Anti-orange peel treatment method for hydraulic forming of 1.4828 stainless steel pipe fitting

Abstract

The invention discloses a 1.4828 material stainless steel pipe fitting hydraulic forming anti-orange-peel treatment method which comprises the following steps: cleaning and pretreating a 1.4828 stainless steel pipe fitting, putting the pipe fitting into a high-temperature area of a crawler-type bright annealing furnace, controlling the conveying speed to carry out high-temperature recrystallization on pipe fitting grains, and carrying out rapid cooling annealing on the recrystallized pipe fitting in a cooling area, and the annealed pipe fitting is subjected to bulging on an inner high-pressure forming machine. According to the method, through precise high temperature, annealing and transmission speed control, grains of the 1.4828 stainless steel pipe fitting are fully recrystallized, grain boundary slippage during hydraulic forming is reduced, the surface roughness Ra is smaller than 1.6 microns, subsequent grinding and polishing are not needed, the machining cost is reduced, meanwhile, the influence of polishing on the product size is avoided, the orange peel problem can be eliminated, and the pipe fitting quality is improved.

Description

Technical Field

[0001] This invention relates to the field of anti-orange peel technology for 1.4828 stainless steel pipe fittings, and more particularly to a method for anti-orange peel treatment of 1.4828 stainless steel pipe fittings by hydraulic forming. Background Technology

[0002] 1.4828 stainless steel (equivalent to AISI 309S), as a high-chromium-nickel austenitic stainless steel, is widely used in fields with stringent material performance requirements, such as chemical equipment and heat exchangers, due to its excellent high-temperature oxidation resistance and corrosion resistance. In actual production, this material is often used to process pipe fittings with complex shapes, such as hump pipes and corrugated pipes, and hydroforming is a key process for manufacturing such complex pipe fittings.

[0003] However, during the hydroforming process, the bulging area of ​​1.4828 stainless steel pipe fittings undergoes significant plastic deformation. During this deformation, grain boundary slippage easily occurs within the material, directly leading to noticeable orange peel defects on the pipe fitting surface. This orange peel phenomenon not only severely damages the product's appearance integrity but also reduces the surface density of the pipe fitting, thereby weakening its corrosion resistance and negatively impacting product quality and service life. This has become a significant technical challenge restricting the hydroforming processing of 1.4828 stainless steel pipe fittings.

[0004] To address the orange peel problem, the industry has tried various methods, but all have significant limitations: First, the traditional annealing temperature adjustment method attempts to improve the material's microstructure by increasing the annealing temperature; however, this method cannot completely eliminate the work hardening effect generated during the initial processing. In the subsequent bulging process, materials that have not completely eliminated work hardening will still exhibit uneven grain deformation, failing to fundamentally solve the orange peel problem. Second, the bulging parameter optimization method includes measures such as reducing the bulging rate, increasing the number of forming cycles, and optimizing lubrication conditions. While these methods can alleviate the orange peel phenomenon to some extent, their effectiveness is very limited. Furthermore, reducing the bulging rate and increasing the number of forming cycles significantly prolongs the production cycle and increases production costs, which is not conducive to large-scale industrial production. At the same time, over-reliance on lubrication condition optimization is difficult to adapt to the processing needs of pipe fittings of different specifications and complexities. Third, the subsequent surface treatment method involves adding a grinding or polishing process after hydroforming to remove surface orange peel defects. While this method can improve the appearance of the product, the additional processing steps significantly increase the manufacturing cost. Furthermore, the grinding and polishing process may affect the dimensional accuracy of the pipe fittings. Especially for thin-walled or complex-shaped pipe fittings, improper control of the processing force can easily lead to product scrap, further reducing the production yield.

[0005] In summary, the prior art solutions cannot remove the orange peel under the premise of ensuring production efficiency, controlling cost and not affecting the size accuracy of the product, therefore, in order to effectively solve the problem of orange peel in the hydraulic forming process of 1.4828 stainless steel pipe fittings, a high-temperature annealing process capable of optimizing the material organization state before hydraulic forming to avoid the generation of orange peel from the root cause is needed to break through the current technical bottleneck of 1.4828 stainless steel pipe fitting processing. SUMMARY

[0006] In view of the above problems, the purpose of the present application is to provide a 1.4828 material stainless steel pipe fitting hydraulic forming anti-orange peel treatment method to solve the problem of orange peel in the hydraulic forming process of 1.4828 stainless steel pipe fittings, improve the appearance quality, surface density and corrosion resistance of the product, and ensure production efficiency, control cost and not affect the size accuracy of the product.

[0007] The purpose of the present application can be achieved by the following technical solution: a 1.4828 material stainless steel pipe fitting hydraulic forming anti-orange peel treatment method, comprising the steps of:

[0008] S1, cleaning and pretreating the 1.4828 stainless steel pipe fitting;

[0009] S2, placing the pretreated 1.4828 stainless steel pipe fitting into the high-temperature zone of the tracked bright annealing furnace, and controlling the conveying speed to perform pipe fitting grain high-temperature recrystallization;

[0010] S3, rapidly cooling and annealing the recrystallized 1.4828 stainless steel pipe fitting in the cooling zone of the tracked bright annealing furnace;

[0011] S4, expanding the annealed 1.4828 stainless steel pipe fitting on the internal high-pressure forming machine.

[0012] As a further improvement of the present application, the cleaning and pretreatment in S1 comprises:

[0013] JL-801 metal cleaner is used to clean the 1.4828 stainless steel pipe fitting, and the ratio is 1:50, and then the pipe fitting is rinsed with clean water.

[0014] As a further improvement of the present application, the high-temperature zone of the tracked bright annealing furnace adopts four-zone continuous, and the temperature of the four zones is set to 1080℃±10℃.

[0015] As a further improvement of the present application, the protective gas in the annealing furnace adopts H2 and N2 mixed protective gas with H2≤5%, and the dew point of the mixed protective gas is ≤-60℃.

[0016] As a further improvement of the present application, the conveying speed in S2 is controlled to be 16-20 meters / hour, and the residence time of the stainless steel pipe fitting in the high-temperature zone is ≥15 minutes.

[0017] As a further place of the present application, the cooling zone of the S3 bright annealing furnace adopts the outer circulating water cooling.

[0018] As a further place of the present application, in the S4, the bulging rate is 0.5-1.0 mm / s, and the bulging amount is 30%-40%.

[0019] As a further place of the present application, in the S4, when the internal high-pressure forming machine is used, the mold locking pressure is 6000-7000 KN, the water bulging internal pressure is 100-120 MPa, the water pressure bulging is to 25% deformation amount, and the pressure maintaining time is 3-5 seconds.

[0020] The beneficial effects of the present application are:

[0021] 1. The method of the present application can make the 1.4828 stainless steel pipe grain fully recrystallize through precise high-temperature annealing and speed control transmission, reduce the crystal boundary slip during hydraulic forming, and the surface roughness Ra is less than 1.6 microns, without subsequent polishing, reduce the processing cost, avoid the influence of polishing on the product size, eliminate the orange peel problem and improve the surface quality.

[0022] 2. By using the method of the present application, the grain size after annealing is stable at ASTM 6-7 level, the bulging amount during hydraulic forming reaches 30%-40% without cracking, the yield strength is greater than or equal to 210 MPa, and the elongation is greater than or equal to 40%, which meets the performance requirements of pipe fittings in many industries, avoids subsequent polishing or rework, improves the yield, reduces the rework loss, and ensures the product reliability. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The principle flowchart of the method of the present application is shown in the figure;

[0024] Figure 2 The orange peel effect diagram of the pipe before applying the method of the present application is shown in the figure;

[0025] Figure 3 The orange peel elimination effect diagram of the pipe after applying the method of the present application is shown in the figure. DETAILED DESCRIPTION

[0026] The embodiments of the present application are described in detail below, and the examples of the embodiments are shown in the drawings, wherein the same or similar symbols represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application.

[0027] The present application discloses a kind of 1.4828 material stainless steel pipe hydraulic forming anti-orange peel processing method:

[0028] First, the 1.4828 stainless steel pipe fittings are cleaned and pretreated.

[0029] A metal cleaner (e.g., JL-801) is mixed with water at a ratio of about 1:50 to form a mixed cleaning solution. The 1.4828 stainless steel pipe fittings are cleaned with the mixed cleaning solution, then rinsed with clean water to remove surface oil and impurities, and achieve a clean surface state, creating good conditions for subsequent processing procedures.

[0030] Then, the pretreated 1.4828 stainless steel pipe fittings are placed in the high-temperature zone of the crawler-type bright annealing furnace, and the conveying speed is controlled to perform high-temperature recrystallization of the pipe fittings.

[0031] A crawler-type four-zone continuous bright annealing furnace is used, and H2≤5% N2 and H2 mixed protective gas is introduced into the annealing furnace, with a dew point of the mixed protective gas ≤-60℃ to prevent oxidation.

[0032] The four-zone temperature of the high-temperature zone of the annealing furnace is set to 1080℃±10℃ to ensure sufficient recrystallization of the stainless steel pipe fitting material. If the temperature is too high, the grains will grow excessively, leading to a decrease in the mechanical properties of the pipe fittings, reducing their strength and toughness, and affecting the service life and safety of the pipe fittings. If the temperature is too low, it cannot fully achieve high-temperature recrystallization of the grains, cannot effectively improve the microstructure of the pipe fittings, and cannot achieve the effect of preventing orange peel.

[0033] The pipe fitting products are evenly placed on the crawler of the crawler-type annealing furnace, and the conveying speed of the crawler is adjusted to 16-20 meters / hour to ensure that the pipe material stays in the high-temperature zone for ≥15 minutes, homogenizes the grains, and optimizes the internal microstructure of the pipe material. During the high-temperature recrystallization of the pipe fitting grains, the temperature in the annealing furnace and the proportion and dew point of the mixed protective gas are monitored in real time. If the temperature deviation exceeds ±10℃ or the parameters of the mixed protective gas do not meet the requirements, adjustments should be made immediately to ensure the stability and consistency of the recrystallization process.

[0034] S3, the recrystallized 1.4828 stainless steel pipe fittings are rapidly cooled in the cooling zone of the crawler-type bright annealing furnace.

[0035] The stainless steel pipe fittings are rapidly cooled in the cooling zone of the crawler-type bright annealing furnace. The furnace is filled with N2-H2 mixed protective gas, and the outside is cooled by circulating water to prevent the precipitation of carbides and ensure the stability of the microstructure of the pipe fittings. The cooling speed needs to be strictly controlled within a certain range to ensure that the pipe fittings have a good balance of hardness and toughness. During the cooling process, the pressure and composition of the mixed protective gas in the furnace are continuously monitored to prevent gas leakage or composition changes from affecting the cooling effect. At the same time, the temperature and flow of the circulating water are closely monitored to maintain their stability and ensure the uniformity of the cooling.

[0036] S4, the 1.4828 stainless steel pipe after annealing on the internal high pressure forming machine for bulging.

[0037] The annealed pipe is bulged on the internal high pressure forming machine, the bulging rate is controlled at 0.5-1.0 mm / s, and the bulging amount can reach 30%-40%. In this process, the bulging pressure is precisely controlled to ensure that the pipe can deform uniformly during bulging, avoiding local over-bulging or insufficient bulging.

[0038] Application verification:

[0039] As shown in Figure 2 , the material uses 1.4828 stainless steel pipe with a thickness of 2 mm, which is pretreated by pickling to remove the oxide layer.

[0040] The four-zone furnace temperature in the bright annealing furnace high-temperature zone is between 1070-1090℃, the crawler-type mesh belt conveying speed is 17 meters / hour, the total high-temperature and annealing time is about 110 minutes, the furnace protective gas uses N2-H2 mixed protective gas, and the dew point is -65℃. High temperature, annealing and precise speed control are achieved by using the bright annealing furnace to make the pipe grain fully recrystallize.

[0041] The mold locking pressure of the internal high pressure forming machine mold is 6400KN, the water bulging internal pressure is 112MPa, the water pressure bulging is to 25% deformation, and the pressure holding time is 4.5 seconds.

[0042] Test results:

[0043] As shown in Figure 3 , the stainless steel pipe surface is free of orange peel, the grain size is ASTM 6.5 grade, the yield strength is ≥210MPa, and the elongation is ≥40%.

[0044] Through the above application verification, it can be concluded that the 1.4828 stainless steel pipe through the above pretreatment, bright annealing furnace high-temperature annealing precise speed control, and internal high pressure forming mold water bulging, etc. A series of process operations, successfully realized the good effect of hydraulic forming anti-orange peel. This processing method not only effectively avoids the appearance of orange peel on the surface of the pipe, but also ensures that the pipe has good microstructure and mechanical properties. The grain size reaches ASTM 6.5 grade, indicating that the grain size of the material is relatively uniform and appropriate, which helps to improve the comprehensive performance of the pipe. The yield strength is ≥210MPa and the elongation is ≥40%, which means that the pipe can not only have enough resistance to deformation when subjected to external force, but also have good plastic deformation ability, which can meet the needs of various engineering application scenarios.

[0045] It can be seen that the processing method has high feasibility and application value in actual production, can provide effective technical reference for stainless steel pipe production of related industries, can improve production efficiency and economic benefits while ensuring product quality, and promotes the development of stainless steel pipe manufacturing industry to a higher quality direction.

[0046] The above describes only a preferred embodiment of the present application, but the protection scope of the present application is not limited to this, any person skilled in the art can make equivalent replacement or change according to the technical scheme and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.

[0047] In the present application, unless otherwise explicitly specified and limited, the first feature is "on" or "under" the second feature, which can be direct contact of the first and second features, or indirect contact of the first and second features through an intermediate medium. Moreover, the first feature "above", "over" and "on" the second feature can be directly above or obliquely above the first feature, or only indicate that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "under" and "under" the second feature can be directly below or obliquely below the first feature, or only indicate that the horizontal height of the first feature is less than that of the second feature.

Claims

1. A method of hydraulic forming of 1.4828 material stainless steel pipe fitting with anti-orange peel treatment, characterized in that, The application relates to a 1.4828 stainless steel pipe fitting production method. S1, cleaning and pretreating 1.4828 stainless steel pipe fittings; S2, putting the pretreated 1.4828 stainless steel pipe fittings into a high-temperature zone of a crawler-type bright annealing furnace, controlling the conveying speed to perform high-temperature recrystallization of the pipe fitting grains; S3, rapidly cooling and annealing the recrystallized 1.4828 stainless steel pipe fittings in a cooling zone of the crawler-type bright annealing furnace; S4, expanding the annealed 1.4828 stainless steel pipe fittings on an internal high-pressure forming machine.

2. The method of claim 1, wherein the 1.4828 stainless steel pipe is a 1.4828 stainless steel pipe for a hydraulic forming process for preventing orange peel treatment. The cleaning and pretreating in S1 comprises the following steps: JL-801 metal cleaning agent is diluted with water at a ratio of 1:50 to clean the 1.4828 stainless steel pipe fittings, and then the pipe fittings are rinsed with clean water.

3. The method of claim 1, wherein the 1.4828 stainless steel pipe is a 1.4828 stainless steel pipe for a hydraulic forming process for preventing orange peel treatment. The high-temperature zone of the crawler-type bright annealing furnace adopts four-zone continuity, and the temperatures of the four zones are all set to 1080 DEG C + / - 10 DEG C.

4. The method of claim 1, wherein the 1.4828 stainless steel pipe is a 1.4828 stainless steel pipe for a hydraulic forming process for preventing orange peel treatment. The protective gas in the annealing furnace adopts H2 and N2 mixed protective gas with H2 being less than or equal to 5%, and the mixed protective gas has a dew point less than or equal to -60 DEG C.

5. The method of claim 1, wherein the 1.4828 stainless steel pipe is a 1.4828 stainless steel pipe for a hydraulic forming process for preventing orange peel treatment. The conveying speed is controlled to be 16-20 m / h in S2, and the stainless steel pipe fittings stay in the high-temperature zone for more than or equal to 15 min.

6. The method of claim 1, wherein the 1.4828 stainless steel pipe is a 1.4828 stainless steel pipe for a hydraulic forming process for preventing orange peel treatment. The cooling zone of the crawler-type bright annealing furnace adopts furnace hearth outer circulating water cooling in S3.

7. The method of claim 1, wherein the 1.4828 stainless steel pipe is a 1.4828 stainless steel pipe for a hydraulic forming process for preventing orange peel treatment. The expansion rate is 0.5-1.0 mm / s, and the expansion amount is 30%-40% in S4.

8. The method of claim 7, wherein the 1.4828 stainless steel pipe is a 1.4828 stainless steel pipe for a hydraulic forming process for preventing orange peel treatment. The internal high-pressure forming machine is used in S4, the mold locking pressure of the mold is 6000-7000 KN, the water expansion internal pressure is 100-120 MPa, the water pressure expansion is to 25% deformation, and the pressure is kept for 3-5 s.

Images