Cold rolling method for reducing wave shape of TC4 titanium alloy seamless tube

Abstract

The invention provides a cold rolling method for reducing the wave shape of a TC4 titanium alloy seamless pipe, and relates to the technical field of cold rolling machining of titanium alloy seamless pipes, and the cold rolling method comprises the steps that the length distribution proportion of a finishing section and a working section in a pass deformation area is calculated according to the feeding amount, the rotation amount, rolling mill parameters and material characteristics; and rolling the blank into a finished blank according to the length distribution proportion of the finishing section and the working section. By optimizing deformation tools such as a core rod and a roller hole pattern, the feeding amount and the rotation angle are reasonably adjusted, and wave shapes of the inner surface and the outer surface are effectively generated; according to the characteristics and technical requirements of different TC4 titanium alloy seamless tubes, the cold rolling tube manufacturing process is implemented, the surface defect loss of the titanium alloy tube is reduced, the effect of improving the surface rolling quality is continuous and stable, and the effects of energy conservation, emission reduction and consumption reduction are remarkable.

Description

Technical Field

[0001] The invention relates to the technical field of cold rolling processing of titanium alloy seamless pipes, and in particular to a cold rolling method for reducing the wave shape of TC4 titanium alloy seamless pipes, which is suitable for cold rolling pipe production of TC4 titanium alloy seamless pipes with a finished product outer diameter of 10 mm to 50 mm. Background Art

[0002] Titanium alloy has the characteristics of low density, high specific strength, non-magnetic, good sound permeability, impact and vibration resistance, good processability, excellent corrosion resistance, etc., especially resistance to seawater and marine atmospheric corrosion, and is an excellent material for ships and marine engineering. Titanium alloy seamless pipes are mainly used in ship power systems, seawater desalination and other heat exchangers, ships, offshore oil platforms and other water and oil pipelines, as well as island municipal engineering pipelines. At present, titanium alloy seamless pipes are usually made of titanium alloy seamless pipe billets through cold rolling. Seamless pipe cold rolling technology has become the main method for the production and preparation of titanium alloy seamless pipes due to its high rolling precision, fast speed, large production capacity, high yield rate, and easy production organization and process technology adjustment.

[0003] At present, the conventional preparation method of titanium alloy seamless pipe mainly includes the following steps: titanium ingot preparation → rough pipe preparation (tube blank heating, high temperature extrusion, rough pipe inspection) → rough pipe pickling → rough pipe finishing (cutting to length, surface grinding) → cold rolling pipe → pickling → finishing (straightening) → pickling → cutting → finished product inspection and other process flows.

[0004] It can be seen from the above process that the cold rolling tube making process is the key process that determines the production quality and efficiency of TC4 titanium alloy seamless tubes. The cold rolling tube making process of seamless steel tubes is to use a combination of a plug and a hole type to form countless continuous inclusive rings from large to small under normal temperature conditions to achieve continuous cold deformation (metal extrusion) of seamless steel tubes. Among them, the hole type is a medium-hole cylinder with a semicircular groove on the surface, which is installed on the rolling device and is used for metal deformation processing of the outer circular shape of seamless steel tubes. The plug is a conical and slender metal rod with a curve. The material is usually tool steel or die steel. It is installed at the front end of the mandrel and is used for metal deformation processing of the inner wall (inner hole shape) of the seamless steel tube. The hole type and the plug are both heat-treated and quenched, and together constitute the deformation tool for cold rolling production of seamless steel tubes. They match each other and are indispensable. In production practice, the plug is installed at the front end of the mandrel, and intermittently rotates under the drive of the mandrel chuck mechanism; the hole type is installed in pairs in the middle of the roll, and the horizontal reciprocating motion output by the transmission mechanism is converted into the synchronous rotation motion of the hole type through the gear pair at the end of the roll, thereby realizing the function of cold rolling deformation processing of the billet tube continuously and uniformly transported by the feed rotary mechanism. Due to changes in rolling specifications, equipment wear and other reasons, it is necessary to adjust the technical parameters such as rolling speed, feed rate, and rotation amount in a timely manner. The adjustment process and parameters of these parameters are the key process parameters of cold rolling pipe making, and are also the core elements that determine the quality and production capacity of cold-rolled seamless steel pipes.

[0005] At present, one of the main problems of TC4 tube rolling is the wave-shaped defect, which is the annular unevenness distributed along the length direction of the outer circumference, just like the continuous or intermittent deformation of the wave, which mainly occurs in LG60, LG40, LG30H high-speed cold rolling mills. The main reason is the unreasonable design of the bottom curve of the roll hole and the mandrel curve, and it is also closely related to the feed amount and wall thickness reduction during rolling.

[0006] Different roll hole curves are required according to the specifications and materials of the seamless pipes being processed. The roll hole curve mainly includes the front rotary feed section, the front rotary feed section, the working section, and the finishing section. Among them:

[0007] Front rotary feeding section: This section is the final stage of the entire tube rolling process. The rollers and the tube no longer contact each other, and the finished tube will be sent out from here. The tube rolling is completed here. The arc radius Rx of the hole section in this section changes basically linearly, and it belongs to the straight line section. In the entire tube rolling process, the precision requirement of this section is not high, as long as it is smooth, it can meet the use requirements.

[0008] Rear rotary feeding section: This section is the stage where the tube billet begins to enter the processing. The tube billet is fed forward and rotated a certain angle in this section. Since the rollers do not contact the tube, the requirements for the hole processing accuracy in this section are not high. This is a standard arc section with a constant radius size Rx.

[0009] Pressing section: This section is the main deformation zone of tube rolling and the most important stage in the whole rolling process. The center angle of the section is the largest, reaching more than 180°. The arc radius Rx of the roller section in this section gradually decreases from large to small. Its processing accuracy directly affects the size and shape accuracy of the finished parts. It is a section with higher requirements in the entire roller hole surface. The pressing section can be subdivided into the diameter reduction section and the wall reduction section.

[0010] Finishing section: This section makes the outer diameter and wall thickness of the pipe reach the designed size, and the inverted cone section can ensure that the finished pipe has good surface quality.

[0011] Therefore, the present invention proposes a cold rolling method for reducing the corrugation of TC4 titanium alloy seamless pipe by calculating the length distribution ratio of the finishing section and the working section in the hole deformation zone. Summary of the invention

[0012] According to the above technical problem that the existing titanium alloy seamless pipe has wavy defects due to unreasonable design of the bottom curve of the roller pass and the mandrel curve in the cold rolling pipe making process, a cold rolling method for reducing the wavy shape of TC4 titanium alloy seamless pipe is provided. The present invention mainly optimizes the pass curve and reasonably adjusts the feed amount and the rotation angle to effectively reduce the wavy shape of the seamless pipe.

[0013] The technical means adopted by the present invention are as follows:

[0014] A cold rolling method for reducing the corrugation of a TC4 titanium alloy seamless tube, comprising:

[0015] Calculate the length distribution ratio of the finishing section and the working section in the pass deformation zone according to the feed amount, rotation amount, rolling mill parameters and material properties;

[0016] The billet is rolled into finished product billets according to the length distribution ratio of the finishing section and the working section.

[0017] Furthermore, the length distribution ratio of the finishing section and the working section in the pass deformation zone is calculated according to the feed amount, the rotation amount, the rolling mill parameters and the material properties:

[0018] Calculation formula for finishing section length:

[0019] L jz =s·m·L mt

[0020] Among them: s is the number of finishing times; m is the feed amount, in mm; Lmt is the elongation coefficient.

[0021] Furthermore, the roll hole curve Dxk and the mandrel hole curve DxD of the working section are:

[0022] Roller hole curve Dxk:

[0023]

[0024] Mandrel curve DxD:

[0025]

[0026] Where: EXP1 is the influence coefficient of the roll pass curve, which is determined by the characteristics of the rolled metal, EXP1 = 2.0 ~ 3.5;

[0027] EXP2 is the gap coefficient of the roller hole pressing section, EXP2=2.0.

[0028] EXP3 is the influence coefficient of the core rod hole curve; EXP3 = 1.7 ~ 3.5;

[0029] Z is the minimum taper of the roll pass required in the diameter direction, in mm;

[0030] Dxk is the cone diameter of the calculated section; D L The outer diameter of the tube D F is the outer diameter of the finished pipe;

[0031] It is the ratio of the distance between the end of the deformation zone and the calculated section to the total length of the deformation zone;

[0032] l i is the gap between the inner diameter of the tube and the large end of the mandrel; l a It is the gap between the outer diameter of the tube and the hole type;

[0033] DxD is the diameter of the mandrel in the calculated section; d F is the outer diameter of the finished pipe; d L --Inner diameter of tube blank.

[0034] Furthermore, according to the length distribution ratio of the finishing section and the working section, a two-roller cold rolling mill is used to roll the billet with a specification of Ф76×7.5mm into a finished billet with a specification of Ф25×3mm.

[0035] Further, the two-roller cold rolling mill includes the following passes:

[0036] Pass 0: A two-roll cold rolling mill is used to roll the billet with a specification of Ф76×7.5mm into a billet with a specification of Ф57×4.5mm;

[0037] Pass 1: A two-roll cold rolling mill is used to roll the billet with a specification of Ф57×4.5mm into a billet with a specification of Ф26×3.0mm.

[0038] Furthermore, in the pass 0, the rolling speed of the LG-60 two-roll cold rolling mill is 70 times / minute, the hole gap is 0.8 mm, the feed amount is 3 mm, the lubrication method adopts online large-flow thin oil lubrication, the billet is re-inspected before rolling, and the hole is re-inspected after rolling three pipes.

[0039] Furthermore, in the pass 1, the rolling speed of the LG-30H two-roll cold rolling mill is 60 times / minute, the hole gap is 0.5mm, the feed amount is 1mm, the lubrication method adopts online large-flow thin oil lubrication, the billet is re-inspected before rolling, and the hole is re-inspected after rolling three pipes.

[0040] Compared with the prior art, the present invention has the following advantages:

[0041] 1. The process design is reasonable, the process organization is smooth, safe, reliable, practical and efficient, which meets the technical requirements of TC4 titanium alloy seamless pipe cold rolling and promotes the core competitiveness of the enterprise.

[0042] 2. According to the characteristics and technical requirements of different TC4 titanium alloy seamless tubes, the cold rolling tube making process is organized and implemented, which reduces the surface defect loss of titanium alloy tubes, improves the surface rolling quality, and has a sustained and stable effect on energy saving, emission reduction and consumption reduction.

[0043] 3. Use LG-60 two-roller cold rolling mill → LG-30H two-roller cold rolling mill to roll the billet specification of Ф76×7.5mm into Ф25×3.0mm finished product, shorten the process to reduce the production cost of rolling pipe making, and control the wall thickness accuracy to 0.1mm.

[0044] 4. By optimizing deformation tools such as mandrel and roller pass, and reasonably adjusting the feed rate and rotation angle, the wave shape of the inner and outer surfaces can be effectively eliminated.

[0045] 5. It has strong versatility and has certain reference, promotion and application value for the research and development and industrial-scale production of cold-rolled seamless titanium alloy pipes in the industry. It promotes the localization of key materials in the field of key domestic engineering equipment. It has broad market application prospects and considerable economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] 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 labor.

[0047] Figure 1 The figure is a flow chart of the method of the present invention.

[0048] Figure 2 It is a schematic diagram of the cold rolling working section curve of the seamless pipe in the present invention. DETAILED DESCRIPTION

[0049] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0050] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0051] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0052] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, the numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be clear that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be regarded as part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0053] like Figure 1-2As shown, the present invention provides a cold rolling method for reducing the wave shape of TC4 titanium alloy seamless tube. Based on the feed amount, rotation amount, rolling mill parameters, and material properties, the length distribution ratio of the finishing section and the pressing section in the hole deformation zone is calculated to reduce the wave defects of the TC4 titanium alloy cold-rolled tube during rolling.

[0054] Calculation formula for finishing section length:

[0055] L jz =s·m·L mt

[0056] Among them: s is the number of finishing times; m is the feed amount, in mm; Lmt is the elongation coefficient.

[0057] At the same time, the bottom curve Dxk of the roll pass working section and the mandrel curve DxD are currently mainly calculated using the following formula:

[0058] Roller hole curve Dxk:

[0059]

[0060] Mandrel curve DxD:

[0061]

[0062] Where: EXP1 is the influence coefficient of the roll pass curve, which is determined by the characteristics of the rolled metal, EXP1 = 2.0 ~ 3.5;

[0063] EXP2 is the gap coefficient of the roller hole pressing section, EXP2=2.0.

[0064] EXP3 is the influence coefficient of the core rod hole curve; EXP3 = 1.7 ~ 3.5;

[0065] Z is the minimum taper of the roll pass required in the diameter direction, in mm;

[0066] Dxk is the cone diameter of the calculated section; D L The outer diameter of the tube D F is the outer diameter of the finished pipe;

[0067] It is the ratio of the distance between the end of the deformation zone and the calculated section to the total length of the deformation zone;

[0068] l i is the gap between the inner diameter of the tube and the large end of the mandrel; l a It is the gap between the outer diameter of the tube and the hole type;

[0069] DxD is the diameter of the mandrel in the calculated section; d F is the outer diameter of the finished pipe; d L --Inner diameter of tube blank.

[0070] Embodiment 1:

[0071] For seamless pipes of different materials and specifications, the present invention provides a pipe making method for reducing surface defects of TC4 titanium alloy cold-rolled seamless pipes by selecting different parameter combinations in the above three formulas, taking the rolling of a billet with a specification of Ф76×7.5mm into a finished billet with a specification of Ф25×3mm as an example.

[0072] Pass 0: A two-roll cold rolling mill is used to roll the billet with a specification of Ф76×7.5mm into a billet with a specification of Ф57×4.5mm;

[0073] Pass 1: A two-roll cold rolling mill is used to roll the billet with a specification of Ф57×4.5mm into a billet with a specification of Ф26×3.0mm;

[0074] In the pass 0, the rolling speed of the LG-60 two-roller cold rolling mill is 70 times / minute, the pass gap is 0.8 mm, the feed amount is 3 mm, the lubrication method adopts online large-flow thin oil lubrication, the billet is re-inspected before rolling, and the pass is re-inspected after rolling three branches;

[0075] In the design of the roll hole curve, the roll hole curve influence coefficient EXP1 and the mandrel hole curve influence coefficient EXP3 are taken as 2.8, the roll hole pressure section gap coefficient EXP2 is taken as 2.0, the mandrel minimum taper Z' is taken as 1.8, and the roll hole minimum taper Z is taken as 1.8. The working section length and the finishing section length are calculated. For difficult-to-deform materials such as TC4 titanium alloy, the finishing times are selected as 20 to 25 times, the feed amount is 3mm, and the elongation coefficient is the ratio of the cross-sectional area of ​​the billet to the cross-sectional area of ​​the finished product, which is 2.174. The calculated finishing section length is 130.4mm. The total length of the deformation section of the LG60 rolling mill is 800mm, and the working section length is 669.5mm.

[0076] In the pass 1, the rolling speed of the LG-30H two-roll cold rolling mill is 60 times / minute, the hole gap is 0.5mm, the feed amount is 1mm, the lubrication method adopts online large-flow thin oil lubrication, the billet is re-inspected before rolling, and the hole is re-inspected after rolling three pipes;

[0077] In the design of the roll hole curve, the roll hole curve influence coefficient EXP1 and the mandrel hole curve influence coefficient EXP3 are 2.9, the roll hole pressure section gap coefficient EXP2 is 2.0, the mandrel minimum taper Z' is 1.5, and the roll hole minimum taper Z is 1.5. The length of the working section and the length of the finishing section are calculated. For difficult-to-deform materials such as TC4 titanium alloy, the number of finishing times is 20 to 25 times, the feed amount is 1mm, and the elongation coefficient is the ratio of the cross-sectional area of ​​the billet to the cross-sectional area of ​​the finished product, which is 3.42. The calculated length of the finishing section is 85.59mm. The total length of the deformation section of the LG60 rolling mill is 475mm, and the length of the working section is 389.40mm.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cold rolling method for reducing the corrugation of TC4 titanium alloy seamless tube, characterized in that: include: Calculate the length distribution ratio of the finishing section and the working section in the pass deformation zone according to the feed amount, rotation amount, rolling mill parameters and material properties; The billet is rolled into finished product billets according to the length distribution ratio of the finishing section and the working section.

2. The cold rolling method for reducing the corrugation of TC4 titanium alloy seamless pipe according to claim 1, characterized in that: The length distribution ratio of the finishing section and the working section in the hole deformation zone is calculated according to the feed amount, rotation amount, rolling mill parameters and material properties: Calculation formula for finishing section length: L jz =s·m·L mt Among them: s is the number of finishing times; m is the feed amount, in mm; Lmt is the elongation coefficient.

3. The cold rolling method for reducing the corrugation of TC4 titanium alloy seamless pipe according to claim 1 or 2, characterized in that: Roller hole curve Dxk and mandrel hole curve DxD in the working section: Roller hole curve Dxk: Mandrel curve DxD: Where: EXP1 is the influence coefficient of the roll pass curve, which is determined by the characteristics of the rolled metal, EXP1 = 2.0 ~ 3.5; EXP2 is the clearance coefficient of the roller hole pressing section, EXP2 = 2.0; EXP3 is the influence coefficient of the core rod hole curve; EXP3 = 1.7 ~ 3.5; Z is the minimum taper of the roll pass required in the diameter direction, in mm; Dxk is the cone diameter of the calculated section; D L The outer diameter of the tube D F is the outer diameter of the finished pipe; It is the ratio of the distance between the end of the deformation zone and the calculated section to the total length of the deformation zone; l i is the gap between the inner diameter of the tube and the large end of the mandrel; l a It is the gap between the outer diameter of the tube and the hole type; DxD is the diameter of the mandrel in the calculated section; d F is the outer diameter of the finished pipe; d L --Inner diameter of tube blank.

4. The cold rolling method for reducing the corrugation of TC4 titanium alloy seamless pipe according to claim 1, characterized in that: According to the length distribution ratio of the finishing section and the working section, a two-roll cold rolling mill is used to roll the billet with a specification of Ф76×7.5mm into a finished billet with a specification of Ф25×3mm.

5. The cold rolling method for reducing the corrugation of TC4 titanium alloy seamless pipe according to claim 4, characterized in that: The two-roll cold rolling mill includes the following passes: Pass 0: A two-roll cold rolling mill is used to roll the billet with a specification of Ф76×7.5mm into a billet with a specification of Ф57×4.5mm; Pass 1: A two-roll cold rolling mill is used to roll the billet with a specification of Ф57×4.5mm into a billet with a specification of Ф26×3.0mm.

6. The cold rolling method for reducing the corrugation of TC4 titanium alloy seamless pipe according to claim 5, characterized in that: In the pass 0, the rolling speed of the LG-60 two-roll cold rolling mill is 70 times / minute, the hole gap is 0.8mm, the feed amount is 3mm, the lubrication method adopts online large-flow thin oil lubrication, the billet is re-inspected before rolling, and the hole is re-inspected after rolling three pipes.

7. The cold rolling method for reducing the corrugation of TC4 titanium alloy seamless pipe according to claim 5, characterized in that: In the pass 1, the rolling speed of the LG-30H two-roll cold rolling mill is 60 times / minute, the hole gap is 0.5mm, the feed amount is 1mm, the lubrication method adopts online large-flow thin oil lubrication, the billet is re-inspected before rolling, and the hole is re-inspected after rolling three pipes.

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