A fixed-diameter argon-blowing flow control plug rod and its manufacturing method

Abstract

The present invention relates to the field of stopper rod technology, and in particular to a caliber argon-blown flow-controlled stopper rod and a manufacturing method thereof, wherein the caliber argon-blown flow-controlled stopper rod comprises a stopper rod body, a stopper rod head is provided at the bottom of the stopper rod body, a gas channel is provided inside the stopper rod body, an air outlet channel is provided inside the stopper rod head, an air guide tube is provided inside the air outlet channel, at least one air guide channel is provided inside the air guide tube, the air guide channel is connected to the air outlet channel, the upper end surface of the air guide tube is higher than the top end of the air outlet channel, and a limiting structure for limiting the downward movement of the air guide tube is provided in the stopper rod head; the limiting structure limits the air guide tube to be limited in the stopper rod, thereby avoiding the technical problem that the stopper rod is eroded and the air guide tube falls off, thereby affecting the service life of the stopper rod.

Description

Technical Field

[0001] The present invention relates to the technical field of stopper rods, in particular to a calibered argon-blowing flow-control stopper rod and a manufacturing method thereof. Background Art

[0002] With the continuous advancement of technology and improved performance, the application areas of argon-blown stoppers have gradually expanded. Currently, they are widely used in metallurgical fields such as steel, aluminum alloys, and copper alloys, playing a vital role in the casting of molten steel, aluminum, and copper. In addition, with the continuous development of continuous casting technology, argon-blown stoppers have also been widely used in the argon-blowing process of the submerged nozzle of the continuous casting mold, effectively preventing nozzle blockage and improving the quality of the cast billet.

[0003] Chinese patent CN104096827A discloses a porous, calibrated argon-blowing stopper for continuous casting. The stopper comprises a stopper body and a stopper head connected to the bottom of the stopper body. The stopper body defines an argon passageway, and the stopper head includes an alumina gas conduit. The conduit and the argon passageway are coaxial, and the bottom of the conduit is aligned with the bottom of the stopper head. The conduit is evenly distributed with at least two gas-conducting holes. Compared to existing technologies, this invention offers the advantage of allowing the number and size of the internal holes of the porous conduit within the stopper body to be arbitrarily combined, allowing argon bubbles of varying numbers and sizes to enter the sprue, effectively removing solid impurities of varying particle sizes from the molten steel.

[0004] However, in this technical solution, the stopper rod is corroded by molten steel during use, which causes the air guide tube to easily separate from the stopper rod, resulting in the stopper rod being unable to be used normally, affecting the service life of the stopper rod and affecting normal production. Summary of the Invention

[0005] The purpose of the present invention is to address the shortcomings of the existing technology and provide a fixed-diameter argon blowing flow control stopper rod. Through a limiting structure, the gas guide tube is limited inside the stopper rod, thereby preventing the stopper rod from being corroded and causing the gas guide tube to fall off, thereby shortening the service life of the stopper rod.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A fixed-size argon-blowing flow control stopper rod comprises a stopper rod body, a stopper rod head is provided at the bottom of the stopper rod body, a gas channel is provided inside the stopper rod body, an air outlet channel is provided inside the stopper rod head, an air guide tube is provided inside the air outlet channel, at least one air guide channel is provided inside the air guide tube, the air guide channel is connected to the air outlet channel, the upper end surface of the air guide tube is higher than the top end of the air outlet channel, and a limiting structure for limiting the downward movement of the air guide tube is provided inside the stopper rod head.

[0008] As an improvement, the limiting structure is a step limiting portion, and the air guide tube is clamped at the step limiting portion.

[0009] As an improvement, the air guide tube is cylindrical or boss cylindrical.

[0010] As an improvement, the limiting structure is a conical limiting portion, the air guide tube is in a frustum shape, and the outer diameter surface of the air guide tube matches the conical limiting portion.

[0011] As an improvement, the lower end surface of the air guide tube is higher than the bottom end of the air outlet channel.

[0012] As an improvement, the lower end surface of the air guide tube is aligned with the bottom end of the air outlet channel.

[0013] As an improvement, the outer diameter surface of the air guide tube is provided with a plurality of positioning portions along its axial direction; the positioning portions are positioning protrusions or positioning grooves.

[0014] Another object of the present invention is to address the shortcomings of the prior art and provide a method for manufacturing a caliber argon-blown flow control stopper rod, by supporting the gas guide tube during the press-forming process of the gas guide tube and the stopper rod, thereby avoiding the problem of the gas guide tube being easily broken during the press-forming process.

[0015] To achieve the above object, the present invention provides the following technical solutions:

[0016] A method for manufacturing a fixed-size argon-blown flow control plug rod, used to manufacture the fixed-size argon-blown flow control plug rod described in the above embodiment, comprises the following steps:

[0017] Step 1: Positioning the air guide tube: placing the air guide tube in a molding cavity formed between an outer molding die and an inner molding die and positioning the air guide tube. A molding portion for forming a limiting structure is formed between the outer molding die and the inner molding die;

[0018] Step 2: Pressing and molding: introducing the refractory material used to make the stopper rod body into the molding cavity, and pressing the refractory material in the molding cavity into shape;

[0019] Step 3: demoulding, after demoulding, a pressed stopper rod is obtained;

[0020] Step 4: Firing, firing the stopper rod after demoulding in step 3 to obtain a finished stopper rod.

[0021] As an improvement, in step one, the forming portion includes a mold core for forming the air outlet channel and the outer contour of the air duct, and the mold core extends into the air duct of the air duct to support the air duct and simultaneously form the air outlet channel.

[0022] As an improvement, in step one, the forming part includes a support member arranged inside the air guide tube and the outer contour of the air guide tube, the upper end of the support member penetrates into the air guide channel, and the lower end of the support member passes through the lower end of the air guide tube and abuts against the inner wall of the forming outer mold for forming the air outlet channel.

[0023] As an improvement, the gasification temperature of the support member is lower than the firing temperature in step four, and the support member is gasified during the firing process.

[0024] The beneficial effects of the present invention are:

[0025] (1) The present invention presses the air guide tube and the stopper rod body into an integral shape and utilizes the function of the limiting structure to solve the problem that the air guide tube falls off due to the erosion of the stopper rod during use, thereby affecting the service life of the stopper rod.

[0026] (2) The present invention improves the limiting stability of the air guide tube by providing a step limiting portion, thereby solving the problem that the air guide tube is easy to fall off during the use of the stopper rod. At the same time, multiple sets of positioning steps can be provided to achieve multi-level positioning, further improving the firmness of the air guide tube during use and preventing the problem of the air guide tube falling off due to erosion of the stopper rod head.

[0027] (3) The present invention sets the air guide tube as a conical structure, and forms a conical limiting structure between the air guide tube and the plug rod head, thereby achieving the limitation of the air guide tube. At the same time, the size of the top conical structure is increased, thereby improving the overall strength of the air guide tube and increasing the service life.

[0028] (4) The present invention arranges the lower end surface of the air guide tube higher than the bottom end of the air outlet channel, thereby preventing the stopper rod head from being corroded and affecting the service life of the air guide tube, thereby improving the service life of the air guide tube. In particular, for the air guide tube being a high-strength and fragile product structure, this arrangement can improve the overall service life of the stopper rod.

[0029] (5) When forming the argon-blown flow control plug rod, the present invention uses a forming inner mold or a forming outer mold to fix the air guide tube, and introduces a mold core for forming the air outlet channel into the interior of the air guide tube. During the press-forming process of the plug rod, the air guide tube is supported to prevent the fragile air guide tube from being crushed during the press-forming process, thereby greatly improving the product molding qualification rate.

[0030] (6) When forming the argon-blown flow control stopper rod, the present invention uses a support member arranged inside the air guide tube to support the air guide tube and form the air outlet channel at the same time. After pressing and forming, there is no need to demold the support member inside the air guide tube. During the firing process of the pressed stopper rod, the support member is gasified by high temperature, thereby improving the qualified rate of the stopper rod molding and avoiding the problem of the air guide tube being damaged during the demolding process.

[0031] (7) The present invention uses easily vaporized materials as support members, so that the support members can be in full contact with the inner wall of the air duct, providing good supporting force, thereby solving the problem that the traditional mold support requires operations such as demolding and wearing the mold, and requires a large gap between the mold core and the air duct, and the mold core cannot fully support the air duct.

[0032] In summary, the present invention has the advantages of long service life, the air guide tube will not fall off, and a simple manufacturing method. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0034] Figure 2 Schematic diagram of the installation state of the air guide tube of the present invention Figure 1 ;

[0035] Figure 3 Schematic diagram of the installation state of the air guide tube of the present invention Figure 2 ;

[0036] Figure 4 Schematic diagram of the installation state of the air guide tube of the present invention Figure 3 ;

[0037] Figure 5 Schematic diagram of the installation state of the air guide tube of the present invention Figure 4 ;

[0038] Figure 6 Schematic diagram of the installation state of the air guide tube of the present invention Figure 5 ;

[0039] Figure 7 Schematic diagram of the installation state of the air guide tube of the present invention Figure 6 ;

[0040] Figure 8 Schematic diagram of the stopper rod forming mold assembly of the present invention Figure 1 ;

[0041] Figure 9 Schematic diagram of the stopper rod forming mold assembly of the present invention Figure 2 ;

[0042] Figure 10 Schematic diagram of the stopper rod forming mold assembly of the present invention Figure 3 ;

[0043] Figure 11 Schematic diagram of the cross section of the air guide tube of the present invention. DETAILED DESCRIPTION

[0044] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0045] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0046] Example 1

[0047] like Figure 1-Figure 7 、 Figure 11 As shown, this embodiment provides a fixed-size argon-blowing flow-controlled stopper rod, comprising a stopper rod body 1, a stopper rod head 2 being provided at the bottom of the stopper rod body 1, a transition section 12 being provided between the stopper rod head 2 and the stopper rod body 1, the transition section 12 being used to connect the stopper rod head 2 and the stopper rod body 1, a gas channel 11 being provided inside the stopper rod body 1, a gas outlet channel 21 being provided inside the stopper rod head 2, a high-temperature resistant gas guide tube 3 being provided inside the gas guide tube 3, at least one gas guide channel 31 being provided inside the gas guide tube 3, the gas guide channel 31 being communicated with the gas outlet channel 21, the upper end surface of the gas guide tube 3 being higher than the top end of the gas outlet channel 21, so as to prevent impurities from accumulating in the gas channel 11 and clogging the gas outlet channel 21, and a limiting structure 22 being provided inside the stopper rod head 2 for limiting the downward movement of the gas guide tube 3.

[0048] It should be noted that the size of the air outlet channel 21 is smaller than the outer diameter of the bottom end of the air guide tube 3, thereby forming a limiting structure 22;

[0049] like Figure 11As shown, several air guide channels 31 are evenly distributed along the cross section of the air guide tube 3 . Preferably, the air guide channels 31 are arranged at the center of the air guide tube 3 , or several air guide channels 31 are evenly distributed along the circumference of the air guide tube 3 .

[0050] Preferably, the air guide tube 3 is preferably a ceramic tube or an alumina tube.

[0051] As an improvement, the limiting structure 22 is a step limiting portion, and the air guide tube 3 is clamped at the step limiting portion.

[0052] As an improvement, the air guide tube 3 is cylindrical; it should be noted that the cylindrical air guide tube 3 cooperates with the step limiter to achieve positioning of the air guide tube 3 and prevent the air guide tube 3 from falling off during use, thereby increasing the service life of the stopper rod.

[0053] As an improvement, Figure 3 、 Figure 7 As shown, the outer diameter surface of the air guide tube 3 is provided with a plurality of positioning portions 32 along its axial direction; the positioning portions 32 are positioning protrusions or positioning grooves.

[0054] It should be noted that, through the design of the positioning portion 32, the air guide tube 3 and the stopper rod are formed into an integral structure during the press-forming process of the stopper rod, and the engagement of the positioning portion improves the firmness of the air guide tube 3. At the same time, when the air outlet channel 21 is corroded during the use of the stopper rod, the engagement of the positioning portion 32 prevents the air guide tube 3 from falling, thereby improving the service life of the stopper rod.

[0055] In this embodiment, the air guide tube 3 and the stopper rod body 1 are integrally formed by press molding, and a suitable molding method is selected according to different usage conditions and service life of customers.

[0056] Furthermore, according to different molding processes of the stopper rod, the air guide tube 3 and the stopper rod head 2 may also be integrally pressed and molded.

[0057] In addition, the present application can press-form the air guide tube 3 and the stopper rod head 2 and then connect them to the stopper rod body 1. The stopper rod head 2 is made of high-strength material to increase the service life of the stopper rod.

[0058] Example 2

[0059] like Figure 4 、 Figure 5 As shown, the components identical or corresponding to those in the first embodiment are designated by the corresponding reference numerals in the first embodiment. For simplicity, only the differences from the first embodiment are described below. The second embodiment differs from the first embodiment in that:

[0060] In this embodiment, the air duct 3 is a cylindrical boss with at least one positioning step. This positioning step and the end surface of the air duct 3 mate with the step-stop portion. The step-stop portion can be provided with multiple sets of steps with sequentially varying diameters. It should be noted that the use of multiple steps to position the air duct 3 improves its installation stability and service life.

[0061] Example 3

[0062] like Figure 6 、 Figure 7 As shown, the components identical or corresponding to those in the first embodiment are designated by the corresponding reference numerals in the first embodiment. For simplicity, only the differences from the first embodiment are described below. The differences between the third embodiment and the first embodiment are:

[0063] In this embodiment, the limiting structure 22 is a conical limiting portion, the outer diameter surface of the air guide tube 3 matches the conical limiting portion, and the air guide tube 3 is a frustum. It should be noted that the frustum-shaped structure is used to limit the air guide tube 3, thereby improving the strength of the conical air guide tube 3 and thus improving the service life.

[0064] Example 4

[0065] like Figure 2 、 Figure 3 、 Figure 4 、 Figure 7 As shown, the components identical or corresponding to those in the first embodiment are designated by the corresponding reference numerals in the first embodiment. For the sake of simplicity, only the differences from the first embodiment are described below. The fourth embodiment differs from the first embodiment in that:

[0066] In this embodiment, the lower end surface of the gas guide tube 3 is higher than the bottom end of the gas outlet channel 21. With this arrangement, even if the bottom of the stopper rod head 2 is corroded, the normal gas outlet of the gas guide tube 3 is not affected, and the molten steel is prevented from impacting the gas guide tube 3, thereby avoiding damage to the gas guide tube 3 during use.

[0067] Example 5

[0068] like Figure 5 、 Figure 6 As shown, the components identical or corresponding to those in the first embodiment are designated by the corresponding reference numerals in the first embodiment. For the sake of simplicity, only the differences from the first embodiment are described below. The differences between the fifth embodiment and the first embodiment are as follows:

[0069] In this embodiment, the lower end surface of the air guide tube 3 is aligned with the bottom end of the air outlet channel 21. It should be noted that this arrangement allows the air guide channel 31 to overlap with the air outlet channel 21, utilizing the high strength of the air guide tube 3 to reduce the rate of erosion by molten steel, thereby increasing the service life of the stopper rod.

[0070] Example 6

[0071] like Figure 8 、 Figure 9 As shown, this embodiment provides a method for manufacturing a fixed-size argon-blown flow control plug rod, which is used to manufacture a fixed-size argon-blown flow control plug rod as described in the above embodiment, comprising the following steps:

[0072] Step 1: Positioning the air guide tube 3: placing the air guide tube 3 in a molding cavity 6 formed between an outer molding die 4 and an inner molding die 5 and positioning the air guide tube 3. A molding portion 7 for molding the limiting structure 22 is formed between the outer molding die 4 and the inner molding die 5.

[0073] Preferably, after the air duct 3 is connected and positioned with the inner molding die 5 or the outer molding die 4, the inner molding die 5 is inserted into the outer molding die 4 to achieve positioning and fixation of the air duct 3. In this embodiment, the air duct 3 is preferably connected through the inner molding die 5, and the rigidity of the inner molding die 5 is utilized to improve the positioning accuracy of the air duct 3.

[0074] Step 2: Pressing and forming: the refractory material used to make the stopper rod body 1 is introduced into the forming cavity 6, and the refractory material in the forming cavity 6 is press-formed. It should be noted that the corresponding pressing and forming method is selected according to the material of the stopper rod body 1, such as isostatic pressing, dry pressing or extrusion.

[0075] Step 3: Demolding. After demolding, a pressed stopper rod is obtained. The outer mold and the inner mold are removed in reverse order of assembly, and demolding is completed.

[0076] Step 4: Firing: Firing the stopper rod after demoulding in step 3 to obtain a finished stopper rod. The firing temperature is greater than 900° C., preferably 900° C.-1000° C.

[0077] Preferably, in step one, the molding portion 7 includes a mold core 71 for molding the air outlet channel 21 and the outer contour of the air duct 3 , and the mold core 71 extends into the air duct 31 of the air duct 3 to support the air duct 3 and mold the air outlet channel 21 at the same time.

[0078] It should be noted that if Figure 9 As shown, the mold core 71 for forming the air outlet channel 21 can be connected to the outer mold 4, as shown in FIG. Figure 8 As shown, the mold core 71 for forming the air outlet channel 21 can be connected to the molding inner mold 5. By passing the mold core 71 through the air guide tube 3, the air guide channel 31 and the air outlet channel 21 are coaxial after molding, and the air guide tube is supported at the same time to avoid misalignment that affects the blowing quality and efficiency.

[0079] Example 7

[0080] like Figure 10 As shown, the components identical or corresponding to those in the first embodiment are designated by the corresponding reference numerals in the sixth embodiment. For simplicity, only the differences from the sixth embodiment are described below. The seventh embodiment differs from the sixth embodiment in that:

[0081] In this embodiment, in the step one, the forming portion 7 includes a support member 8 provided inside the air guide tube 3 and the outer contour of the air guide tube 3. The upper end of the support member 8 penetrates into the air guide channel 31 and may be higher than the top end of the air guide channel 31 or may be inside the air guide channel 31. The lower end of the support member 8 passes through the lower end of the air guide tube 3 and abuts against the inner wall of the forming outer mold 4 to form the air outlet channel 21. It should be noted that the provision of the support member 8 avoids the problem of the air guide tube 3 being easily broken during the press molding process.

[0082] In addition, by providing the support member 8, not only the air guide tube 3 is supported during the pressing process, but also the air outlet channel 21 is formed by the support member 8, so that the air outlet channel 21 and the air guide channel 31 of the air guide tube 3 are coaxially connected without a seam, which facilitates the gas flow during the use of the stopper rod.

[0083] Furthermore, the vaporization temperature of the support member 8 is lower than the firing temperature in step 4, so that the support member 8 vaporizes and disappears during the firing process, solving the problem that the use of the core 71 for support leads to unchanged demoulding and the relatively fragile air guide tube 3 is easily damaged during the demoulding process.

[0084] Preferably, the support member 8 is made of a material such as plastic or nylon, which has a gasification temperature lower than the firing temperature. The material is not limited to the above two types. Any material that can meet the requirements of support strength and easy gasification can meet the requirements of this application.

[0085] Preferably, the outer contour size of the support member 8 is not larger than the inner contour size of the air guide channel 31 , so as to achieve rapid assembly and avoid damage to the air guide tube 3 .

[0086] In this embodiment, circular structures of the air guide tube 3 and the support member 8 are preferably used. Of course, structures of other shapes, such as polygonal shapes, can also be used. The selection can be made according to actual working conditions and customer requirements.

[0087] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for manufacturing a fixed-size argon-blown flow control plug rod, characterized in that: A fixed-size argon blowing flow control stopper rod comprises: a stopper rod body (1); a stopper rod head (2) is provided at the bottom of the stopper rod body (1); a gas channel (11) is provided inside the stopper rod body (1); a gas outlet channel (21) is provided inside the stopper rod head (2); a gas guide tube (3) is provided inside the gas outlet channel (21); at least one gas guide channel (31) is provided inside the gas guide tube (3); the gas guide channel (31) is communicated with the gas outlet channel (21); and a limiting structure (22) for limiting the downward movement of the gas guide tube (3) is provided inside the stopper rod head (2); The preparation method comprises the following steps: Step 1: Positioning the air guide tube (3): placing the air guide tube (3) in a molding cavity (6) formed between a molding outer mold (4) and a molding inner mold (5) and positioning the air guide tube. A molding portion (7) for molding a limiting structure (22) is formed between the molding outer mold (4) and the molding inner mold (5); Step 2: Pressing and molding, introducing the refractory material used to make the stopper rod body (1) into the molding cavity (6), and pressing and molding the refractory material in the molding cavity (6); Step 3: demoulding, after demoulding, a pressed stopper rod is obtained; Step 4: Firing, firing the stopper rod after demoulding in step 3 to obtain a finished stopper rod; In the step 1, the forming portion (7) includes a support member (8) provided inside the air guide tube (3) and the outer contour of the air guide tube (3), the upper end of the support member (8) penetrates the air guide channel (31), and the lower end of the support member (8) passes through the lower end of the air guide tube (3) and abuts against the inner wall of the forming outer mold (4) to form the air outlet channel (21).

2. The method for manufacturing a calibrated argon-blown flow control plug rod according to claim 1, characterized in that: In step 1, the molding portion (7) comprises a mold core (71) for molding the air outlet channel (21) and the outer contour of the air guide tube (3); the mold core (71) extends into the air guide channel (31) of the air guide tube (3), supports the air guide tube (3) and simultaneously molds the air outlet channel (21).

3. The method for manufacturing a calibrated argon-blown flow control plug rod according to claim 1, characterized in that: The gasification temperature of the support member (8) is lower than the firing temperature in step four, and the support member (8) is gasified during the firing process.

4. A calibrated argon-blown flow-control stopper rod, produced by the method for manufacturing a calibrated argon-blown flow-control stopper rod according to any one of claims 1 to 3, comprising a stopper rod body (1), a stopper rod head (2) provided at the bottom of the stopper rod body (1), a gas channel (11) provided inside the stopper rod body (1), a gas outlet channel (21) provided inside the stopper rod head (2), a gas guide tube (3) provided inside the gas outlet channel (21), at least one gas guide channel (31) provided inside the gas guide tube (3), the gas guide channel (31) being connected to the gas outlet channel (21), and characterized in that: A limiting structure (22) for limiting the downward movement of the air guide tube (3) is provided in the stopper rod head (2).

5. The caliber argon blowing flow control plug rod according to claim 4, characterized in that: The limiting structure (22) is a step limiting portion, and the air guide tube (3) is clamped at the step limiting portion.

6. The caliber argon blowing flow control plug rod according to claim 4, characterized in that: The air guide tube (3) is cylindrical or boss cylindrical.

7. The calibrated argon blowing flow control plug rod according to claim 4, characterized in that: The limiting structure (22) is a conical limiting portion, the air guide tube (3) is in a frustum shape, and the outer diameter surface of the air guide tube (3) matches the conical limiting portion.

8. The calibrated argon blowing flow control plug rod according to any one of claims 4 to 7, characterized in that: The lower end surface of the air guide pipe (3) is not lower than the bottom end of the air outlet channel (21).

9. The calibrated argon blowing flow control plug rod according to any one of claims 4 to 7, characterized in that: The outer diameter surface of the air guide tube (3) is provided with a plurality of positioning portions (32) along its axial direction; the positioning portions (32) are positioning protrusions or positioning grooves.

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