Cold rolling method for reducing surface cracks of TC4 titanium alloy seamless tube

Abstract

The invention provides a cold rolling method for reducing surface cracks of a TC4 titanium alloy seamless tube, which relates to a cold machining tube manufacturing technology for producing seamless tubes in metallurgy and machinery industries, and comprises the following steps of: rolling a blank with the specification of phi 76 * 7.5 mm into a finished blank with the specification of phi 25 * 3mm by adopting a two-roller cold rolling mill; the left opening and the right opening of the pass used during rolling are asymmetrically designed, Fx1 and Fx4 are not changed, and the sizes of Fx2 and Fx3 are increased by 0.1 mm compared with those of Fx1 and Fx4, so that the long axis part of the section ellipse of the seamless tube can be accommodated; meanwhile, the opening angle is not changed, and the opening angle Fw2 is increased by 5 degrees compared with the opening angle Fw1; deformation tools such as a core rod and a roller pass are optimized, the feeding amount and the rotation angle are reasonably adjusted, and cracks on the inner surface and the outer surface are effectively prevented; 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 patent relates to cold processing pipe making technology for producing seamless pipes in metallurgy and machinery industries, and more specifically, to a cold rolling method for reducing surface cracks of TC4 titanium alloy seamless pipes, which is suitable for cold rolling pipe production of TC4 titanium alloy seamless pipes with a finished outer diameter of 10mm to 50mm. 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 by 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] One of the problems in the current cold rolling tube making process is the cracks on the inner and outer surfaces of the TC4 seamless tube: they appear in the entire process of rolling on the two-roller periodic cold rolling tube mill. The size of the cracks gradually increases with the degree of processing of the titanium alloy seamless tube. The cracks are invisible to the naked eye when they first appear, and expand during subsequent rolling.

[0006] The opening design of the roll hole has the greatest impact on the generation of surface cracks during the rolling of seamless pipes. The roll hole used for cold rolling of seamless pipes is currently formed by the upper rolling groove and the lower rolling groove. The rolling groove profile includes a bottom arc segment and two open arc segments set at both ends of the bottom arc segment, of which Fx1, Fx2, Fx3, and Fx4 are openings, and Fw1 and Fw2 are the opening arc angles. Generally speaking, the hole design is symmetrical, that is, the size of Fw1 is equal to Fw2, and the sizes of Fx1, Fx2, Fx3, and Fx4 are equal. However, this symmetrical design does not take into account the asymmetry of seamless pipes during the rolling process. During rolling, the seamless pipe will increase in width in the horizontal direction each time it contacts the roll and the mandrel. At this time, the cross-section of the seamless pipe is elliptical, and then the seamless pipe rotates, and the ellipse is also placed obliquely. For the above-mentioned seamless pipe placed obliquely, a symmetrically designed hole type will cause the opening of the seamless pipe at Fx1 and Fx4 to be larger, while the opening of Fx2 and Fx3 to be smaller during rolling. This asymmetry will cause cracks on the outer wall. At the same time, the size and angle of the opening also have a great influence on the cracks.

[0007] Secondly, in addition, unreasonable settings of roll gap, rolling speed, feed amount and rotation angle will also cause cracks on the inner surface of TC4 seamless pipe. Summary of the invention

[0008] According to the above technical problem that the roll pass used in the existing cold rolling of seamless pipes will cause cracks on the surface of the seamless pipe during rolling, a cold rolling method for reducing surface cracks on TC4 titanium alloy seamless pipes is provided. The present invention optimizes the opening shape and opening size of the pass, and reasonably adjusts the feed amount and rotation angle to effectively reduce cracks on the inner and outer surfaces.

[0009] The technical means adopted by the present invention are as follows:

[0010] A cold rolling method for reducing surface cracks of a TC4 titanium alloy seamless tube comprises: using a two-roll cold rolling mill to roll a billet with a specification of 76×7.5 mm into a finished billet with a specification of 25×3 mm.

[0011] Furthermore, the method of reducing the surface cracks of the seamless pipe further includes the following passes:

[0012] 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;

[0013] 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 Ф25×3.0mm.

[0014] 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.

[0015] Furthermore, the left and right openings of the hole used for rolling are designed asymmetrically, and Fx1 and Fx4 are distributed in a curve along the rolling direction of the hole. The size range of Fx1 and Fx4 is 0.212-0.057mm, and the size of Fx2 and Fx3 is 0.2mm larger than that of Fx1 and Fx4 to accommodate the major axis of the ellipse of the seamless pipe cross-section; at the same time, the opening angle Fw1 is 15°, and the opening angle Fw2 is 20°.

[0016] Furthermore, the rotation angle of the LG-60 two-roller cold rolling mill is reduced from 57° to 19°.

[0017] 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.

[0018] Furthermore, the left and right openings of the hole profile used for rolling are designed asymmetrically, and Fx1 and Fx4 are distributed in a curve along the rolling direction of the hole profile. The size range of Fx1 and Fx4 is 0.212-0.057mm, and the size of Fx2 and Fx3 is 0.1mm larger than that of Fx1 and Fx4 to accommodate the major axis of the ellipse of the seamless pipe cross section; at the same time, the opening angle Fw1 is 15°, and the opening angle Fw2 is 20°.

[0019] Furthermore, the rotation angle of the LG-30H two-roll cold rolling mill is reduced from 57° to 19°.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 4. The left and right openings of the hole used in rolling are designed asymmetrically. Fx1 and Fx4 remain unchanged, while the sizes of Fx2 and Fx3 are 0.1mm larger than those of Fx1 and Fx4 to accommodate the major axis of the ellipse of the seamless pipe section. At the same time, the opening angle remains unchanged, and the opening angle Fw2 is 5° larger than Fw1. By optimizing deformation tools such as the mandrel and roller hole, the feed amount and rotation angle are reasonably adjusted to effectively prevent the occurrence of cracks on the inner and outer surfaces.

[0025] 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

[0026] 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.

[0027] Figure 1 It is a schematic diagram of the cold rolling roller pass type of the seamless pipe in the method of the present invention. DETAILED DESCRIPTION

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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 numbers 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.

[0032] like Figure 1 As shown, the present invention provides a method for reducing the surface defects of titanium alloy cold-rolled seamless pipes, which is a technical optimization of the cold-rolled pipe making process of TC4 titanium alloy seamless pipes:

[0033] The LG-60 two-roller cold rolling mill and the LG-30H two-roller cold rolling mill are used to roll the billet with a specification of 76×7.5 mm into the finished billet with a specification of 25×3 mm. The cold rolling pipe making process is shown in Table 1 below.

[0034] Table 1: Cold rolling process flow chart of TC4 titanium alloy seamless pipe with finished product specification of Ф25×3mm

[0035]

[0036] As shown in Table 1 above, the cold rolling process of TC4 titanium alloy seamless pipe with finished product specification of Ф25×3mm is as follows:

[0037] Preferably, in the said pass 0, the rolling speed of the LG-60 two-roller 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 re-inspection is added before rolling, and the hole is re-inspected after rolling three branches; different from the conventional, the left and right openings of the hole used for rolling are asymmetrically designed, Fx1 and Fx4 are designed with the usual size, and the size range of Fx1 and Fx4 is 0.212-0.057mm, and the size of Fx2 and Fx3 is 0.2mm larger than that of Fx1 and Fx4. It is used to accommodate the part of the elliptical major axis of the seamless pipe section; the opening angle Fw1 is 15° and the usual size design is adopted, and Fw2 is increased by 5° on the basis of Fw1. Correspondingly, the mill rotation angle is 19° to accommodate the part of the elliptical major axis of the seamless pipe section.

[0038] Preferably, in the said 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 re-inspection is added before rolling, and the hole is re-inspected after rolling three branches; different from the conventional, the left and right openings of the hole used for rolling are asymmetrically designed, Fx1 and Fx4 are designed with the usual size, and the size range of Fx1 and Fx4 is 0.212-0.057mm, and the size of Fx2 and Fx3 is 0.1mm larger than that of Fx1 and Fx4. It is used to accommodate the part of the elliptical major axis of the seamless pipe section; the opening angle Fw1 is 15° and the usual size design is adopted, and Fw2 is increased by 5° on the basis of Fw1. Correspondingly, the mill rotation angle is 19° to accommodate the part of the elliptical major axis of the seamless pipe section.

[0039] 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 with 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 surface cracks of TC4 titanium alloy seamless tube, characterized in that: include: 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.

2. The cold rolling method for reducing surface cracks of TC4 titanium alloy seamless pipe according to claim 1, characterized in that: The method of reducing the surface cracks of the seamless pipe further comprises the following steps: 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 Ф25×3.0mm.

3. The cold rolling method for reducing surface cracks of TC4 titanium alloy seamless pipe according to claim 2, 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.

4. The cold rolling method for reducing surface cracks of TC4 titanium alloy seamless pipe according to claim 3, characterized in that: The left and right openings of the hole used for rolling are designed asymmetrically, and Fx1 and Fx4 are distributed in a curve along the rolling direction of the hole. The size range of Fx1 and Fx4 is 0.212-0.057mm, and the size of Fx2 and Fx3 is 0.2mm larger than that of Fx1 and Fx4 to accommodate the major axis of the ellipse of the seamless pipe section; at the same time, the opening angle Fw1 is 15° and the opening angle Fw2 is 20°.

5. The cold rolling method for reducing surface cracks of TC4 titanium alloy seamless pipe according to claim 4, characterized in that: The rotation angle of the LG-60 two-roller cold rolling mill is reduced from 57° to 19°.

6. The cold rolling method for reducing surface cracks of TC4 titanium alloy seamless pipe according to claim 2, 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.

7. The cold rolling method for reducing surface cracks of TC4 titanium alloy seamless pipe according to claim 6, characterized in that: The left and right openings of the hole used for rolling are designed asymmetrically, and Fx1 and Fx4 are distributed in a curve along the rolling direction of the hole. The size range of Fx1 and Fx4 is 0.212-0.057mm, and the size of Fx2 and Fx3 is 0.1mm larger than that of Fx1 and Fx4 to accommodate the major axis of the ellipse of the seamless pipe section; at the same time, the opening angle Fw1 is 15° and the opening angle Fw2 is 20°.

8. The cold rolling method for reducing surface cracks of TC4 titanium alloy seamless pipe according to claim 7, characterized in that: The rotation angle of the LG-30H two-roll cold rolling mill is reduced from 57° to 19°.

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