Method for removing support structures for titanium and titanium alloy products produced by selective laser melting

Abstract

The application relates to a method for removing a support structure of a titanium and titanium alloy product prepared by selective laser melting, which comprises the following steps: placing a part with a support structure formed by selective laser melting (SLM) in a heat treatment furnace, setting a heat treatment temperature value and a holding time, filling the heat treatment furnace with inert protective gas, starting heat treatment after the oxygen content in the heat treatment furnace is reduced to below the required concentration, and feeding a mixed solution of ammonium hydrogen fluoride, sodium fluoride, sodium chloride, aluminum fluoride and water into the heat treatment furnace after the heat treatment temperature reaches the set heat treatment temperature value. Through the application, the support structure can be vaporized and corroded during heat treatment, the influence on the size precision of the part is small, the shortcomings of insufficient processing capacity of mechanical processing equipment and the need for large-scale manual processing at the present stage are made up, and the comprehensive cost of the additive manufacturing product is effectively reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of 3D printing of titanium and titanium alloy, and more particularly, relates to a method for removing a support structure of a titanium and titanium alloy product prepared by selective laser melting. BACKGROUND

[0002] Additive Manufacturing (AM), also known as three-dimensional printing, direct digital manufacturing or free-form manufacturing, has experienced more than 30 years of development since the emergence of rapid prototyping technology in the late 1980s, and is one of the currently rapidly developing advanced manufacturing technologies. The ISO ASTM 52900-2015 standard defines additive manufacturing as a manufacturing process that differs from subtractive manufacturing in that it builds up a part layer by layer from a three-dimensional model data. Among them, the selective laser melting technology is one of the widely used technologies. In the 1990s, due to the development of fiber laser technology, based on the selective laser sintering technology, the selective laser melting (SLM) technology emerged as the times require. As a cutting-edge laser additive manufacturing technology, its forming principle is similar to that of selective laser sintering technology, and high-energy fiber lasers are used to completely melt metal powder materials and then rapidly cool and solidify to form high-density functional parts. Its main advantages include high-density metal part forming, high part design freedom, strong ability to manufacture complex structure parts, short part production cycle, and high material utilization rate.

[0003] However, due to the characteristics of the SLM technology, appropriate support structures must be added to assist the formation of the parts during preparation. The functions of the support structures mainly include the following points: (1) heat conduction. When sintering a suspended structure, if the laser beam directly scans on the powder, the heat cannot be dissipated in time, and the temperature of the molten pool formed is too high, which can easily cause phenomena such as spheroidization and oxidation. The support structure below the suspended structure can effectively play a good heat conduction role to ensure stable sintering process; (2) preventing deformation. During the SLM forming process, complex and large internal stresses are generated inside the workpiece. Generally, the uppermost layer always produces a large tensile stress, which is manifested as the workpiece edge warping upwards. With the accumulation of layers, the workpiece deformation is macroscopically manifested as serious edge warping. This situation is particularly prominent when there is a suspended structure. Adding a reasonable support structure below the suspended structure can effectively hold the workpiece and resist warping to ensure stable sintering of the workpiece. Due to the above reasons, the parts formed by SLM must contain a large amount of support structures, and at the same time, due to the capacity limitations of traditional mechanical processing equipment and the increasing size of SLM equipment in recent years, a large amount of manpower and material resources is paid to remove the support structures in the later processing.

[0004] Therefore, it is desirable to provide a method for removing the support structure of a titanium and titanium alloy product prepared by selective laser melting. SUMMARY

[0005] In view of the above, the present application provides a process method, which can significantly reduce the strength of the support structure by adding a certain amount of chemical reagent while heat treating the SLM formed part, thereby saving time and manpower and material resources for post-processing.

[0006] To solve the above technical problems, the present application adopts the following technical solutions:

[0007] According to an aspect of the present application, a method for removing the support structure of a titanium and titanium alloy product prepared by selective laser melting is provided, comprising the following steps:

[0008] 1) Place the SLM formed part with support structure in a heat treatment furnace, and set the heat treatment temperature value and holding time;

[0009] 2) Fill the heat treatment furnace with inert protective gas, and start the heat treatment after the oxygen content in the heat treatment furnace is reduced to below the required concentration;

[0010] 3) After the heat treatment temperature reaches the set heat treatment temperature value, introduce a mixed solution of ammonium hydrogen fluoride, sodium fluoride, sodium chloride, aluminum fluoride and water into the heat treatment furnace.

[0011] In an embodiment of the present application, the method further comprises the following steps:

[0012] 4) After the heat treatment is completed, take out the part with the removed support structure.

[0013] In an embodiment of the present application, in step 1), the heat treatment furnace is a muffle furnace.

[0014] In an embodiment of the present application, in step 1), the set heat treatment temperature value is 500-1000℃, and the holding time is 2-4h.

[0015] In an embodiment of the present application, in step 2), the inert protective gas is argon.

[0016] In an embodiment of the present application, in step 2), the required concentration is 1000ppm.

[0017] In an embodiment of the present application, in step 3), the mixed solution is introduced into the heat treatment furnace at a flow rate of 5-50ml / min, and the introduction time is 5-50min.

[0018] In one embodiment of the present application, in step 3), the ammonium bifluoride, sodium fluoride, sodium chloride, aluminum fluoride and water are configured in the following mass ratio: ammonium bifluoride: sodium fluoride: sodium chloride: aluminum fluoride: water = (0.5-2g): (2-4g): (0.8-5g): (4-6g): (50-100g).

[0019] By adopting the technical scheme, the present application has the following advantages compared with the prior art:

[0020] The present application adds a mixed solution with a certain concentration in the heat treatment process of laser additive manufacturing to form a part, so that the mixed solution is vaporized and the support structure is corroded in the heat treatment process, while the size precision of the part is less affected, which makes up for the shortcomings of insufficient processing capacity of mechanical processing equipment and the need for large-scale manual processing at the present stage, and effectively reduces the comprehensive cost of additive manufacturing products. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 A flowchart of a method for removing a support structure of a titanium and titanium alloy product prepared by selective laser melting is shown. DETAILED DESCRIPTION

[0022] It should be understood that the embodiments of the present application shown in the example embodiments are only illustrative. Although only a few embodiments are described in detail in the present application, those skilled in the art can easily appreciate that various modifications are possible without departing from the teachings of the present application subject matter. Accordingly, all such modifications should be included within the scope of the present application. Other substitutions, modifications, changes and omissions can be made to the design, operating conditions and parameters of the following example embodiments without departing from the spirit of the present application.

[0023] As Figure 1 shown, the present application provides a method for removing a support structure of a titanium and titanium alloy product prepared by selective laser melting, comprising the following steps:

[0024] S101: placing a part with a support structure formed by selective laser melting (SLM) in a heat treatment furnace, and setting a heat treatment temperature value and a holding time;

[0025] S102: filling the heat treatment furnace with inert protective gas, and starting the heat treatment after the oxygen content in the heat treatment furnace is reduced to below the required concentration;

[0026] S103: after the heat treatment temperature reaches the set heat treatment temperature value, introducing a mixed solution of ammonium bifluoride, sodium fluoride, sodium chloride, aluminum fluoride and water into the heat treatment furnace.

[0027] The present application adds a mixed solution with a certain concentration in the heat treatment process of laser additive manufacturing of a shaped part, so that the mixed solution is vaporized and the support structure is corroded during the heat treatment process.

[0028] In the above method, the method can further include the following steps:

[0029] After the heat treatment is completed, the part with the removed support structure is taken out.

[0030] In the above method, in step S101, the heat treatment furnace is a muffle furnace; the set heat treatment temperature value is 500-1000℃, and the holding time is 2-4h.

[0031] In the above method, in step S102, the inert protective gas is argon; and the required concentration is 1000ppm.

[0032] In the above method, in step S103, the mixed solution is introduced into the heat treatment furnace at a flow rate of 5-50ml / min, and the introduction time is 5-50min; the ammonium bifluoride, sodium fluoride, sodium chloride, aluminum fluoride and water are configured in the following mass ratio: ammonium bifluoride:sodium fluoride:sodium chloride:aluminum fluoride:water=(0.5-2g):(2-4g):(0.8-5g):(4-6g):(50-100g).

[0033] The above technical solutions of the present application will be described in detail below through specific embodiments.

[0034] The specific process steps of the present application are as follows:

[0035] The part with the support prepared by the SLM technology is placed in the muffle furnace, and then argon is filled as the protective gas; the heat treatment can be performed after the oxygen content in the muffle furnace is reduced to below 1000ppm, wherein the heat treatment temperature is 500-1000℃, and the holding time is 2-4h; after the temperature of the heat treatment reaches the set temperature, the mixed solution with a flow rate of 5-50ml / min is introduced thereinto, and the introduction time is 5-50min; the composition of the solution is ammonium bifluoride:sodium fluoride:sodium chloride:aluminum fluoride:water=0.5g-2g:2g-4g:0.8g-5g:4g-6g:50g-100g.

[0036] Example 1

[0037] A method for removing the support structure of a titanium and titanium alloy product prepared by selective laser melting, comprising the following steps:

[0038] (1) placing the SLM-formed TA0 part in the muffle furnace for heat treatment, and setting the heat treatment parameters to a temperature of 550℃ and a holding time of 2h;

[0039] (2) Fill high-purity argon into the muffle furnace as a protective gas, and start the heat treatment after the oxygen concentration in the muffle furnace is reduced to 1000 ppm. After the temperature reaches the set value of 550℃, a mixed solution of ammonium hydrogen fluoride: sodium fluoride: sodium chloride: aluminum fluoride: water = 0.5g: 2g: 0.8g: 4g: 50g is introduced into the muffle furnace at a flow rate of 50ml / min, and the solution is introduced for 5min;

[0040] (3) The part can be taken out after the heat treatment is completed.

[0041] Through the above embodiment 1, the support structure is completely corroded after the heat treatment of the part, and the next step of processing can be performed.

[0042] Example 2

[0043] A method for removing the support structure of a titanium and titanium alloy product prepared by selective laser melting, comprising the following steps:

[0044] (1) Put the SLM-formed TB2 part into the muffle furnace for heat treatment, and set the heat treatment parameters to a temperature of 750℃ and a holding time of 3h;

[0045] (2) Fill high-purity argon into the muffle furnace as a protective gas, and start the heat treatment after the oxygen concentration in the muffle furnace is reduced to 1000 ppm. After the temperature reaches the set value of 750℃, a mixed solution of ammonium hydrogen fluoride: sodium fluoride: sodium chloride: aluminum fluoride: water = 1g: 3g: 2.9g: 5g: 75g is introduced into the muffle furnace at a flow rate of 25ml / min, and the solution is introduced for 25min;

[0046] (3) The part can be taken out after the heat treatment is completed.

[0047] Through the above embodiment 2, the support structure is completely corroded after the heat treatment of the part, and the next step of processing can be performed.

[0048] Example 3

[0049] A method for removing the support structure of a titanium and titanium alloy product prepared by selective laser melting, comprising the following steps:

[0050] (1) Put the SLM-formed TC4 part into the muffle furnace for heat treatment, and set the heat treatment parameters to a temperature of 950℃ and a holding time of 4h.

[0051] (2) high-purity argon is injected into the muffle furnace as a protective gas, and the heat treatment is started after the oxygen concentration in the muffle furnace is reduced to 1000 ppm, and after the temperature reaches the set value of 950 DEG C, a mixed solution of ammonium hydrogen fluoride: sodium fluoride: sodium chloride: aluminum fluoride: water = 2g: 4g: 5g: 6g: 100g is injected into the muffle furnace at a flow rate of 10 ml / min, and the solution is injected for 45 min;

[0052] (3) the part can be taken out after the heat treatment is completed.

[0053] Through the above-mentioned embodiment 3, the support structure is completely corroded after the heat treatment of the part, and the next step of processing can be performed.

[0054] Therefore, it can be seen that the application adds a mixed solution with a certain concentration in the heat treatment process of the laser additive manufacturing part, so that it is vaporized and corrodes the support structure in the heat treatment process, and has little effect on the size precision of the part, makes up for the shortcomings of insufficient processing capacity of the mechanical processing equipment and the need for large-scale manual processing at the present stage, and effectively reduces the comprehensive cost of the additive manufacturing product.

[0055] The above-mentioned is only the preferred embodiment of the application, and is not used to limit the implementation range of the application; if the modification or equivalent replacement of the application is not deviated from the spirit and range of the application, it should be covered in the protection range of the claims of the application.

Claims

1. A method for removing the support structure of titanium and titanium alloy products prepared by selective laser melting, characterized in that: The following steps are involved: 1) Place the selective laser melting (SLM) part with support structure in a heat treatment furnace and set the heat treatment temperature and holding time. 2) filling the heat treatment furnace with an inert protective gas, and starting the heat treatment after the oxygen content in the heat treatment furnace drops below a desired concentration; 3) After the heat treatment temperature reaches the set heat treatment temperature value, a mixed solution of ammonium bifluoride, sodium fluoride, sodium chloride, aluminum fluoride and water is introduced into the heat treatment furnace; In step 1), the heat treatment temperature is set to 500-1000°C; In step 3), the mixed solution is introduced into the heat treatment furnace at a flow rate of 5-50 ml / min for 5-50 min; In step 3), ammonium bifluoride, sodium fluoride, sodium chloride, aluminum fluoride and water are prepared according to the following mass ratio: ammonium bifluoride: sodium fluoride: sodium chloride: aluminum fluoride: water = (0.5-2g): (2-4g): (0.8-5g): (4-6g): (50-100g).

2. The method for removing the support structure of titanium and titanium alloy products prepared by selective laser melting according to claim 1, characterized in that: The following steps are also included: 4) After the heat treatment is completed, remove the parts with the support structure removed.

3. The method for removing the support structure of titanium and titanium alloy products prepared by selective laser melting according to claim 1, characterized in that: In the step 1), the heat treatment furnace is a muffle furnace.

4. The method for removing the support structure of titanium and titanium alloy products by selective laser melting according to claim 1, wherein in step 1), the holding time is 2-4 hours. 5 . The method for removing support structures of titanium and titanium alloy products prepared by selective laser melting according to claim 1 , wherein in step 2), the inert protective gas is argon. 6 . The method for removing support structures of titanium and titanium alloy products by selective laser melting according to claim 1 , wherein in step 2), the required concentration is 1000 ppm.

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