Method of hybrid welding of cast iron molds

Abstract

The application provides a cast iron mold mixed welding method, and specifically comprises the following steps: quenching convex round corners on a cast iron mold; cleaning the welding area and impurities such as scale, dirt, rust and moisture in a predetermined range on both sides of the welding area; locally preheating a predetermined range of the welding area by using a low-voltage intelligent temperature control box; welding the profile surface welding area by using a stick arc welding method until the welding reaches the welding area close to the convex round corner; welding the profile surface by using the stick arc welding method, and then welding the convex round corner by using a carbon dioxide gas shielded welding method to cover the entire round corner; only one layer of weld is needed to make the welding hardness of the convex round corner reach the preset requirement, and the color difference between the weld and the base material is reduced; the weld is prone to cracking due to the single stick welding failing to reach the hardness requirement; the welding efficiency can be effectively improved, the welding cost can be reduced, and the service life of the mold can be improved.

Description

Technical Field

[0001] This invention relates to a welding method, and more particularly to a mixed welding method for cast iron molds. Background Technology

[0002] The base material for automotive drawing dies is cast iron. During the quality improvement and rectification process, the key factor is ensuring the welding quality. The drawing convex fillet on the die needs to ensure that the welding hardness reaches HRC≥55. Since cast iron is sensitive to temperature, the high hardness of the convex fillet poses a great risk of cracking.

[0003] In existing technologies, to avoid cracking of convex fillets and achieve the required hardness, traditional welding techniques are used to weld convex fillets. This requires a nickel-based underlay or two to three layers of welding. However, welding convex fillets in this way easily leads to insufficient hardness, significant color difference from the base material, cracking, and peeling. Furthermore, this welding method is inefficient and costly. Once a convex fillet cracks using traditional welding techniques, it can easily lead to mold rework or even scrap. The usual solution is to reduce the size of the mold, but this method is time-consuming and requires remachining, heat treatment, adjustment, and polishing of the mold, resulting in repetitive labor and high costs. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the technical problem to be solved by the present invention is to provide a method for hybrid welding of cast iron molds.

[0005] This invention proposes a method for hybrid welding of cast iron molds, specifically including the following steps:

[0006] Step S100: Welding preparation, the convex rounded corners on the cast iron mold are quenched;

[0007] Step S200: Clean impurities in the welding area, including scale, oil, rust, moisture, and other impurities in the welding area and within 50mm on both sides.

[0008] Step S300: Local preheating of the welding area. Use a DWCK-60 low-voltage intelligent temperature control box or flame preheating to locally preheat the welding area ≥50mm. The preheating temperature is 350℃~400℃ and the preheating time is 2h.

[0009] Step S400: Surface welding. Weld the surface welding area using shielded metal arc welding at a welding speed of 80mm / min~90mm / min. The electrode diameter is φ3.2mm, the welding current is 100A~110A, and the welding voltage is 20V, until welding reaches the area close to the convex rounded corner welding area.

[0010] Step S500: Convex fillet welding. Use carbon dioxide gas shielded welding at a welding speed of 90mm / min~100mm / min to weld the convex fillet to cover the entire fillet. The welding rod diameter is φ1.2mm, the welding current is 150A~160A, and the welding voltage is 18V~19V.

[0011] Preferably, in step S400, the electrode used for shielded metal arc welding is NH100s, the electrode baking temperature is 350℃, and the baking time is 2h.

[0012] Preferably, the carbon dioxide gas shielded welding in step S500 uses CIH-1 welding wire.

[0013] Preferably, in step S400, the molded surfaces are welded sequentially until the distance from the convex rounded corner edge is 5mm to 10mm.

[0014] Preferably, the arc termination angle at each weld joint is 10°~20° to avoid cross-sections at the weld termination point.

[0015] Preferably, each weld seam is hammered at its edge using a pneumatic hammer or a rounded hammer. During hammering, the angle between the pneumatic hammer and the weld seam is 70° to 80° to reduce welding stress and improve weld density.

[0016] Preferably, after welding is completed in step S500, asbestos is used to keep the welded area warm and cool it down to below 70°C.

[0017] As described above, the mixed welding method for cast iron molds involved in this invention has the following beneficial effects:

[0018] This invention first welds the profile using shielded metal arc welding (SMAW), then welds the convex fillet using carbon dioxide gas shielded welding (CO2-GAW) to cover the entire fillet. Only one weld layer is needed to achieve a weld hardness of HRC≥55 for the convex fillet, reducing the color difference between the weld and the base material. It also avoids the weld cracking caused by insufficient hardness due to a single welding rod. This invention can effectively improve welding efficiency, reduce welding costs, and extend the service life of the mold. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the welding area of ​​a cast iron mold provided in an embodiment of the present invention.

[0020] Figure 2 This is a partial enlarged view of the welding area of ​​the cast iron mold provided in an embodiment of the present invention.

[0021] Explanation of reference numerals in the attached figures:

[0022] 1. First surface welding area; 2. Second surface welding area; 3. Third surface welding area; 4. Curving angle; 5. Convex fillet welding area. Detailed Implementation

[0023] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0024] It should be understood that the structures, proportions, sizes, etc., illustrated in the accompanying drawings of this specification are merely for illustrative purposes to aid those skilled in the art and are not intended to limit the scope of the invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and purpose of the invention, should still fall within the scope of the technical content disclosed in this invention. Furthermore, the terms such as "upper," "lower," "left," "right," and "middle" used in this specification are merely for clarity and are not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0025] like Figure 1 As shown, this invention provides an embodiment of a hybrid welding method for cast iron molds. The cast iron mold of this invention relates to automotive drawing dies, and specifically includes the following steps:

[0026] Step S100: Welding preparation. The convex fillets on the cast iron mold are quenched to improve their hardness and strength.

[0027] Step S200: Clean impurities in the welding area. Clean the welding area and the area within 50mm on both sides to remove impurities such as oxide scale, oil, rust, and moisture, ensuring that the welding area is free of debris to reduce the phenomenon of hydrogen-induced cracking of the weld.

[0028] Step S300: Local preheating of the welding area. Use a DWCK-60 low-voltage intelligent temperature control box or flame preheating to locally preheat the welding area within a range of ≥50mm. The preheating temperature is 350℃~400℃ and the preheating time is 2h. This is to reduce the cooling rate of the welding area, avoid the formation of brittle and hard structures, and reduce welding stress and deformation during subsequent welding, thereby preventing the formation of welding cracks.

[0029] Step S400: First, perform surface welding. Use shielded metal arc welding (SMAW) at a welding speed of 80mm / min~90mm / min to weld the surface welding area. The electrode diameter is φ3.2mm, the welding current is 100A~110A, and the welding voltage is 20V, until welding reaches the welding area near the convex rounded corner 5. Preferably, the SMAW electrode is NH100s, the electrode baking temperature is 350℃, and the baking time is 2h.

[0030] like Figures 1 to 2 As shown, when welding the profile using shielded metal arc welding (SMAW), the second profile welding area 2 and the third profile welding area 3 are welded sequentially from the first profile welding area 1 until the weld reaches a distance of 5mm to 10mm from the edge of the convex fillet. This allows for a margin for subsequent convex fillet welding and avoids direct contact with the convex fillet during the welding of the profile, which could prevent the hardness of the convex fillet from failing to meet the preset requirements. When welding to the weld joint between the first profile welding area 1, the second profile welding area 2, and the third profile welding area 3, the arc termination angle 4 of the weld is preferably 10° to 20° to avoid a cross-section at the weld termination point. After each weld is completed, a pneumatic hammer is used to hammer the edge of the weld. During hammering, the angle between the pneumatic hammer and the weld is 70° to 80° to reduce welding stress and improve weld density.

[0031] After step S500, when the contour welding is completed, the convex fillet welding is performed. Carbon dioxide gas shielded welding is used at a welding speed of 90mm / min~100mm / min to weld the convex fillet area until the entire fillet is covered. The electrode diameter is φ1.2mm, the welding current is 150A~160A, and the welding voltage is 18V~19V. CIH-1 welding wire is preferred for carbon dioxide gas shielded welding. It should be noted that when welding the convex fillet, the welding is performed by oscillation to cover the entire fillet.

[0032] like Figures 1 to 2 As shown, after the surface welding is completed, when welding the convex fillet with carbon dioxide gas shielded welding, the arc-ending angle 4 at the weld joint is 10°~20° to avoid the appearance of a cross section at the arc-ending point of the weld, so that the hardness of the convex fillet HRC≥55.

[0033] Step S600: After the convex fillet welding is completed, asbestos is used to keep the first to third surface welding areas and the convex fillet welding area 5 warm and cool them down to below 70°C to prevent weld cracks, reduce weld hardness, and avoid generating large stress.

[0034] This invention first welds the profile using shielded metal arc welding (SMAW), then welds the convex fillet using carbon dioxide gas shielded welding (CO2-GAW) to cover the entire fillet. Only one weld layer is needed to achieve a weld hardness of HRC≥55 for the convex fillet, reducing the color difference between the weld and the base material. It also avoids the weld cracking caused by insufficient hardness due to a single welding rod. This effectively improves welding efficiency, reduces welding costs, and extends the service life of the mold.

[0035] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for hybrid welding of cast iron molds, characterized in that, Specifically, the following steps are included: Step S100: Pre-welding preparation, quenching the convex fillets on the cast iron mold; Step S200: Clean impurities in the welding area, including scale, oil, rust, moisture, and other impurities in the welding area and within 50mm on both sides. Step S300: Local preheating of the welding area. Use a DWCK-60 low-voltage intelligent temperature control box or flame preheating to locally preheat the welding area ≥50mm. The preheating temperature is 350℃~400℃ and the preheating time is 2h. Step S400, Surface welding: Using shielded metal arc welding at a welding speed of 80mm / min~90mm / min, weld the second surface welding area (2) and the third surface welding area (3) sequentially from the first surface welding area (1) until the welding reaches 5mm~10mm from the convex rounded corner edge; wherein, the electrode diameter is φ3.2mm, the welding current is 100A~110A, and the welding voltage is 20V; After step S500, when the molded surfaces are welded in sequence, the convex rounded corner welding area is welded using carbon dioxide gas shielded welding at a welding speed of 90mm / min to 100mm / min until the entire rounded corner is covered. The electrode diameter is φ1.2mm, the welding current is 150A to 160A, and the welding voltage is 18V to 19V. Step S600: After welding is completed, asbestos is used to keep the welded area warm and cool it down to below 70°C. The convex fillet welding requires only a single layer of weld, and the weld hardness of the convex fillet welding area is HRC≥55.

2. The method for hybrid welding of cast iron molds according to claim 1, characterized in that, In step S400, the electrode used for shielded metal arc welding is NH100s, the electrode baking temperature is 350℃, and the baking time is 2 hours.

3. The method for mixed welding of cast iron molds according to claim 1 or 2, characterized in that, In step S500, the carbon dioxide gas shielded welding uses CIH-1 welding wire.

4. The method for hybrid welding of cast iron molds according to claim 1, characterized in that, The arc termination angle at each weld joint is 10°~20° to avoid a cross-section at the weld termination point.

5. The method for hybrid welding of cast iron molds according to claim 1, characterized in that, Each weld seam is hammered at its edge using a pneumatic hammer or a rounded hammer. During hammering, the angle between the pneumatic hammer and the weld seam is 70° to 80° to reduce welding stress and improve weld density.

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