CN114540747B - Preparation device and application method of inner surface gradient reinforced steel pipe - Google Patents
Preparation device and application method of inner surface gradient reinforced steel pipe Download PDFInfo
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- CN114540747B CN114540747B CN202210090211.3A CN202210090211A CN114540747B CN 114540747 B CN114540747 B CN 114540747B CN 202210090211 A CN202210090211 A CN 202210090211A CN 114540747 B CN114540747 B CN 114540747B
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/40—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using liquids, e.g. salt baths, liquid suspensions
- C23C8/42—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using liquids, e.g. salt baths, liquid suspensions only one element being applied
- C23C8/48—Nitriding
- C23C8/50—Nitriding of ferrous surfaces
Abstract
The invention relates to a preparation device and an application method of an inner surface gradient reinforced steel pipe, belonging to the field of inner surface reinforcement of pipe members. The device comprises a molten salt pool, a steel pipe, a connecting pipe, a high-temperature molten salt pump and a liquid return pipe. All the components are connected in sequence, and the steel pipe is vertical to the horizontal surface of the molten salt in the molten salt pool. The invention organically combines a high-temperature molten salt pump with equipment such as a traditional salt bath nitriding heat treatment furnace and the like, and provides a flowing molten salt nitriding process. The inner surface strengthening can be carried out on steel pipes with different lengths, calibers, wall thicknesses and inner surface structures. Through the implementation of the method, the position of the steel pipe does not need to be moved and adjusted in the whole nitriding process, the steel pipe is not influenced by nitriding media except the inner surface, and the radial and axial gradient reinforcement of the inner surface of the steel pipe is realized.
Description
Technical Field
The invention belongs to the field of strengthening of the inner surface of a pipe member, and particularly relates to a device for preparing an inner surface gradient strengthened steel pipe and an application method.
Background
In daily use, the steel pipe generally needs to meet the requirements of actual working conditions through inner surface strengthening treatment, and for nitriding process, no matter the traditional gas nitriding and salt bath nitriding, or plasma nitriding, the method for strengthening the inner surface of the steel pipe, such as TWI260954B, is a three-type mode, at present, the whole steel pipe is basically placed into chemical heat treatment equipment, and finally, the inner and the outer of the steel pipe basically show the same strengthening state.
Meanwhile, the existing salt bath nitriding process methods such as CN113088868A and CN111979512A obtain reinforced layers with uniform overall performance, and can meet actual requirements in common service working conditions, but in part of service working conditions requiring two ends with different performance characteristics, one end cannot well meet the service requirements and is damaged in advance, so that the service life of the whole pipe is influenced.
In summary, there is no steel pipe preparation apparatus and method that has both performance and cost advantages, only treats the inner surface and can meet different performance requirements at two ends of the steel pipe, and the existing steel pipe nitriding apparatus and method have the following problems:
(1) The whole is relatively uniform, and the axial and radial performance gradient change of the inner surface of the steel pipe cannot be realized;
(2) The nitriding of the inner surface of the pipe cannot be realized, and the cleaning of the outer surface is kept without influence;
(3) Large length-diameter ratio steel pipes require extremely deep and long salt bath furnaces, which causes waste of molten salt materials and energy.
Disclosure of Invention
Aiming at the defects and shortcomings of the prior art, the invention provides a device for preparing an inner surface gradient reinforced steel pipe and an application method thereof.
The utility model provides an internal surface gradient reinforces steel pipe preparation facilities, contains molten salt pond, preceding connecting pipe, steel pipe, connecting pipe, high temperature molten salt pump, returns the liquid pipe, and all components connect gradually, and the steel pipe is perpendicular to molten salt horizontal plane in the molten salt pond.
Preferably, the wall of the molten salt bath is provided with a heating system for heating and melting the salt for salt bath nitriding and ensuring that the molten salt is at a relatively stable temperature. The heating system comprises a heating pipe, an intelligent temperature controller and a thermocouple, can measure and feed back the temperature of the molten salt in real time, adjusts the running state of the heating pipe according to the set temperature, and keeps the temperature of the molten salt stable and controllable.
Preferably, in order to prevent that high temperature fused salt from having high temperature corrosion to the interface, causing the fused salt to reveal, all adopt high temperature resistant sealing device to seal between connecting pipe and the steel pipe, between connecting pipe and the high temperature fused salt pump and between high temperature fused salt pump and the liquid return pipe.
Preferably, the metal sealing device can select any one of a sealed metal pipe joint, a metal surface sealing element (refer to an SKF metal surface sealing element HDDF), a spring-enhanced metal O ring, an annular sealing metal gasket, a pressing fitting, a metal sleeve and the like according to the appearance, the material and other properties of the steel pipe, or a fluorine rubber ring is matched with a cooling system, so that the leakage of the molten salt at the joint can be effectively prevented.
Preferably, in order to ensure the realization of the nitriding process, the molten salt pool is provided with molten salt, and cyanate ions are generated after the molten salt is molten, so that active ions are provided for the salt bath nitriding.
Preferably, there is preceding connecting pipe between molten salt pond and the steel pipe, and preceding connecting pipe stretches into in the fused salt, and protection steel pipe surface does not receive the fused salt to influence, guarantees simultaneously that nitriding process in fused salt horizontal plane descends and still can carry out the fused salt circulation, prevents that the fused salt horizontal plane decline that produces from causing the steel pipe lower extreme can't absorb the fused salt when many steel pipes use a molten salt pond simultaneously, and is further, adopts preceding connecting pipe can realize the steel pipe of different length and strengthen the processing simultaneously.
Preferably, there is the high temperature resistant adapter of unification more between connecting pipe, the high temperature molten salt pump, realizes that a high temperature molten salt pump drives many steel pipes simultaneous strengthening treatment simultaneously.
Preferably, the periphery of the steel pipe is provided with a temperature control device to make up for the shortage/excess of the temperature gradient and the temperature drop rate of air cooling.
Further preferably, the temperature control device is composed of 2 or more independent temperature controllers, and a heat insulation layer is arranged between every two adjacent independent temperature controllers, so that the accurate control of the temperature gradient is realized.
Further preferably, the temperature control device is a forced cooling device, and provides a temperature drop gradient required by the process; the forced cooling device can take away the heat on the surface of the steel pipe in time, so that the temperature of the molten salt slowly drops in the process of flowing from one end of the steel pipe to the other end of the steel pipe, and the temperature drop amplitude of the two ends of the steel pipe can be flexibly and controllably adjusted according to the process requirement.
Further preferably, the forced cooling device may select different devices according to the required cooling rate, such as a surrounding forced air cooling device, a surrounding liquid cooling device, a surrounding aluminum heat dissipation plate, and even a liquid nitrogen cold trap.
Further preferably, the temperature control device is a heating device, so that different areas of the steel pipe can keep different temperatures. For the condition that the temperature of the molten salt at the two ends of a longer steel pipe or the two ends of the steel pipe is not expected to be greatly reduced, the heating device can be adopted to heat the outer surface of the steel pipe, so that the temperature difference between the external environment of the steel pipe and the molten salt is reduced, the heat loss is reduced, and the purpose of reducing the temperature reduction is achieved. The heating device can select any one or combination of a resistance wire heater, a warm air blower, a ceramic heater, an infrared quartz heater, a high-reflection film heat preservation heater and the like according to the requirements of actual working conditions.
Further preferably, the heating device is composed of a plurality of heaters, each heater independently controls the temperature, and a heat insulation layer is arranged between each heater, so that the periphery of the steel pipe is subjected to gradient heating, the temperature drop control is more flexible, and meanwhile, the whole pipe can be uniformly reinforced through the gradient heating when necessary.
Meanwhile, the invention provides an application method of the device, which comprises the following steps:
s1: pretreating a steel pipe;
s2: the molten salt pool, the front connecting pipe, the steel pipe, the connecting pipe, the high-temperature molten salt pump and the liquid return pipe are sequentially connected, and one end of the liquid return pipe is placed in the molten salt pool;
s3: confirming that each part is well sealed, starting a high-temperature molten salt pump, setting the flow of the high-temperature molten salt pump, enabling molten salt to return to a molten salt pool from the lower end of the steel pipe through the inner surface of the steel pipe, the inside of the connecting pipe, the high-temperature molten salt pump and the inside of the liquid return pipe, and starting nitriding;
s4: after nitriding is finished, post-treatment is carried out on the nitrided steel pipe;
the steel pipe inner surface strengthening layer after S1-S4 has gradient characteristics in the axial and radial directions.
Preferably, the front connecting pipe is used before the steel pipe, and when multiple steel pipes are nitrided simultaneously, the steel pipe is used, and an all-in-one high-temperature-resistant adapter is added between the connecting pipes.
Preferably, the pretreatment comprises any one or a combination of several of water washing, acid washing, oil removal, activation, drying, sand blasting, pre-oxidation and catalytic layer coating.
Different pretreatment combinations can be flexibly selected according to parameters such as the surface state, the structure, the components and the like of the steel pipe, and for example, the steps of acid washing, oil removal and the like can be omitted for the steel pipe after electrochemical polishing; for the material with higher nitriding difficulty, pre-oxidation for 10-30 minutes or catalytic layer coating with the thickness of 1-3 mu m can be properly added.
Preferably, further preferably, the post-treatment comprises one or a combination of cleaning, drying, shot blasting, sand blasting and oxidation, and the post-treatment process can be flexibly selected according to the overall process requirements of the steel pipe. Such as a mode of only water washing and drying; if the nitriding time is long and it is desired to remove the loose layer on the nitrided surface, post shot blasting cleaning and drying may be performed.
Preferably, when the front connecting pipe is not used, the horizontal surface of the molten salt in the molten salt pool is not less than 10mm over the lower end of the steel pipe.
The technical key points of the invention are as follows:
one or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:
(1) Due to the design of the flow nitriding process, the design of axial and radial double gradients can be realized, and the inner surface strengthening layer and the substrate of the steel pipe have better bonding force and thermal shock resistance while the requirement of different performance differences (one end has high hardness and high wear resistance and the other end has high toughness and high thermal shock resistance) at the two ends of the inner surface of the steel pipe is ensured.
(2) Due to the molten salt path design, the inner surface of the steel pipe can be strengthened, the outer surface is not influenced by the molten salt, and extra pollution and unnecessary seeping layers are not generated.
(3) Due to the design of the front connecting pipe and the high-temperature adapter, the steel pipes with different lengths can be simultaneously strengthened, and meanwhile, the simultaneous treatment of the steel pipes with different processes (different steel pipe nitriding temperatures) can be realized by heating or cooling the molten salt in the front connecting pipe by combining different cooling or heating devices.
(4) Due to the design of the forced cooling device and the heating device, the invention can realize the continuous adjustable control of the molten salt in the steel pipe from constant temperature to different temperature drops, adapt to different process requirements, and prepare the steel pipe with different axial and radial performance (including hardness, wear resistance, plasticity and toughness and impact resistance) gradients.
(5) Due to the design idea of the flow type nitriding, the heat treatment of a large steel pipe by a small furnace body and a small amount of molten salt can be realized (compared with the original immersion type nitriding), the material is saved, and the method is green and environment-friendly.
Drawings
FIG. 1 is a schematic view of an apparatus for manufacturing an inner surface gradient reinforced steel pipe;
in the figure: 1. the molten salt pond, 2, molten salt pond heating system, 3, fused salt, 4, preceding connecting pipe, 5, high temperature resistant sealing device, 6, temperature regulating device, 7, steel pipe, 8, connecting pipe, 9, liquid return pipe, 10, high temperature fused salt pump.
Detailed Description
In order to better understand the technical solutions, the technical solutions will be described in detail with reference to specific embodiments. It should be noted that the following detailed description is given by way of illustration only, and is not intended to limit the invention to the particular form disclosed, but it will be apparent to those skilled in the art that the invention may be practiced by other than the specific embodiments, or with equivalent arrangements of some features. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Example 1
The steel pipe is made of H13 steel, and is 900mm long, 22mm in outer diameter and 8mm in inner diameter.
The specific treatment steps are as follows:
s1: the interior of the steel pipe 7 is in an electrochemical polishing state, the pretreatment is carried out by washing with water and drying with compressed air, and finally, the steel pipe is pre-oxidized for 20min;
s2: the molten salt 3 is selected from 520 ℃ and CNO - Nitriding salt with the concentration of 33 percent, wherein the maximum heating power of a molten salt pool heating system 2 is 25kW; sequentially connecting a molten salt pool 1, a 100mm front connecting pipe 4, a steel pipe 7, a connecting pipe 8, a high-temperature molten salt pump 10 and a liquid return pipe 9; sealed metal pipe joints 5 are adopted for sealing between the connecting pipe and the steel pipe, between the connecting pipe and the high-temperature molten salt pump and between the high-temperature molten salt pump and the liquid return pipe; the liquid return pipe 9 is arranged in the molten salt pool 1, and the liquid level of the molten salt 3 in the molten salt pool 1 is 10mm above the lower end of the steel pipe;
s3: confirming that each part is well sealed, starting a high-temperature molten salt pump 10, setting the high-temperature molten salt pump to be 0.1L/min, enabling molten salt 3 to return to a molten salt pool 1 from the lower end of a steel pipe 7 through the inner surface of the steel pipe 7, the inside of a connecting pipe 8, the high-temperature molten salt pump 10 and the inside of a liquid return pipe 9, coating an electric heating film 6 on the periphery of the steel pipe 7 for heat preservation and heating, reducing the temperature of two ends of the steel pipe to be 30 ℃, and nitriding for 180min;
s4: and stopping the high-temperature molten salt pump 10 after nitriding is finished, washing the steel pipe with water at 50 ℃, removing residual nitriding molten salt on the inner surface of the pipe, and then airing.
Samples at two ends and the middle position of the steel pipe are obtained by linear cutting, are polished by 200-2000 meshes of sand paper, are polished by a diamond polishing agent with the diameter of 1.5 mu m, and the hardness of the inner surface and the hardness of the cross section are measured by a micro Vickers hardness tester to determine the effectivenessThe depth of the strengthening layer was followed by 4% nital etching to observe the thickness of the compound layer in the strengthening layer. Steel pipe matrix hardness 487HV 0.05 The hardness of the inner surface of one end is 1085HV 0.05 The depth of the effective strengthening layer is 120 μm (the thickness of the compound layer is 8 μm); the hardness of the inner surface of the intermediate position is 965HV 0.05 The effective strengthening layer depth is 102 μm (the thickness of the compound layer is 3.9 μm); the hardness of the inner surface of the other end is 840HV 0.05 (thickness of compound layer 2.1 μm), effective strengthening layer depth 87 μm. The steel pipe inner surface strengthening layer after S1-S4 has gradient characteristics in the axial and radial directions. The external surface of the reinforced steel pipe keeps the original structure and performance except for 10mm of the steel pipe immersed in the molten salt, and no pollution is caused.
Example 2
The steel pipe 7 is made of 5 pieces of 20Cr steel, and is 1500mm long, 55mm in outer diameter and 40mm in inner diameter.
The specific treatment steps are as follows:
s1: the pretreatment comprises the steps of sand blasting, clean water flushing and nitrogen blow drying;
s2: the molten salt 3 is selected from 520 ℃ and CNO - Nitriding salt with the concentration of 30.5 percent, and the maximum heating power of a molten salt pool heating system 2 is 30kW; sequentially connecting a molten salt pool 1, a steel pipe 7, a connecting pipe 8, a five-turn adapter, a high-temperature molten salt pump 10 and a liquid return pipe 9; metal sealing gaskets 5 are adopted for sealing between the connecting pipe 8 and the steel pipe 7, between the connecting pipe 8 and the high-temperature molten salt pump 9 and between the high-temperature molten salt pump 10 and the liquid return pipe 9; the liquid return pipe 9 is arranged in the molten salt pool 1, and the level of the molten salt 3 in the molten salt pool 1 is 30mm above the lower end of the steel pipe;
s3: confirming that each part is well sealed, starting a high-temperature molten salt pump 10, setting the high-temperature molten salt pump to be 0.5L/min, enabling molten salt 3 to return to a molten salt pool 1 from the lower end of the steel pipe through the inner surface of the steel pipe 7, the inside of a connecting pipe 8, the high-temperature molten salt pump 10 and the inside of a liquid return pipe 9, controlling the temperature of the periphery of the steel pipe 7 by adopting a surrounding type hot air blower, reducing the temperature of two ends of the steel pipe to be 40 ℃, and nitriding for 180min;
s4: and stopping the high-temperature molten salt pump 10 after nitriding is finished, cooling the steel pipe by water, washing the steel pipe by water at 50 ℃ to remove residual nitriding molten salt on the inner surface of the steel pipe, and drying the steel pipe at 90 ℃.
Randomly selecting a treated steel pipe, and cutting by adopting a lineSamples at two ends and the middle position of the steel pipe are obtained by cutting, after the samples are polished by 200-2000 meshes of sand paper, a diamond polishing agent with the diameter of 1.5 mu m is adopted for polishing, the hardness of the inner surface and the hardness of the section are measured by a micro Vickers hardness tester, the depth of an effective strengthening layer is determined, and then the thickness of a compound layer in the strengthening layer is observed by etching with 4% nitric acid and alcohol. Matrix hardness of steel pipe 291HV 0.05 Hardness of inner surface at one end is 633HV 0.05 The effective strengthening layer depth is 165 μm (the thickness of the compound layer is 6.5 μm); the hardness of the inner surface of the middle position is 611HV 0.05 The effective strengthening layer depth is 132 μm (the thickness of the compound layer is 4.6 μm); the hardness of the inner surface of the other end is 586HV 0.05 (thickness of compound layer 3.5 μm), effective strengthening layer depth 90 μm. The external surface of the reinforced steel pipe keeps the original structure and performance except 30mm of the reinforced steel pipe immersed in the molten salt, and no pollution is caused.
Example 3
The steel pipe 7 is made of 1 piece of 2Cr13 steel, and is 5000mm long, 180mm in outer diameter and 130mm in inner diameter.
The specific treatment steps are as follows:
s1: the steel pipe 7 is pretreated by sand blasting and then cleaned by compressed air;
s2: the molten salt 3 is nitridized salt with the temperature of 520 ℃ and the CNO-concentration of 30.5 percent, and the maximum heating power of the molten salt pool heating system 2 is 60kW; sequentially connecting a molten salt pool 1, a steel pipe 7, a connecting pipe 8, a high-temperature molten salt pump 10 and a liquid return pipe 9; metal sealing gaskets are adopted between the connecting pipe 8 and the steel pipe 7, between the connecting pipe 8 and the high-temperature molten salt pump 10 and between the high-temperature molten salt pump 10 and the liquid return pipe 9 for sealing; the liquid return pipe 9 is arranged in the molten salt pool 1, and the level of the molten salt 3 in the molten salt pool 1 is 100mm above the lower end of the steel pipe;
s3: confirming that each part is well sealed, starting a high-temperature molten salt pump 10, setting the high-temperature molten salt pump to be 6L/min, enabling molten salt 3 to return to a molten salt pool 1 from the lower end of a steel pipe through the inner surface of the steel pipe 7, the inside of a connecting pipe 8, the high-temperature molten salt pump 10 and the inside of a liquid return pipe 9, circularly heating the periphery of the steel pipe 7 by adopting a resistance heating pipe, reducing the temperature of two ends of the steel pipe to be 40 ℃, and nitriding for 180min;
s4: and stopping the high-temperature molten salt pump 10 after nitriding is finished, cooling the steel pipe by water, washing the steel pipe by water at 50 ℃, removing residual nitriding molten salt on the inner surface of the steel pipe, and then naturally drying the ventilated part.
Samples at two ends and the middle position of the steel pipe are obtained by linear cutting, after the samples are polished by 200-2000 meshes of sand paper, a diamond polishing agent with the diameter of 1.5 mu m is adopted for polishing, the internal surface hardness and the section hardness are measured by a micro Vickers hardness tester, the depth of an effective strengthening layer is determined, and then the thickness of a compound layer in the strengthening layer is observed by etching with 4% nitric acid and alcohol. Hardness of steel pipe base 403HV 0.3 Hardness of inner surface at one end is 1302HV 0.3 The depth of the effective strengthening layer is 65 mu m; the hardness of the inner surface of the middle position is 1145HV 0.3 The depth of the effective strengthening layer is 51 mu m; the hardness of the inner surface of the other end is 1043HV 0.3 The depth of the effective strengthening layer is 38 mu m. The steel pipe inner surface strengthening layer after S1-S4 has gradient characteristics in the axial and radial directions. The external surface of the reinforced steel pipe keeps the original structure and performance except 100mm of the steel pipe immersed in the molten salt, and no pollution is caused.
Claims (8)
1. The utility model provides an internal surface gradient reinforces steel pipe preparation facilities which characterized in that: the system comprises a molten salt pool, a front connecting pipe, a steel pipe, a connecting pipe, a high-temperature molten salt pump and a liquid return pipe, wherein all components are connected in sequence, and the steel pipe is vertical to the horizontal plane of molten salt in the molten salt pool;
the periphery of the steel pipe is provided with a temperature control device to make up for the shortage/excess of the temperature gradient and the temperature drop rate of air cooling; the temperature control device consists of 2 or more independent temperature controllers, and a heat insulation layer is arranged between every two adjacent independent temperature controllers; the temperature control device is a forced cooling device or a heating device and provides temperature drop gradient required by the process.
2. The device for preparing the steel pipe with the inner surface gradient reinforcement according to claim 1, is characterized in that: the wall of the molten salt pool is provided with a heating system for heating and melting salt for salt bath nitriding and ensuring that the molten salt is at a relatively stable temperature; the heating system comprises a heating pipe, an intelligent temperature controller and a thermocouple, can measure and feed back the molten salt temperature in real time, and can adjust the running state of the heating pipe according to the set temperature to keep the molten salt temperature stable and controllable.
3. The device for preparing the steel pipe with the inner surface gradient reinforcement according to claim 1, is characterized in that: in order to prevent the high-temperature molten salt from corroding the interface at high temperature, so that the molten salt is prevented from leaking; and high-temperature resistant sealing devices are adopted for sealing between the connecting pipe and the steel pipe, between the connecting pipe and the high-temperature molten salt pump and between the high-temperature molten salt pump and the liquid return pipe.
4. The device for preparing the steel pipe with the inner surface gradient reinforcement according to claim 1, is characterized in that: in order to ensure the realization of the nitriding process, molten salt is arranged in the molten salt pool, and cyanate ions are generated after the molten salt is molten to provide active ions for the salt bath nitriding.
5. The device for preparing the steel pipe with the inner surface gradient reinforcement according to claim 1, is characterized in that: the front connecting pipe is arranged between the molten salt pool and the steel pipe and extends into the molten salt, so that the outer surface of the steel pipe is protected from the molten salt, molten salt circulation can be still carried out when the molten salt level is lowered in the nitriding process, the condition that the lower end of the steel pipe cannot absorb the molten salt due to the fact that the molten salt level is lowered when a plurality of steel pipes use one molten salt pool at the same time is prevented, and further, the front connecting pipe can be adopted to realize the simultaneous reinforcement treatment of the steel pipes with different lengths; have the high temperature resistant adapter of unification more between connecting pipe, the high temperature molten salt pump, realize that a high temperature molten salt pump drives many steel pipes and intensive processing simultaneously.
6. The application method of the device for preparing the steel pipe with the inner surface gradient reinforcement according to any one of claims 1 to 5, is characterized in that: comprises the following steps:
s1: pretreating a steel pipe;
s2: the molten salt pool, the front connecting pipe, the steel pipe, the connecting pipe, the high-temperature molten salt pump and the liquid return pipe are sequentially connected, and one end of the liquid return pipe is placed in the molten salt pool;
s3: confirming that each part is well sealed, starting a high-temperature molten salt pump, setting the flow of the high-temperature molten salt pump, enabling molten salt to return to a molten salt pool from the lower end of the steel pipe through the inner surface of the steel pipe, the inside of the connecting pipe, the high-temperature molten salt pump and the inside of the liquid return pipe, and starting nitriding;
s4: after nitriding is finished, post-treatment is carried out on the nitrided steel pipe;
the steel pipe inner surface strengthening layer after S1-S4 has gradient characteristics in the axial and radial directions.
7. The method of applying the device according to claim 6, wherein: the pretreatment comprises any one or combination of more of sand blasting, oil removing, pre-oxidation and catalytic layer coating.
8. The method of applying the device according to claim 6, wherein: the post-treatment comprises one or more of cleaning, drying, shot blasting, sand blasting and oxidation.
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| GB1213190A (en) * | 1968-01-15 | 1970-11-18 | Gen Electric | Process and apparatus for internally nitriding tubes |
| AT356631B (en) * | 1974-07-12 | 1980-05-12 | Canzler Fa Carl | METHOD FOR COOLING A SALT MELT FOR HEAT TREATMENT AND DEVICE FOR CARRYING OUT THE METHOD |
| JPH05146753A (en) * | 1991-11-25 | 1993-06-15 | Sumitomo Metal Ind Ltd | Method for discriminating quality of coating on inside face of metal tube |
| RU2032762C1 (en) * | 1992-06-03 | 1995-04-10 | Государственный научно-исследовательский и конструкторско-технологический институт трубной промышленности | Apparatus for the application of coating on the inner surface of pipes |
| RU2152453C1 (en) * | 1999-04-20 | 2000-07-10 | Открытое акционерное общество "УралЛУКтрубмаш" | Process of chemical and thermal treatment of internal surfaces of pipes in melt of cyanates and gear for its implementation |
| JP2002239439A (en) * | 2001-02-20 | 2002-08-27 | Matsushita Electric Ind Co Ltd | Method for coating inside surface of straight pipe with liquid material and apparatus therefor |
| JP2008163394A (en) * | 2006-12-28 | 2008-07-17 | Nhk Spring Co Ltd | Apparatus for and method of hardening conductive hollow pipe |
| CN105401107B (en) * | 2015-11-12 | 2017-06-06 | 中南大学 | A kind of device and method for obtaining aluminium alloy axial gradient mechanical property |
| CN106702313B (en) * | 2016-12-29 | 2019-04-19 | 青岛丰东热处理有限公司 | A kind of low-temperature ion cure process device of austenitic stainless steel elongated tubular |
| CN207672119U (en) * | 2017-12-29 | 2018-07-31 | 机械科学研究总院青岛分院有限公司 | A kind of device for long narrow tube inner wall gas nitriding |
| CN207900895U (en) * | 2018-05-02 | 2018-09-25 | 徐海燕 | A kind of pipe material inner wall derusting device |
| CN110055544B (en) * | 2019-05-23 | 2023-06-16 | 宝武特冶航研科技有限公司 | Vertical steel pipe pickling tank |
| CN210367813U (en) * | 2019-07-22 | 2020-04-21 | 苏州市昶智热处理有限公司 | Molten salt quick-heating type vacuum gas quenching furnace |
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