Mandrel rod of mandrel pipe

Abstract

A mandrel mandrel comprises a mandrel body (1) and a mandrel head (2), the mandrel body (1) is in threaded connection with the mandrel head (2), the mandrel head (2) is in an arc bullet shape, the longitudinal overall length L of the mandrel head (2) from the head tip to the head foot is 255-350 mm, the diameter d of the head tip of the mandrel head (2) is 50-70 mm, and the diameter of the head foot of the mandrel head (2) is the same as that of the mandrel body (1). And the internal arc curve of the core rod head (2) is calculated and drawn according to an arc curvature radius formula. The core rod head (2) of a traditional core rod is designed into an inherent conical shape, and the head of the core rod head (2) is designed into an arc bullet shape, so that abrasion and steel adhesion of the head of the core rod head (2) can be reduced, the service life of the core rod is prolonged, meanwhile, the defect that the inner surface of a pipe is scratched is reduced, and the product quality is improved.

Description

Technical Field

[0001] The utility model belongs to the technical field of steel rolling and relates to a mandrel of a continuous tube rolling machine. The head of the mandrel is in the shape of a bullet head with an arc. Background Art

[0002] As an important internal deformation tool of the continuous rolling mill, the mandrel forms a closed hole together with the continuous rolling rollers to limit the deformation of the rough tube during rolling, thereby obtaining a rough tube with a specific wall thickness. The three-roller limited mandrel continuous rolling mill used in the prior art is to clamp the tail of the mandrel on the clamping sleeve of the limiting mechanism on the main rolling line, and push the front end of the mandrel to a predetermined position in the continuous rolling mill through the gear and rack transmission system. During this process, the mandrel partially passes through the inside of the rough tube, and the part of the mandrel that enters the rolling mill is supported by the support rollers of the mandrel support frame, so that the mandrel is always located at the center of the mill hole. When the front end of the mandrel enters the preset position of the rolling mill, the clamping roller clamps the rough tube into the rolling mill, and the rough tube and the mandrel enter the continuous rolling mill for rolling together.

[0003] The mandrel head of the prior art is designed as a "cone" to ensure that the head is inserted into the capillary tube more smoothly and reduce wear and deformation of the head. Figure 1 As shown. Since the mandrel needs to be inserted into the rough tube during steel tube rolling, the head of the mandrel is generally designed with a conical structure. This structural design is mainly conducive to the guiding effect when the mandrel is inserted. However, due to the influence of various factors such as the straightness of the rough tube, the stability of the front stage of the continuous rolling, the opening of the small frame, etc. during the working process, the mandrel head may scratch the inner surface of the rough tube during the insertion of the mandrel into the rolling mill, or when the mandrel head passes through the support roller of the mandrel support frame, due to the conical structure, when inserting the support roller of the mandrel support frame, the impact on the support roller of the mandrel support frame is a high-speed impact, and the mandrel head is easily scratched by the support roller surface, resulting in defects such as steel sticking and meat falling on the mandrel head, which further affects the quality of the inner surface of the steel tube. Utility Model Content

[0004] The utility model aims to provide a new type of continuous tube rolling mill mandrel, and the structure of the mandrel head is modified from the original "cone" structure to the current "bullet head" structure, so as to improve the defects of steel sticking and meat falling of the mandrel head.

[0005] The utility model realizes the purpose of the technical solution:

[0006] A mandrel for a continuous tube rolling mill comprises a mandrel body and a mandrel head, wherein the mandrel body and the mandrel head are connected by threads, and the mandrel head is characterized in that: the mandrel head is in the shape of a bullet head with an arc, the longitudinal length of the mandrel head from the head tip to the head foot is L=255~350mm, the diameter of the mandrel head tip is d=50~70mm; the diameter of the mandrel head foot is the same as that of the mandrel body.

[0007] Furthermore, the arc curve inside the mandrel head is calculated and drawn according to the curvature radius formula:

[0008]

[0009] Wherein R is the arc radius, d is the tip diameter of the mandrel head (2), and D is the diameter of the mandrel body (1).

[0010] Principle of the invention:

[0011] The utility model changes the core rod head from the conical structure of the prior art to a bullet-shaped shape to solve the following main technical problems:

[0012] Due to the deadweight of the mandrel itself, after the mandrel is inserted into the inner surface of the tube, when it does not contact the pre-rolling support roller, the longer the tube is, the longer the mandrel is suspended in the tube. The normal single-side clearance of the mandrel in the continuous rolling mill is 6-8mm. After the mandrel sags due to its deadweight, the head of the mandrel may scratch the inner surface of the tube. At this time, if a conical structure is used, when the mandrel head and the inner surface of the tube are scratched, the contact is a right-angle point contact, which is more likely to scratch the inner surface of the tube. When a bullet head structure is used, when there is contact, it is a circular arc, which generally does not cause scratches on the inner surface of the tube.

[0013] When the mandrel is inserted into the predetermined position of the rolling mill for rolling, before the rough pipe enters the rolling mill, the mandrel support frame between the continuous rolling mill frames used to support the mandrel is in a closed state. When the rough pipe is bitten by the roller, the mandrel support frame support roller is generally opened after the first two rolling mills of the mandrel support frame have a steel biting signal and a specific delay (to ensure that the mandrel support frame support roller must be in an open state when the steel pipe passes through the mandrel support frame). In order to ensure that the mandrel support frame support roller can hold the mandrel tightly, the opening degree of the mandrel support frame support roller is generally larger than the mandrel size. The size is 3~5mm smaller, so when the mandrel is inserted into the inner surface of the rough tube at high speed, before entering the support roller of the mandrel support frame, the support roller of the mandrel support frame is in a closed state. If the mandrel head adopts a conical structure design, the mandrel head will have an instantaneous impact on the support roller of the mandrel support frame and be stretched open, resulting in a large force on the connection between the mandrel head and the mandrel body, the chromium layer will fall off at the body position, and the mandrel body will be further damaged. At the end of rolling, when the rod is removed, the damaged mandrel head will scratch the rough tube, causing scratches on the inner surface of the rough tube and problems such as steel sticking to the mandrel head. If a bullet head structure is adopted, the impact of the mandrel on the support roller of the mandrel support frame will be reduced when the mandrel is inserted, and the expansion of the support roller of the mandrel support frame by the conical structure will be accompanied by a bullet head structure of the mandrel head, resulting in an indirect high-speed impact, which will reduce the force on the mandrel head. At the same time, the mandrel head and the body are connected in an arc shape, which will disperse the force on the mandrel head, thereby avoiding the chromium layer of the mandrel body from falling off and the body from being damaged. When the mandrel is removed from the mandrel, the arc structure also prevents the mandrel head from scratching the inner surface of the steel pipe.

[0014] The existing technology adopts a conical structure instead of a bullet head shape. The main reason is that the conical structure is convenient for processing the core rod head. The conical structure only needs to be turned on a general lathe to meet the requirements, while the bullet head structure generally needs to be processed on an automatic lathe.

[0015] The beneficial effects of the utility model are as follows: breaking the inherent conical shape of the traditional mandrel design, changing the mandrel head into a bullet head shape with an arc. The innovative transformation of the mandrel head reduces the wear and adhesion of the mandrel head, increases the service life of the mandrel, and improves the scratch defects on the inner surface of the steel pipe, thereby improving product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The present invention is a structural diagram of a cone-shaped head of a core rod in the prior art.

[0017] Figure 2 This is the structural diagram of the core rod support frame.

[0018] Figure 3 This is a structural diagram of a core rod of the utility model in the shape of a bullet head.

[0019] Figure 4 The utility model is a schematic diagram of the arc-shaped structure of the core rod bullet head.

[0020] In the figure: 1- mandrel body, 2- mandrel head, 3- mandrel support roller, 4- wool tube. DETAILED DESCRIPTION

[0021] The following is further described with reference to the accompanying drawings and embodiments.

[0022] Figure 3 As shown: This embodiment is a mandrel for a continuous tube rolling mill, comprising a mandrel body 1 and a mandrel head 2, wherein the mandrel body 1 and the mandrel head 2 are connected by a thread; the characteristic is that the mandrel head 2 is in the shape of a bullet head with an arc, the longitudinal length of the mandrel head 2 from the head tip to the head foot is 300 mm, the diameter d1 of the head tip of the mandrel head 2 is 60 mm, and the head foot has the same diameter as the mandrel body 1.

[0023] Figure 4 As shown: The curvature of the arc curve inside the mandrel head body along the diameter direction is the formula:

[0024]

[0025] Where R is the arc radius, d is the tip diameter of the mandrel head, and D is the mandrel body diameter.

[0026] This structure changes the mandrel head into an arc shape under the premise that the length of the mandrel head can meet the rolling requirements, so that the mandrel head can be more smoothly in contact with key contact points such as the tail end of the blank tube 4 and the mandrel support roller 3 when the mandrel is inserted, thereby improving the violent collision phenomenon of the mandrel head 2, thereby increasing the service life of the mandrel, reducing the rolling cost, and improving the internal and surface quality of the product.

[0027] Figure 2 As shown in the figure, the mandrel support frame includes: a support frame body, three mandrel support rollers 3 that can rotate 120° to each other, a swing arm connecting the mandrel support rollers 3, a cylinder that controls the movement of the swing arm, and a worm box that controls the opening degree of the mandrel support rollers 3. The main function of the mandrel support rollers 3 is to limit and support the mandrel head 2 and the mandrel body 1, ensuring that the mandrel body 1 is in the center of the hole during rolling, and supporting the mandrel body 1 after the rolling mill is cast, so as to prevent the mandrel body 1 from sagging due to its own weight and scraping the rollers, resulting in damage to the surface of the mandrel body 1.

Claims

1. A mandrel for a continuous tube mill, comprising a mandrel body (1) and a mandrel head (2), wherein the mandrel body (1) and the mandrel head (2) are connected by threads, and characterized in that: The interior of the mandrel head (2) is in the shape of a bullet head with an arc, the longitudinal total length L of the mandrel head (2) from the head tip to the head foot is 255-350 mm, the head tip diameter d of the mandrel head (2) is 50-70 mm, and the foot of the mandrel head (2) has the same diameter as the mandrel body (1).

2. A continuous tube mill mandrel according to claim 1, characterized in that: The internal arc curve of the mandrel head (2) is calculated and drawn according to the curvature radius formula: ； Wherein R is the arc radius, d is the tip diameter of the mandrel head (2), and D is the diameter of the mandrel body (1).

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