A method of welding and sealing a titanium alloy case to a stainless steel igniter

Abstract

A welding sealing method of titanium alloy shell and stainless steel igniter, comprising: placing the solder containing flux at the welding position of the titanium alloy ring, assembling into the stainless steel ring by using the limiting tool, cleaning the overflow, and obtaining the adapter ring structure; putting the adapter ring structure into the vacuum brazing furnace as a whole, setting the vacuum degree, temperature, holding time, and the pressure applied to the whole; grinding the residue at the brazing position of the adapter ring; detecting the air tightness of the adapter ring by using the air tightness detection device; sleeving the adapter ring into the igniter, laser welding and sealing the igniter and the stainless steel ring side of the adapter ring; assembling the igniter with the adapter ring into the titanium alloy shell, laser welding and sealing the titanium alloy shell and the titanium alloy ring side of the adapter ring; inputting the gas with the required pressure into the input end of the titanium alloy shell and keeping the pressure for a certain time, detecting that there is no air leakage phenomenon at the laser welding and brazing position; cleaning the weld, coating a layer of three-proofing protective agent at each welding position and curing at room temperature.

Description

Technical Field

[0001] This invention relates to a welding and sealing method for a titanium alloy housing and a stainless steel igniter, applicable to the sealing connection between the housing and the igniter of starter products, and belongs to the field of pyrotechnics. Background Technology

[0002] After starter-type pyrotechnic devices are activated, the high-temperature, high-pressure gas within the working chamber needs to be sealed for an extended period. The combustion chamber shell is typically made of high-strength titanium alloy, while the igniter connected to it is usually made of stainless steel. The connection between the two uses a metal gasket and is sealed under a significant torque. However, under prolonged high temperature and pressure (≥300℃, ≥10MPa), maintaining a stable and effective seal is difficult. Furthermore, this torque-based sealing method carries the risk of stress relaxation after long-term storage, failing to achieve a stable seal during extended storage.

[0003] Based on this, a welding method is proposed to achieve a long-term sealed connection between the titanium alloy starter housing and the stainless steel igniter. Since both the titanium alloy housing and the stainless steel igniter contain explosives and other non-metallic components, direct high-temperature brazing (≥150℃) is not feasible. Low-heat fusion welding (laser welding, electron beam welding) cannot reliably achieve a high-strength seal. Therefore, it is proposed to first braze a dissimilar metal sealing ring, and then laser weld it to both the titanium alloy housing and the stainless steel igniter. This ultimately achieves a stable sealed connection between the two.

[0004] Patent CN110421223A discloses a method for high-strength laser welding of titanium alloy and stainless steel using copper-based brazing filler metal. This method places a 0.2mm thick copper-based brazing filler metal sheet between the stainless steel and titanium alloy joints, and uses a continuous fiber laser to weld the dissimilar metal joints. The laser is controlled to be offset towards the stainless steel side by (1-1.5)mm. The laser melts the stainless steel and copper-based brazing filler metal, causing the copper-based brazing filler metal to wet the titanium alloy side and form a brazed connection. This eliminates the risk of direct contact between stainless steel and titanium alloy forming brittle intermetallic compounds. The welded structure is free of cracks and other defects, with a tensile strength of 210MPa. Direct laser welding of stainless steel and titanium alloy requires extremely precise control. Even a slight deviation in laser offset can cause the titanium alloy to melt, risking the formation of brittle intermetallic compounds and joint cracking. This is unacceptable in the aerospace field; therefore, a more reliable and stable connection method is needed to achieve a sealed connection between stainless steel and titanium alloy. Summary of the Invention

[0005] The technical problem solved by the present invention is to overcome the shortcomings of the prior art and provide a welding and sealing method for a titanium alloy shell and a stainless steel igniter, thereby achieving a laser welding and sealing connection between the titanium alloy and the stainless steel.

[0006] The technical solution of the present invention is: a welding and sealing method for a titanium alloy shell and a stainless steel igniter, comprising: welding the igniter and the titanium alloy shell to an adapter ring respectively to achieve a seal; the adapter ring comprises: a stainless steel ring, a titanium alloy ring, and brazing filler metal;

[0007] The welding sealing method is as follows:

[0008] Place the flux-containing solder on the titanium alloy ring to be soldered, assemble the stainless steel ring using a limiting fixture, and clean off any excess flux and contaminants to obtain the adapter ring structure.

[0009] The entire adapter ring structure is placed in a vacuum brazing furnace, and the vacuum level, temperature, holding time, and pressure applied to the entire structure are set.

[0010] Clean the residue from the brazing joint of the adapter ring; test the airtightness of the adapter ring using an airtightness testing device;

[0011] Insert the adapter ring into the igniter, and then laser weld the igniter to the stainless steel ring side of the adapter ring for sealing.

[0012] The igniter with the adapter ring is installed into the titanium alloy housing, and the titanium alloy housing and the titanium alloy ring side of the adapter ring are laser welded and sealed.

[0013] Gas at the required pressure is introduced into the input end of the titanium alloy shell and the pressure is maintained for a certain period of time. The laser welding and brazing joints should be checked for leaks.

[0014] Clean the weld seam thoroughly, apply a layer of three-proof protective agent to each weld location, and allow it to cure at room temperature.

[0015] Preferably, the stainless steel ring is made of 1Cr18Ni9Ti, the titanium alloy ring is made of TC4, and the brazing filler metal is made of silver-based brazing filler metal Ag72Cu28.

[0016] Preferably, when placing the entire adapter ring structure into the vacuum brazing furnace, the vacuum level is set to: 3×(10) -2 ~10 -3 The temperature is set to 850℃±10℃, the holding time is set to 8min~15min, and the pressure is 0.05MPa~0.3MPa applied to the entire structure of the transition ring.

[0017] Preferably, when using an airtightness testing device to test the airtightness of the adapter ring, the airtightness should meet the requirement of no leakage at 12MPa / 10min.

[0018] Preferably, when laser welding is performed to seal the igniter to the stainless steel ring side of the adapter ring, the laser welding parameters are as follows:

[0019] The laser spot diameter is 100 μm, the laser power is 500 W ± 50 W, the welding time is 1.5 s to 2 s, the defocusing amount is 0 mm to -0.5 mm, and the argon flow rate is 10 L / min to 15 L / min.

[0020] Preferably, when the titanium alloy housing and the titanium alloy ring side of the adapter ring are laser welded together for sealing, the laser welding parameters are as follows:

[0021] The laser spot diameter is 100 μm, the laser power is 600 W ± 50 W, the welding time is 1.5 s to 2 s, the defocusing amount is 0 mm to -0.5 mm, and the argon flow rate is 10 L / min to 15 L / min.

[0022] Preferably, when the gas at the required pressure is introduced into the input end of the titanium alloy shell and the pressure is maintained for a certain period of time, the parameter is set to 12MPa / 10min.

[0023] Preferably, the three-proof protective agent is DBSF-6102;

[0024] Curing time is 2-3 hours at room temperature.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] (1) The present invention adopts the laser welding sealing method of the adapter ring, which can realize a high-strength sealed connection between the stainless steel igniter and the titanium alloy shell. The adapter ring can be adjusted according to the different product structures, which has the advantages of good design and good appearance of the product after welding.

[0027] (2) The present invention uses a brazed dissimilar metal transition ring to laser weld seal titanium alloy and stainless steel. The weld heat input is low, the overall temperature rise of the product is small, and it has no effect on non-metallic components and explosives inside the product, thus ensuring good safety.

[0028] (3) The present invention uses laser welding of the adapter ring to seal stainless steel and titanium alloy, which can withstand harsh mechanical and environmental conditions, has good long-term storage properties, and the product has stable sealing performance in high temperature and high pressure environments (≤500℃, ≤12MPa). Attached Figure Description

[0029] Figure 1 This is a cross-sectional view of the brazing structure of the adapter ring of the present invention;

[0030] Figure 2 This is a cross-sectional view of the laser-welded sealing structure of the titanium alloy shell and the stainless steel igniter of the present invention. Detailed Implementation

[0031] The technical solution of this invention includes an adapter ring (composed of a stainless steel ring (1Cr18Ni9Ti), a titanium alloy ring (TC4), and brazing filler metal (silver-based brazing filler metal Ag72Cu28)), a stainless steel igniter, and a TC4 titanium alloy housing. The adapter ring is prepared by brazing the stainless steel ring and the titanium alloy ring together in a vacuum environment using silver-based brazing filler metal. The adapter ring is then laser-welded to both the stainless steel igniter and the titanium alloy housing to achieve a seal.

[0032] The welding sealing method mainly includes the following steps:

[0033] 1) In 3×(10 -2 ~10 -3 In a vacuum environment of (850±10)℃, the stainless steel / titanium alloy adapter ring was brazed and sealed using Ag72Cu28 brazing filler metal. The brazing temperature was (850±10)℃, the holding time was (8~15)min, and the pressure was (0.05~0.3)MPa.

[0034] 2) Use sandpaper to polish the brazing area to remove any excess brazing filler metal and flux residue;

[0035] 3) Use an airtightness testing device to test the airtightness of the brazed parts of the stainless steel / titanium alloy adapter ring. The airtightness should meet the requirement of no leakage at 12MPa / 10min.

[0036] 4) Insert the adapter ring into the stainless steel igniter, and then perform laser welding to seal the stainless steel side of the igniter and the stainless steel side of the adapter ring (laser welding parameters: spot diameter 100um, laser power (500±50)W, welding time (1.5~2)s, defocusing amount (0~-0.5)mm, argon flow rate (10~15)L / min);

[0037] 5) Install the igniter with the adapter ring into the titanium alloy housing, and seal the titanium alloy side of the housing with the titanium alloy side of the adapter ring by laser welding (laser welding parameters: spot diameter 100um, laser power (600±50)W, welding time (1.5~2)s, defocusing amount (0~-0.5)mm, argon flow rate (10~15)L / min);

[0038] 6) Introduce the required pressure of gas into the input end of the titanium alloy shell and maintain the pressure for a certain period of time (e.g., 12MPa / 10min). Check that there is no gas leakage at the laser welding and brazing joints.

[0039] Example:

[0040] like Figure 1As shown, the present invention discloses a welding and sealing method for titanium alloy and stainless steel, comprising a 1Cr18Ni9Ti stainless steel ring 1, an Ag72Cu28 brazing filler metal 2, a TC4 titanium alloy ring 3, a 1Cr18Ni9Ti igniter 4, and a TC4 titanium alloy housing 5. The adapter ring comprises: a stainless steel ring 1 (1Cr18Ni9Ti), a titanium alloy ring 3 (TC4), and brazing filler metal 2 (silver-based brazing filler metal Ag72Cu28).

[0041] The implementation steps of this invention are as follows:

[0042] 1. Place the Ag72Cu28 solder 2 containing flux on the titanium alloy ring 3 to be soldered, and use the limiting tool to assemble the 1Cr18Ni9Ti stainless steel ring 1, and clean the overflow flux and contaminants.

[0043] 2. Place the entire assembly into a vacuum brazing furnace and set the vacuum level to 3×(10). -2 ~10 -3 The temperature was (850±10)℃, the holding time was (8~15)min, and the overall pressure was approximately (0.05~0.3)MPa.

[0044] 3. Use sandpaper to clean the solder joints of the adapter ring, removing any excess flux, solder, or other residue. Use an airtightness testing device to check the adapter ring for airtightness (12MPa / 10min) and ensure there is no leakage.

[0045] 4. Insert the adapter ring into the stainless steel igniter, and then perform laser welding to seal the stainless steel side of the igniter and the stainless steel side of the adapter ring (laser welding parameters: spot diameter 100um, laser power (500±50)W, welding time (1.5~2)s, defocusing amount (0~-0.5)mm, argon flow rate (10~15)L / min).

[0046] 5. Install the igniter with the adapter ring into the titanium alloy housing 5, and seal the titanium alloy side of the housing with the titanium alloy side of the adapter ring by laser welding (laser welding parameters: spot diameter 100um, laser power (600±50)W, welding time (1.5~2)s, defocusing amount (0~-0.5)mm, argon flow rate (10~15)L / min);

[0047] 6. Introduce the required pressure of gas into the input end of the titanium alloy shell and maintain the pressure for a certain period of time (e.g., 12MPa / 10min). Check that there is no gas leakage at the laser welding and brazing joints.

[0048] 7. Clean the weld seam thoroughly, apply a thin layer of three-proof protective agent (DBSF-6102) to each weld location and allow it to cure at room temperature for 2-3 hours.

[0049] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

Claims

1. A welding and sealing method for a titanium alloy shell and a stainless steel igniter, characterized in that... include: The igniter (4) and the titanium alloy housing (5) are welded to the adapter ring to achieve a seal; the adapter ring includes: a stainless steel ring (1), a titanium alloy ring (3), and brazing filler metal (2); The welding sealing method is as follows: Place the flux-containing solder (2) on the titanium alloy ring (3) to be welded, and use the limiting tool to assemble the stainless steel ring (1). Clean the overflowing flux and contaminants to obtain the adapter ring structure. The entire adapter ring structure is placed in a vacuum brazing furnace, and the vacuum level, temperature, holding time, and pressure applied to the entire structure are set. Clean the residue from the brazing joint of the adapter ring; test the airtightness of the adapter ring using an airtightness testing device; Insert the adapter ring into the igniter, and then laser weld the igniter (4) to the stainless steel ring (1) side of the adapter ring for sealing. The igniter with the adapter ring is installed into the titanium alloy housing (5), and the titanium alloy housing (5) is laser welded to the titanium alloy ring (3) side of the adapter ring for sealing. Gas of the required pressure is introduced into the input end of the titanium alloy shell (5) and the pressure is maintained for a certain time. The laser welding and brazing joints should be checked to ensure there is no gas leakage. Clean the weld seam thoroughly, apply a layer of three-proof protective agent to each weld location, and allow it to cure at room temperature.

2. The welding and sealing method for a titanium alloy shell and a stainless steel igniter according to claim 1, characterized in that: The stainless steel ring (1) is made of 1Cr18Ni9Ti, the titanium alloy ring (3) is made of TC4, and the brazing filler metal (2) is made of silver-based brazing filler metal Ag72Cu28.

3. The welding and sealing method for a titanium alloy shell and a stainless steel igniter according to claim 1, characterized in that: When placing the entire adapter ring structure into the vacuum brazing furnace, set the vacuum level to: 3×(10) -2 ~10 -3 The temperature is set to 850℃±10℃, the holding time is set to 8min~15min, and the pressure is 0.05MPa~0.3MPa applied to the entire structure of the transition ring.

4. The welding and sealing method for a titanium alloy shell and a stainless steel igniter according to claim 1, characterized in that: When testing the air tightness of the adapter ring using an air tightness testing device, the air tightness should meet the requirement of no leakage at 12MPa / 10min.

5. The welding and sealing method for a titanium alloy shell and a stainless steel igniter according to claim 1, characterized in that: When the igniter (4) is laser welded to the stainless steel ring (1) side of the adapter ring for sealing, the laser welding parameters are as follows: The laser spot diameter is 100 μm, the laser power is 500 W ± 50 W, the welding time is 1.5 s to 2 s, the defocusing amount is 0 mm to -0.5 mm, and the argon flow rate is 10 L / min to 15 L / min.

6. The welding and sealing method for a titanium alloy shell and a stainless steel igniter according to claim 1, characterized in that: When the titanium alloy housing (5) and the titanium alloy ring (3) side of the adapter ring are laser welded together for sealing, the laser welding parameters are as follows: The laser spot diameter is 100 μm, the laser power is 600 W ± 50 W, the welding time is 1.5 s to 2 s, the defocusing amount is 0 mm to -0.5 mm, and the argon flow rate is 10 L / min to 15 L / min.

7. The welding and sealing method for a titanium alloy shell and a stainless steel igniter according to claim 1, characterized in that: When the gas at the required pressure is introduced into the input end of the titanium alloy shell (5) and the pressure is maintained for a certain period of time, the parameter is set to 12MPa / 10min.

8. The welding and sealing method for a titanium alloy shell and a stainless steel igniter according to claim 1, characterized in that: The three-proof protective agent used is DBSF-6102; Curing time is 2-3 hours at room temperature.

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