A method of welding a metal mold tungsten alloy electrode

Abstract

The present application relates to a kind of metal mold die tungsten alloy electrode welding method, and argon arc welding is used to weld backing welding;Argon arc welding transition layer welding;Argon arc welding base welding;Tungsten alloy weld cap welding;The present application adopts argon arc welding backing tungsten alloy electrode cap welding technology, fundamentally solves the difficulty of local improvement of surface hardness in mold cavity;The present application is improved conveniently, and the local hardness of mold is high, no wear, and the service life is basically consistent with the service life of mold.

Description

[0001] field

[0002] This invention belongs to the field of mold technology and relates to a method for welding tungsten alloy welding rods for metal molds. Background Technology

[0003] Metal molds generally have an overall hardness between HRC44 and 48. Therefore, defects such as pitting caused by wear on the mold surface, chipping from impact, and pitting corrosion can occur inside the mold cavity. Molds need to be repaired after a certain number of production runs, which wastes time and costs and causes significant problems for production.

[0004] Currently, metal molds both domestically and internationally typically utilize tungsten alloy inserts or integral blocks. However, existing laser cold welding machines using tungsten alloy coating technology for mold welding result in low strength, rough surfaces, and poor resistance to molten metal erosion, failing to achieve the desired welding effect. Furthermore, tungsten alloy welding technology is limited to rough welding applications with low precision requirements, such as agricultural machinery, mining machinery, and building materials machinery. It is only used to improve the hardness and wear resistance of cold-worked parts that are not susceptible to deformation or cracking, primarily for enhancing the surface hardness and wear resistance of large equipment. There is no unified process standard for welding tungsten alloys onto mold surfaces, either domestically or internationally.

[0005] Patent document CN202210996941.X relates to an ultrasonic-assisted brazing method for magnesium alloy and tungsten alloy. This patent is a metallurgical bonding of magnesium alloy and tungsten alloy through ultrasonic vibration, which is a non-mold welding process.

[0006] Patent document CN202210799940.6 relates to a welding method for copper-tungsten and steel. This patent is a welding method for copper-tungsten base materials and steel base materials by using copper powder to fill the gaps between the base materials and vacuum sintering, which is a non-mold welding process.

[0007] Patent document CN202123182082.0 relates to a gas shielded welding equipment based on adding a tungsten carbide alloy wear-resistant layer. This patent is a welding machine for adding a tungsten carbide alloy wear-resistant layer. This welding machine is not suitable for welding tungsten alloy coatings on metal molds. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the above-mentioned problems existing in the prior art and to provide a method for welding tungsten alloy welding rods for metal molds.

[0009] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0010] To solve the above-mentioned technical problems, the present invention is implemented using the following technical solution:

[0011] A method for welding metal molds with tungsten alloy welding electrodes, characterized in that:

[0012] The root pass is welded using argon arc welding.

[0013] Argon arc welding of transition layer;

[0014] Argon arc welding base welding;

[0015] Tungsten alloy weld cover welding.

[0016] Furthermore, before performing the argon arc welding root pass, pre-welding preparations are carried out; specifically including:

[0017] (1) Locate the surface on the mold cavity surface that needs to be hardened and mark it with lines;

[0018] (2) Cut a groove in the mark. The groove diameter is 50mm-80mm and the depth is ≥8mm. Choose a U-shaped bevel. The inner bottom concave plane of the bevel should be made into a grid-shaped groove. The groove width is 3-5mm and the grooves are crisscrossed.

[0019] (3) Preheating before welding; heating temperature is 220℃~240℃;

[0020] (4) The mold material is 1.2344 steel, and the main components (%) are: C: 0.4, Si: 1, Mn: 0.4, Cr: 3.3, Mo: 1.5, V: 1, S: ≤0.030, P: ≤0.03;

[0021] (5) ERNi-1 pure nickel argon arc welding wire was selected for the root pass transition layer welding. The wire diameter was selected as follows: For cover welding, use tungsten alloy D998 welding rods;

[0022] (6) Selection of gas flow rate, ceramic nozzle, and tungsten electrode for argon arc welding: Gas flow rate is 8-10 L / min, ceramic nozzle is size 5-6, and tungsten electrode diameter is selected accordingly. Cerium-tungsten electrodes or thorium-tungsten electrodes;

[0023] (7) For argon arc welding machines, DC positive polarity should be selected; for electric welding machines, DC reverse polarity should be selected.

[0024] (8) Selection of welding current for argon arc welding root pass: The current of the argon arc welding machine should be 110-135A.

[0025] Furthermore, when using argon arc welding for the root pass, only one layer of weld needs to be fused together, without the need to add welding wire, and the weld is fused to the bottom of the weld using an electric arc.

[0026] Furthermore, the argon arc welding transition layer welding, specifically:

[0027] (1) Select ERNi-1 pure nickel argon arc welding wire, Φ2.5mm, current is 110-135A;

[0028] (2) When welding, the left welding method is used to keep the welding wire in the molten pool. The molten droplets are continuously fed into the molten pool. Every 2 seconds, the end of the welding wire enters the molten pool to stir. The weld height is controlled at about 2mm.

[0029] (3) Pure nickel metal is selected for the first pass of the mold for the transition weld.

[0030] Furthermore, the argon arc welding base welding specifically includes: using 1.2343 argon arc welding wire to weld a weld around the bevel to form a base.

[0031] Furthermore, the tungsten alloy weld capping welding specifically includes:

[0032] (1) After the pure nickel argon arc welding transition welding is completed, clean the weld surface with a steel brush, preheat the mold welding area, and perform tungsten alloy D998 welding when the temperature reaches 220℃.

[0033] (2) The welding machine should be DC reverse polarity selected, and the diameter of the D998 welding electrode should be selected accordingly. Before welding, the welding rod needs to be kept in a 250℃ drying oven for 1 hour before it can be taken out and used; the welding current should be 100A~130A; the angle between the welding rod and the weld plane should be 60°~70°; the welding rod does not need to be swung during welding; the arc height should be controlled at 3~4mm; the welding speed should be medium; and the weld should be flat and orderly.

[0034] When welding the second weld, overlap the first weld by 1 / 3 and weld accordingly. Subsequent welds should overlap the previous weld by 1 / 3. The weld height should be controlled at around 2mm, and the width of a single weld should be 5-6mm.

[0035] (3) After welding with D998 welding rods, remove the flux coating and clean the weld surface. Then, use a flat hammer, hand hammer, or planer hammer to hammer the weld surface in a sequential manner, gradually expanding the hammering direction from the center outwards to both sides, every 25mm.2 It contains 6 to 8 evenly distributed striking points, with the diameter of each striking point being within...

[0036] (4) Tungsten alloy weld overlay: The thickness of the tungsten alloy weld below the mold surface is greater than 5mm; the final cover weld is 1-3mm higher than the mold surface and 1-5mm narrower than the base.

[0037] A method for welding tungsten alloy welding rods for metal molds, which also includes post-weld heat treatment.

[0038] Furthermore, the post-weld heat treatment specifically includes:

[0039] Immediately after welding, post-heat treatment is carried out using natural gas for overall heating. When the mold is heated to 400°C and maintained at this temperature for 3 hours, the heating source is turned off and covered with an asbestos blanket to keep it warm and slowly cool it down to 60°C before grinding the weld surface.

[0040] Furthermore, the post-weld heat treatment specifically includes:

[0041] Welding is performed by directly heating the mold with a flame;

[0042] During heating, the nozzle flame moves relative to the mold weld for uniform heating, and the combustion gas is selected from oxygen-acetylene, natural gas or liquefied petroleum gas.

[0043] Furthermore, the main components of the tungsten alloy D998 welding electrode are as follows: the electrode core is manganese and chromium alloy steel; chemical composition: C: 0.4, Mn: 0.3, Cr: 0.4, balance is steel;

[0044] Tungsten alloy D998 welding electrode coating composition:

[0045] W: 50%, B: 1.5%, and the remainder is iron powder binder.

[0046] Compared with the prior art, the beneficial effects of the present invention are:

[0047] This invention employs an argon arc welding technique with a tungsten alloy welding rod as the base coat and a tungsten alloy welding rod as the cover coat, fundamentally solving the problem of locally increasing surface hardness within the mold cavity. This invention is easy to improve, results in high localized mold hardness, eliminates wear, and has a service life essentially consistent with the mold's service life.

[0048] This invention utilizes a combined argon arc welding and electric welding process. This welding technique offers advantages such as simple operation, short processing time, and low cost, making it suitable for welding metal molds, tooling, and fixtures. The main process involves replacing a layer of tungsten alloy on the mold body surface using welding technology. This improves the impact resistance, wear resistance, and hardness of both cold-working and hot-working molds, achieving a hardness of approximately HRC ≥ 63-67 degrees. This effectively increases the mold's service life by more than three times, enhances its operational availability, reduces mold procurement costs, and is an effective means of extending mold lifespan. Attached Figure Description

[0049] The invention will now be further described with reference to the accompanying drawings:

[0050] Figure 1 A schematic diagram of the argon arc welding root pass;

[0051] Figure 2 This is a schematic diagram of the argon arc welding transition layer.

[0052] Figure 3 This is a schematic diagram of argon arc welding base welding;

[0053] Figure 4 A schematic diagram of the tungsten alloy weld cover welding. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are some, but not all, embodiments of this invention. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this invention, and should not be construed as limiting the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. The embodiments of this invention will be described in detail below with reference to the accompanying drawings.

[0055] In the description of this invention, it should be understood that the terms "center", "longitudinal", "lateral", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this 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 limiting the scope of protection of this invention.

[0056] The present invention will now be described in detail with reference to the accompanying drawings:

[0057] Mold Welding Practice: A combined manual argon arc welding and manual electric arc welding process was employed on 1.2344 hot work die steel. This welding technique was primarily used for product positioning points in casting molds and for the core box cavities of core-making molds, where ultra-hard mold surfaces were required. The welding areas of the molds required ultra-hard, wear-resistant, aluminum molten metal-resistant, and high-temperature resistant surfaces, while ensuring dimensional accuracy, improving mold mobility, and extending mold lifespan.

[0058] Process method:

[0059] I. Pre-welding preparation

[0060] (1) Locate the plane (curved surface) on the mold cavity surface where the hardness needs to be increased, and mark it first by drawing lines.

[0061] (2) Grooves are made in the markings by manual or mechanical processing. Generally, the groove diameter is 50mm-80mm and the depth is ≥8mm. The bevel is U-shaped and the inner bottom concave plane of the bevel is made into a grid-shaped groove with a groove width of 3-5mm and crisscrossing. Grooving can improve the bonding force between the weld and the base material, uniformly reduce the compressive and tensile stress of the weld, and effectively improve the mechanical properties of the weld. Its adhesion strength after welding is equivalent to the screw welding method in cast iron welding.

[0062] (3) Preheating is necessary before welding. It is best to use natural gas to heat the mold as a whole. The mold temperature should be between 220℃ and 240℃. If the mold is too large to be heated as a whole, local preheating can be used. The part to be welded can be heated with gas welding. The gas welding flame should be a carburizing flame. When heating, the mold should be heated evenly around the part to be welded. The heating temperature should be higher, generally controlled at around 260℃ (because the local heating area is small and the mold surface temperature is high, the mold temperature will drop by 30℃ to 40℃ during the preheating period before welding).

[0063] (4) The mold material is German grade 1.2344 steel. Main components (%): C: 0.4, Si: 1, Mn: 0.4, Cr: 3.3, Mo: 1.5, V: 1, S: ≤0.030, P: ≤0.03

[0064] (5) ERNi-1 pure nickel argon arc welding wire was selected for the root pass transition layer welding. The wire diameter was selected as follows: It is advisable to use tungsten alloy D998 welding rods for cover welding.

[0065] D998 main components (%): The electrode core is made of manganese and chromium alloy steel, with the following chemical composition: C: 0.4%, Mn: 0.3%, Cr: 0.4%, and the balance being steel. Electrode coating composition:

[0066] W: 50%, B: 1.5%, and the remainder is iron powder binder. The weld hardness of D998 welding rods is generally around HRC: 63-67, which belongs to the super-hard welding technology.

[0067] (6) Selection of gas flow rate, ceramic nozzle, and tungsten electrode for argon arc welding: The gas flow rate is generally 8-10 L / min, the ceramic nozzle is size 5-6, and the tungsten electrode diameter is selected accordingly. Cerium-tungsten electrodes (gray-head) or thorium-tungsten electrodes (red-head).

[0068] (7) For argon arc welding machines, the DC positive polarity method should be selected (e.g., the workpiece is connected to the + level), while for electric welding machines, the DC reverse polarity method should be selected. The characteristics of the DC reverse polarity method are: shallow welding penetration, low electrode dilution rate, and for multi-layer surfacing technology, it has the advantages of stable welding arc, low welding stress, fast weld surface formation, and narrow heat-affected zone.

[0069] (8) Selection of welding current for the root pass in argon arc welding: The current selected for the argon arc welding machine is around 110-135A. Practice has shown that when the welding current exceeds 145A-155A, the heat input of the weld increases with the welding current, resulting in greater shrinkage stress in the weld. This leads to a significant decrease in the mechanical and mechanical properties of the weld, and in severe cases, stress concentration occurs, causing stress cracks in the weld. This results in through-cracks in the weld after the hot-working die is put into service, leading to weld failure. This type of weld failure due to stress concentration causes great damage to the die body, as the weld cracks quickly penetrate into the die, breaking through the cooling channels and rendering the die unusable.

[0070] II. TIG welding for the root pass, see reference. Figure 1 ;

[0071] When using argon arc welding for the root pass, only one layer of weld needs to be fused together. No additional welding wire is required. The weld can be fused to the bottom of the weld using an electric arc.

[0072] III. Argon arc welding transition layer welding, see reference. Figure 2 ;

[0073] (1) Select ERNi-1 pure nickel argon arc welding wire, Φ2.5mm, current is 110-135A.

[0074] (2) When welding, the left welding method should be used to keep the welding wire in the molten pool. The molten droplets should be continuously fed into the molten pool, and the end of the welding wire should be inserted into the molten pool for stirring every 2 seconds. The purpose of this intermittent insertion of the welding wire into the molten pool for stirring is to reduce the temperature of the molten pool, increase the deposition rate of the weld, and reduce the dilution rate of the weld. The weld height should be controlled at about 2 mm to effectively reduce the shrinkage stress of the weld after the molten pool crystallizes.

[0075] (3) Pure nickel is chosen for the first pass of the mold's root pass transition weld. The main reason is that pure nickel is relatively soft with an elongation of 33%. As a transition weld, it acts like a sofa cushion, greatly relieving stress in the weld. After welding, the root pass weld should not be hammered because the tensile strength of pure nickel is only 360 MPa, which is very low. If the weld is hammered, grain boundary cracks will be generated in the fusion zone of the root pass weld under the action of external force, resulting in the loss of the weld structure.

[0076] IV. Argon arc welding base welding, see reference. Figure 3 ;

[0077] Use 1.2343 argon arc welding wire to weld a ring of weld around the bevel to form a base.

[0078] V. Welding process technology for D998 tungsten alloy weld capping, see reference. Figure 4 ;

[0079] (1) After the pure nickel argon arc welding transition welding is completed, the weld surface should be cleaned with a steel brush, and then the mold welding area should be preheated. Tungsten alloy D998 welding can only be carried out when the temperature reaches 220℃.

[0080] (2) The welding machine should be DC reverse polarity selected, and the diameter of the D998 welding electrode should be selected accordingly. Before welding, the welding rods need to be kept in a 250℃ drying oven for 1 hour before use. The welding current should be 100A-130A. The angle between the welding rod and the weld plane should be 60°-70°. The welding rod does not need to be swung during welding; the arc height should be controlled at 3-4mm, and the welding speed should be medium, resulting in a smooth and orderly weld. When welding the second weld, it should overlap the first weld by 1 / 3, and so on. This welding sequence ensures a full weld area, a weld height of approximately 2mm, a single weld width of 5-6mm, uniform weld height, low weld stress, and fewer welding defects.

[0081] (3) After welding with D998 welding rods, remove the flux coating and clean the weld surface with a steel brush. Then, use a flat hammer, hand hammer, or planer hammer to hammer the weld surface in a sequential manner, gradually expanding the hammering direction from the center outwards to both sides. The hammering force should not be too great, but the hammering points should be dense, generally every 25mm. 2 It contains 6 to 8 evenly distributed striking points, and the diameter of each striking point is generally within [missing information]. The weld hammering process can effectively induce plastic deformation in the weld metal, thereby releasing 80-90% of the compressive and tensile stress in the tungsten alloy weld. Therefore, the post-weld hammering process is also a very important stress release step.

[0082] (4) Tungsten alloy weld overlay: The overlay welding process of tungsten alloy welding rod D998 is basically the same as the first pass, ensuring that the thickness of the tungsten alloy weld below the mold surface is greater than 5mm. Finally, the overlay weld is 1-3mm higher than the mold surface and 1-5mm narrower than the base.

[0083] VI. Post-weld heat treatment

[0084] (1) After welding, post-heat treatment should be carried out immediately. It is best to use natural gas for overall heating. When the mold is heated to 400°C and this temperature is maintained for 3 hours, the heating source is turned off and covered with an asbestos blanket to keep it warm and slowly cool it down to 60°C before grinding the weld surface.

[0085] (2) Another method is to directly heat the mold with a flame for welding.

[0086] For the weld surface, during heating, the nozzle flame should move relative to the mold weld seam for uniform heating. The combustion gas can be oxy-acetylene, natural gas, liquefied petroleum gas, etc. The flame-assisted heating method is a manual heating process, the same as the mold-assisted heating process described above.

[0087] After welding, the service life of the hardened weld seam of hot-work casting molds is generally 40,000 cycles. When cracks or detachment occur at the weld seam, the above-mentioned process can be used to re-weld the mold for reuse until the end of its lifespan. For cold-work core box molds, because the resin sand is sprayed into the mold cavity at high speed and high pressure through the nozzle for curing, the resin sand impacts the mold surface after entering the mold through the nozzle, causing wear and rendering the affected areas unusable. When mold weld seam hardening technology is used, the surface hardness of the mold can reach HRC 63-67, which can extend the repair cycle of this area by more than three times.

[0088] This welding process is used to repair worn areas of the cylinder head casting mold and core box of the EA888 Gen3 engine, thereby improving the service life of the mold.

[0089] Laser tungsten rod coating welding results in low surface strength and poor heat resistance, making it unsuitable for casting mold cavities. Its rough surface also precludes its use in cold-working mold cavities. Electric welding and gas welding of tungsten alloys suffer from large deformation and cracking issues, limiting their application to parts without precision requirements.

[0090] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be included within the scope of protection of the present invention. Furthermore, all content not described in detail in this specification is prior art known to those skilled in the art.

Claims

1. A method for welding metal molds with tungsten alloy welding electrodes, characterized in that: Pre-welding preparations are required; specifically including: Locate the surfaces on the mold cavity surface that require increased hardness and mark them with lines. Cut a groove inside the mark. The groove diameter is 50mm-80mm and the depth is ≥8mm. The bevel is U-shaped. The inner bottom concave plane of the bevel should be made into a grid-shaped groove. The groove width is 3-5mm and the grooves are crisscrossed. The mold material is 1.2344 steel, with the following main components (%): C: 0.4, Si: 1, Mn: 0.4, Cr: 3.3, Mo: 1.5, V: 1, S: ≤0.030, P: ≤0.03; Selection of gas flow rate, ceramic nozzle, and tungsten electrode for argon arc welding: gas flow rate is 8-10 L / min, use a No. 5-6 ceramic nozzle, and use a 2.4 mm diameter cerium tungsten electrode or thorium tungsten electrode; The root pass is welded using argon arc welding; only one weld layer needs to be fused, and no additional welding wire is required. Argon arc welding of the transition layer; details: (1) Use ERNi-1 argon arc welding wire, Φ2.5mm, current is 110-135A; (2) When welding, use the left welding method to keep the welding wire in the molten pool at all times, keep the molten droplets continuously fed into the molten pool, and stir the welding wire end into the molten pool every 2 seconds. The weld height is controlled at 2mm. Argon arc welding base welding; specifically including: using 1.2343 argon arc welding wire to weld a weld around the bevel to form a base; Tungsten alloy weld capping welding; specifically including: (1) After the argon arc welding transition welding is completed, clean the weld surface with a steel brush, preheat the mold welding area, and perform tungsten alloy D998 welding when the temperature reaches 220℃. (2) The welding machine adopts DC reverse polarity. The diameter of the D998 welding rod is Ø2.5mm. Before welding, the welding rod needs to be kept in a 250℃ drying oven for 1 hour before it can be taken out for use. The welding current is 100A~130A. The angle between the welding rod and the weld plane is 60°~70°. The welding rod does not need to be swung during welding. The arc height is controlled at 3~4mm. The welding speed is medium speed. The weld is flat and orderly. When welding the second weld, overlap the first weld by 1 / 3 and weld accordingly. Subsequent welds should overlap the previous weld by 1 / 3. The weld height should be controlled at 2mm, and the width of a single weld should be 5-6mm. (3) After welding with D998 welding rod, remove the flux coating and clean the weld surface. Then, hammer the weld surface in a sequential manner, gradually expanding the hammering direction from the middle outwards to both sides, every 25mm. 2 It contains 6 to 8 evenly distributed striking points, with a striking point diameter of Ø2 to Ø3 mm; (4) Tungsten alloy weld overlay: The thickness of the tungsten alloy weld below the mold surface is greater than 5mm; the final cover weld is 1-3mm higher than the mold surface and 1-5mm narrower than the base.

2. The welding method for tungsten alloy welding electrodes for metal molds according to claim 1, characterized in that: It also includes post-weld heat treatment.

3. The welding method for tungsten alloy welding electrodes for metal molds according to claim 2, characterized in that: The post-weld heat treatment specifically includes: Immediately after welding, post-heat treatment is carried out using natural gas overall heating. The mold is heated to 400℃ and maintained at this temperature for 3 hours. Then, the heating source is turned off and the mold is covered with an asbestos blanket to keep it cool slowly to 60℃ before the weld surface is ground.

4. The welding method for tungsten alloy welding electrodes for metal molds according to claim 2, characterized in that: The post-weld heat treatment specifically includes: Heat the mold directly with a flame; During heating, the nozzle flame moves relative to the mold weld for uniform heating, and the combustion gas is oxy-acetylene, natural gas, or liquefied petroleum gas.

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