CN120819692A - A wear-resistant, high-temperature oxidation-resistant and deformation-resistant small-diameter composite pipe and its preparation method - Google Patents

Abstract

The invention discloses a wear-resistant high-temperature oxidation-resistant deformation-resistant small-caliber composite pipe and a preparation method thereof, and belongs to the technical field of composite pipe materials. The composite tube includes an inner layer (Al ₂O₃ ceramic), an intermediate layer tube (310S or 314 stainless steel), a protective layer (Gr ₂O₃ or SiO ₂), a thermally insulating air gap layer, and a deformation preventing tube. The combination of the functions of wear resistance, high-temperature oxidation resistance and deformation resistance is realized through the cooperation of the multilayer structure. The inner layer is prepared by adopting a self-propagating dead weight separation process, the Vickers hardness is more than or equal to 1500HV, the wear resistance is excellent, the middle layer pipe is high-temperature resistant and provides structural support, a Gr ₂O₃ or SiO ₂ protective layer is formed on the outer layer of the middle layer pipe in situ to enhance the high-temperature oxidation resistance, a 0.1-1mm heat insulation air gap layer is reserved between the middle layer pipe and the deformation-resistant pipe and between the middle layer pipe and the multi-layer deformation-resistant pipe to slow down heat transfer, the deformation-resistant pipe is of a segmented structure (100-500 mm in each segment), is dip-coated with high-temperature resistant paint, telescopic gaps of 0.2-10mm are arranged in a staggered mode in a segmented interval, and is fixed through plug welding and used for relieving thermal stress, so that the wear resistance, high-temperature oxidation resistance and deformation resistance are realized cooperatively. Enhancing the deflection resistance. The composite pipe is suitable for high-temperature high-wear-resistance working conditions of 1000-1350 ℃, has excellent comprehensive performance and stable structure, and can be widely applied to industries such as metallurgy, chemical industry and the like.

Description

Wear-resistant high-temperature oxidation-resistant deformation-resistant small-caliber composite pipe and preparation method thereof

Technical Field

The invention belongs to the technical field of composite pipes, in particular to a composite pipe suitable for high-temperature and high-wear working conditions, and particularly relates to a multi-layer small-caliber composite structure pipe with wear resistance, high-temperature oxidation resistance and deformation resistance and a preparation method thereof.

Background

In industrial production, the pipe under the working condition of high temperature and high abrasion faces the challenge of multiple performances, namely on one hand, the inner wall of the pipe is subjected to strong abrasion by conveying media (such as high-temperature slag, ore pulp, blast furnace coal injection and the like), so that the pipe wall is thinned and leaked, on the other hand, the high-temperature oxidation of the pipe is accelerated by a high-temperature environment (more than 1000 ℃), the structural strength is reduced, and in addition, the deformation (such as bending, swelling and cracking) of the pipe caused by uneven thermal expansion at high temperature directly influences the safety and the service life of the system.

In the prior art, the pipe material made of a single material and the simple composite pipe material are difficult to meet the comprehensive requirements, namely, a stainless steel pipe (such as 310S) and the like have certain high temperature resistance, but the oxidation rate is high at the high temperature of 1000 ℃, the wear resistance is poor, the pipe material is easy to wear and oxidation failure after long-term use, and the pipe material is easy to deform and bend in a high-temperature environment. Ceramic tubes (such as Al ₂O₃ ceramic) and the like have excellent wear resistance, but have large brittleness, poor impact resistance, difficult metal connection and easy fracture due to thermal stress at high temperature. The traditional composite pipe (such as a stainless steel-ceramic composite pipe) mostly adopts an integral outer layer wrapping structure, the difference of thermal expansion coefficients of an outer layer and an inner layer is large, and interfacial stress is easy to generate at high temperature, so that layering and integral deformation are caused. At the same time, the glass fiber reinforced plastic composite material is in a high-temperature environment for a long time, the outer surface is severely oxidized. And is easy to deform and bend at high temperature. There are also composite tubes in which a multi-layer high temperature resistant steel tube is sleeved with a ceramic composite tube, but the durable high temperature resistance of the multi-layer high temperature resistant steel tube is below 1100 ℃, so that the high temperature oxidation and thermal deformation cannot be fundamentally solved.

Therefore, developing a composite pipe which realizes the synergistic effect of wear resistance, high temperature oxidation resistance and deformation resistance through structural optimization becomes a key for solving the technical problems.

Disclosure of Invention

Object of the invention

The invention provides a wear-resistant high-temperature oxidation-resistant deformation-resistant small-caliber composite pipe (hereinafter referred to as composite pipe) and aims to overcome the defects that a composite pipe in the prior art is single in performance and easy to deform under the working condition of high temperature and high wear, and provides a small-caliber composite pipe (the drift diameter is DN 10-DN 40) with stable structure and excellent comprehensive performance and a preparation method thereof, and the organic combination of the wear resistance, high-temperature oxidation resistance and deformation resistance is realized through the cooperation of a multilayer structure design and a process.

(II) technical scheme

In order to achieve the aim, the invention provides a small-caliber composite pipe with the functions of wear resistance, high-temperature oxidation resistance and deformation resistance, which structurally comprises 5 parts, namely an inner layer (Al ₂O₃ ceramic), an intermediate layer pipe, a protective layer, a heat insulation air gap layer and a deformation-resistant pipe, wherein the deformation-resistant pipe can be formed by a single layer in other 4 parts or can be formed by two or more layers in other 4 parts. The method comprises the following steps:

The inner layer (Al ₂0₃ ceramic) is prepared by self-propagating gravity separation process. The Vickers hardness of the ceramic is up to more than 1500HV, the wear resistance is 10-20 times that of stainless steel, and the ceramic can effectively resist the abrasion of a conveying medium. The self-propagating process utilizes a chemical exothermic reaction to melt and bond the ceramic precursor to the inner surface of the intermediate tube. The bonding strength can be above 100MPa, and the ceramic layer is prevented from falling off.

The middle layer tube is 314 or 310S stainless steel. The Gr and Ni elements can form a stable oxide layer at high temperature, the service temperature can reach more than 1200 ℃, the oxidation resistance is more excellent, the Gr and Ni elements both have good high-temperature strength, the tight combination of the middle layer pipe and the inner layer (Al ₂0₃ ceramic) improves the integral rigidity (the bending strength is improved by more than 30 percent compared with single stainless steel) and can provide foundation structural support as the middle layer pipe.

The protective layer is a high-temperature in-situ protective layer of Gr ₂O₃ (1-5 μm) formed on the outer layer of the 310S tube and SiO ₂ (3-8 μm) formed on the outer layer of the 314 tube at the high temperature of 2200 ℃ in the self-propagating reaction process, so that the high-temperature oxidation resistance is obviously improved.

A gap of 0.1-1mm is reserved between the outer surface of the middle layer tube and the inner surface of the deformation-preventing tube, so that a heat-insulating air gap layer is formed. If the deformation-preventing pipe is formed into two or more layers, a gap of 0.1-1mm is also reserved between the inner layer and the outer layer of the deformation-preventing pipe, and a heat-insulating air gap layer is also formed. The heat transfer between each layer of deformation-preventing pipe and the middle layer pipe is slowed down, so that the high-temperature oxidation resistance and high Wen Fangbian shape performance of the middle layer pipe and each layer of deformation-preventing pipe are obviously improved. Wherein, each section of the deformation-preventing pipe is a 310S or 314 stainless steel pipe, and the whole body is dip-coated with high temperature resistant heat insulation coating (such as ZS-322 coating, which can work stably at a high temperature of about 2000 ℃)

The length of each section of the deformation-preventing pipe with the segmented structure is selected between 100mm and 500mm, the expansion gap is reserved between 0.2 mm and 10mm (selected according to the technical requirements of the length, thickness and the like of the composite pipe), for example, two layers or multiple layers are sleeved, the expansion gaps are reserved between 0.2 mm and 10mm of the same gap value, but the expansion gaps of all layers cannot be arranged at the same axial position in a staggered mode. The segmented nesting can provide local support and enhance the flexural resistance of the composite tube. And the deformation-preventing pipe and the middle layer pipe or the deformation-preventing pipes are fixed by symmetrical plug welding or multi-point uniform plug welding in the middle of each section, so that synchronous stress between the middle layer pipe and the deformation-preventing pipes or between the deformation-preventing pipes is ensured, the thermal expansion difference is avoided, and the warping caused by thermal stress is reduced. The whole body has the functions of heat insulation, high-temperature oxidation resistance and high-temperature deformation resistance.

The above structure cooperates to obviously improve the comprehensive properties of the composite pipe, such as wear resistance, high-temperature oxidation resistance, deformation resistance and the like in the high-temperature environment with the temperature of more than 1200 ℃.

The invention also provides a preparation method of the composite pipe, which comprises the following steps:

Step 1, preparation of inner layer and middle layer tube

Selecting proper 310S and 314 stainless steel pipes as intermediate pipes according to market and technical requirements, and removing surface oil stains by adopting ultrasonic cleaning (a cleaning agent is 5% NaOH solution, the temperature is 60 ℃ and the time is 30 min).

Preparing inner layer (Al ₂O₃ ceramic) by self-propagating dead weight separation process, and properly adjusting thermit ratio to control combustion temperature at 2200 deg.C. Meanwhile, the outer surface of the middle layer tube is naturally oxidized at high temperature to form a Gr ₂O₃ or SiO ₂ protective layer.

Step 2, assembling the deformation-preventing pipe

The deformation-preventing pipe is prepared by selecting 310S and 314 stainless steel pipes according to market and technical requirements (the inner diameter of the deformation-preventing pipe is larger than the outer diameter of the middle layer pipe by 0.1-1mm, so as to ensure gaps, such as two or more layers of deformation-preventing pipes, wherein the inner diameter of the outer deformation-preventing pipe is also larger than the outer diameter of the inner deformation-preventing pipe by 0.1-1mm, the thickness of the deformation-preventing pipe is 2-3 mm), cutting the deformation-preventing pipe into segments of 100-500mm according to the length of the middle layer pipe and the technical requirements, reserving 0.2-10mm expansion joints between the segments, such as two or more layers of expansion joints, wherein the expansion joints are respectively reserved with the same gap value of 0.2-10mm, but the expansion joints of all layers cannot be distributed in the same axis position in a staggered manner. (avoiding the defects of hot cracking, folding, swelling and the like caused by temperature fluctuation, heat expansion and cold contraction)

And cleaning agent for the segmented deformation-preventing pipes is 5% NaOH solution, the temperature is 60 ℃, and the time is 30min to remove oil stains on the surfaces. The whole is dip-coated with high temperature resistant heat insulation coating (as ZS 322), the working temperature is controlled between 10 ℃ and 70 ℃ during dip-coating, and the room temperature is cooled by natural air.

And (3) sleeving the segmented deformation-preventing pipes in sequence along the axial direction of the middle pipe, and controlling the gaps by laminating fusible rings (ring diameter=the size of the heat insulation air gap layer) on the outer surface of the middle pipe, wherein if the deformation-preventing pipes are two or more layers, the layers are sleeved and controlled to be in gaps according to the same method, but one layer is required to be sleeved and fixed, and the other layer is required to be sleeved. Graphite gaskets (the thickness of the gaskets=the size of the telescopic gap) are respectively arranged at the two ends of each section of deformation-preventing pipe to ensure uniform gaps, and the deformation-preventing pipe is fixed by a temporary clamp after being sleeved so as to prevent each layer of pipe from sliding. ( It shows that the fusible ring can be naturally fused at high temperature of more than 500 ℃. The graphite gasket may naturally fracture upon telescoping. )

Step 3, fixing the deformation-preventing pipe

The plug welding process comprises symmetrically distributing 2 plug welding holes or uniformly distributing multiple plug welding holes (with aperture of phi 6-phi 10 according to pipe diameter of outer layer) in the middle of each section of deformation-preventing pipe by adopting numerical control plug welding equipment (such as NBC-500), welding with current of 80-150A (thicker outer layer and larger current) for 1-2S, removing spatter after Ar (flow of 15-20L/min), and checking that the welding spot has no air hole and crack.

(III) beneficial effects

Compared with the prior art, the invention has the following beneficial effects:

1. The composite pipe has excellent comprehensive performance, the inner layer Al ₂O₃ ceramic realizes high wear resistance (the wear amount is less than or equal to 0.01 g/h), the protective layer on the outer surface of the middle layer pipe ensures that the high-temperature oxidation weight loss rate is less than or equal to 0.5g/m ² · h and the high-temperature oxidation resistance performance is remarkably improved at about 1200 ℃, and the deformation-preventing pipe is integrally dip-coated with the heat-insulating high-temperature-resistant heat-preserving coating and adopts a sectional structure design to ensure that the composite pipe is not deformed under the heat shock at about 1200 ℃ and meets the severe working condition.

2. The structure stability is high, the problems of thermal expansion mismatch are cooperatively solved by segmental nesting, plug welding, gap design and coating protection, the interface bonding strength is high (more than or equal to 100 Mpa), the layering risk is avoided, the overall bending strength is more than or equal to 300Mpa, and the deflection is less than or equal to 0.5mm/m (load 1000N). The deformation-preventing pipe is integrally dip-coated with heat-insulating high-temperature-resistant heat-insulating paint, and the high-temperature-resistant metal oxide in the paint can generate lattice phase change at high temperature, so that the change of the packing density of the paint is caused, and a net-shaped true space zone is naturally formed to play a role in shielding heat energy. The heat conductivity coefficient can reach 0.035W/m.k (the coating is cooled to 70 ℃ above 1000 ℃ under the heating)

3. The process economy is good, the self-propagating dead weight separation process can synchronously finish the preparation of the ceramic inner layer and the protective layer, no additional high-temperature oxidation treatment is needed, the plug welding process is simple and easy to operate, batch production is used, and the manufacturing cost is low. The dip-coating process is simple and convenient, and is also very suitable.

4. The method has wide application range, can select the parameters such as the material (310S or 314), the ceramic thickness, the layering segmentation length and the like of the middle layer pipe and the deformation-preventing pipe according to working conditions, and is suitable for various occasions with the temperature of 1000-1350 ℃ and the abrasion loss of 0.05-0.5 g/h.

Drawings

For a clearer description of the structure of the present invention, the following description is made with reference to the accompanying drawings;

FIG. 1 is a schematic view of a radial cut of a composite tube according to the present invention

FIG. 2 is an axial partial schematic view of a composite tube according to the present invention

In the figure, the structure comprises a 1-middle layer pipe, a 2-inner layer (Al ₂O₃ ceramic), a 3-protective layer (Gr ₂O₃、SiO₂), a 4-deformation-proof pipe, a 5-heat-insulating air gap layer and a 6-plug welding point

Note that in the drawing, the inner surface of the middle layer tube 1 is an Al ₂O₃ ceramic layer 2, the outer surface is a Gr ₂O₃ or SiO ₂ protective layer 3, the deformation preventing tubes 4 are respectively sleeved outside the middle layer tube 1, and a heat insulation air gap layer 5 is arranged between the two layers. If the deformation preventing pipe 4 is formed by sleeving two or more layers, the outer diameter of the inner deformation preventing pipe is also formed into the heat insulation air gap layer 5 with the inner diameter of the outer deformation preventing pipe, and the plug welding points 6 are symmetrically distributed (or uniformly distributed at multiple points) in the middle of the deformation preventing pipe 4, so that the deformation preventing pipe 4 is fixed with the middle layer pipe 1 or each layer of deformation preventing pipe 4.

Detailed Description

The invention is further illustrated by the following specific examples, but the invention is not limited to this example;

the embodiment is a composite pipe (coal injection gun) suitable for conveying pulverized coal in 1350 ℃ wind-temperature metallurgy iron making.

Stainless steel tube with thickness of 2.5mm on inner surface of middle layer tube 1:310S, diameter of 27mm x 3mm x 1000mm (outer diameter of wall thickness of wall of length of wall) inner layer of Al ₂O₃ ceramic 2, protective layer of 10 μm thickness of Gr ₂O₃ 3 anti-deformation tube 4:314 stainless steel tube with thickness of 32mm x 2.2mm (outer diameter of wall) is formed on outer surface of the inner layer tube, cut into 200mm long sections, expansion joint of 2mm between sections and interval of 0.3mm between middle layer tube 1 (the composite tube is single-layer anti-deformation tube) dip-coating ZS-322 high temperature resistant heat insulation paint.

The plug welding points 6 are symmetrically distributed in the middle of each section of deformation-preventing pipe 4, the diameter of each welding point is 8mm, and the welding current is 100A and the time is 2S.

The preparation method comprises the following steps:

1. After the 310S stainless steel pipe is cleaned by NaOH, an inner layer (Al ₂O₃ ceramic) 2 is obtained by adopting a self-propagating dead weight separation process

2. When the inner layer (Al ₂O₃ ceramic) 2 is prepared, the thermite proportion is properly adjusted to control the reaction temperature to be about 2200 ℃ to obtain Gr ₂0₃ oxidation protection layer 3

Cutting the deformation-preventing pipe 4 according to 200mm of each section, using a cleaning agent which is 5% NaOH solution, removing oil stains on the surface at 60 ℃ for 30min, and naturally drying. The whole dip-coating ZS-322 high temperature resistant heat insulation coating is naturally dried, and the working temperature is controlled between 10 ℃ and 70 ℃ during dip-coating. And then, punching phi 8 holes in the middle of each section of deformation-preventing pipe for sleeving, and when sleeving, laminating and placing a fusible ring with the ring diameter of 0.3mm on the outer surface of the middle layer pipe, so as to ensure that the gap of the heat insulation air gap layer is 0.3mm, controlling the gap of each section by using a graphite gasket with the diameter of 1mm, and fixing by using a clamp.

3. Numerical control plug welding to obtain composite pipe

And performing plug welding on each hole of the deformation-preventing pipe by adopting numerical control plug welding equipment NBC-500, wherein the welding parameters are that the current is 100A, the welding time is 2S, the splash is removed after the Ar (the flow is 15L/min) protective gas is welded, and the welding spot is checked to be free of air holes and cracks.

The performance test shows that the coal powder (Vickers hardness 1500 HV) is conveyed at 1350 ℃ under the air temperature, the abrasion loss of the inner wall is 0.08mm, the oxidation weight loss rate is 0.3g/m ² · h, and the straightness deviation of the coal powder conveyed at 1350 ℃ under the air temperature is 0.1mm/m, and the coal powder has no obvious change.

The above examples are only preferred embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (7)

1. The wear-resistant high-temperature oxidation-resistant deformation-resistant small-caliber composite pipe is characterized by comprising an inner layer (Al ₂O₃ ceramic), a middle layer pipe, a protective layer, a heat-insulating air gap layer and an deformation-resistant pipe which are sequentially arranged from inside to outside;

The inner layer is an Al ₂O₃ ceramic layer and is prepared by a self-propagating dead weight separation process, and is combined with the inner surface of the middle layer pipe, and the combination strength is more than or equal to 100MPa;

the middle layer pipe is a 310S or 314 stainless steel pipe;

the protective layer is an oxide layer formed on the outer surface of the middle layer pipe in situ at high temperature, wherein the outer layer of the 310S stainless steel pipe forms a Gr ₂O₃ layer with the thickness of 1-5 mu m, and the outer layer of the 314 stainless steel pipe forms a SiO ₂ layer with the thickness of 3-8 mu m.

The heat insulation air gap layer is a gap between the outer surface of the middle layer pipe and the inner surface of the deformation preventing pipe, and the size of the gap is 0.1-1mm;

The deformation-preventing pipe is of a segmented structure, the length of each segment is 100-500mm, a telescopic gap of 0.2-10mm is reserved between the segments, the deformation-preventing pipe base body is a 310S or 314 stainless steel pipe, the whole body is dip-coated with high-temperature-resistant heat-insulating paint, and the deformation-preventing pipe is fixed with the middle layer pipe through symmetrical plug welding or multi-point uniform plug welding.

2. The composite tube of claim 1, wherein the deformation preventing tubes are two or more layers, a heat insulation air gap layer of 0.1-1mm is reserved between every two adjacent layers of deformation preventing tubes, and the expansion gaps of the deformation preventing tubes of each layer are distributed in a staggered manner and are not in the same axis position.

3. The composite tube of claim 1, wherein the high temperature resistant, thermally insulating coating is ZS-322 coating.

4. The composite tube of claim 1, wherein the composite tube has an electrical path of DN10-DN40.

5. A method for preparing the wear-resistant high-temperature oxidation-resistant deformation-resistant small-caliber composite pipe as claimed in any one of claims 1 to 4, comprising the following steps:

Step 1, preparation of inner layer and middle layer tube

Selecting a 310S or 314 stainless steel pipe as an intermediate layer pipe, and removing oil stains on the surface by ultrasonic cleaning, wherein the cleaning agent is 5% NaOH solution, the cleaning temperature is 60 ℃, and the cleaning time is 30min.

And preparing an inner layer, namely preparing an Al ₂O₃ ceramic inner layer on the inner surface of the middle layer pipe by adopting a self-propagating dead weight separation process, so that the ceramic layer is combined with the inner surface of the middle layer pipe.

Step 2, processing and assembling the deformation-preventing pipe

Pretreatment of deformation-preventing pipe, namely cutting 310S or 314 stainless steel pipe into segments of 100-500mm, ultrasonic cleaning to remove surface oil stains, cleaning with 5% NaOH solution at 60 ℃ for 30min, and drying. The whole is dip-coated with high temperature resistant heat insulation coating and dried.

And (3) sleeving and fixing, namely sleeving the pretreated deformation-preventing pipe segment on the outer side of the middle pipe, forming a heat insulation air gap layer with the thickness of 0.1-1mm between the outer surface of the middle pipe and the inner surface of the deformation-preventing pipe, reserving a telescopic gap with the thickness of 0.2-10mm in a segment manner, and fixing the deformation-preventing pipe and the middle pipe through symmetrical plug welding or multi-point uniform plug welding.

6. The method according to claim 5, wherein when the deformation preventing tube is formed by two or more layers, after the layers are sleeved in a segmented manner, a heat insulation air gap layer with the thickness of 0.1-1mm is reserved between the adjacent layers, the expansion gaps of the layers are distributed in a staggered manner, and the deformation preventing tube of each layer is fixed by plug welding.

7. The method according to claim 5, wherein the high temperature resistant heat insulation coating in step 2 is ZS-322 coating.