and its manufacturing process belong to the field of powder metallurgy preparation of composite pipes. A first pre-bonding layer is formed by spraying a slurry containing metal-based powder and a binder on the outer surface of a ceramic liner pipe, and a slurry containing a high melting point powder and a binder is sprayed on the outer surface of the first pre-bonding layer to form a second pre-bonding layer. Then, the metal matrix pipe and the ceramic liner pipe are assembled into a preform with the metal matrix pipe as the outer layer and the ceramic liner pipe as the inner layer. The preform is sintered to form a porous metallurgical sintering layer in the first pre-bonding layer, and a bonding sintering layer in the second pre-bonding layer. The present invention adopts a powder metallurgy composite process to manufacture a composite pipe, which simplifies the manufacturing process. The porous metallurgical sintering layer can ensure the combination with the ceramic liner pipe. The bonding sintering layer provides yielding properties while allowing a part of the low melting point metal in the porous metallurgical sintering layer to penetrate and form a metallurgical overlap point with the metal matrix pipe of the outer layer, thereby ensuring the composite strength of the inner and outer pipes.

Description

Technical Field

[0001] The invention belongs to the field of preparing composite pipes by powder metallurgy, and specifically relates to a ceramic composite pipe for desulfurization and a manufacturing process thereof. Background Art

[0002] In the prior art, ceramic composite pipes for desulfurization are generally produced by manufacturing a ceramic composite layer inside a steel pipe matrix. Since the melting point of ceramics is generally higher than that of the steel pipe matrix, the two cannot be slowly sintered. Therefore, in most processes, aluminum thermal combustion and other methods are used to quickly form a ceramic melt inside the steel pipe matrix and then the ceramic melt is quickly condensed to form a metallurgical composite with the steel pipe matrix.

[0003] The disadvantages of the above process are manifested in at least two aspects:

[0004] First, the rapid hot melt condensation composite method usually requires the use of centrifugal equipment, which requires high equipment investment and complex process. Moreover, the process conditions of the rapid hot melt condensation composite method, especially the temperature conditions, are difficult to control, resulting in the thickness of the formed ceramic layer being difficult to control.

[0005] Second, the ceramic layer obtained by solidifying the melt has a very high density and is metallurgically bonded to the steel pipe matrix to form a dense whole. When the ceramic composite pipe is used in a high-temperature environment for a long time, the difference in expansion coefficients between the metal and the ceramic causes the dense ceramic layer to be subjected to cold and heat stress for a long time, which is prone to cracks or ruptures, reducing its service life. Summary of the invention

[0006] To solve the above problems, the present invention provides a ceramic composite pipe for desulfurization and a manufacturing process thereof. The composite pipe is manufactured by a simple powder metallurgy composite process, which not only simplifies the process but also reduces the damage of the ceramic layer during the manufacturing process and during long-term high-temperature service.

[0007] The technical solution adopted by the present invention is:

[0008] The present invention first provides a ceramic composite pipe for desulfurization, comprising an inner layer material, an outer layer material and a composite stress relief layer located between the inner layer material and the outer layer material, the outer layer material is a metal matrix tube, the inner layer material is a ceramic liner tube, the composite stress relief layer is a composite sintered layer, comprising a porous metallurgical sintered layer adjacent to the ceramic liner tube and a bonding sintered layer adjacent to the metal matrix tube, the porous metallurgical sintered layer is formed by metallurgical sintering of a metal-based powder at a sintering temperature lower than the melting point of the metal matrix tube, and has pores formed during the sintering process, and the bonding sintered layer is formed by sintering and consolidating a high melting point powder in a non-metallurgical state.

[0009] In a further preferred embodiment, the metal-based powder comprises one or more metal powders, and the high melting point powder is metal powder, ceramic powder or a mixture thereof.

[0010] In an optional embodiment, the metal-based powder further comprises at least one non-metallic powder.

[0011] In a further preferred embodiment, the thickness of the inner layer material is smaller than the thickness of the outer layer material, and the thickness of the composite stress relief layer is smaller than the thickness of the inner layer material.

[0012] In a further preferred embodiment, the thickness of the bonding sintered layer is less than the thickness of the porous metallurgical sintered layer.

[0013] The present invention also provides a manufacturing process for the above-mentioned ceramic composite pipe for desulfurization, comprising the steps of:

[0014] S1, spraying a slurry containing metal-based powder and a binder on the outer surface of the ceramic lined pipe to form a first pre-bonding layer;

[0015] S2, spraying a slurry containing high melting point powder and a binder on the outer surface of the first pre-bonding layer to form a second pre-bonding layer;

[0016] S3, assembling the metal base tube and the ceramic liner tube obtained in step S2 into a preform having the metal base tube as an outer layer and the ceramic liner tube as an inner layer;

[0017] S4, sintering the preform, so that the first pre-bonding layer forms the porous metallurgical sintering layer, and the second pre-bonding layer forms the bonding sintering layer.

[0018] In a further preferred embodiment, after step S1 and after step S2, the ceramic lined pipe is dried respectively.

[0019] In a further preferred embodiment, the sintering in step S4 is performed in a vacuum sintering furnace or a protective atmosphere sintering furnace.

[0020] In a further preferred embodiment, in step S4, the temperature is directly raised to the final sintering temperature and then sintering is performed at a maintained temperature.

[0021] In a further preferred embodiment, the outer surface of the ceramic lined tube in step S1 is processed to have a roughened structure that is concave and / or convex on the surface.

[0022] Beneficial effects:

[0023] The ceramic composite pipe for desulfurization provided by the present invention and its manufacturing process adopt a simple powder metallurgy composite process to manufacture the composite pipe, and do not need to adopt aluminum thermal combustion and complex high-speed centrifugal technology, thereby simplifying the manufacturing process. In particular, through the unique composite stress relief layer, two guarantees are provided for stress relief, and it is dedicated to high-temperature service environment above 300 degrees Celsius. The porous metallurgical sintered layer is directly adjacent to the ceramic liner pipe to ensure the combination with the ceramic liner pipe. The bonding sintered layer has better yieldability because it has not reached the metallurgical state. At the same time, it can also allow a part of the low-melting point metal in the porous metallurgical sintered layer to penetrate, thereby forming many metallurgical overlap points with the metal matrix pipe of the outer layer, thereby ensuring the composite strength of the inner and outer pipes. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A structural principle diagram of a ceramic composite pipeline for desulfurization provided in an embodiment of the present invention.

[0025] Figure 2 Schematic diagram of the roughened structure of the outer surface of a ceramic lined pipe.

[0026] The components represented by the reference numerals in the figure are:

[0027] Inner layer material 1, roughened structure 11, outer layer material 2, composite stress relief layer 3, porous metallurgical sintered layer 31, bonding sintered layer 32. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0029] Example 1

[0030] See also Figure 1 This embodiment provides a ceramic composite pipe for desulfurization, including an inner layer material 1 and an outer layer material 2.

[0031] As a ceramic composite pipe for desulfurization, the inner layer material 1 is a ceramic lined pipe, such as an alumina ceramic pipe, and the outer layer material 2 is a metal matrix pipe, generally a steel pipe. In the above-mentioned prior art, the ceramic composite pipe for desulfurization is generally produced by manufacturing a ceramic composite layer inside a steel pipe matrix. Since the melting point of ceramic is generally higher than that of the steel pipe matrix, slow sintering of the two cannot be performed. Therefore, in most processes, aluminum thermal combustion and other methods are used to quickly form a ceramic melt inside the steel pipe matrix and then the ceramic melt is quickly condensed to form a metallurgical composite with the steel pipe matrix.

[0032] As introduced in the background technology, the disadvantages of the above-mentioned process of the prior art are manifested in at least the following two aspects: first, the use of this rapid hot melt condensation composite method usually requires the use of centrifugal equipment, which requires high equipment investment and complicated process. Moreover, the process conditions of this rapid hot melt condensation composite method, especially the temperature conditions, are not easy to control, which leads to the thickness of the formed ceramic layer being difficult to control; second, the ceramic layer obtained by solidifying the melt has a very high density and is metallurgically combined with the steel pipe matrix to form a dense whole. When the ceramic composite pipe is used in a high temperature environment for a long time, the difference in expansion coefficients between the metal and the ceramic causes the dense ceramic layer to be subjected to cold and heat stress for a long time, which is prone to cracks or ruptures, reducing the service life.

[0033] Different from the prior art, the embodiment of the present invention no longer adopts the production method of manufacturing the ceramic composite layer inside the steel pipe matrix, but directly adopts the prepared metal matrix tube and ceramic liner tube (that is, the metal matrix tube and the ceramic liner tube are both prefabricated parts), and the metal matrix tube and the ceramic liner tube are compounded through a powder metallurgy composite process.

[0034] like Figure 1 As shown, through the powder metallurgy composite process of the embodiment of the present invention, a composite stress relief layer 3 is formed between the outer layer material 2 and the inner layer material 1 as an intermediate connecting layer.

[0035] As the second important improvement of the embodiment of the present invention, the composite stress relief layer 3 is a composite sintered layer, including a porous metallurgical sintered layer 31 adjacent to the ceramic liner tube and a bonding sintered layer 32 adjacent to the metal matrix tube.

[0036] Furthermore, the porous metallurgical sintered layer 31 is formed by metallurgical sintering of a metal-based powder at a sintering temperature lower than the melting point of the metal matrix tube, and has pores formed during the sintering process. The metal-based powder described herein includes one or more metal powders, and is not limited to copper and aluminum alloys. It can be 100% composed of metal powders, and can also include at least one non-metallic powder, such as ceramic materials. It should be noted that the purpose of the sintering temperature being lower than the melting point of the metal matrix tube is to prevent the metal matrix tube from being damaged during the sintering process, and the metal-based powder having a sintering temperature lower than the melting point of the metal matrix tube means that the sintering temperature of the metal-based powder as a whole is lower than the melting point of the metal matrix tube. If the metal-based powder is a mixture of multiple metal materials or metal materials and non-metal materials, it is not excluded that there is a material whose melting point may be equal to or higher than the melting point of the metal matrix tube. For example, a certain amount of high-melting-point cast iron powder is added to the powder of mainly low-melting-point copper alloy, and the cast iron powder of not less than 2wt% can adjust the infiltration behavior of the copper alloy powder.

[0037] In addition, preferably, the porosity of the metal-based powder formed during the sintering process is above 35%.

[0038] Furthermore, the above-mentioned bonding sintered layer 32 is formed by sintering and consolidating high-melting-point powder in a non-metallurgical state. The high-melting-point powder mentioned here is preferably metal powder, ceramic powder or a mixture thereof, and other high-melting-point refractory materials are not excluded. Combined with the main purpose of the present invention, it can be easily understood that the "high melting point" here in the present application only needs to be achieved so that the powder is not metallurgically sintered during the sintering process, and its absolute melting point is not required to be very high.

[0039] like Figure 1 As shown, in order to adapt to the industrial application of ceramic composite pipes for desulfurization and to better carry out the connection and production of composite pipes, in the embodiment of the present invention, the thickness of the inner layer material 1 is controlled to be much smaller than the thickness of the outer layer material 2, so as to better play the basic supporting role of the external supporting layer and the working performance of the inner working layer, and the thickness of the composite stress relief layer 3 is even smaller than the thickness of the inner layer material 1, so as to control the material used in the middle layer as much as possible.

[0040] As for the relationship between the two layers in the composite stress relief layer 3, the porous metallurgical sintered layer is directly adjacent to the ceramic lined tube in order to ensure the bonding with the ceramic lined tube. The bonding sintered layer has better yieldability because it has not reached the metallurgical state, but it is also necessary to allow a portion of the low-melting-point metal in the porous metallurgical sintered layer to penetrate, thereby forming many metallurgical overlap points with the outer metal matrix tube. Therefore, it is preferred to design and adjust the sizes of the two while satisfying the requirement that the thickness of the bonding sintered layer 32 is less than the thickness of the porous metallurgical sintered layer 31.

[0041] Example 2

[0042] The present invention provides a manufacturing process for the ceramic composite pipe for desulfurization in Example 1. After the required metal base pipe and ceramic inner liner pipe are prepared, step S1 is implemented: spraying a slurry containing metal base powder and a binder on the outer surface of the ceramic inner liner pipe to form a first pre-bonding layer. The slurry preferably contains a pore-forming agent, and a binder with a large gas generation amount can also be used.

[0043] Preferably, after the ceramic lined pipe of step S1 is dried to dry the first pre-bonding layer, step S2 is performed: spraying a slurry containing high melting point powder and a binder on the outer surface of the first pre-bonding layer to form a second pre-bonding layer.

[0044] After the ceramic lined tube of step S2 is dried to dry the second pre-bonded layer (the drying process after step S1 above can also be directly combined with step S2), step S3 is implemented: the metal base tube and the ceramic lined tube obtained in step S2 are assembled into a preform with the metal base tube as the outer layer and the ceramic lined tube as the inner layer.

[0045] In the next step S4, the preform in step S3 is sintered in a vacuum sintering furnace or a protective atmosphere sintering furnace, so that the first pre-bonding layer is sintered after the binder is removed to form the porous metallurgical sintering layer 31, and the second pre-bonding layer is basically kept in a non-metallurgical state after the binder is removed to form the bonding sintering layer 32. The heating control technique of this step is not to set a special fat removal temperature section, but to directly heat up to the final sintering temperature and then perform heat preservation sintering, so that the porosity can be increased by relying on the rapid decomposition of the organic components in the binder in the process.

[0046] The starting point of the above technology provided by the embodiment of the present invention is to use a simple powder metallurgy composite process to produce a ceramic composite pipe for desulfurization, avoiding the use of aluminum thermal combustion and complex high-speed centrifugal technology, while protecting the ceramic liner pipe and improving the service life of the pipe. In particular, through the unique composite stress relief layer, two guarantees are provided for stress relief. The porous metallurgical sintered layer 31 is directly adjacent to the ceramic liner pipe to ensure the combination with the ceramic liner pipe. The bonding sintered layer 32 has better yieldability because it has not reached the metallurgical state. At the same time, Figure 1 As can be seen from the schematic diagram, the bonding sintered layer 32 can also allow a portion of the low-melting-point metal in the porous metallurgical sintered layer 31 to penetrate, thereby forming many metallurgical overlap points with the outer metal matrix tube, which appears as a mesh overlap on the entire contact surface, ensuring the composite strength of the inner and outer tubes.

[0047] Example 3

[0048] This embodiment is a preferred embodiment of Embodiment 2. Figure 2 As shown, before manufacturing the ceramic composite pipe for desulfurization according to the process provided above, a ceramic lined pipe with a micro-roughened structure 11 on the outer surface is selected. This micro-roughened structure 11 can be a micro-concave structure recessed on the surface as shown in the figure, or a micro-convex structure convex on the surface, or both. The depth or height is preferably less than 0.5 mm, or even smaller, reaching the micron level. This structure can be in different shapes such as dots and lines. Preferably, its total area coverage of the outer surface of the ceramic lined pipe is more than 10%, but preferably not more than 30%.

[0049] The principle of improvement of this embodiment is that even if the porous metallurgical sintered layer is directly adjacent to the ceramic lined pipe, due to the difference in the natural properties of the two materials, metal and ceramic, there is a certain degree of deficiency in the joint strength. This micro-roughened structure can further improve the bonding strength between the intermediate layer and the ceramic lined pipe without affecting the release of all-directional stress.

[0050] Verify the effect

[0051] In production, the steel metal base pipe and the α-alumina ceramic liner pipe are connected according to the process described in Example 2. The metal-based powder used in the composite stress relief layer is brass powder (cast iron powder regulator accounts for about 4.5%). The spray slurry contains a polymer binder and a carbonate compound. The high melting point powder directly uses cheap micron cast iron powder. The spray slurry does not contain carbonate compounds. Sintering below 800°C can produce a ceramic composite pipe for desulfurization that meets production requirements. This pipe is applied to the flue gas treatment equipment of a forging enterprise. After being used at high temperature for three months, it is dismantled for cleaning and inspection. There is almost no hidden cracks on the inner surface of the ceramic, and the apparent quality far exceeds the commercially available ceramic composite pipe of the same material in service at the same time.

[0052] The high melting point powder was successively replaced with alumina ceramic powder and an equal proportion mixture of alumina ceramic powder and cast iron powder (all micron powders), and the effect was the same.

[0053] The above description is only a preferred specific implementation manner of the present invention. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A manufacturing process for a ceramic composite pipe for desulfurization, characterized in that: The ceramic composite pipe for desulfurization comprises an inner layer material (1), an outer layer material (2) and a composite stress relief layer (3) located between the inner layer material (1) and the outer layer material (2); the outer layer material (2) is a metal matrix tube, the inner layer material (1) is a ceramic liner tube, the composite stress relief layer (3) is a composite sintered layer, comprising a porous metallurgical sintered layer (31) adjacent to the ceramic liner tube and a bonding sintered layer (32) adjacent to the metal matrix tube; the porous metallurgical sintered layer (31) is formed by metallurgical sintering of a metal-based powder at a sintering temperature lower than the melting point of the metal matrix tube, and has pores formed during the sintering process; the bonding sintered layer (32) is formed by sintering and consolidating a high melting point powder in a non-metallurgical state; The manufacturing process comprises the steps of: S1, spraying a slurry containing metal-based powder and a binder on the outer surface of the ceramic lined pipe to form a first pre-bonding layer; S2, spraying a slurry containing high melting point powder and a binder on the outer surface of the first pre-bonding layer to form a second pre-bonding layer; S3, assembling the metal base tube and the ceramic liner tube obtained in step S2 into a preform having the metal base tube as an outer layer and the ceramic liner tube as an inner layer; S4, sintering the preform, so that the first pre-bonding layer forms the porous metallurgical sintered layer (31), and the second pre-bonding layer forms the bonding sintered layer (32); The high melting point powder is metal powder, ceramic powder or a mixture thereof, and "high melting point" means that the melting point is such that the powder is not metallurgically sintered during the sintering process.

2. The manufacturing process of a ceramic composite pipe for desulfurization according to claim 1, characterized in that: The metal-based powder comprises one or more metal powders.

3. The manufacturing process of a ceramic composite pipe for desulfurization according to claim 2 is characterized in that: The metal-based powder further comprises at least one non-metallic powder.

4. The manufacturing process of a ceramic composite pipe for desulfurization according to claim 1, characterized in that: The thickness of the inner layer material (1) is smaller than the thickness of the outer layer material (2), and the thickness of the composite stress relief layer (3) is smaller than the thickness of the inner layer material (1).

5. The manufacturing process of a ceramic composite pipe for desulfurization according to claim 4, characterized in that: The thickness of the bonding sintered layer (32) is smaller than the thickness of the porous metallurgical sintered layer (31).

6. The manufacturing process of the ceramic composite pipe for desulfurization according to claim 1, characterized in that: After step S1 and after step S2, the ceramic lined pipe is dried respectively.

7. The manufacturing process of the ceramic composite pipe for desulfurization according to claim 1, characterized in that: The sintering in step S4 is performed in a vacuum sintering furnace or a protective atmosphere sintering furnace.

8. The manufacturing process of the ceramic composite pipe for desulfurization according to claim 1, characterized in that: In step S4, the temperature is directly raised to the final sintering temperature and then sintered at the maintained temperature.

9. The manufacturing process of the ceramic composite pipe for desulfurization according to claim 1, characterized in that: In step S1, the outer surface of the ceramic lined pipe is processed to have a roughened structure (11) that is concave and / or convex on the surface.

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