Method for controlling welding quality of α+β type titanium alloy ingot

Abstract

This invention discloses a method for controlling the welding quality of α+β type titanium alloy ingots, including surface cleaning of the welding area of ​​the α+β type duplex titanium alloy ingot; dividing the welding area between the first and second ingots into three temperature-controlled zones: the weld groove center zone, the near-weld heat-affected zone, and the base material matrix; each zone is equipped with at least one independently controlled electromagnetic induction coil for differentiated heating; the entire welding process is protected by a vacuum atmosphere or by adding a protective inert gas; after welding, the welding area is heat-treated and finally naturally cooled to room temperature. This invention's pre-weld, during-weld, and post-weld temperature control system mitigates the phase transformation rate throughout the welding process, avoids the formation of brittle structures, and solves the problem of crack initiation in the weld, fusion line, or heat-affected zone of α+β type titanium alloy ingots, effectively improving the strength and toughness of the welded area and ensuring stable melting of the welded ingot.

Description

Technical Field

[0001] This invention relates to the field of titanium alloy ingot welding technology, specifically to a method for regulating and controlling the welding quality of α+β type titanium alloy ingots. Background Technology

[0002] α+β type titanium alloys are currently the most widely used duplex titanium alloy system in the industrial field. Typical examples include grades TC4, TC11, and TC17. They possess comprehensive properties such as low density, excellent corrosion resistance, high-temperature mechanical stability, and biocompatibility, making them indispensable key metal materials for high-end equipment manufacturing industries such as aerospace, medical, and marine engineering.

[0003] Currently, the production of titanium alloys still mainly relies on vacuum arc remelting (VAR). The process involves pressing raw materials into electrode blocks, welding these blocks together to form an initial electrode, and then melting the initial electrode in a VAR furnace. After multiple melting processes, a finished titanium alloy ingot is obtained. During each melting, the ingot height decreases while the diameter increases. Therefore, in actual production, the size of the finished ingot produced from a single initial electrode is limited, which not only restricts production efficiency but also affects the ingot yield. One solution is to melt two initial electrodes separately into primary ingots, and then weld these two primary ingots together for subsequent melting. However, for α+β type duplex titanium alloys, the welding thermal cycle disrupts the original stable α / β dual-phase ratio of the matrix, inducing the formation of brittle acicular α' martensite structure. Simultaneously, it causes grain coarsening in the heat-affected zone and stress concentration at the phase interface, significantly increasing the material's embrittlement and cracking susceptibility. Meanwhile, the low thermal conductivity and small coefficient of thermal expansion of titanium alloys lead to severe local heat accumulation during welding. This results in significant uneven volume shrinkage during cooling, creating high-amplitude residual stress, which provides a core driving force for the initiation and propagation of microcracks. Furthermore, the high hardness and low plasticity α-hardened layer naturally present on the ingot surface, along with process defects such as porosity and lack of fusion that easily occur during welding, further exacerbate the stress concentration effect. This promotes the rapid initiation and propagation of cracks in the weld, fusion line, or heat-affected zone, ultimately causing the entire ingot to fracture, forcing the smelting process to be interrupted, and even leading to serious production safety accidents.

[0004] At present, most of the publicly disclosed patented technologies for welding α+β type titanium alloys focus on optimizing the welding process of finished components. There is no effective technical solution to completely avoid the failure problem in the welding process of ingots due to the metallurgical properties of the ingot itself and the thermal coupling effect of welding.

[0005] In view of this, based on the microstructure evolution and fracture mechanism of the welding process of α+β type titanium alloy ingots, this invention proposes a method for controlling the welding quality of α+β type titanium alloy ingots, which has important engineering value for improving the production efficiency and yield of α+β type titanium alloy ingots. Summary of the Invention

[0006] In view of the above-mentioned shortcomings of the existing technology, the purpose of this invention is to provide a method for regulating and controlling the welding quality of α+β type titanium alloy ingots, which can avoid the formation of brittle structures during the welding process and prevent cracks from initiating in the weld, fusion line or heat-affected zone of α+β type titanium alloy ingots, thereby improving the strength and toughness of the welded area of ​​titanium alloy ingots and improving the specifications of finished ingots.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0008] A method for regulating and controlling the welding quality of α+β type titanium alloy ingots, characterized by comprising the following steps:

[0009] (1) Perform overall surface cleaning treatment on the α+β type duplex titanium alloy ingot to be welded area to remove oxide scale and surface impurities;

[0010] (2) Divide the welding area between the first and second ingots to be welded into three temperature control zones: the weld groove center zone, the near-weld heat-affected zone, and the base material matrix. Use multiple sets of independent electromagnetic induction coils, with at least one set of independently controlled electromagnetic induction coils in each zone to implement independent and differentiated heating for each zone.

[0011] (3) Vacuum atmosphere protection is used throughout the welding process, or protective inert gas is added;

[0012] (4) After welding is completed, the welded area is heat-treated according to the process requirements and then naturally cooled to room temperature.

[0013] A further feature is that in step (1), the α+β type dual-phase titanium alloy ingot is TC4, TC11, or TC17, which are industrial general-purpose titanium alloy grades, and the ingot diameter ranges from φ190 to 660 mm.

[0014] A further feature is that, in step (2), the width of the weld groove center area is 20~60mm, the width of the near-weld heat-affected zone is 40~80mm, and the width of the base material matrix area is 60~100mm.

[0015] Further features include: the weld groove center zone is 450-550℃, the near-weld heat-affected zone is 300-450℃, and the far-end base material is 200-300℃; the temperature gradient in the preheating zone is controlled at ≤20℃ / mm.

[0016] A further feature is that in step (3), the vacuum degree of the welding atmosphere is ≤1.0Pa, or a protective inert gas or nitrogen is added.

[0017] A further feature is that, in step (4) of the present invention, the welding depth is 20~60mm;

[0018] A further feature is that in step (4), the welding area is subjected to heat treatment, including one or two or all three of the following: homogenization treatment, solution treatment and aging treatment; the main process parameters for the homogenization treatment of the welding area are: temperature 600~700℃, duration 1.0~3.0h; the main process parameters for the solution treatment are: 820~960℃, duration 1.0~3.0h; the main process parameters for the aging treatment are: temperature 500~600℃, duration 2.0~4.0h, and then cooled to room temperature.

[0019] Compared with existing technologies, the method for regulating and controlling the welding quality of α+β type titanium alloy ingots of this invention has the following advantages:

[0020] 1. This invention features a unique full-process temperature control system from pre-weld to during-weld to post-weld. By gradually reducing the phase transformation rate throughout the welding process, it avoids the formation of brittle structures and solves the problem of crack initiation in the weld, fusion line, or heat-affected zone of α+β type titanium alloy ingots. It effectively improves the strength and toughness of the welded area of ​​titanium alloy ingots, ensuring stable melting of the ingots after welding and completely avoiding production interruptions caused by ingot welding fractures. It is highly applicable to improving the specifications of finished ingots.

[0021] 2. This invention achieves excellent microstructure by coordinating and controlling the gradient temperature field throughout the entire process from pre-weld to during-weld to post-weld. It sets up three temperature control zones: the weld groove center zone, the near-weld heat-affected zone, and the far-end base metal matrix. It implements independent and differentiated preheating for each zone, effectively suppressing the formation of brittle acicular martensite and weakening the gradient abrupt change in the weld microstructure. Ultimately, it obtains a superior microstructure across the entire domain, characterized by a fine basketweave structure in the weld, a smooth transition in the heat-affected zone, and a homogeneous and stable dual-state structure in the base metal.

[0022] 3. This invention can achieve homogenization of the microstructure of the welded joint, reduce residual stress, and balance mechanical properties, effectively solving the technical problems of easy brittleness, easy cracking, easy deformation, and large performance dispersion of α+β dual-phase titanium alloy ingots, and significantly improving the overall welding quality and smelting process stability of titanium alloy ingots.

[0023] 4. This invention can increase the size of finished ingots in a single furnace by 2.03 to 2.07 times, and increase the ingot yield from the current approximately 87.50% by 3.57 to 5.26%. Attached Figure Description

[0024] To make the objectives, technical solutions, and advantages of the invention clearer, the invention will now be described in further detail with reference to the accompanying drawings, wherein:

[0025] Figure 1 This is a schematic diagram of the partitioning of the control method of the present invention.

[0026] The reference numerals in the accompanying drawings include: 1—first ingot, 2—second ingot, 3—center zone of weld groove, 4—heat-affected zone near weld, and 5—base material matrix. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] 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 a part of the embodiments of the present invention, not all of them. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to represent selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0029] It should be noted that similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the figures, or the orientation or positional relationship commonly used when the product is in use. They are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance. In addition, the terms "horizontal," "vertical," etc., do not indicate that the component is required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted. In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0030] The following detailed explanation illustrates the specific implementation methods:

[0031] This invention discloses a method for regulating and controlling the welding quality of α+β type titanium alloy ingots, comprising the following steps:

[0032] (1) Perform overall surface cleaning treatment on the α+β type duplex titanium alloy ingot to be welded area to completely remove oxide scale and surface impurities;

[0033] (2) The welding area between the first ingot 1 and the second ingot 2 to be welded is divided into three temperature control zones: the weld groove center zone 3, the near-weld heat-affected zone 4, and the base material matrix 5. Multiple sets of independent electromagnetic induction coils are used, and at least one set of independently controlled electromagnetic induction coils is set in each zone to implement zoned independent differential heating.

[0034] (3) Vacuum atmosphere protection is used throughout the welding process, or protective inert gas is added;

[0035] (4) After welding, the welding area is heat-treated according to the process requirements and then naturally cooled to room temperature to make the microstructure of the welding area uniform and refined and to relieve residual stress.

[0036] In step (1) of the present invention, the α+β type dual-phase titanium alloy ingot is TC4, TC11, TC17, which are industrially common titanium alloy grades, and the ingot diameter range is φ190~660mm; the oxide scale and surface impurities can be removed by turning on a lathe.

[0037] In step (2) of this invention, three sets of electromagnetic induction coils are set up, corresponding to three temperature control zones: the weld bevel center zone 3, the near-weld heat-affected zone 4, and the base metal substrate 5. The ingot welding area is divided as follows: the width of the weld bevel center zone is approximately 20-60 mm, the width of the near-weld heat-affected zone is approximately 40-80 mm, and the width of the base metal substrate zone is approximately 60-100 mm. The differentiated preheating temperatures for each zone are: approximately 450-550℃ for the weld bevel center zone, approximately 300-450℃ for the near-weld heat-affected zone, and approximately 200-300℃ for the far-end base metal substrate; the optimal temperature gradient in the preheating zone is controlled at ≤20℃ / mm. The specific temperature range of the three temperature control zones—weld bevel center zone 3, near-weld heat-affected zone 4, and base metal substrate 5—is controlled by process requirements, mainly referring to the specific alloy ratios of the first ingot 1 and the second ingot 2, as well as the welding process parameters and requirements.

[0038] In step (3) of the present invention, the welding atmosphere is: vacuum degree ≤1.0Pa, or a protective gas is added, such as inert gas or nitrogen.

[0039] In step (4) of this invention, the welding depth is 20~60mm; the heat treatment of the welding area includes homogenization treatment, solution treatment and aging treatment, one, two or three of which; the main process parameters of the homogenization treatment of the welding area are: temperature 600~700℃, duration 1.0~3.0h; the main process parameters of the solution treatment process are: 820~960℃, duration 1.0~3.0h; the main process parameters of the aging treatment are: temperature 500~600℃, duration 2.0~4.0h, and after completion, cooling to room temperature, wherein the temperature gradient of each treatment process is strictly controlled ≤10℃ / mm.

[0040] In steps (1) to (4) of the present invention, the welding area of ​​the α+β type titanium alloy ingot ultimately forms a differentiated gradient microstructure consisting of a dense mesh structure of the weld, a heat-affected zone, and a dual-state structure of the base material, which is the optimal mechanical matching configuration for the welded joint of the ingot.

[0041] Example 1:

[0042] In this embodiment, we take welding a TC4 titanium alloy ingot as an example, with an ingot diameter of 250mm.

[0043] Remove oxide scale and impurities from the surface of TC4 ingots;

[0044] Set the weld width of the ingot to 20mm and the preheating temperature to 450~470℃; the heat-affected zone width near the weld to 40mm and the preheating temperature to 300~320℃; and the base metal zone width at the far end to 60mm and the preheating temperature to 200~220℃.

[0045] Control the vacuum level of the welding atmosphere to ≤1.0Pa, or add argon as a protective gas;

[0046] The welding depth of the ingot welding area is 20mm. After welding, the uniform microstructure is treated as follows: temperature 620~630℃, duration 1.0h, furnace cooling; solution treatment: temperature 920~930℃, duration 1.0h, air cooling; aging treatment: temperature 530~540℃, duration 2.0h, air cooling.

[0047] Example 2:

[0048] In this embodiment, we take the welding of TC11 titanium alloy ingot as an example, with an ingot diameter of 570mm.

[0049] Remove oxide scale and impurities from the surface of TC11 ingots;

[0050] Set the weld width of the ingot to 40mm and the preheating temperature to 480~500℃; the heat-affected zone width near the weld to 60mm and the preheating temperature to 350~360℃; and the base metal zone width at the far end to 80mm and the preheating temperature to 280~290℃.

[0051] Control the vacuum level of the welding atmosphere to ≤1.0 Pa;

[0052] The welding depth of the ingot welding area is 40mm. After welding, the uniform microstructure is treated as follows: temperature 640~650℃, duration 2.0h, furnace cooling; solution treatment: temperature 940~950℃, duration 2.0h, air cooling; aging treatment: temperature 520~530℃, duration 3.0h, air cooling.

[0053] Example 3:

[0054] In this embodiment, we take the welding of TC17 titanium alloy ingot as an example, with an ingot diameter of 660mm.

[0055] Remove oxide scale and impurities from the surface of TC17 ingots;

[0056] Set the weld width of the ingot to 50mm and the preheating temperature to 510~520℃; the heat-affected zone width near the weld to 80mm and the preheating temperature to 390~400℃; and the base metal zone width at the far end to 80mm and the preheating temperature to 290~300℃.

[0057] Control the vacuum level of the welding atmosphere to ≤1.0 Pa;

[0058] The welding depth of the ingot welding area is 50mm. After welding, the uniform microstructure is treated as follows: temperature 620~630℃, duration 2.5h, furnace cooling; solution treatment: temperature 885~895℃, duration 2.5h, air cooling; aging treatment: temperature 520~530℃, duration 3.0h, air cooling.

[0059] The aforementioned embodiments of the present invention all take the welding of α+β type titanium alloy ingots as an example. By coordinating and controlling the gradient temperature field throughout the entire process from pre-weld to during-weld to post-weld, the generation of brittle acicular martensite in welding is effectively suppressed, and the microstructure of the welded joint is homogenized, thus solving the problems of easy brittleness, easy cracking, and easy deformation in the welding of α+β dual-phase titanium alloy ingots.

[0060] 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 the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A method for regulating and controlling the welding quality of α+β type titanium alloy ingots, characterized in that, Includes the following steps: (1) Perform overall surface cleaning treatment on the α+β type duplex titanium alloy ingot to be welded area to remove oxide scale and surface impurities; (2) Divide the welding area between the first ingot (1) and the second ingot (2) to be welded into three temperature control zones: the weld groove center zone (3), the near-weld heat-affected zone (4), and the base material matrix (5). Use multiple sets of independent electromagnetic induction coils, and set at least one set of independently controlled electromagnetic induction coils in each zone to implement independent and differentiated heating in each zone. (3) Vacuum atmosphere protection is used throughout the welding process, or protective inert gas is added; (4) After welding is completed, the welded area is heat-treated according to the process requirements and then naturally cooled to room temperature.

2. The method for controlling the welding quality of α+β type titanium alloy ingots according to claim 1, characterized in that: In step (1), the α+β type dual-phase titanium alloy ingot is TC4, TC11, or TC17, which are industrial general-purpose titanium alloy grades, and the ingot diameter range is φ190~660mm.

3. The method for controlling the welding quality of α+β type titanium alloy ingots according to claim 1 or 2, characterized in that: In step (2), the width of the weld groove center area is 20~60mm, the width of the heat-affected zone near the weld is 40~80mm, and the width of the base metal matrix area is 60~100mm.

4. The method for controlling the welding quality of α+β type titanium alloy ingots according to claim 3, characterized in that: The temperature ranges from 450 to 550°C in the center zone of the weld groove, 300 to 450°C in the near-weld heat-affected zone, and 200 to 300°C in the far-end base material; the temperature gradient in the preheating zone is controlled at ≤20°C / mm.

5. A method for controlling the welding quality of α+β type titanium alloy ingots according to claim 1 or 2, characterized in that: In step (3), the vacuum degree of the welding atmosphere is ≤1.0Pa, or a protective inert gas or nitrogen is added.

6. The method for regulating and controlling the welding quality of α+β type titanium alloy ingots according to claim 4, characterized in that: In step (4) of the present invention, the welding depth is 20~60mm.

7. A method for controlling the welding quality of α+β type titanium alloy ingots according to claim 1 or 2, characterized in that: In step (4), the welding area is subjected to heat treatment, including one or two or all three of the following: homogenization treatment, solution treatment and aging treatment. The main process parameters for the homogenization treatment of the welding area are: temperature 600-700℃, duration 1.0-3.0h; the main process parameters for the solution treatment are: 820-960℃, duration 1.0-3.0h; the main process parameters for the aging treatment are: temperature 500-600℃, duration 2.0-4.0h, followed by cooling to room temperature.

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