Ti2AlNb-based alloy multi-step special-shaped casing ring piece forming method

Abstract

The invention discloses a Ti2AlNb-based alloy multi-step special-shaped casing ring piece forming method which is characterized in that a net near forming method is adopted, the shape of a forge piece is designed along the outline of a part, and the material utilization rate from the forge piece to the part is improved to a great extent. The difficult point of the method lies in calculation of the blanking weight, a forge piece is equally divided into n forge pieces in the height direction, the volume of a blank is obtained by calculating the volume of each section, and the volume and the weight of a blanking bar are finally obtained by considering the loss of a punching core material. According to the method, the material utilization rate is increased on the basis that the structure performance of the Ti2AlNb-based alloy ring piece is guaranteed. The method is suitable for rolling forming of the Ti2AlNb-based alloy special-shaped ring piece.

Description

Technical Field

[0001] The present invention relates to a forming method for a ring-shaped part, in particular to a forming method for a multi-step special-shaped casing ring made of Ti2AlNb-based alloy. Background Art

[0002] Ti2AlNb-based alloy is a new type of lightweight high-temperature structural material, which is an intermetallic compound composed of Ti, Al, and Nb. This type of alloy has a two-phase or three-phase composite structure composed of O phase, B2 / β phase, and α2 phase, and has the advantages of low density, high elastic modulus, high high-temperature strength, high fracture performance, high creep resistance, low thermal expansion performance, non-magnetic, and good flame retardant performance. Compared with high-temperature titanium alloys, it has a higher service temperature, creep resistance, and high-temperature strength, and its density and thermal expansion coefficient are significantly lower than those of nickel-based superalloys. It is the best choice to replace titanium alloys and superalloys in the future aerospace field and has broad application prospects.

[0003] The Chinese invention patent specification CN104139139A published on November 12, 2014 discloses a rolling forming and heat treatment method for a Ti2AlNb-based alloy casing ring. A rolling forming method with multiple heating passes and small deformation amounts is adopted to realize the rolling forming of the Ti2AlNb-based alloy casing ring, and an ideal fine-grained basketweave structure is obtained through a reasonable heat treatment method to improve the room-temperature strength, high-temperature strength, and high-temperature creep performance of the Ti2AlNb-based alloy casing ring. This method only solves the forming of rectangular or simple special-shaped casing rings made of Ti2AlNb-based alloy. For most casings with very complex structures, if the forgings are designed as rectangular or simple special-shaped rings (such as Figure 1 shown), the later machining amount of the casing is very large and the material waste is huge. Ti2AlNb-based alloy is a very precious metal material, which is about more than 1000 yuan per kilogram, and it is necessary to improve the material utilization rate. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a net-shape forming method for multi-step special-shaped rings, which improves the material utilization rate on the basis of ensuring the tissue performance of the Ti2AlNb-based alloy ring.

[0005] To solve the above technical problem, the forming method for the Ti2AlNb-based alloy multi-step special-shaped casing ring of the present invention includes the following steps in its technical solution:

[0006] Import the part drawing into the drafting software, identify the contour points of the part, then connect the identified contour points, and add machining allowances on the contour. The machining allowance at the contour points is 5-10 mm, and the machining allowance at the connecting surface between two adjacent contour points is 3-6 mm to obtain the shape and size of the forging;

[0007] Design the intermediate ring blank according to the shape and size of the forging, divide the forging into n equal sections along the height direction, h1 = h2 = h3 = ...; according to the rolling ratio k and the inner diameter D of a certain section of the ring na , inner diameter D nb , determine the inner diameter of the ring blank outer diameter According to the height H of the ring, determine the height of the ring blank h = (1.05 ~ 1.10) H, where h = h1 + h2 + h3 ...;

[0008] Take a Ti2AlNb-based alloy rod of a certain specification, the weight of the rod is m=ρV, where ρ is the density of the Ti2AlNb-based alloy and V is the volume of the rod; Among them, V1 is the volume of the punching core material;

[0009] After the bar is heated to a certain temperature, it is upset, punched, and pre-rolled to obtain a rectangular ring blank. The height of the rectangular ring blank is the same as that of the special-shaped ring blank. The outer diameter of the rectangular ring blank is D0 = (0.75 ~ 0.85) D, where D is the minimum outer diameter of the special-shaped ring blank and the inner diameter of the rectangular ring blank is A rectangular ring blank is placed in the female die of the tire membrane, and the male die is driven to extrude and deform from the top of the inner hole of the rectangular ring blank to the bottom. The rectangular ring blank is first extruded and deformed into a conical ring blank using a male die with a certain taper, and then the conical ring blank is extruded and deformed into a special-shaped ring blank using a male die with the same contour as the inner wall of the special-shaped ring blank and a female die with the same contour as the outer wall of the special-shaped ring blank; the special-shaped ring blank is inserted into the core roller of the ring rolling mill, the ring rolling mill is driven to rotate at an angular velocity of 0.8 to 1.2 rad / s, and the core roller is driven to drive the special-shaped ring blank to feed to the main roller at a feed speed of 0.2 mm / s to 2.0 mm / s, so that the wall thickness of the special-shaped ring blank becomes thinner and the outer diameter is enlarged, and finally it is rolled into a special-shaped ring forging.

[0010] Furthermore, the deformation amount k during the final rolling forming is 25% to 40%.

[0011] Compared with the prior art, the present invention has the following beneficial effects:

[0012] The Ti2AlNb-based alloy multi-step special-shaped casing ring forming method of the present invention adopts a net near forming method, and the shape of the forging is designed along the part contour, which greatly improves the material utilization rate from the forging to the part. The difficulty of this method lies in the calculation of the blanking weight. The present invention divides the forging into n forgings in the height direction, calculates the volume of each section, obtains the volume of the blank, and then considers the loss of the punching core material, and finally obtains the volume and weight of the blanking bar. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0014] Figure 1 It is a schematic diagram of a conventional designed special-shaped ring forging.

[0015] Figure 2 It is a schematic diagram for identifying the contour points of a part.

[0016] Figure 3 It is a schematic diagram of the special-shaped ring forging described in the present invention.

[0017] Figure 4 It is a schematic diagram of the diaphragm forming of the special-shaped ring blank described in the present invention.

[0018] Figure 5 It is a schematic diagram of the shape change of the diaphragm-formed ring blank described in the present invention.

[0019] Figure 6 It is a schematic diagram of the final rolling forming of the special-shaped ring forging described in the present invention. Specific implementation manner

[0020] To implement the reverse rolling forming method of the Ti2AlNb-based alloy special-shaped ring described in the present invention, equipment such as a forging heating furnace, a press, a ring rolling mill, and a manipulator need to be provided, and tools such as drafting software need to be used. The specific implementation manner of this method:

[0021] For the Ti2AlNb-based alloy described in the present invention, its nominal chemical composition is: Ti-22Al-25Nb.

[0022] The steps of this method are as follows:

[0023] Step 1: Design the forging

[0024] Import the part drawing into the drafting software, identify the contour points of the part, and identify a total of 23 contour points A to W. Figure 2 As shown, then connect the identified contour points, and add machining allowances on the contour. The machining allowance at the contour points is 5 - 10 mm, and the machining allowance at the connecting surface between two adjacent contour points is 3 - 6 mm, to obtain the shape and dimensions of the forging. As Figure 3 shown, the structure of forging 2 is similar to that of part 1, and the machining allowance is small.

[0025] Step 2: Design the intermediate ring blank

[0026] Design the intermediate ring blank 3 according to the shape and dimensions of forging 2. Divide forging 2 into n segments along the height direction, h1 = h2 = h3 =...; According to the rolling ratio k and the inner diameter D of a certain section of the ring na Inner diameter D nb , determine the inner diameter of this section of the ring blank Outer diameter According to the height H of the ring-shaped part, determine the height h of the ring blank, where h = (1.05 - 1.10)H, and h = h1 + h2 + h3….

[0027] Step 3: Calculate the blanking weight

[0028] The blanking weight is the sum of the weights of the punched core material and the intermediate ring blank. The blanking weight is m = ρV, where ρ is the density of the Ti2AlNb-based alloy and V is the volume of the bar. Among them, V1 is the volume of the punched core material.

[0029] Step 4: Prepare a rectangular ring blank

[0030] After heating the bar to a certain temperature, a rectangular ring blank is obtained through upsetting, punching, and pre-rolling. The height of the rectangular ring blank is the same as that of the special-shaped ring blank. The outer diameter D0 of the rectangular ring blank is D0 = (0.75 - 0.85)D, where D is the minimum outer diameter of the special-shaped ring blank, and the inner diameter of the rectangular ring blank

[0031] Step 5: Prepare a special-shaped ring blank

[0032] As Figure 4 shown, place the rectangular ring blank in the female die of the die set, and drive the male die to extrude and deform from above the inner hole of the rectangular ring blank. First, use a male die with a certain taper to extrude and deform the rectangular ring blank into a conical ring blank, and then use a male die 1 with the same inner wall contour as the special-shaped ring blank and a female die 3 with the same outer wall contour as the special-shaped ring blank 2 to extrude and deform the conical ring blank into the special-shaped ring blank 2; the cross-sectional change of the ring blank is as Figure 5 shown.

[0033] Step 6: Roll forming

[0034] As Figure 6 shown, put the special-shaped ring blank 2 on the core roll 6 of the ring rolling mill, drive the ring rolling mill to rotate at an angular velocity of 0.8 - 1.2 rad / s, and drive the core roll 6 to drive the special-shaped ring blank to feed towards the main roll 5 at a feed rate of 0.2 mm / s - 2.0 mm / s, so that the wall thickness of the special-shaped ring blank becomes thinner and the outer diameter expands, and finally a special-shaped ring forging is rolled.

Claims

1. A forming method for a multi-step special-shaped casing ring of a Ti2AlNb-based alloy, characterized in that, It includes the following steps: Import the part drawing into the drafting software, identify the contour points of the part, then connect the identified contour points, and add machining allowance to the contour. The machining allowance at the contour points is 5 - 10 mm, and the machining allowance at the connecting surface between two adjacent contour points is 3 - 6 mm, to obtain the shape and dimensions of the forging; Design the intermediate ring blank according to the shape and size of the forging. Divide the forging into n segments along the height direction, h1 = h2 = h3 =...; According to the rolling ratio k and the inner diameter D of a certain section of the ring part na , the inner diameter D nb , determine the inner diameter of the ring blank for this section Outer diameter Determine the height h of the ring blank according to the height H of the ring part, h = (1.05 - 1.10)H, where h = h1 + h2 + h3...; Take a Ti2AlNb-based alloy bar of a certain specification. The weight of the bar is m = ρV, where ρ is the density of the Ti2AlNb-based alloy and V is the volume of the bar; where V1 is the volume of the punching core material; After heating the bar to a certain temperature, a rectangular ring blank is obtained through upsetting, punching, and pre-rolling. The height of the rectangular ring blank is the same as that of the special-shaped ring blank. The outer diameter D0 of the rectangular ring blank is (0.75 - 0.85)D, where D is the minimum outer diameter of the special-shaped ring blank, and the inner diameter of the rectangular ring blank Place the rectangular ring blank in the female die of the die set, and drive the male die to perform extrusion deformation from top to bottom through the inner hole of the rectangular ring blank. First, use a male die with a certain taper to extrude the rectangular ring blank into a conical ring blank, and then use a male die with the same inner wall contour as the special-shaped ring blank and a female die with the same outer wall contour as the special-shaped ring blank to extrude the conical ring blank into a special-shaped ring blank; put the special-shaped ring blank on the core roll of the ring rolling mill, drive the ring rolling mill to rotate at an angular velocity of 0.8 - 1.2 rad / s, and drive the core roll to drive the special-shaped ring blank to feed towards the main roll at a feed speed of 0.2 mm / s - 2.0 mm / s, so that the wall thickness of the special-shaped ring blank becomes thinner and the outer diameter expands, and finally a special-shaped ring forging is rolled.

2. The forming method of the multi-step special-shaped casing ring of the Ti2AlNb-based alloy according to claim 1, wherein, The nominal chemical composition of the Ti2AlNb-based alloy is Ti - 22Al - 25Nb.

3. The forming method of the multi-step special-shaped casing ring of the Ti2AlNb-based alloy according to claim 1, characterized in that, The deformation amount k = 25% - 40%.

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