DISSIMILAR FRICTION WELDING PRODUCT AND PROCESS WITH LOCALIZED HEATING

Abstract

This technology describes a dissimilar friction welding process with localized heating. The process involves obtaining a high-strength weld, comprising a head formed by a highly deformed area in its upper region. The high-strength weld is based on the friction stir welding (FSW) method using localized heating, known as hybrid friction stir welding (HFSW). In addition to producing a high-strength weld, the process reduces wear on the welding tool and reduces welding forces. The technology is applicable to welding between metals or metal alloys with high melting points, such as steel, and lightweight metallic materials (with low melting points), such as aluminum and magnesium alloys. It can be applied in the aerospace and transportation industries.

Description

"PRODUCT AND PROCESS OF DISSIMILAR FRICTION WELDING WITH LOCALIZED HEATING"

[01] The present technology refers to a process for obtaining a high mechanical strength weld, comprising a head formed by a highly deformed area in its upper region (weld head). The process for obtaining the high strength weld is based on the friction stir welding (FSW) method using localized heating, called Hybrid Friction Stir Welding (HFSW). In addition to allowing the production of a high mechanical strength weld, the process provides a reduction in welding tool wear and a reduction in welding forces. The technology applies to welding between metals or metal alloys with high melting points, such as steel, and light metallic materials (with low melting points), such as aluminum and magnesium alloys. It can be applied in the aerospace and transportation industries.

[02] Dissimilar friction stud welding with localized heating (HFSW) has already been described in the literature, as discussed below.

[03] The article entitled Effect of Preheating on Mechanical Properties of Hybrid Friction Stir Welded Dissimilar Joint (DOI:https: / / doi.org / 10.1063 / 1.4975160) from 12 / 12 / 2014, presents dissimilar metal / alloy welding using the HFSW process, in which localized plasma heating is applied to the relatively harder material with a higher melting point (copper) compared to the other metal in the welded joint (aluminum). The pin is introduced perpendicularly onto the welding surface, offset by approximately 1 millimeter towards the aluminum side (offset = 1 mm). The feed rate used was 98 millimeters per minute (mm / min), and the pin rotation speed was 815 revolutions. Petition 870190140716, dated 12 / 27 / 2019, p. 8 / 18 2 / 7 per minute (rpm), and the temperatures reached in the process were approximately 200 degrees Celsius (200°C). In this article, although the weld produced exhibits greater mechanical strength, the geometries for the mixed zone do not indicate the formation of a high mechanical strength element with the characteristics of a "weld head," as described in the present technology.

[04] The article entitled Gas tungsten arc welding assisted hybrid friction stir welding of dissimilar materials AI6061-T6 aluminum alloy and STS304 stainless steel (DOI:10.1016 / j.matdes.2011.12.018), dated 12 / 17 / 2011, presents dissimilar welding between an aluminum alloy and steel using the HFSW process, in which localized plasma heating is applied to the relatively harder material with a higher melting point (steel) compared to the other metal in the welded joint (aluminum). The pin is introduced perpendicularly onto the welding surface, offset approximately 8 millimeters towards the steel side (offset = 8 mm). The feed rate used was 48 millimeters per minute (mm / min), the pin rotation was a maximum of 600 revolutions per minute (rpm), and the temperatures reached in the process were up to 500 degrees Celsius (500°C).In this article, although the weld produced exhibits greater mechanical strength, the geometries for the mixed zone do not indicate the formation of a high mechanical strength element with the characteristics of a "weld head," as described in the present technology.

[05] Patent KR101007592B1, entitled “Friction stir welding with tungsten inert gas welding type hybrid welding apparatus”, with priority of 09 / 11 / 2009, presents a welding apparatus and a FSW welding method. The method can be applied to welding aluminum and steel alloys and the apparatus contains means for preheating the steel on the advance side. The proposed offset is 1 mm displaced to the side Petition 870190140716, dated 12 / 27 / 2019, page 9 / 18 3 / 7 of the steel. The geometry for the mixed zone does not present a high mechanical strength element with the characteristics of a "weld head", as described in the present technology.

[06] Analysis of the state of the art closest to the technology presented here indicates that there is a set of technical elements that are unique to the process and product now proposed, namely: 1) formation of a reinforcing element in the weld called “weld head”; 2) in the proposed HFSW welding process, the pin is inserted directly into the welding interface (offset = 0); and 3) an inclination of the tool in relation to the plane of the welding surface is caused, which is determinant for obtaining the product defined here. BRIEF DESCRIPTION OF THE FIGURES

[07] Figure 1 shows macrographs of the welded joints with zero offset: (A) without preheating; (B) with preheating at 250 °C; (C) with preheating at 350 °C; (D) with preheating at 450 °C. The macrographs were made from a cross-section of the welded joints. On the right side of the figure, representing the advance side (LA) of the welding process, is the SAE 1020 steel; on the left side of the figure is the return side of the welding process (LR), which is the side of the 5052 H34 aluminum alloy. In the center are the welded joints containing the reinforcing element called the “weld head” (1), delimited by the circle. DETAILED DESCRIPTION OF THE TECHNOLOGY

[08] The present technology refers to a process for obtaining a high mechanical strength weld, comprising a head formed by a highly deformed area in its upper region. The process for obtaining the high strength weld is based on the friction stir welding (FSW) method using localized heating, called Hybrid. Petition 870190140716, dated 12 / 27 / 2019, page 10 / 18 4 / 7 Friction Stir Welding (HFSW). This process, in addition to producing high-strength welds, reduces wear on the welding tool and reduces welding stress.

[09] The weld of the present technology contains an element (1) called “weld head”, formed by a highly deformed area in its upper region.

[010] The proposed HFSW welding process is performed under the following conditions: 1) the pin is inserted directly into the welding interface (offset = 0); and 2) the tool is tilted relative to the welding surface plane, the tilt being between 1 and 5 degrees.

[011] The size of the “welding head” (1) is directly proportional to the heat input on the advance side (LA) which, together with the material flow produced by the rotation of the tool, allows for greater mixing of the materials and enhances the mechanical strength of the welded joint.

[012] In the technology, as demonstrated in figure 1, the contact area between the materials becomes larger due to the angular transfer of the plasticized material, from the material with the higher melting point to the material with the lower melting point, as a function of preheating on the advancing side (LA).

[013] Dissimilar friction welding process with localized heating, which includes the following steps: a) Preheat the welding advance side of the metal or metal alloy with the higher melting point relative to the side of the metal or metal alloy with the lower melting point; b) to cause an inclination in the rotating tool relative to the welding plane; c) Insert the tool directly into the welding interface. Petition 870190140716, dated 12 / 27 / 2019, p. 11 / 18 5 / 7

[014] In stage a, the heating methods can be plasma, inductive heating, laser, electric heating, flame heating, among others.

[015] In step b, the value of the rotary tool tilt angle relative to the welding plane is in the range of -1 to 5 degrees.

[016] In step b, the rotary tool speed ranges from 100 to 700 rpm for welding aluminum and steel, and may even be higher (1250 rpm) for materials with a lower melting point.

[017] In step c, the rotary tool offset value is between -1 and 10 mm, preferably 0 mm.

[018] In step b, the metal or metal alloy with the higher melting point may be steel and the metal or metal alloy with the lower melting point may be aluminum or an aluminum alloy, which is not limiting.

[019] The dissimilar friction welding product with localized heating is a weld. This product is defined by the process described above and has as constituent elements a metal or a metal alloy on the advance side (LA) of the welding process, a metal or a metal alloy on the return side of the welding process (LR) which includes a welded joint located between the LA and LR sides where the welded joint includes a reinforcing element called a “weld head” (1).

[020] The metal or metal alloy on the back side of the welding process (LR) is aluminum or an aluminum alloy or another material with a low melting point, such as copper, and the metal or metal alloy on the forward side (LA) of the welding process is steel, or another material with a higher melting point.

[021] The present invention can be better understood by means of the following example, without limitation: Petition 870190140716, dated 12 / 27 / 2019, page 12 / 18 6 / 7

[022] Example 1 - Obtaining a welded joint from an aluminum alloy 5052 H34 and SAE 1020 steel In this research, butt welds were made of SAE 1020 carbon steel and 5052 H34 aluminum alloy, 3 mm thick, using a specially developed welding head adapted to a COMAU NJ5000 anthropomorphic robot with 6 degrees of freedom and a 500 kg capacity. Tools with tapered pins were used for welding the samples, made of AISI H13 steel, with a shoulder diameter of 18 mm and a larger pin diameter of 6 mm. The tool's rotational speed was maintained at 500 rpm, with a tool inclination angle of 2°. Sample preheating was performed by adapting a plasma cutting machine, where the temperature and current were varied at: 0 °C (no preheating), 250 °C (40 A), 350 °C (50 A), and 450 °C (60 A). The tool offset was varied between zero and -2.5 mm.The mechanical strength of the samples was identified through tensile tests, and microstructural characterization was performed using optical and scanning electron microscopy and X-ray diffraction (XRD). An increase in the mechanical strength of the joints was observed with increasing preheating temperature. When an offset of zero was used and the preheating temperature was 450 °C, there was an increase of approximately 111% in mechanical strength compared to the process without preheating. During metallographic analyses, the formation of a highly deformed region in the upper part of the samples subjected to preheating with an offset of zero, defined in this work as the "head," was identified and characterized. This region acts as a reinforcement of the weld and will be larger the greater the heat input on the advancing side, favoring the mechanical strength of the joint. The increase in preheating temperature... Petition 870190140716, dated 12 / 27 / 2019, page 13 / 18 7 / 7 preheating was favorable for reducing welding forces and tool wear. The tools used for welding the samples with preheating at 250 and 350 °C experienced a reduction in pin volume of approximately 90.47% and 75.39%, respectively. For the tool used in the test with preheating at 450 °C, a reduction of only 3.44% in pin volume was observed.

Claims

1) DISSIMILAR FRICTION WELDING PROCESS WITH LOCALIZED HEATING, which includes a step to preheat the welding advance side of the metal or metal alloy with a higher melting temperature relative to the metal or metal alloy with a lower melting temperature, characterized by comprising the following steps: a) causing an inclination in the rotating tool relative to the welding plane, with an angle of inclination between 1 and 5 degrees; b) introducing the tool directly into the welding interface, with the offset value of the rotating tool being 0 mm; c) obtaining a welded joint that includes, in its mixed zone, a reinforcing element that includes a head formed by a highly deformed area in its upper region called the “weld head” (1) with a length between 0 and 30 mm. 2) A DISSIMILAR FRICTION WELDING PROCESS WITH LOCALIZED HEATING, according to claim 1, characterized by the heating means being plasma, inductive heating, LASER, electric heating, flame or variations thereof. 3) DISSIMILAR FRICTION WELDING PROCESS WITH LOCALIZED HEATING, according to claim 1, characterized in that, in step a, the rotation speed of the rotating tool is in the range of 100 to 1250 rpm. 4) DISSIMILAR FRICTION WELDING PROCESS WITH LOCALIZED HEATING, according to claim 1, characterized in that, in step a, the metal or metal alloy with the higher melting point is steel or another material with a higher melting point and the metal or metal alloy with the lower melting point is aluminum or an aluminum alloy, or another material with a lower melting point, such as copper. 5) DISSIMILAR FRICTION WELDING PRODUCT WITH LOCALIZED HEATING, formed by a metal or a metal alloy with a higher melting temperature on the advance side (LA) of the welding process, and a metal or a metal alloy with a lower melting temperature on the retreat side of the welding process (LR), obtained by the process defined in claim 1, characterized by comprising the welded joint generated in step c located between the advance (LA) and retreat (LR) sides, wherein said welded joint includes, in its mixed zone, the reinforcing element which includes the head formed by a highly deformed area in its upper region called “weld head” (1) with a length ranging from 0 to 30 mm. 6) DISSIMILAR FRICTION WELDING PRODUCT WITH LOCALIZED HEATING, according to claim 5, characterized in that the metal or metal alloy on the back side of the welding process (LR) is aluminum or an aluminum alloy or another material with a low melting point, such as copper, and the metal or metal alloy on the forward side (LA) of the welding process is steel, or another material with a higher melting point.

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