Perforating method for eliminating iron lugs of tubular billet of large-diameter seamless steel tube

Abstract

The invention discloses a perforating method for eliminating iron lugs of a tubular billet of a large-diameter seamless steel tube, which is suitable for the process of perforating a discharged tube blank into a tubular billet, and realizes perforating by matching a perforating machine positioned outside the tube blank with an ejector head for perforating in the tube blank. Meanwhile, the part, where iron lugs are generated, of the tail of the pipe blank is removed through a centering machine, the tapping temperature of the pipe blank ranges from 1230 DEG C to 1300 DEG C, the hole pattern ovality of the perforating machine is set to be 1.10-1.20, and the diameter-wall ratio of the tubular billet is 15; the bite angle of the perforating machine is 8-12, and the centering depth of the centering machine is 20-50 mm. According to the invention, the generation of iron lugs is reduced through various factors during perforation, and the iron lugs can be eliminated even after the iron lugs are generated.

Description

Technical Field

[0001] This invention relates to the field of perforation processing technology for large-diameter thin-walled steel pipes, and in particular to a method for eliminating the iron lugs in the cap of large-diameter seamless steel pipes. Background Technology

[0002] In the production of large-diameter thin-walled steel pipes, iron burrs are very prone to appear at the tail end of the pierced tube. Mild cases present as burrs and round iron sheets at the tail end; moderate cases present as long sickle-shaped burrs; and severe cases form a ring. When the mandrel is pre-pierced at the front of the continuous rolling mill, the mandrel head carries the iron burrs into the tube. After rolling, the iron burrs adhere to the inner surface of the rough tube, forming large internal folds. After the rough tube passes through the sizing mill for diameter reduction, because the iron burrs cannot be fused with the tube during continuous rolling, but are simply pressed into the inner surface, they detach or partially detach during the sizing mill due to the diameter reduction, forming large internal scabs or large internal folds. This results in a large proportion of short lengths and scrap.

[0003] To address this issue, we propose a method to eliminate the perforation of the iron lugs in the capillary of large-diameter seamless steel pipes. Summary of the Invention

[0004] The purpose of this invention is to provide a method for eliminating the perforation of the iron lugs in the cap of large-diameter seamless steel pipes, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for eliminating iron lumps in the piercing of large-diameter seamless steel tube blanks is disclosed. This method is applicable to the process of piercing a furnace-exit tube blank into a tube blank. Piercing is achieved using a piercing machine located outside the tube blank and a mandrel piercing inside the tube blank. Simultaneously, a centering machine is used to remove the iron lumps from the tail end of the tube blank. The furnace temperature of the tube blank is 1230–1300℃, the ellipticity of the piercing machine's hole shape is set to 1.10–1.20, the diameter-to-wall ratio of the tube blank is 15, the bite angle of the piercing machine is 8–12º, and the centering depth of the centering machine is 20–50 mm.

[0006] In a further embodiment, the temperature difference between the tube blank exiting the furnace and entering the piercing mill is 20° to 40°.

[0007] In a further embodiment, the ellipticity is 1.16 to 1.20.

[0008] In a further embodiment, the bite angle of the perforator is 10 to 12 degrees.

[0009] In a further embodiment, the punching machine bite angle is 9–11º.

[0010] In a further embodiment, the nose of the top head has a diameter of 50-60 mm, a working length of 1000-1100 mm, and a cone diameter of 900-1200 mm.

[0011] Compared with the prior art, the beneficial effects of the present invention are: The invention reduces the formation of iron lugs by considering various factors during the perforation process, and can eliminate them even after they have formed. Attached Figure Description

[0012] Figure 1 A graph showing the relationship between furnace exit temperature and the ratio of iron lug formation. Figure 2 A graph showing the relationship between aperture ellipticity and the probability of iron lug formation. Figure 3 A graph showing the relationship between pipe diameter-to-wall ratio and the probability of iron lumps forming. Figure 4 This is a graph showing the results of the experiment. Figure 5 This is a schematic diagram of the top structure. Detailed Implementation

[0013] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0014] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] A method for eliminating the piercing of iron lugs in the cap of large-diameter seamless steel pipes, the process of which is as follows: billet enters high-temperature furnace / heating furnace -> heating / temperature control -> billet exits furnace -> piercing -> cap inspection.

[0017] Specifically: Many factors influence the formation of lugs, but this discussion primarily focuses on process control factors, which are more conducive to on-site guidance and operability. Since the composition of rolled products varies, their thermal properties also differ. Therefore, under the premise of the same material, extensive classification experiments and statistical work were conducted on-site. By comparing the quantity and morphological changes of lugs, the following process factors were ultimately determined to have a significant impact on lug formation: billet temperature Ovality of the hole shape in the perforation machine Capillary diameter to wall ratio Perforation machine bite angle The wall reduction of the perforated cone at the top Calm and composed First, several key factors are set to initial values. When analyzing the impact of a change in a single factor on the probability of iron lugs, all other factors remain unchanged from their initial values. Specifically, the furnace exit temperature of the rolled product is set to 1230–1300℃; the ellipticity of the piercing mill pass is set to 1.10–1.20; the diameter-to-wall ratio of the tube is 15; and the bite angle of the piercing mill is 8–12º.

[0018] The typical hole types for the test were set as 383–508, with a theoretical outer diameter of 430–590 mm. The typical steel grades for the test were: carbon steel (20# steel), structural steel (Q345), and alloy steel (42CrMo).

[0019] Effect of heating temperature With other factors remaining constant, the furnace exit temperature of the rolled product was gradually increased from 1270℃ to 1295℃, and the changing pattern of the probability of iron lumps forming at the tail of the pierced tube was statistically analyzed. The results are presented in a table. Figure 1 .

[0020] from Figure 1The curve shows that temperature variations have little impact on the formation of iron buds. However, based on long-term practical tracking and statistics, temperature uniformity does have some influence on iron bud formation. When the temperature is uneven, with a maximum temperature difference of 20°C to 40°C, the capillary tail is prone to uneven wall thickness, resulting in a large slant, which is accompanied by the mass production of iron buds.

[0021] Effect of ellipticity Under the condition that other factors remain unchanged, this study analyzes the influence of the ellipticity of the perforation machine hole shape on the probability of iron lugs forming at the end of the capillary tube. Data collected through experiments is then plotted. Figure 2 The relationship curve shown.

[0022] from Figure 2 As can be seen from the curve, the change in the ellipticity of the piercing mill die has a significant impact on the iron lugs. Relatively speaking, a larger ellipticity is more likely to suppress the formation of iron lugs. However, if the ellipticity of the die is too large, it will cause production and quality problems such as uneven wall thickness, internal folding defects, and rolling jamming. Therefore, a balanced approach is needed when adjusting the die.

[0023] The effect of capillary diameter-to-wall ratio on iron lugs.

[0024] Generally speaking, thin-walled tubes are more prone to developing lumps because the rolling effect between the inner and outer metal layers of the rolled product is more intense. Figure 3 It is a curve showing the relationship between the capillary diameter-to-wall ratio and the probability of iron lug formation.

[0025] from Figure 3 The curve shows that the capillary diameter-to-wall ratio has a significant impact on lugs, especially when the ratio exceeds 15, the probability of lug formation increases rapidly. This also verifies the long-held belief that the thinner the capillary wall, the easier it is for lugs to form.

[0026] The effect of the punching machine's bite angle.

[0027] Adjusting the piercing bite angle will cause changes in the amount of deformation per pass, and will also have some microscopic effects on the formation of iron lugs. Figure 4 It is the curve tracked by the experiment.

[0028] When the bite angle is adjusted between 9º and 11º, the larger the bite angle, the lower the probability of iron lugs. However, when the bite angle exceeds 11º, the probability of iron lugs does not change significantly with the bite angle.

[0029] The wall reduction of the perforated cone at the top The original mandrel design for the 508 mill had a mandrel nose diameter F = 0.18 * DD, where F is the mandrel nose diameter, DD is the mandrel diameter, and 0.19 is an empirical value given by the CARTA system (0.18-0.2 for large mandrels); then RD is calculated according to the formula. Based on the principle of lug formation and breaking with the original design concept, the hot rolling operation area boldly attempted mandrel modification, setting the mandrel nose diameter F to 50-60mm, calculating RD to be 1000-1100mm, increasing the wall reduction amount of the piercing cone, thereby reducing lug formation.

[0030]

[0031] The use of cold calming Iron lumps are excess waste material generated at the tail end of the billet. The Tianhuai 508 mill removes these lumps from the tail end of the billet using a centering machine. With a centering depth of 20-50mm, the tubes produced by the piercing mill are virtually free of iron lumps. This is also the method many steel mills use to eliminate iron lumps through cold centering.

[0032] The above The furnace exit temperature has little impact on the shape of the tube lugs. By controlling the heating rhythm, ensuring heating time, and ensuring uniform heating, the temperature difference can be maintained between 20°C and 40°C. The temperature difference can be reduced by controlling the tube length. The ellipticity of the perforation hole has a significant impact on the production of iron lugs. Without significantly increasing other production defects, the ellipticity is selected to be 1.16 to 1.20. The diameter-to-wall ratio of the piercing tube has a significant impact on the formation of lumps. This method is more suitable for piercing tubes with a diameter-to-wall ratio of 16 or less. While meeting the rolling load requirements of subsequent tools and ensuring product quality, slightly increasing the wall thickness of the piercing tube to control the diameter-to-wall ratio below 16 can reduce the formation of lumps. A larger bite angle is more conducive to reducing capillary lugs; 10° to 12° is selected. Reducing the curvature of the mandrel's perforated cone and increasing its wall reduction can effectively control the ring-shaped and large sickle-shaped lugs, reducing equipment damage, minimizing downtime, and improving production efficiency. A specialized mandrel with a nose diameter of 50–60 mm, a working length of 1000–1100 mm, and a cone diameter of 900–1200 mm is used. When working conditions are suitable, cold centering with a centering depth of 20-50mm is used to reduce the formation of iron lumps. The purpose of tube tail centering is to reduce the metal in the center of the end face of the billet tail. This reduces the amount of deformation when the core metal tears and folds outward during tube breakage, thereby reducing the amount of iron lumps.

[0033] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0034] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for eliminating iron lumps in the tube blank of a large-diameter seamless steel pipe, the method being applicable to the process of piercing a tube blank after it has been fired into a tube blank, utilizing a piercing machine located outside the tube blank and a mandrel for piercing inside the tube blank to achieve piercing, while simultaneously using a centering machine to remove the iron lumps at the tail end of the tube blank, characterized in that: The billet exit temperature is 1230-1300℃, the ellipticity of the piercing machine hole is set to 1.10-1.20, the diameter-to-wall ratio of the tube is 15, the bite angle of the piercing machine is 8-12º, and the centering depth of the centering machine is 20-50mm.

2. The method for eliminating perforations in the capillary iron lugs of large-diameter seamless steel pipes according to claim 1, characterized in that: The temperature difference between the tube blank exiting the furnace and entering the piercing mill is 20° to 40°.

3. The method for eliminating perforations in the capillary iron lugs of large-diameter seamless steel pipes according to claim 1, characterized in that: The ellipticity is 1.16 to 1.

20.

4. The method for eliminating perforations in the capillary iron lugs of large-diameter seamless steel pipes according to claim 1, characterized in that: The biting angle of the perforating machine is 10 to 12 degrees.

5. The method for eliminating perforations in the capillary iron lugs of large-diameter seamless steel pipes according to claim 1, characterized in that: The biting angle of the perforating machine is 9 to 11 degrees.

6. The method for eliminating perforations in the capillary iron lugs of large-diameter seamless steel pipes according to claim 1, characterized in that: The nose of the top head has a diameter of 50-60mm, a working length of 1000-1100mm, and a cone diameter of 900-1200mm.

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