A cold rolling method for reducing surface cracks of TC4 titanium alloy seamless pipe

Abstract

The application provides a cold rolling method for reducing surface cracks of TC4 titanium alloy seamless pipes, relates to a cold rolling pipe manufacturing technology in the metallurgical and mechanical industries, and comprises the following steps: adopting a two-roller cold rolling machine to roll a blank with a specification of Ф76*7.5mm into a finished product with a specification of Ф25*3mm. When rolling, the left and right openings of the groove are designed to be asymmetric, Fx1 and Fx4 are constant, the sizes of Fx2 and Fx3 are 0.1mm larger than those of Fx1 and Fx4, and the sizes are used to accommodate part of the long axis of the cross-section ellipse of the seamless pipe; meanwhile, the opening angle is constant, and the opening angle Fw2 is 5° larger than Fw1. Through optimization of the deformation tools such as the mandrel and the roller groove, reasonable adjustment of the feed amount and the rotation angle, the occurrence of the effective inner and outer surface cracks is effectively reduced. According to the characteristics and technical requirements of different TC4 titanium alloy seamless pipes, the cold rolling pipe manufacturing process is organized and implemented, the surface defect loss of the titanium alloy pipe is reduced, the surface rolling quality is continuously and stably improved, and the energy saving, emission reduction and consumption reduction effects are remarkable.

Description

Technical Field

[0001] This invention patent relates to cold-working tube-making technology for seamless tube production in the metallurgical and machinery industries. More specifically, it relates to a cold rolling method for reducing surface cracks in TC4 titanium alloy seamless tubes, applicable to the cold rolling production of TC4 titanium alloy seamless tubes with an outer diameter of 10mm to 50mm. Background Technology

[0002] Titanium alloys possess characteristics such as low density, high specific strength, non-magnetic properties, good sound transmission, impact and vibration resistance, good machinability, and excellent corrosion resistance. In particular, they are resistant to seawater and marine atmospheric corrosion, making them excellent materials for shipbuilding and marine engineering. Seamless titanium alloy tubes are mainly used in marine power systems, heat exchangers in seawater desalination plants, water and oil pipelines in ships and offshore oil platforms, and pipeline networks in municipal engineering projects on islands. Currently, seamless titanium alloy tubes are typically manufactured by cold rolling seamless titanium alloy tube blanks. Cold rolling technology for seamless tubes has become the main method for producing seamless titanium alloy tubes due to its high rolling precision, high speed, large production capacity, high yield, and ease of production organization and process technology adjustment.

[0003] The conventional method for manufacturing seamless titanium alloy tubes mainly includes the following steps: titanium ingot preparation → raw tube preparation (bulk heating, high-temperature extrusion, raw tube inspection) → raw tube pickling → raw tube finishing (cutting to length, surface grinding) → cold rolling → pickling → finishing (straightening) → pickling → cut to length → finished product inspection, etc.

[0004] As can be seen from the above process, the cold rolling process is a key step in determining the production quality and efficiency of TC4 titanium alloy seamless tubes. The cold rolling process for seamless steel tubes involves continuous cold deformation (metal extrusion) of the seamless steel tube at room temperature using a combination of a mandrel and a die, forming numerous continuous enclosing rings of varying sizes. The die is a cylindrical body with a semi-circular groove on its surface, mounted on a rolling mill, used for deforming the outer diameter of the seamless steel tube. The mandrel is a slender, conical metal rod with a curved shape, typically made of tool steel or die steel, mounted at the front end of a mandrel, used for deforming the inner wall (inner hole shape) of the seamless steel tube. Both the die and the mandrel undergo heat treatment and quenching, together forming the deformation tools for the cold rolling production of seamless steel tubes; they are mutually compatible and indispensable. In production practice, the mandrel is installed at the front end of the mandrel and rotates intermittently under the drive of the mandrel chuck mechanism. The die is installed in pairs in the middle of the rolls, and the horizontal reciprocating motion output from the transmission mechanism is converted into synchronous rotational motion of the die through gear pairs at the roll ends. This enables the cold rolling deformation of the billet tube, which is continuously and uniformly fed by the feed and rotary mechanism. Due to changes in rolling specifications and equipment wear, it is necessary to adjust technical parameters such as rolling speed, feed rate, and rotation rate in a timely manner. The adjustment process and parameters of these parameters are the key process parameters for cold-rolled tube production and are also the core factors determining the quality and production capacity of cold-rolled seamless steel tubes.

[0005] One of the current problems with cold-rolled tube manufacturing is the cracks on the inner and outer surfaces of TC4 seamless tubes. These cracks appear throughout the entire rolling process of a two-roll periodic cold rolling mill. The size of the cracks gradually increases with the degree of processing of the titanium alloy seamless tube. The cracks are not visible to the naked eye when they first appear, but they expand during subsequent rolling.

[0006] The opening design of the roll pass has the greatest impact on the formation of surface cracks during seamless tube rolling. Currently, the roll pass used for cold rolling of seamless tubes consists of an upper and lower groove. The groove profile includes a bottom arc segment and two open arc segments at both ends of the bottom arc segment. Fx1, Fx2, Fx3, and Fx4 are the openings, and Fw1 and Fw2 are the opening arc angles. Typically, the roll pass design is symmetrical, meaning Fw1 is equal in size to Fw2, and Fx1, Fx2, Fx3, and Fx4 are all equal in size. However, this symmetrical design does not take into account the asymmetry of the seamless tube during the rolling process. During rolling, after each contact with the rolls and mandrel, the seamless tube increases in width in the horizontal direction, at which point the cross-section of the seamless tube becomes elliptical. Subsequently, the seamless tube rotates, and the ellipse becomes oblique. For the aforementioned seamless tubes placed at an angle, using a symmetrical die design will result in larger openings at Fx1 and Fx4, and smaller openings at Fx2 and Fx3 during rolling. This asymmetry can lead to cracks on the outer wall. Furthermore, the size and angle of the openings also significantly influence crack formation.

[0007] Secondly, improper settings of roll gap, rolling speed, feed rate, and rotation angle can also cause cracks on the inner surface of TC4 seamless tubes. Summary of the Invention

[0008] To address the technical problem of surface cracking caused by existing roll pass designs in seamless tube cold rolling, this invention provides a cold rolling method to reduce surface cracking in TC4 titanium alloy seamless tubes. This invention effectively reduces cracking on both the inner and outer surfaces by optimizing the roll pass shape and size, and simultaneously adjusting the feed rate and rotation angle.

[0009] The technical means employed in this invention are as follows:

[0010] A cold rolling method for reducing surface cracks in TC4 titanium alloy seamless tubes includes: rolling a billet with specifications of Ф76×7.5mm into a finished billet with specifications of Ф25×3mm using a two-roll cold rolling mill.

[0011] Furthermore, the reduction of surface cracks in the seamless tube further includes the following passes:

[0012] Pass 0: A two-roll cold rolling mill is used to roll a 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 0th pass, the rolling speed of the LG-60 two-roll cold rolling mill is 70 times / minute, the pass gap is 0.8mm, the feed rate is 3mm, the lubrication method is online high-flow thin oil lubrication, the billet is re-inspected before rolling, and the pass is re-inspected after rolling three branches.

[0015] Furthermore, the rolling pass uses an asymmetrical design for its left and right openings. Fx1 and Fx4 are distributed in a curved pattern along the rolling direction of the pass, with the values ​​of Fx1 and Fx4 ranging from 0.212 to 0.057 mm. The values ​​of Fx2 and Fx3 are 0.2 mm larger than those of Fx1 and Fx4 to accommodate the major axis of the ellipse of the seamless tube 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-roll cold rolling mill is reduced from 57° to 19°.

[0017] Furthermore, in the first pass, the rolling speed of the LG-30H two-roll cold rolling mill is 60 times / minute, the pass gap is 0.5mm, the feed rate is 1mm, the lubrication method is online high-flow thin oil lubrication, the billet is re-inspected before rolling, and the pass is re-inspected after rolling three branches.

[0018] Furthermore, the rolling pass uses an asymmetrical design for its left and right openings. Fx1 and Fx4 are distributed in a curved pattern along the rolling direction of the pass, with the values ​​of Fx1 and Fx4 ranging from 0.212 to 0.057 mm. The values ​​of Fx2 and Fx3 are 0.1 mm larger than those of Fx1 and Fx4 to accommodate the major axis of the ellipse of the seamless tube 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 was 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 cold rolling of TC4 titanium alloy seamless tubes and promotes the core competitiveness of enterprises.

[0022] 2. Based on the characteristics and technical requirements of different TC4 titanium alloy seamless tubes, the cold rolling tube process was organized and implemented, which reduced the loss of surface defects in titanium alloy tubes, improved the surface rolling quality continuously and stably, and had significant energy-saving, emission-reduction and consumption-reducing effects.

[0023] 3. The billet with specifications of Ф76×7.5mm is rolled into a finished product of Ф25×3.0mm by adopting the LG-60 two-roll cold rolling mill → LG-30H two-roll cold rolling mill. The short process reduces the production cost of rolling tubes and controls the wall thickness accuracy to 0.1mm.

[0024] 4. The rolling pass uses an asymmetrical design for the left and right openings. Fx1 and Fx4 remain unchanged, while the sizes of Fx2 and Fx3 are increased by 0.1mm compared to Fx1 and Fx4 to accommodate the major axis of the ellipse of the seamless tube cross-section. At the same time, the opening angle remains unchanged, and the opening angle Fw2 is increased by 5° compared to Fw1. By optimizing the mandrel, roll pass, and other deformation tools, and reasonably adjusting the feed rate and rotation angle, the occurrence of cracks on the inner and outer surfaces is effectively prevented.

[0025] 5. It has strong versatility and has certain reference, promotion and application value for the research and development and industrial-scale production of seamless titanium alloy tubes in the industry. It promotes the localization of key materials in the field of key engineering equipment in China, has broad market application prospects and considerable economic benefits. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the roll profile for cold rolling of seamless tubes in the method of the present invention. Detailed Implementation

[0028] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. 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.

[0030] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0031] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0032] like Figure 1 As shown, this invention provides a tube manufacturing method for reducing surface defects in cold-rolled seamless titanium alloy tubes, which is a technical optimization of the cold-rolling process for TC4 titanium alloy seamless tubes.

[0033] The billet with a specification of Ф76×7.5mm was rolled into a finished billet with a specification of Ф25×3mm using an LG-60 two-roll cold rolling mill and an LG-30H two-roll cold rolling mill in sequence. The cold rolling tube manufacturing process is shown in Table 1 below.

[0034] Table 1: Cold Rolling Process Flowchart for TC4 Titanium Alloy Seamless Tubes with Finished Specifications of Ф25×3mm

[0035]

[0036] The cold rolling process for TC4 titanium alloy seamless tubes with finished specifications of Ф25×3mm is shown in Table 1 above.

[0037] Preferably, in pass 0, the LG-60 two-roll cold rolling mill has a rolling speed of 70 times / minute, a pass gap of 0.8mm, a feed rate of 3mm, and uses online high-flow-rate thin oil lubrication. A billet re-inspection is added before rolling, and a pass re-inspection is performed after rolling three tubes. Unlike conventional methods, the pass openings used for rolling are asymmetrically designed. Fx1 and Fx4 are of standard size, ranging from 0.212 to 0.057mm. Fx2 and Fx3 are 0.2mm larger than Fx1 and Fx4 to accommodate the elliptical major axis of the seamless tube cross-section. The opening angle Fw1 is 15° of standard size, and Fw2 is 5° larger than Fw1. Correspondingly, the mill rotation angle is 19° to accommodate the elliptical major axis of the seamless tube cross-section.

[0038] Preferably, in pass 1, the LG-30H two-roll cold rolling mill has a rolling speed of 60 times / minute, a pass gap of 0.5mm, a feed rate of 1mm, and uses online high-flow thin oil lubrication. A billet re-inspection is added before rolling, and a pass re-inspection is performed after rolling three tubes. Unlike conventional methods, the pass openings used for rolling are asymmetrically designed. Fx1 and Fx4 are of standard size, ranging from 0.212 to 0.057mm. Fx2 and Fx3 are 0.1mm larger than Fx1 and Fx4 to accommodate the elliptical major axis of the seamless tube cross-section. The opening angle Fw1 is 15° of standard size, and Fw2 is 5° larger than Fw1. Correspondingly, the mill rotation angle is 19° to accommodate the elliptical major axis of the seamless tube cross-section.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions 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 in TC4 titanium alloy seamless tubes, characterized in that, include: A two-roll cold rolling mill is used to roll a billet with a specification of Ф76×7.5mm into a finished billet with a specification of Ф25×3mm; The method for reducing surface cracks in seamless tubes further includes the following steps: Pass 0: A two-roll cold rolling mill is used to roll a 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; In the aforementioned pass 0, the rolling speed of the LG-60 two-roll cold rolling mill is 70 times / minute, the pass gap is 0.8mm, the feed rate is 3mm, the lubrication method is online high-flow thin oil lubrication, the billet is re-inspected before rolling, and the pass is re-inspected after rolling three branches. The rolling pass uses an asymmetrical design for its left and right openings. Fx1 and Fx4 are distributed in a curved pattern along the rolling direction of the pass, with values ​​ranging from 0.212 to 0.057 mm. Fx2 and Fx3 are 0.2 mm larger than Fx1 and Fx4 to accommodate the major axis of the elliptical cross-section of the seamless tube. At the same time, the opening angle Fw1 is 15° and the opening angle Fw2 is 20°. The roll pass is formed by an upper and a lower groove. The groove profile includes a bottom arc segment and two open arc segments at both ends of the bottom arc segment. Fx1 and Fx2 are the openings at the left and right ends of the upper groove, Fx3 and Fx4 are the openings at the left and right ends of the lower groove, and Fw1 and Fw2 are the arc angles of the openings at the left and right ends of the upper groove.

2. The cold rolling method for reducing surface cracks in TC4 titanium alloy seamless tubes according to claim 1, characterized in that, The rotation angle of the LG-60 two-roll cold rolling mill was reduced from 57° to 19°.

3. The cold rolling method for reducing surface cracks in TC4 titanium alloy seamless tubes according to claim 1, characterized in that, In the first pass, the rolling speed of the LG-30H two-roll cold rolling mill is 60 times / minute, the pass gap is 0.5mm, the feed rate is 1mm, the lubrication method is online high-flow thin oil lubrication, the billet is re-inspected before rolling, and the pass is re-inspected after rolling three branches.

4. The cold rolling method for reducing surface cracks in TC4 titanium alloy seamless tubes according to claim 3, characterized in that, The rolling pass uses an asymmetrical design for its left and right openings. Fx1 and Fx4 are distributed in a curved pattern along the rolling direction of the pass, and their values ​​range from 0.212 to 0.057 mm. The sizes of Fx2 and Fx3 are 0.1 mm larger than those of Fx1 and Fx4, in order to accommodate part of the major axis of the ellipse of the seamless tube cross-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 in TC4 titanium alloy seamless tubes according to claim 4, characterized in that, The rotation angle of the LG-30H two-roll cold rolling mill has been reduced from 57° to 19°.

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