High-pressure hot air expansion composite molding process in pipe fitting

Abstract

The invention relates to a metal pipe fitting forming process, in particular to a high-pressure hot air expansion composite forming process in a pipe fitting. Comprising the following steps that S1, a pipe fitting is placed in a hydraulic expansion mold, the two ends of the pipe fitting are sealed, an inner cavity of the pipe fitting is filled with liquid expansion forming liquid, and a liquid expansion forming pipe is obtained; s2, the liquid expansion forming pipe is heated until internal crystals are completely converted into austenite, and a heating forming pipe fitting is obtained; s3, the heating forming pipe fitting is placed in a hot air expansion forming mold, the two ends of the pipe fitting are sealed, an inner cavity of the pipe fitting is filled with ultrahigh-pressure air to serve as a support, and a hot air expansion forming pipe fitting is obtained; and S4, cooling quenching treatment is conducted on the hot air expansion forming pipe fitting, and a product is obtained. The high-pressure hot air expansion composite forming process in the pipe fitting has the advantages of being good in product forming and saving cost.

Description

Technical Field

[0001] This invention relates to a forming process for metal pipe fittings, specifically a high-pressure hot gas expansion composite forming process for pipe fittings. Background Technology

[0002] The existing hot gas expansion technology is based on heating high-strength steel pipes until all grains are converted into austenite, then placing them in a mold and expanding them with high-pressure gas. After the expansion is completed, rapid cooling is performed to achieve the purpose of quenching treatment, so that the pipe strength can reach 20GPa.

[0003] Because the existing hot air expansion technology mold is in a cold state, when the heated pipe is placed into the mold, the pipe temperature will drop rapidly, causing the pipe to cool down prematurely and the expansion will not be complete. This results in a relatively small expansion amount. For complex products or products with a large expansion amount, the existing process will cause the product to expand incompletely or crack, and the manufactured product will not meet the qualification requirements. Summary of the Invention

[0004] The present invention aims to provide a high-pressure hot gas expansion composite molding process for pipe fittings that results in better product molding and reduced production costs.

[0005] The high-pressure hot gas expansion composite molding process for pipe fittings in this solution includes the following steps: S1, placing the pipe fitting in a hydraulic expansion mold, sealing both ends of the pipe fitting and filling the inner cavity of the pipe fitting with liquid expansion molding liquid to obtain a liquid expansion molded pipe (201); S2, heating the liquid expansion molded pipe (201) until all the internal crystals are transformed into austenite to obtain a heat-formed pipe fitting (211); S3, placing the heat-formed pipe fitting (211) in a hot gas expansion molding mold, sealing both ends of the pipe fitting and filling the inner cavity of the pipe fitting with ultra-high pressure air (801) as support to obtain a hot gas expansion molded pipe fitting (221); S4, cooling and quenching the hot gas expansion molded pipe fitting (221) to obtain the product.

[0006] First, the product is shaped using hydraulic expansion molding, a very mature process capable of forming complex tubular parts. It offers high stability and good consistency. Because the expansion pressure in hydraulic expansion molding can reach over 400 MPa, it can form relatively thick tubular parts. Next, the hydraulically expanded tubular part is heated to convert all the internal crystals into austenite. Then, it is placed in a hot gas expansion mold, and ultra-high pressure gas is injected into the tubular part as internal support, causing it to adhere to the mold. Finally, cooling water is introduced for in-mold quenching.

[0007] Further, in step S1, the hydraulic bulging mold includes a hydraulic bulging upper mold (101) and a hydraulic bulging lower mold (102). After the pipe fitting is closed between the hydraulic bulging upper mold (101) and the hydraulic bulging lower mold (102), it is sealed by a hydraulic bulging forming sealing pusher (301) and filled with hydraulic bulging forming emulsion (401) to obtain a hydraulically bulging formed pipe (201). The hydraulic bulging forming emulsion (401) is filled into the pipe fitting under a preset pressure, causing the pipe fitting to bulge. The hydraulic bulging forming sealing pusher (301) can seal and ensure the liquid pressure inside the pipe fitting.

[0008] Furthermore, in step S2, the liquid-expanded forming tube (201) is placed in a heating furnace and heated to 930°C to 950°C by a heating device (501) until all the internal crystals are transformed into austenite. The heating tubes of the heating device (501) are evenly distributed on the liquid-expanded forming tube (201) to ensure uniform heating.

[0009] Furthermore, in step S3, the hot air expansion molding mold includes a hot air expansion molding upper mold (601) and a hot air expansion molding lower mold (602). The heated forming pipe (211) is placed in the hot air expansion molding lower mold (602). After the hot air expansion molding upper mold (601) is closed, it is sealed by the hot air expansion molding sealing pusher (701), and ultra-high pressure air (801) is injected into the pipe as support.

[0010] Furthermore, the hot gas expansion molding mold is equipped with a cooling water channel (901). In step S4, flowing cooling water is introduced into the cooling water channel (901) within the hot gas expansion molding mold to cool and quench the hot gas expansion molding pipe (221). Because the cooling water channel (901) is located within the hot gas expansion molding mold, cooling can be performed without opening the mold to remove the part, simplifying the operation process. Furthermore, both the upper mold (601) and the lower mold (602) for hot air expansion molding are provided with cooling water channels (901). The cooling water channels in both the upper and lower molds make the cooling more uniform and improve the quality of the finished product.

[0011] Furthermore, the pressure of the ultra-high pressure air (801) is 50 MPa to 80 MPa.

[0012] Furthermore, the heating temperature in the heating furnace is 950°C via the heating device (501).

[0013] Furthermore, the pressure of the ultra-high pressure air (801) is 60 MPa to 70 MPa.

[0014] Furthermore, the pressure of the ultra-high pressure air (801) is 70 MPa.

[0015] The advantages of this invention are: compared with existing hot gas expansion technology, this patented solution can form complex and thick tubular parts, and the requirements for the gas source used in hot gas expansion are not high, which can reduce the investment in ultra-high pressure gas generator equipment and the compressor used in hot gas expansion. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the equipment used in the high-pressure hot gas expansion composite molding process for pipe fittings according to the present invention. Figure 2 This is a schematic diagram of the equipment in step S1 of the high-pressure hot gas expansion composite molding process for pipe fittings according to the present invention; Figure 3 This is a schematic diagram of the equipment in step S2 of the high-pressure hot gas expansion composite molding process for pipe fittings according to the present invention; Figure 4 This is a schematic diagram of the equipment in steps S3 and S4 of the high-pressure hot gas expansion composite molding process for pipe fittings according to the present invention. Detailed Implementation

[0017] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: Because existing hot air expansion technology uses cold molds, the temperature of the heated pipe drops rapidly after being placed in the mold, causing premature cooling and incomplete expansion. This results in a relatively small expansion amount. For complex products or those with large expansion amounts, existing processes can lead to incomplete expansion or cracking, resulting in substandard products. This problem is solved by the first expansion stage of a high-pressure hot air expansion composite molding process for pipe fittings, as described in this invention. The first expansion stage uses a water expansion process to achieve a perfect shape. The product is then heated to 950°C to completely transform the metal grains into austenite before being placed in a hot air expansion mold for further hot air expansion processing. This process yields complex hot air expanded products with large expansion amounts. Furthermore, the air source pressure used in this hot air expansion process is lower, correspondingly reducing the clamping force requirements of the equipment.

[0018] according to Figures 1 to 4 As shown, the specific operation steps of a high-pressure hot gas expansion composite molding process for pipe fittings in this solution are as follows: S1 fluid swelling, such as Figure 1 and Figure 2As shown, the pipe fitting 200 is placed in a hydraulic expansion mold, both ends of the pipe fitting are sealed, and a hydraulic expansion molding liquid is filled into the inner cavity of the pipe fitting to obtain a hydraulically expanded pipe 201. In this embodiment, the hydraulic expansion mold includes a hydraulic expansion upper mold 101 and a hydraulic expansion lower mold 102. After the pipe fitting is closed by the hydraulic expansion upper mold 101 and the hydraulic expansion lower mold 102, it is sealed by a hydraulic expansion molding sealing pusher 301 and filled with a hydraulic expansion molding emulsion 401 to obtain a hydraulically expanded pipe 201.

[0019] In this process, the swelling emulsion 401 is injected into the pipe under a preset pressure, causing the pipe to swell. The swelling sealing pusher 301 can seal and ensure the liquid pressure inside the pipe. The swelling emulsion 401 used in this embodiment is a common swelling emulsion used in the swelling molding industry, and its composition is a mixture of oil, emulsion, and water. First, the product is shaped through swelling molding. Swelling molding is a very mature process that can shape complex tubular parts. It has high stability and good consistency. Since the swelling pressure of swelling molding can reach more than 400MPa, it can shape relatively thick tubular parts.

[0020] S2, austenitization, such as Figure 3 As shown, the liquid-expanded forming tube 201 is heated until all the internal crystals are transformed into austenite, resulting in a heat-formed tube 211. Specifically, the liquid-expanded forming tube 201 is placed in a heating furnace and heated to a temperature of 930°C to 950°C by a heating device 501 until all the internal crystals are transformed into austenite. The heating tubes of the heating device 501 are evenly distributed in the liquid-expanded forming tube 201 to ensure uniform heating. In this embodiment, the heating temperature in the heating furnace by the heating device 501 is 950°C.

[0021] S3, thermal expansion, such as Figure 4 As shown, the heated forming pipe 211 is placed in the hot air expansion forming mold, wherein the hot air expansion forming mold includes a hot air expansion forming upper mold 601, a hot air expansion forming lower mold 602 and a cooling water channel 901, and both the hot air expansion forming upper mold 601 and the hot air expansion forming lower mold 602 are provided with cooling water channels 901.

[0022] The heated forming tube 211 is placed inside the lower mold 602 for hot air expansion forming. After the upper mold 601 for hot air expansion forming closes, it is sealed by the hot air expansion forming sealing pusher 701, and ultra-high pressure air 801 is injected into the tube as support. The two ends of the tube are sealed, and ultra-high pressure air 801 is injected into the inner cavity of the tube as support, resulting in the heated forming tube 221. The pressure of the ultra-high pressure air 801 is 50 MPa to 80 MPa. Preferably, the pressure of the ultra-high pressure air 801 is 60 MPa to 70 MPa. In this embodiment, the pressure of the ultra-high pressure air 801 is 70 MPa.

[0023] S4, cooling and quenching, such as Figure 4 As shown, flowing cooling water is introduced into the cooling water channel 901 within the hot gas expansion molding mold to cool and quench the hot gas expansion molding pipe 221, thereby obtaining the product. Because the cooling water channel 901 is located within the hot gas expansion molding mold, cooling can be performed without opening the mold to remove the part, simplifying the operation process. Compared with existing hot gas expansion technology, this patent can form complex and thick tubular parts, and the requirements for the gas source used in hot gas expansion are not high, which can reduce the investment in ultra-high pressure gas generator equipment and the compressor used in hot gas expansion.

[0024] Because it first uses liquid expansion molding to form the product, liquid expansion molding is a very mature process that can form complex tubular parts. It has high stability and good consistency. Since the expansion pressure of liquid expansion molding can reach more than 400MPa, it can form thicker tubular parts.

[0025] The tubular part, after being formed by liquid expansion, is then heated to convert all the internal crystals into austenite. It is then placed in a hot gas expansion mold, and ultra-high pressure gas is injected into the tubular part as internal support, causing it to adhere to the mold. Cooling water is then introduced for in-mold quenching. This process, with its hot gas expansion, has lower requirements for the press and high-pressure gas source equipment.

[0026] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics in the solutions is not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. A high-pressure hot gas expansion composite molding process for pipe fittings, characterized in that, Includes the following steps: S1, place the pipe fitting in the hydraulic expansion mold, seal both ends of the pipe fitting and fill the inner cavity of the pipe fitting with hydraulic expansion molding liquid to obtain the hydraulic expansion molded pipe (201). S2, the liquid-expanded tube (201) is heated until all the internal crystals are transformed into austenite to obtain the heat-formed tube (211). S3, place the heated forming pipe (211) in the hot air expansion forming mold, seal both ends of the pipe and fill the inner cavity of the pipe with ultra-high pressure air (801) as support to obtain the hot air expansion forming pipe (221). S4, the hot gas expansion forming pipe fitting (221) is cooled and quenched to obtain the product.

2. The high-pressure hot gas expansion composite molding process for pipe fittings according to claim 1, characterized in that: In step S1, the hydraulic expansion mold includes a hydraulic expansion upper mold (101) and a hydraulic expansion lower mold (102). After the pipe is closed by the hydraulic expansion upper mold (101) and the hydraulic expansion lower mold (102), it is sealed by the hydraulic expansion forming sealing pusher (301) and filled with the hydraulic expansion forming emulsion (401) to obtain the hydraulic expansion forming pipe (201).

3. The high-pressure hot gas expansion composite molding process for pipe fittings according to claim 1, characterized in that: In step S2, the liquid-expanded tube (201) is placed in a heating furnace and heated to 930°C to 950°C by a heating device (501) until all the internal crystals are transformed into austenite.

4. The high-pressure hot gas expansion composite molding process for pipe fittings according to claim 1, characterized in that: In step S3, the hot air expansion molding mold includes a hot air expansion molding upper mold (601) and a hot air expansion molding lower mold (602). The heated forming pipe (211) is placed in the hot air expansion molding lower mold (602). After the hot air expansion molding upper mold (601) is closed, it is sealed by the hot air expansion molding sealing pusher (701), and ultra-high pressure air (801) is injected into the pipe as support.

5. The high-pressure hot gas expansion composite molding process for pipe fittings according to claim 1 or 4, characterized in that: The hot gas expansion molding mold is provided with a cooling water channel (901). In step S4, flowing cooling water is introduced into the cooling water channel (901) in the hot gas expansion molding mold to cool and quench the hot gas expansion molding pipe (221).

6. The high-pressure hot gas expansion composite molding process for pipe fittings according to claim 4, characterized in that: Cooling water channels (901) are provided in both the upper mold (601) and the lower mold (602) for hot air expansion forming.

7. The high-pressure hot gas expansion composite molding process for pipe fittings according to claim 4, characterized in that: The pressure of the ultra-high pressure air (801) is 50 MPa to 80 MPa.

8. The high-pressure hot gas expansion composite molding process for pipe fittings according to claim 3, characterized in that: The heating temperature in the furnace is 950°C via the heating device (501).

9. The high-pressure hot gas expansion composite molding process for pipe fittings according to claim 7, characterized in that: The pressure of the ultra-high pressure air (801) is 60 MPa to 70 MPa.

10. A high-pressure hot gas expansion composite molding process for pipe fittings according to claim 4 or 7, characterized in that: The pressure of the ultra-high pressure air (801) is 70 MPa.

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