Production process of arc-shaped bracket investment casting

Abstract

The invention provides an arc-shaped support investment casting production process. The arc-shaped support investment casting production process comprises the following steps that S1, a part mold is designed and manufactured; s2, a cold wax block assembly is pressed, specifically, the cold wax block assembly is put into a part mold, a part wax mold is pressed, a plurality of inner sprues are formed in the part wax mold, the inner sprues and a pouring system are connected to obtain a module, and the module is subjected to shell making to obtain a mold shell; s3, roasting the mold shell; s4, melting the steel ingot in a medium-frequency electric furnace to obtain molten steel; s5, the molten steel is poured and cooled; s6, the mold shell is cleaned, cut and polished, and a part with the needed shape is obtained; and S7, the cleaned part is put into a vacuum gas quenching heat treatment furnace, homogenization treatment, solution treatment and aging heat treatment are sequentially conducted, and the arc-shaped support investment casting with qualified performance is obtained. The deformation amount of the arc-shaped support type investment casting can be reduced, the internal structure performance of the arc-shaped support type investment casting is improved, and the product percent of pass is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of aviation precision casting, and in particular to a production process for investment castings of arc-shaped brackets. Background Art

[0002] With the development of the casting industry, customers have higher and higher requirements for castings. Some products originally produced by sand casting can no longer meet the requirements of customers (such as surface quality, dimensional accuracy, etc.), and they begin to switch to investment casting. Different casting methods have their own advantages and disadvantages. For example, for some connecting structure castings, the surface quality of sand-cast products is much worse than that of investment castings, and the dimensional accuracy is also insufficient. However, sand-cast castings are buried in the entire sand box, so the deformation of the castings is relatively small. At the same time, when sand casting is carried out, the sand box is at room temperature, and the cooling rate of molten steel is faster, making it easier to obtain a finer-grained internal structure, and making it easier for the mechanical properties of the product to meet the requirements. When this type of structural part is switched to investment casting, deformation is difficult to avoid during the wax injection and pouring stages, and post-shaping is required to meet the product requirements. At the same time, due to the reason of hot shell pouring in investment casting, the solidification rate of molten steel is slower and the grains are coarser, making it more difficult to meet the mechanical property requirements of the product. Summary of the Invention

[0003] The purpose of the present invention is to overcome and supplement the deficiencies existing in the prior art, and to provide a production process for investment castings of arc-shaped brackets, which reduces the deformation amount of investment castings of arc-shaped brackets, improves their internal tissue properties, and improves the product qualification rate.

[0004] The technical solution adopted by the present invention is as follows: A production process for investment castings of arc-shaped brackets, which includes the following steps: Step S1. Design the structure of the mold-opening part. The structure of the mold-opening part includes two arc-shaped structures and the connecting structure between the two arc-shaped structures. Tie bars are arranged on the same side of the two arc-shaped structures and between the ends of each arc-shaped structure, and an anti-deformation amount structure is arranged on the outer periphery of the inner ends of the two arc-shaped structures. The part mold is designed and manufactured according to the designed structure of the mold-opening part. Step S2. Press a cold wax block assembly, place the cold wax block assembly into the part mold, and fill the part mold with medium-temperature wax to press into a part wax mold. A plurality of ingates are arranged on the part wax mold, and the ingates are connected to the gating system to obtain a mold assembly. Then the mold assembly is shelled to obtain a mold shell. Step S3. Stick ceramic thermal insulation cotton on the runner part of the mold shell, and then bake the mold shell. Step S4. Melt an ingot in an intermediate frequency electric furnace to obtain molten steel. Then, electrolytic manganese and ferrosilicon are added to the molten steel for preliminary deoxidation, and then calcium silicate alloy is added for final deoxidation. Finally, the composition of the molten steel is controlled to be qualified by spectroscopic analysis. Step S5. Take out the mold shell from the roasting furnace and transfer it to the sand tray, then pour molten steel into the pouring cup of the mold shell for casting, then let it stand and cool, and finally blow-cool the mold shell; Step S6. Clean and cut and polish the mold shell to obtain parts with the required shape; Step S7. Put the cleaned parts into a vacuum quenching heat treatment furnace, and successively carry out homogenization treatment, solution treatment and aging heat treatment to obtain arc-shaped bracket investment castings with qualified performance.

[0005] Preferably, in the production process of the arc-shaped bracket investment casting, in Step S3, the roasting temperature is 1050±20°C and the roasting time is 1.5 - 2h.

[0006] Preferably, in the production process of the arc-shaped bracket investment casting, in Step S4, calculated by mass fraction, the steel ingot includes the following components: C≤0.04%, Mn 0.5 - 0.7%, Si 0.5 - 1%, P≤0.025%, Ni 4.0 - 4.60%, Cr15.50 - 16.0%, Cu 2.80 - 3.50%, Nb 0.15 - 0.40%, Al ≤0.05%, S≤0.025%, Sn≤0.02%, N≤0.04%, Ta≤0.045%, and the rest is Fe, and the sum of the above components is 100%.

[0007] Preferably, in the production process of the arc-shaped bracket investment casting, in Step S4, the addition amount of electrolytic manganese is 0.1 - 0.3% of the weight of the molten steel, the addition amount of ferrosilicon is 0.05 - 0.15% of the weight of the molten steel, and the addition amount of calcium-silicon alloy is 0.1 - 0.15% of the weight of the molten steel.

[0008] Preferably, in the production process of the arc-shaped bracket investment casting, in Step S5, the casting is carried out by sub-contracting casting, and the pouring temperature of the molten steel is 1640 - 1650°C.

[0009] Preferably, in the production process of the arc-shaped bracket investment casting, in Step S5, the standing cooling time is 1min and the blowing cooling time is 10min.

[0010] Preferably, in the production process of the arc-shaped bracket investment casting, in Step S7, the homogenization treatment temperature is 1149±10°C, the holding time is 100±10min, and after the holding ends, it is cooled to room temperature with argon.

[0011] Preferably, in the production process of the arc-shaped bracket investment casting, in Step S7, the solution treatment temperature is 1038±10°C, the holding time is 100±10min, and after the holding ends, it is cooled to room temperature with argon.

[0012] Preferably, in the investment casting process of the arc-shaped bracket, in step S7, the aging treatment temperature is 621 ± 10 °C, the heat preservation time is 240 ± 20 min, and after the heat preservation is completed, it is cooled in the furnace under argon protection to 90 °C and then taken out of the furnace.

[0013] Advantages of the present invention: (1) In the investment casting process of the arc-shaped bracket of the present invention, through reasonable gating system design, methods such as shell wrapping with cotton and blowing after pouring are used to accelerate the solidification rate of the casting, and at the same time achieve the effect of sequential solidification, avoid the generation of internal shrinkage defects, refine the grain structure, and make the mechanical properties of the product body test bar qualified.

[0014] (2) In the investment casting process of the arc-shaped bracket of the present invention, through internal control of the product chemical composition and reasonable heat treatment process, the mechanical properties of the product are further optimized; by designing a special structure of a dedicated cold wax block and placing it in the pressure body wax mold die, the deformation caused by wax mold shrinkage is reduced, and the size is stabilized.

[0015] (3) In the investment casting process of the arc-shaped bracket of the present invention, by increasing the anti-deformation amount and adding process ribs when opening the mold, the deformation generated during the production of the casting is reduced, so that the casting can achieve the effect of not requiring shaping or only slight shaping. Description of the drawings

[0016] Figure 1 It is a schematic structural diagram of the investment casting of the arc-shaped bracket of the present invention.

[0017] Figure 2 It is a schematic structural diagram of the mold with ribs provided.

[0018] Figure 3 It is a schematic structural diagram of the mold with an anti-deformation amount structure provided.

[0019] Figure 4 It is a schematic structural diagram of the cold wax block assembly of the present invention.

[0020] Figure 5 It is a schematic structural diagram of the wax mold of the present invention with multiple ingates provided.

[0021] Figure 6 It is a schematic structural diagram of the module of the present invention.

[0022] Figure 7 It is a schematic structural diagram of the ceramic insulation cotton pasted on the runner part of the mold shell of the present invention.

[0023] Figure 8 It is a schematic structural diagram of the mold shell of the present invention being blown for cooling.

[0024] Figure 9It is a sampling position diagram for the mechanical property detection of the part body test bar. Specific implementation mode

[0025] The present invention will be further described below in conjunction with specific drawings and embodiments.

[0026] Embodiment 1 A production process for investment castings of arc-shaped brackets, which includes the following steps: Step S1. Design the structure of the die-opening part, such as Figure 1 and Figure 2 , the die-opening part structure includes two arc-shaped structures 1 and the connection structure 1 between the two arc-shaped structures 1. Tie bars 3 are arranged on the same side of the two arc-shaped structures 1 and between the ends of each arc-shaped structure 1, such as Figure 3 , an anti-deformation amount structure 4 with a shape fit is arranged on the outer periphery of the inner ends of the two arc-shaped structures 1. The thickness of the anti-deformation amount structure 4 is 1 mm, and the material is the same as that of the part. Remove 1 mm of material from the outside of the arc-shaped structure 1 at position 7 to obtain the die-opening part structure; design and manufacture a part mold according to the designed die-opening part structure; Step S2. Such as Figure 4 , press a cold wax block assembly. The cold wax block assembly includes two cold wax blocks 8 that fit the shape of the arc-shaped structure 1. Place the cold wax block assembly into the part mold, and fill the part mold with medium-temperature wax to press into a part wax mold, such as Figure 5 , set a plurality of internal gates 5 on the part wax mold, and connect the internal gates 5 with the gating system to obtain a mold assembly, such as Figure 6 , the gating system includes a main runner 9. Two cross runners 10 are vertically arranged on the main runner 9. The inner side of the cross runner 10 is connected to the internal gate 5. The cross runner 10, the internal gate 5 and the main runner 9 are interconnected. A pouring cup 6 is arranged at the top of the main runner 9. Then, shell the mold assembly to obtain a mold shell; The shelling is carried out in 9 layers. The first layer is the facing layer, the second layer is the transition layer, and the 3-9th layers are the backing layers; immerse the mold assembly in the facing layer slurry, take it out and sprinkle 80-120 mesh zircon sand on the surface, then dry it. Subsequently, immerse the mold assembly in the transition layer slurry, take it out and sprinkle 30-60 mesh mullite sand on the surface, dry it. Finally, immerse the mold assembly in the backing layer slurry, take it out and sprinkle 16-30 mesh mullite sand on the surface, dry it, and immerse the mold assembly in the backing layer slurry and sprinkle sand and dry it 6 times and dewax it to obtain a mold shell; The facing layer slurry includes colloidal silica and zircon powder with a weight ratio of 1:5. Mix the colloidal silica and zircon powder and stir for 24 h until evenly mixed. The slurry viscosity is 50 s, the drying time after shelling is 5 h, and the drying temperature is 24 °C; The transition layer slurry includes colloidal silica and mullite powder with a weight ratio of 1:2. Stir the colloidal silica and mullite powder for 24 h until evenly mixed. The slurry viscosity is 20 s, the drying time after shelling is 7 h, and the drying temperature is 24 °C; The back layer slurry consists of silica sol and mullite powder in a weight ratio of 1:1.4. The silica sol and mullite powder are mixed and stirred for 8 hours until evenly mixed. The viscosity of the slurry is 17 s. After shell making, the drying time is 12 hours and the drying temperature is 24 °C. Step S3. As Figure 7 , ceramic insulation cotton 11 is pasted on the gating part of the mold shell, namely the main runner 9 and the cross runner 10, and then the mold shell is baked at a baking temperature of 1050 °C for 1.5 hours. Step S4. The ingot is melted in an intermediate frequency electric furnace to obtain molten steel. Then, electrolytic manganese and ferrosilicon are added to the molten steel for preliminary deoxidation, and then calcium silicate alloy is added for final deoxidation. Finally, the composition of the molten steel is controlled to be qualified by chemical analysis using a spectroscope. The material of the ingot is 17-4PH. To ensure qualified mechanical properties, its composition has been internally controlled. Calculated by mass fraction, the ingot includes the following components: C 0.03%, Mn 0.52%, Si 0.72%, P 0.02%, Ni: 4.2%, Cr 15.80%, Cu 3.10%, Nb 0.23%, Al 0.004%, S 0.001%, Sn 0.005%, N 0.002%, Ta 0.008%, and the rest is Fe. The sum of the above components is 100%. The addition amount of electrolytic manganese is 0.2% of the weight of the molten steel, the addition amount of ferrosilicon is 0.1% of the weight of the molten steel, and the addition amount of calcium silicate alloy is 0.12% of the weight of the molten steel. Step S5. The mold shell is taken out of the baking furnace with a steel fork, and then the mold shell is clamped with iron pliers and transferred to the sand tray 12. The molten steel at 1645 °C is poured into the pouring cup 6 of the mold shell for pouring. The pouring is carried out by ladle pouring. The pouring temperature of the molten steel is 1645 °C, and then it is left to stand and cool for 1 minute. Finally, a fan is aimed at the mold shell for blowing and cooling for 10 minutes. The blowing direction is shown in Figure 8 ; Step S6. The mold shell is cleaned, cut, and polished to obtain parts of the required shape. Step S7. The cleaned parts are put into a vacuum gas quenching heat treatment furnace, and homogenization treatment, solution treatment, and aging heat treatment are carried out in sequence. The temperature of the homogenization treatment is 1139, the holding time is 90 minutes, and after the holding ends, it is cooled to room temperature with argon. The temperature of the solution treatment is 1028 °C, the holding time is 90 minutes, and after the holding ends, it is cooled to room temperature with argon. The temperature of the aging treatment is 611 °C, the holding time is 220 minutes, and after the holding ends, it is cooled with the furnace under argon protection to 90 °C and then taken out of the furnace to obtain arc-shaped bracket investment castings with qualified performance.

[0027] Example 2 The difference between Example 2 and Example 1 is that the homogenization treatment temperature is 1149 °C, the holding time is 100 min, and after the holding is completed, it is cooled to room temperature with argon; the solution treatment temperature is 1038 °C, the holding time is 100 min, and after the holding is completed, it is cooled to room temperature with argon; the aging treatment temperature is 621 °C, the holding time is 240 min, and after the holding is completed, it is cooled in the furnace under argon protection to 90 °C and then taken out of the furnace, obtaining a precision investment casting of an arc-shaped bracket with qualified performance.

[0028] Example 3 The difference between Example 3 and Example 1 is that the homogenization treatment temperature is 1159 °C, the holding time is 110 min, and after the holding is completed, it is cooled to room temperature with argon; the solution treatment temperature is 1048 °C, the holding time is 110 min, and after the holding is completed, it is cooled to room temperature with argon; the aging treatment temperature is 631 °C, the holding time is 260 min, and after the holding is completed, it is cooled in the furnace under argon protection to 90 °C and then taken out of the furnace.

[0029] Take 9 specimen bars from the precision investment castings of the arc-shaped brackets in Examples 1 - 3 to test the mechanical properties. The positions for taking the specimen bars are shown in the appendix Figure 9 , and the mechanical property results of the specimen bars are shown in the table. The required mechanical properties of the product are: tensile strength ≥ 900 MPa, yield strength ≥ 700 MPa, elongation ≥ 15%. The product performances of the three heat treatment tests are all qualified.

[0030] Example 1

[0031] Example 2

[0032] Example 3

[0033] The overall profile tolerance requirement of the precision investment casting of the arc-shaped bracket is within 1.5 mm. After heat treatment of the precision investment casting of the arc-shaped bracket, the arc-shaped bracket precision investment castings in Examples 1 - 3 were subjected to three-coordinate measurement and 3D scanning. The overall profiles of the arc-shaped bracket precision investment castings prepared in Examples 1 - 3 are all within 1.5 mm, no shaping is required, and the product dimensions are qualified.

[0034] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and are not restrictive. Although the present invention has been described in detail with reference to the examples, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A production process for investment castings of arc-shaped brackets, characterized in that: It includes the following steps: Step S1. Design the structure of the die-opening part. The structure of the die-opening part includes two arc structures (1) and the connecting structure (2) between the two arc structures (1). Tension ribs (3) are arranged on the same side of the two arc structures (1) and between the ends of each arc structure (1), and an anti-deformation amount structure (4) is arranged on the outer periphery of the inner ends of the two arc structures (1). The part die is designed and manufactured according to the designed structure of the die-opening part; Step S2. Press the cold wax block assembly. Put the cold wax block assembly into the part die, and fill the part die with medium-temperature wax to press into a part wax pattern. Set a plurality of ingates (5) on the part wax pattern, connect the ingates (5) with the gating system to obtain a module, and then shell the module to obtain a shell mold; Step S3. Stick ceramic thermal insulation cotton on the runner part of the shell mold, and then roast the shell mold; Step S4. Melt the steel ingot in an intermediate frequency furnace to obtain molten steel. Then add electrolytic manganese and ferrosilicon to the molten steel for pre-deoxidation, and then add calcium silicate alloy for final deoxidation. Finally, control the composition of the molten steel to be qualified by spectrometric analysis; Step S5. Take out the shell mold from the roasting furnace and transfer it to a sand tray. Then pour the molten steel into the pouring cup (6) of the shell mold for pouring, then let it stand and cool, and finally blow-cool the shell mold; Step S6. Clean and cut and polish the shell mold to obtain a part with the required shape; Step S7. Put the cleaned part into a vacuum quenching heat treatment furnace, and perform homogenization treatment, solution treatment and aging heat treatment in sequence to obtain a qualified arc bracket investment casting; 2. The investment casting production process of the arc bracket according to claim 1, wherein: In Step S3, the roasting temperature is 1050±20°C, and the roasting time is 1.5 - 2h.

3. The investment casting production process of the arc-shaped bracket according to claim 1, characterized in that: In Step S4, calculated by mass fraction, the steel ingot includes the following components: C≤0.04%, Mn 0.5 - 0.7%, Si 0.5 - 1%, P≤0.025%, Ni 4.0 - 4.60%, Cr 15.50 - 16.0%, Cu 2.80 - 3.50%, Nb 0.15 - 0.40%, Al ≤0.05%, S≤0.025%, Sn≤0.02%, N≤0.04%, Ta≤0.045%, and the rest is Fe. The sum of the above components is 100%.

4. The investment casting production process of the arc-shaped bracket according to claim 1, characterized in that: In Step S4, the addition amount of electrolytic manganese is 0.1 - 0.3% of the weight of the molten steel, the addition amount of ferrosilicon is 0.05 - 0.15% of the weight of the molten steel, and the addition amount of calcium silicate alloy is 0.1 - 0.15% of the weight of the molten steel.

5. The investment casting process of the arc-shaped bracket according to claim 1, characterized in that: In Step S5, the pouring is carried out by a ladle pouring method, and the pouring temperature of the molten steel is 1640 - 1650°C.

6. The investment casting process of the arc-shaped bracket according to claim 1, characterized in that: In Step S5, the standing cooling time is 1min, and the blowing cooling time is 10min.

7. The investment casting production process of the arc bracket according to claim 1, characterized in that: In Step S7, the temperature of the homogenization treatment is 1149±10°C, the holding time is 100±10min, and after the holding is completed, it is cooled to room temperature by argon.

8. The investment casting process of the arc-shaped bracket according to claim 1, characterized in that: In Step S7, the temperature of the solution treatment is 1038±10°C, the holding time is 100±10min, and after the holding is completed, it is cooled to room temperature by argon.

9. The investment casting process of the arc bracket according to claim 1, characterized in that: In step S7, the aging treatment temperature is 621 ± 10 °C, the heat preservation time is 240 ± 20 min. After the heat preservation is completed, it is cooled with the furnace under argon protection until it reaches 90 °C and then taken out of the furnace.

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