A cold rolling process for effectively controlling the dimensions of titanium alloy ribbed tubes

Abstract

The present invention relates to a cold rolling process for effectively controlling the external dimensions of titanium alloy ribbed tubes, including steps S1, roll pass design; S2, roll pass installation and adjustment; S3, front and rear chuck design; S4, start rolling, etc. The present invention can roll titanium alloy straight ribbed tubes that meet technical requirements in terms of rib height, base circle outer diameter, wall thickness, and inner hole diameter on an LG15 two-roller cold rolling tube mill through unique pass design, variable rolling parameter setting, precise pass adjustment, and unique front and rear supporting tooling for the rolling mill, and various dimensional data are stable; the process concept has guiding significance for the production of the same type of special-shaped tubes.

Description

Technical Field

[0001] The invention relates to the technical field of cold rolling of titanium alloy straight rib tubes, and in particular to a cold rolling process for effectively controlling the external dimensions of titanium alloy straight rib tubes. Background Art

[0002] In the field of nuclear power pipes, there is a titanium alloy pipe with external ribs, the nominal size of which is Φ14×2.0, rib width 1.3mm, rib height 0.50mm, left-hand spiral, spiral angle 3.145°, and pitch 800mm. It has high dimensional accuracy requirements and must pass the inspection of inner and outer diameter go gauges, stop gauges, and inner diameter through gauges. It is very difficult to achieve the required size.

[0003] Among them, the wall thickness S is required to be 2.0±0.12mm, the diameter of the circumscribed circle of the rib top D+ is required to be 15.0±0.1mm, the outer diameter of the base circle D is required to be 14.0±0.1mm, and the inner diameter d is required to be 10.0±0.1mm. This size is the final product size, but the cold-rolled titanium alloy straight rib tube must also undergo hot twisting, heat treatment, straightening, pickling and other processes to meet the finished product size requirements. During the processing of these processes, the outer dimensions of the titanium alloy straight rib tube have been changing, so the initial size of the titanium alloy straight rib tube must be compared with the final product size. The margin for the change in the outer dimensions must be left to ensure the final product size. In addition to meeting the dimensional tolerance requirements of the technical conditions, the final product size must also meet the inspection requirements of the inner diameter and outer diameter go gauges, stop gauges, and inner diameter through gauges, making its initial size range and tolerance range extremely narrow, and production control is extremely difficult.

[0004] At present, the LG15 two-roll cold rolling mill is generally used to roll straight ribbed tubes. However, the rib height of the straight ribbed tubes rolled by the existing LG15 two-roll cold rolling mill has not met the standards required by the technical conditions. Although the ribs are formed, the rib height can only reach the lower limit of the technical conditions. After subsequent torsion and straightening, the base circle outer diameter and rib height are reduced, and the final rib height cannot meet the minimum rib height requirement in the technical conditions. At the same time, for the rolling process of straight ribbed tubes, two-roll rolling on the LD10 three-roll rolling mill frame is also used. Since the nominal diameter of the rolls is much smaller than that of the LG15 two-roll cold rolling mill, its final pass deformation rate is much lower than that of the two-roll pass deformation rate, making the performance of the final product rolled by the three-roll rolling mill slightly lower than that of the product rolled by the two-roll rolling mill. Summary of the invention

[0005] In view of the above problems, the purpose of the present invention is to provide a cold rolling process for effectively controlling the external dimensions of titanium alloy ribbed tubes. Through unique hole design, variable rolling parameter settings, precise hole adjustment, and unique front and back end matching tooling of the rolling mill, titanium alloy straight ribbed tubes with rib height, base circle outer diameter, wall thickness, and inner hole diameter that meet the technical requirements can be rolled on the LG15 two-roll cold rolling tube mill, and various dimensional data are stable.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A cold rolling process for effectively controlling the external dimensions of a titanium alloy ribbed tube proposed by the present invention comprises the following steps:

[0008] S1. Roller pass design: Reduce the effective deformation zone length of the existing cold rolling mill roll pass in the rolling direction by half; in order to achieve the required rib height, the depth of the groove inside the pass must be greater than the maximum value of the actual required rib height; at the same time, in order to meet the requirements of wall thickness after rolling, it is necessary to determine the rebound value after the inner hole of the titanium alloy tube is separated from the mandrel sizing section after rolling, so as to determine the appropriate mandrel sizing section diameter, and finally obtain the wall thickness of the rolled titanium alloy tube that meets the requirements;

[0009] S2, roller pass installation and adjustment;

[0010] S3. Front and rear chuck design: A polyurethane protective sleeve is inserted into the front chuck. Through interference fit with the blank tube, the blank tube is ensured to rotate with the chuck, and the closing of the front chuck is prevented from causing excessive impact on the outer surface of the blank tube; a polyurethane protective sleeve is also inserted into the rear chuck, and its inner hole is interference fit with the outer diameter of the rib of the ribbed tube after rolling, canceling the closing action of the rear chuck and retaining only the function of synchronous rotation with the rolled piece;

[0011] S4. Start rolling.

[0012] Furthermore, the step S2 specifically includes: ensuring that the deviation of the center lines of the front stage, the rolling mill body and the back stage of the cold rolling mill does not exceed 0.02mm; the deviation of the center line of the upper and lower roller hole types and the center line of the mandrel does not exceed 0.02mm, and the deviation of the left and right roll gaps of the upper and lower rollers does not exceed 0.02mm; the remaining height after pressing the lead wire is measured by manually pressing the lead wire in the left and right roll gaps, and the error value of the left and right data does not exceed 0.02mm; when the outer diameter value of the base circle of the ribbed tube after rolling is subsequently adjusted to change the roll gap value, the changes in the roll gap values ​​on both sides must also be synchronized; and the electrical control system for the rotation of the mandrel and the electrical control system for the rotation of the chuck are the same electrical control system.

[0013] Further, the step S4 specifically includes: to satisfy that the straight ribs of the titanium alloy strip are 90° to each other in four directions, the parameters are set as follows: the front rotation angle is set to 0°, and the rear rotation angle is set to 90°; the rolling frequency is 40 to 50 times / minute, which is adjusted by the stepless speed knob; the forward feed is set to 0mm, and the rear feed is adjusted between 1.5mm and 2.5mm according to the original wall thickness of the billet tube and the required rib height value; the position of the mandrel is preliminarily set; after the parameters are set in place, rolling is started; According to the actual results of the rolled base circle outer diameter, rib outer edge diameter, and wall thickness, the initially set parameters are adjusted. If the rib height exceeds the standard, the feed amount for each pass is increased; if the wall thickness is too thick, the mandrel position is adjusted to move in the rolling direction; if the base circle outer diameter is too large, the gap between the upper and lower rolls is reduced; among them, there is a deviation between the dimensional data of the 0.5m long ribbed tube at the beginning of rolling and the data after stable rolling. Therefore, continuous rolling can only be carried out after the length of the rolled ribbed tube exceeds 0.5m and the dimensional data is stable, until the rolling of the titanium alloy tube is completed.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] The present invention can roll titanium alloy straight rib tubes with rib height, base circle outer diameter, wall thickness and inner hole diameter that meet the technical requirements on the LG15 two-roller cold rolling mill through unique hole design, variable rolling parameter setting, precise hole adjustment and unique front and back end matching tooling of the rolling mill, and various dimensional data are stable. This process concept has guiding significance for the production of the same type of special-shaped tubes. The titanium alloy straight rib tubes rolled according to the process of the present invention can meet the requirements of the technical requirements in terms of appearance, size and performance of the sample tubes after subsequent hot twisting, hot stretch straightening, heat treatment and pickling. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of the rolling process of the present invention;

[0017] Figure 2 It is a schematic diagram comparing the roll pass profile of the present invention and the existing roll pass profile.

[0018] Wherein, the figure marks are: 1-roller; 2-mandrel; 3-blank tube. DETAILED DESCRIPTION

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] The cold rolling process for effectively controlling the external dimensions of a titanium alloy ribbed tube proposed in the present invention specifically comprises the following steps:

[0021] S1. Roller pass design: Figure 1 and 2 As shown, for existing cold rolling mills, such as LG15 cold rolling mill, the general hole design is to use the effective stroke of the cold rolling mill to evenly distribute the length of the deformation zone to the rollers to make the deformation uniform. However, if this method is used to roll straight rib tubes, it is generally impossible to obtain external ribs that meet the rib height. The reason is that the metal has less resistance when flowing longitudinally and is not easy to flow in the radial groove direction of the hole. The straight ribs after rolling are not easy to form, or the rib height is very small.

[0022] To this end, the present invention shortens the effective deformation zone length of the pass along the rolling direction by about half. Figure 2 As shown in the figure, the effective deformation zone length of the roll of the existing two-roll cold rolling tube mill is the length of the dotted line connection area from the clockwise position at 7:30 to the clockwise position at 10:30; while the present invention shortens the effective deformation zone by about half, that is, only the length of the dotted line connection area from the clockwise position at 7:30 to the clockwise position at 3:00 is used. In the area from the counterclockwise position at 3:00 to 10:30, although the hole is still moving forward, since the hole diameter is much larger than the ribbed tube after rolling, this section of the hole actually has no deformation effect on the rolled piece; the design of the roll hole enables the metal to be formed in a shorter distance during the rolling process, thereby increasing the longitudinal flow resistance of the metal, and the metal is more likely to flow in the direction of the hole groove, so that the convex rib can be effectively formed, and the rib height meets the requirements;

[0023] In order to achieve the required rib height, the depth of the groove on the roller must be greater than the maximum value of the actual required rib height. Only during rolling can the rib height obtained after rolling be adjusted by adjusting the rolling parameters. At the same time, in order to meet the requirements of wall thickness after rolling, the rebound value after the inner hole of the titanium alloy tube and the sizing section of the mandrel must be determined. Only in this way can the appropriate mandrel sizing section diameter be determined, and finally the wall thickness of the rolled titanium alloy tube that meets the requirements be obtained. Only under the premise of reasonable design of deformation tools such as the roller hole type, groove depth, and mandrel diameter can the rib height, outer diameter, and wall thickness that meet the technical requirements be rolled.

[0024] S2. Roller pass installation and adjustment: Since the outer surface of the rolled titanium alloy ribbed tube has four convex ribs, the rolling of this type of tube has stricter requirements on the mill tooling than the rolling of ordinary round tubes. Otherwise, the outer surface of the rolled ribbed tube is prone to defects such as burrs.

[0025] The mill tooling includes overall tooling and local tooling; among them, the overall tooling is the overall center line of the cold rolling mill, etc., to ensure that the center line deviation of the front desk, the rolling mill body, and the back desk of the cold rolling mill does not exceed 0.02mm; the local center line includes the center line of the upper and lower roller holes and the center line of the mandrel, the deviation cannot exceed 0.02mm, and the deviation of the left and right roll gaps of the upper and lower rollers cannot exceed 0.02mm; only in this way can the outer diameter and wall thickness deviations of the rolled titanium alloy ribbed tube meet the requirements; the adjustment standard of the local tooling is whether the center lines of the upper and lower rollers are horizontal and whether the left and right roll gaps are symmetrical; generally, the left and right roll gaps are manually pressed with lead wire to measure the remaining height after pressing the lead wire, and the error value of the left and right data cannot exceed 0.02mm; including the subsequent adjustment of the outer diameter value to change the roll gap value, the changes in the roll gap values ​​on both sides must also be synchronized.

[0026] S3. Design of front and rear chucks: Due to the uniqueness and precision requirements of the rolling of titanium alloy ribbed straight tubes, in addition to the 90° rotation of the mandrel in each pass during the rolling process, the billet tube and finished tube at the front and rear ends of the cold rolling tube mill must also rotate synchronously with the mandrel, and no error is allowed, otherwise the ribs just rolled out will be flattened, and this synchronous action is completed by the front and rear end chucks; at the same time, the chuck always has an opening and closing action during a rolling pass conversion process. Improper design can easily damage the billet tube and the ribs. For this reason, the present invention installs a set of interference fit polyurethane protective covers at the front and rear end chucks of the cold rolling tube mill, which can enable the billet tube and the finished tube to rotate synchronously with the mandrel without damaging the billet tube or the ribs; in order to ensure synchronization, the electrical control system for the rotation of the mandrel and the electrical control system for the rotation of the chuck are the same electrical control system to ensure rotation synchronization during the rolling process.

[0027] The function of the front chuck is to ensure that the roller is loosened when rolling forward, so that the billet tube can extend longitudinally in the deformation zone, and to lock the billet tube when the roller moves backward to prevent the billet tube from moving backward; since the front chuck is constantly opened and closed during the rolling process, it has a certain impact effect on the billet tube. For this reason, a section of polyurethane protective sleeve is inserted into the front chuck. The polyurethane protective sleeve has an interference fit with the billet tube, which ensures that the billet tube rotates with the chuck and avoids excessive impact on the outer surface of the billet tube caused by the closing of the front chuck; a section of polyurethane protective sleeve is also inserted into the rear chuck, but its inner hole has an interference fit with the outer diameter of the ribbed tube after rolling, so the closing action of the chuck is cancelled and only the front chuck is kept closed. The function of synchronous rotation with the rolled piece is to ensure not only the precise rotation of 90°, but also to ensure that when the tail end of the billet tube leaves the front chuck, the remaining part of the billet tube can rotate synchronously with the subsequently rolled billet tube, so as to maintain the continuity and stability of the longitudinally rolled outer ribs; the role of the rear chuck is mainly to guide, while taking into account that after the billet tube leaves the front chuck, the remaining billet tube can rotate synchronously with the mandrel; and the rear chuck is interference fit with the rolled outer ribs of the straight rib tube, so it consumes a lot in actual use. The purpose of using polyurethane to make the protective cover is not only to ensure that the billet tube rotates synchronously with the core rod, but also to ensure that the polyurethane will not damage the outer surface of the billet tube and the finished tube.

[0028] S4. Start rolling: Since the size of the billet tube fluctuates, and the cold rolling mill is extremely sensitive to the fluctuation of the billet size, it is necessary to find the correlation between the change of rolling parameters and the change of the final product size, so as to ensure the final product size by adjusting the rolling parameters; in order to meet the requirement that the straight ribs of the titanium alloy strip are 90° to each other in four directions, the parameters are set as follows: the front rotation angle is set to 0°, and the rear rotation angle is set to 90°; the rolling frequency is 40 to 50 times / minute, which is adjusted by the stepless speed knob; the forward feed is set to 0mm, and the rear feed is between 1.5mm and 2.5mm according to the original wall thickness of the billet tube and the required rib height value. Adjustment; preliminary setting of the mandrel position, etc.; after the parameters are set in place, start rolling; adjust the initial set parameters according to the actual results of the base circle outer diameter, rib outer edge diameter, and wall thickness of the rolled titanium alloy straight ribbed tube; if the rib height exceeds the standard, increase the feed amount per pass; if the wall thickness is too thick, adjust the mandrel position to move in the rolling direction; if the base circle outer diameter is too large, reduce the gap between the upper and lower rolls; the dimensional data of the ribbed tube at the beginning of rolling at a length of 0.5m has a deviation from the data after stable rolling, so continuous rolling can only be carried out after the length of the rolled ribbed tube exceeds 0.5m and the dimensional data is stable, until the rolling of the titanium alloy tube is completed;

[0029] The second titanium alloy tube is rolled continuously. After the rolled length exceeds 0.5m, the machine needs to be stopped to check the size of the rolled titanium alloy ribbed tube. Rolling can only be continued after it meets the requirements. The subsequent rolling of titanium alloy ribbed tubes also requires interval spot checks on dimensional accuracy. If the dimensional change exceeds the requirements, the machine needs to be stopped to adjust the relevant parameters until all billet tubes are rolled and titanium alloy ribbed straight tubes that meet the dimensional requirements are produced.

[0030] Matters not covered by the present invention are known technologies.

[0031] The embodiments described above are merely descriptions of preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A cold rolling process for effectively controlling the external dimensions of a titanium alloy ribbed tube, characterized in that: The process comprises the following steps: S1. Roller pass design: Reduce the effective deformation zone length of the existing cold rolling mill roll pass in the rolling direction by half; in order to achieve the required rib height, the depth of the groove inside the pass must be greater than the maximum value of the actual required rib height; at the same time, in order to meet the requirements of wall thickness after rolling, it is necessary to determine the rebound value after the inner hole of the titanium alloy tube is separated from the mandrel sizing section after rolling, so as to determine the appropriate mandrel sizing section diameter, and finally obtain the wall thickness of the rolled titanium alloy tube that meets the requirements; S2, roller pass installation and adjustment; S3. Front and rear chuck design: A polyurethane protective sleeve is inserted into the front chuck. Through interference fit with the blank tube, the blank tube is ensured to rotate with the chuck, and the closing of the front chuck is prevented from causing excessive impact on the outer surface of the blank tube; a polyurethane protective sleeve is also inserted into the rear chuck, and its inner hole is interference fit with the outer diameter of the rib of the ribbed tube after rolling, canceling the closing action of the rear chuck and retaining only the function of synchronous rotation with the rolled piece; S4, start rolling; The cold rolling mill is a LG15 two-roller cold rolling mill, and the effective deformation zone length of the roll pass is from the clockwise position at 7:30 to the clockwise position at 10:30 in the counterclockwise direction.

2. A cold rolling process for effectively controlling the external dimensions of a titanium alloy ribbed tube according to claim 1, characterized in that: The step S2 specifically includes: ensuring that the deviation of the center lines of the front stage, the rolling mill body and the back stage of the cold rolling mill does not exceed 0.02mm; the deviation of the center line of the upper and lower roller pass profiles and the center line of the mandrel does not exceed 0.02mm, and the deviation of the left and right roll gaps of the upper and lower rollers does not exceed 0.02mm; the remaining height after pressing the lead wire is measured by manually pressing the lead wire between the left and right roll gaps, and the error value of the left and right data does not exceed 0.02mm; when the outer diameter value of the base circle of the ribbed tube after rolling is subsequently adjusted to change the roll gap value, the changes in the roll gap values ​​on both sides must also be synchronized; and the electrical control system for the rotation of the mandrel and the electrical control system for the rotation of the chuck are the same electrical control system.

3. A cold rolling process for effectively controlling the external dimensions of a titanium alloy ribbed tube according to claim 1, characterized in that: The step S4 specifically includes: to ensure that the straight ribs of the titanium alloy strip are 90° to each other in four directions, the parameters are set as follows: the front rotation angle is set to 0°, and the rear rotation angle is set to 90°; the rolling frequency is 40 to 50 times / minute, which is adjusted by the stepless speed knob; the forward feed is set to 0mm, and the rear feed is adjusted between 1.5mm and 2.5mm according to the original wall thickness of the billet tube and the required rib height value; the position of the mandrel is preliminarily set; after the parameters are set in place, rolling is started; according to The actual results of the rolled base circle outer diameter, rib outer edge diameter, and wall thickness are used to adjust the initially set parameters. If the rib height exceeds the standard, the feed amount for each pass is increased; if the wall thickness is too thick, the mandrel position is adjusted to move in the rolling direction; if the base circle outer diameter is too large, the gap between the upper and lower rolls is reduced; among them, there is a deviation between the dimensional data of the 0.5m long ribbed tube at the beginning of rolling and the data after stable rolling. Therefore, continuous rolling can only be carried out after the length of the rolled ribbed tube exceeds 0.5m and the dimensional data is stable, until the rolling of the titanium alloy tube is completed.

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