Processing method of special-shaped spiral core rod

Abstract

The application relates to a processing method of a special-shaped spiral core filling rod and relates to a processing method of a core filling rod. The application is used for solving the problems of low powder compactness, difficult control of geometric size and uneven wall thickness defects of the special-shaped spiral core filling rod processed by the prior art. The steps of the application comprise the following steps: step 1, a blank round pipe is pre-formed into a primary multi-leaf shape sheath pipe by using a drawing device; step 2, powder core material is filled into the multi-leaf shape sheath pipe; and step 3, the multi-leaf shape sheath pipe filled with the powder core material is placed in a multi-roller skew rolling device, the multi-leaf shape sheath pipe filled with the powder core material is gradually spirally rolled by a plurality of roller groups in the multi-roller skew rolling device, and finally, the multi-leaf shape sheath pipe filled with the powder core material is rolled into a special-shaped multi-leaf spiral core filling rod. The application belongs to the technical field of special-shaped rod processing.

Description

Technical Field

[0001] This invention relates to a method for processing a filler rod, belonging to the field of irregular rod processing technology. Background Technology

[0002] Core filler rods are powder / tube composite materials, currently widely used. The interior consists of compressible powder particles, often metal powders or ceramics, while the cladding is made of metal. By designing the shape of the cladding tube, the structural strength of the core filler rod is improved. Furthermore, through deformation processing and subsequent heat treatment, the density of the core and its cross-sectional bonding strength with the outer cladding are enhanced, resulting in composite core filler rods with superior rigidity and overall mechanical properties. Currently, this method is mainly applied domestically and internationally in fields such as high-temperature superconducting wires, flux-cored welding wires, powder cladding materials, and nuclear fuel elements, and is processed using techniques such as drawing, rolling, forging, and equal-channel extrusion.

[0003] Due to the significant differences in physical properties between the core powder and the cladding tube, it is difficult to control defects such as low powder density, difficulty in controlling geometric dimensions, and uneven wall thickness during the composite forming process of powder cores and cladding tubes with complex shapes and high precision requirements.

[0004] Current research on various core filler rods, both domestically and internationally, reveals several issues: core / tube composite core filler rods often have simple shapes, low powder density, difficulty in controlling geometric dimensions, and uneven wall thickness. Furthermore, the processing methods are primarily limited to simple drawing, rolling, and extrusion. However, research on manufacturing methods for complex-shaped, thin-walled composite core filler rods, especially irregularly shaped multi-bladed spiral core filler rods, is relatively scarce. Summary of the Invention

[0005] To address the problems of low powder density, difficulty in controlling geometric dimensions, and uneven wall thickness in the processing of irregular spiral filler rods by existing technologies, this invention proposes a processing method for irregular spiral filler rods.

[0006] The technical solution adopted by the present invention to solve the above problems is as follows: The steps of the present invention include:

[0007] Step 1: Use a drawing device to pre-form the billet round tube into a preliminary multi-leaf shaped cladding tube;

[0008] Step 2: Fill the powder core material into the multi-leaf shaped casing tube;

[0009] Step 3: Place the multi-leaf shaped cladding tube filled with powder core material in a multi-roll skew rolling device. Use multiple roll groups in the multi-roll skew rolling device to perform step-by-step spiral rolling on the multi-leaf shaped cladding tube filled with powder core material, and finally roll it into an irregular multi-leaf spiral core rod.

[0010] Furthermore, the drawing device described in step 1 includes an outer mold, and the outer mold has through holes penetrating the left and right sides of the outer mold. The through holes are provided with a transition zone and a sizing zone area from left to right. The billet tube is inserted into the transition zone and the sizing zone area from left to right. The billet tube is provided with a core rod, and the right end of the core rod is connected to a core head.

[0011] Furthermore, the pre-drawn and formed cladding tube is subjected to vacuum annealing to eliminate work hardening. The annealing temperature is 1000℃ and the annealing time is 30 minutes.

[0012] Furthermore, the cross-sectional area S of the pre-drawn tube 拉拔 and core η 振实 The mathematical relationship between powder tap density and compaction density is as follows:

[0013] η 振实 ×S 拉拔 =η 轧实 ×S 轧实 ×γ①,

[0014] γ=1.025+0.0027*exp(7.51×v) ②

[0015] In formula ①, η 轧实 S represents the rolling density of the filler rod. 轧实 γ represents the cross-sectional area of ​​the filler rod, and γ represents the rolling elongation coefficient, which ranges from 1.02 to 1.2 and is related to the powder used as filler. During processing, the rolling density η of the filler rod is... 轧实 Cross-sectional area S of the filler rod 轧实 Yes, that's certain. And the elongation coefficient γ determines the cross-sectional area S of the pre-drawn tube. 轧实 With the vibrational density η 振实 The mathematical relationship between them. This invention selects Al-WC mixed powder, in which the value of the elongation coefficient γ is positively correlated with the volume v of WC, as shown in formula ②. Therefore, the elongation coefficient γ is determined based on the volume fraction of WC in the powder.

[0016] Furthermore, in step 2, the cross-sectional area S of the pre-drawn tube can be designed according to process requirements. 轧实 and vibrational density η 振实 For example, when the cross-sectional area S of the self-designed pre-drawn tube... 拉拔 It is determined that the rolling elongation γ of the filler rod becomes the tap density η. 振实 The determining factor is the volume fraction of WC. After determining the volume fraction of WC, the elongation coefficient γ can be obtained through the functional relationship formula ②. Then, the optimal tap density η of the Al-WC mixture can be calculated using formula ①. 振实 ,vice versa.

[0017] Furthermore, in step 3, the roll groove size of each roll group in the multi-roll skew rolling device decreases gradually from the inlet to the outlet. The roll groove size of the roll group near the inlet of the multi-roll skew rolling device is the same as the outer cross-sectional size of the pre-drawn cladding tube. The roll groove size of the two roll groups near the outlet of the multi-roll skew rolling device is the same as the cross-sectional shape size of the finally rolled irregular multi-leaf spiral filler rod.

[0018] Furthermore, the upper and lower rolls of each roll group are intersected at an angle α along the axis of the filler bar, and the distance between the front and rear rolls is D. Multiple roll groups maintain the same layout with the same distance D between them.

[0019] The crossing angle α between the two rolls and the distance D between the front and rear roll groups are calculated using the helical pitch M of the finished helical filler bar. The calculation formula is as follows:

[0020] v 轧辊 ×sin(α / 2)t=πd③,

[0021] In formula ③, v 轧辊 The value represents the rotational speed of the rolls, α represents the roll crossing angle, t represents the time taken for the tube to complete each helical pitch, and d represents the outermost diameter of the filler rod.

[0022] v 轧辊 ×cos(α / 2)t=M④,

[0023] In formula ④, M represents the helical pitch of the finished filler rod;

[0024] Combining formulas ③ and ④, we get:

[0025] α=2arctan(πd / M)⑤,

[0026] In formula ⑤, the helical pitch M and the outermost diameter d of the filler rod are determined, and the roll crossing angle α is calculated.

[0027] D = M / n⑥,

[0028] In Formula ⑥, D represents the distance between the front and rear roll groups, and n represents the number of blades in the multi-bladed spiral filler rod.

[0029] The beneficial effects of this invention are as follows: This invention manufactures irregularly shaped multi-leaf core fillers through a composite drawing and multi-roll skew rolling process. By combining drawing and skew rolling processes and adopting a step-by-step deformation method, the deformation difficulty of each step is reduced and the processing accuracy of each pass is improved. The tube is spirally rolled using a multi-roll skew rolling method, and the spiral structure of the tube is refined in each pass. The tube cross-sectional dimensional accuracy is better after the skew rolling is distributed in a stepped manner, and the pitch uniformity of the core filler is better, thereby improving the dimensional accuracy and yield of the irregularly shaped multi-leaf spiral core filler. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the drawing die structure of the drawing device in this invention;

[0031] Figure 2 This is a schematic diagram of the cross-sectional dimensions of the tube after the drawing device has completed the drawing process;

[0032] Figure 3 This is a schematic diagram of the distribution of each group of rolls and the roll profile structure in the rolling mill;

[0033] Figure 4 It is a schematic diagram of the cross-section and longitudinal section of the tube structure after the fuel rod has been rolled by the rolling device;

[0034] Figure 5 This is a schematic diagram of the roll distribution of multiple skew rolling mills;

[0035] Figure 6 This is a schematic diagram of the cross-section and longitudinal section of a spiral simulated fuel rod after multiple sets of skew rolling processes;

[0036] Figure 1 In the middle, 1-Blank tube, 2-Core rod, 3-Outer mold, 4-Core head, 5-Sizing zone area, 6-Transition zone. Detailed Implementation

[0037] Example 1: As Figure 1 As shown, the target product is a multi-leaf spiral filler rod with a four-leaf cross-section. The target product has a pitch of 800mm, a total length of 1600mm, an outer diameter of 8mm, a shell tube wall thickness of 0.22mm, a core density of 92%, and a cross-sectional area of ​​S. 轧实 26mm 2 The specific steps of the processing method for the irregular spiral filler rod include: selecting Al-WC mixed powder with a particle size of 40-130 μm, wherein the WC volume fraction is 40%, i.e., v = 0.4.

[0038] Step 1: Based on the shape of the target product and the shape and cross-sectional area of ​​the pre-drawn tube, calculate the compaction density of the powder filled in the drawn tube and determine the powder weight of each tube.

[0039] The packing density η is determined by calculation formula:

[0040] η 振实 ×S 拉拔 =η 轧实 ×S 轧实 ×γ

[0041] γ=1.025+0.0027*exp(7.51×v)

[0042] The volume fraction of WC is 40%, i.e., v = 0.4, therefore the elongation coefficient γ = 1.08 is calculated.

[0043] The cross-section of the pre-drawn pipe is as follows Figure 2 As shown, the length l of the drawn tube 管 The length is 1600mm, and the cross-sectional area is S. 拉拔 45mm 2 The wall thickness is 0.2 mm; the cross-sectional area of ​​the rolled bar is 26 mm². 2 The compaction density is not less than 92%, and the tapped compaction density η is calculated using the above formula. 振实 The content is 59%, and the core weight required for each drawn tube is 334.32g, of which the weight of aluminum powder is 68.82g and the weight of WC is 265.5g;

[0044] Step 2 and the plate-pulling device used in Step 1 include a core rod 2, an outer mold 3, and a core head 4. The outer mold 3 is a pre-formed multi-petal hollow structure, and the core rod 4 is also a proportionally scaled-down pre-formed multi-petal solid structure. The core head 4 is finally embedded in the outer mold 3 and cooperates with the outer mold to form a pre-formed multi-petal cavity. The core head 4 is connected to the core rod 2 and placed together in the round tube blank 1. The end of the blank tube 1, the tapered head 1a, is placed in the transition area 6 of the mold 3. The tapered head 1a passes through the sizing zone area 5 of the mold 3 and is fixed on the traction device of the drawing device to complete the drawing and forming. The shape of the drawn shell cross section is 7b.

[0045] like Figure 2 As shown, the multi-petal outer shell 7b is a pre-drawn multi-petal shape. The shell tube is made of stainless steel. The cross-section of the drawn tube is a centrally symmetrical structure. The dimensions of the shell cross-section 7b11, 7b12, 7b13, and 7b14 are the same, and the dimensions of 7b21, 7b22, 7b23, and 7b24 are the same.

[0046] Step 3: Perform vacuum stress-relief annealing on the drawn cladding tube at a temperature of 1000℃ for 30 minutes.

[0047] Step 4: Fill the core powder into the cladding tube and compact it.

[0048] The core powder is selected from pure aluminum powder, with a purity requirement of not less than 99.99% and a particle size of 40-130μm. The powder is dried under vacuum in a vacuum drying oven at a temperature of 60-100℃ and a vacuum degree of not less than 10. -3 MPa, drying time not less than 1 hour, to ensure that the metal matrix powder and simulated fuel powder are dry. Each tube is filled with 334.32g of powder, of which aluminum powder weighs 68.82g and WC weighs 265.5g.

[0049] Step 5: Roll the core-filled drawing tube using 18 sets of skew rolls;

[0050] The intersection α of the upper and lower rollers in each group along the axis of the filler rod is calculated based on the helical pitch of the multi-leaf helical filler rod, and the distribution spacing D of the front and rear groups of rollers is calculated. The helical pitch of the filler rod is 800 mm, and the maximum circular diameter of the finished helical filler rod is 8 mm.

[0051] ν 轧辊 ×sin(α / 2)t=πd

[0052] ν 轧辊 ×cos(α / 2)t=M

[0053] In the formula ν 轧辊 α is the rotational speed of the rolls, t is the roll crossing angle, d is the time taken for the tube to complete each helical pitch, and M is the outermost diameter of the filler rod.

[0054] By combining the formulas, we can obtain:

[0055] α = 2arctan(πd / M)

[0056] The calculated roll crossing angle α is 3.6°;

[0057] D = M / n

[0058] In the formula, n is the number of blades, and the calculated front and rear roll spacing D is 200mm;

[0059] Step 6: Perform multi-roll rolling on the preformed multi-leaf core bar after filling with simulated fuel powder;

[0060] like Figure 3 As shown, based on the cross-sectional shape and dimensions of the final formed simulated fuel rod, an 18-roll rolling device was designed. The inclination angle α of each group of rolls along the axis is 3.6°, and the spacing D between each group of rolls is 200mm. Figure 5 As shown, each set of rolls employs a two-roll relative distribution configuration, with each roll rotating around its own axis. The fuel rod to be rolled moves along the axis under the influence of the roll friction force. Figure 4 As shown.

[0061] The roller distribution of each set of rolls 8 is the same as that of rolls 9 and rolls 10, forming roll grooves 11. The groove size of each set of rolls gradually transitions from the pre-drawing size 7b to the final forming size 12. During the rolling process, the main forming is the roll forming by 8a and 8b acting on the outer wall of the simulated fuel rod. The cross-section of the core rod gradually decreases in diameter under the action of 18 sets of rolls and undergoes helical deformation along the axial direction. During the progressive roll forming process of multiple rolls, the gradual deformation of the outer shell causes the core to gradually deform into a multi-leaf helical core rod 12.

[0062] The key parts 12b and 12c are formed to the target size under the action of the roll grooves 8a and 8b. The filling powder 12a increases in density under the action of the roll grooves 8a and 8b and is formed into the irregular multi-leaf filling rod along with the shell.

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent substitutions, and improvements made to the above embodiments without departing from the scope of the present invention, based on the technical essence of the present invention and within the spirit and principles of the present invention, shall still fall within the protection scope of the present invention.

Claims

1. A method for processing an irregularly shaped spiral filler rod, characterized in that, The specific steps include: Step 1: Use a drawing device to pre-form the billet round tube into a preliminary multi-leaf shaped cladding tube; Step 2: Fill the powder core material into the multi-leaf shaped casing tube; Step 3: Place the multi-leaf shaped shell tube filled with powder core material in a multi-roll skew rolling device, and use multiple roll groups in the multi-roll skew rolling device to perform step-by-step spiral rolling on the multi-leaf shaped shell tube filled with powder core material, and finally roll it into an irregular multi-leaf spiral core rod. The roll groove size of each roll group in the multi-roll skew rolling mill decreases step by step from the inlet to the outlet. The roll groove size of the roll group near the inlet of the multi-roll skew rolling mill is the same as the outer cross-sectional size of the pre-drawn cladding tube. The roll groove size of the two roll groups near the outlet of the multi-roll skew rolling mill is the same as the cross-sectional shape of the finally rolled irregular multi-leaf spiral filler rod. The upper and lower rolls of each roll group are aligned along the axis of the filler bar. α The rolls are distributed at an angle, with the distance between the front and rear rolls being D, and multiple sets of rolls maintaining the same distance D between them. The crossing angle α between the two rolls and the distance D between the front and rear roll groups are calculated using the helical pitch M of the finished helical filler bar. The calculation formula is as follows: ③， In formula ③, Indicates the rotational speed of the rolls. Indicates the roll crossing angle. This indicates the time taken for the pipe to complete each spiral pitch. Indicates the outermost diameter of the filler rod; ④， In formula ④, M represents the helical pitch of the finished filler rod; Combining formulas ③ and ④, we get: ⑤， In formula ⑤, the helical pitch M and the outermost diameter of the filler rod are... It is determined by calculation of the roll cross angle. ; ⑥， In formula ⑥, Indicates the distance between the front and rear sets of rolls. Indicates the number of blades in a multi-bladed spiral filler rod; Cross-sectional area of ​​pre-drawn pipe and core The mathematical relationship between powder tap density and density is as follows: ①， ②， In formula ①, This indicates the rolling density of the filler rod. This represents the cross-sectional area of ​​the filler rod. This represents the rolling elongation coefficient, with a value between 1.02 and 1.2, depending on the powder being filled in; In formula ②, v This indicates the volume fraction of the powder being filled in.

2. The processing method of an irregularly shaped spiral filler rod according to claim 1, characterized in that, The drawing device described in step 1 includes an outer mold (3), which has through holes on both sides of the outer mold (3). The through holes are provided with a transition zone (6) and a sizing zone (5) from left to right. The billet tube (1) is inserted into the transition zone (6) and the sizing zone (5) from left to right. The billet tube (1) is provided with a core rod (2), and the right end of the core rod (2) is connected to a core head (4).

3. The processing method of an irregularly shaped spiral filler rod according to claim 1, characterized in that, The pre-drawn and formed cladding tube is subjected to vacuum annealing to eliminate work hardening. The annealing temperature is 1000℃ and the annealing time is 30min.

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