Steel alloy, article, and method

Abstract

A steel alloy, an article made from the steel alloy, and a method for welding a welding stud to a substrate material are disclosed.

Description

Technical Field

[0001] This document describes steel alloys and articles made therefrom. Further described is a method for welding a stud to a substrate material. Background Art

[0002] In many applications, it is necessary to join components. One such application is joining two components by welding a fastening element, such as a stud, to a substrate material, such as a steel plate, using a welding gun. A welding current is applied to the stud to liquefy the materials of the stud and the substrate. Then, the stud is immersed in the liquefied material before the liquefied material solidifies. A possible material for such a fastening element is steel that contains carbon to some extent. The amount of electrical energy (hereinafter referred to as "welding energy") used for a single stud during the welding method is typically much higher than 10 kJ, yet in some applications, it can be as low as less than 3 kJ.

[0003] One limitation of steel, especially when used in welding applications, involves a reduction in strength due to embrittlement. In some cases, especially at low welding energy, embrittlement may be caused by the formation of brittle regions of carbon in the steel.

[0004] It may be useful to provide an alternative design that addresses some or all of the above limitations or at least provides an option to the public. Summary of the Invention

[0005] Throughout the specification, any indication of a percentage ("%") should be understood as the fraction (weight percentage) of the corresponding alloying component relative to the weight or mass of the overall steel alloy.

[0006] According to one aspect, the above limitations are addressed by a steel alloy consisting essentially of: 0 - 0.08% carbon, 0 - 1% silicon, 0 - 2% manganese, 0 - 0.045% phosphorus, 0 - 0.03% sulfur, 16% - 20% chromium, 2.0% - 3.0% molybdenum, 8% - 14% nickel, 0 - 0.1% nitrogen, 0 - 0.7% titanium, The balance is iron and impurities, and incidental amounts of residual elements that do not adversely affect the basic and novel properties provided by the alloy.

[0007] Too high a carbon or sulfur content may result in undesired levels of brittle phases, e.g., after liquefaction of the steel, such as during a welding process, especially at low welding energy and / or low welding current, e.g., at an amperage below 350 A. In a preferred embodiment, the steel alloy contains 0 - 0.03% carbon and / or 0 - 0.012% sulfur.

[0008] It has been found that silicon and titanium compensate for detrimental carbon in terms of brittleness. In a preferred embodiment, the steel alloy contains 0.5% - 0.75% silicon and / or 0.2% - 0.7% titanium. In another preferred embodiment, the sum of the silicon content and the titanium content amounts to at least 0.5%. In an even more preferred embodiment, the sum of the silicon content and the titanium content is at least 0.5% more than the carbon content. In other preferred embodiments, the ratio of the titanium content to the carbon content is greater than 6, i.e., the titanium content is more than six times the carbon content, e.g., to ensure compensation for detrimental carbon. In an even more preferred embodiment, the ratio of the titanium content to the carbon content is greater than 8, or greater than 10.

[0009] In other preferred embodiments, the steel alloy contains 16% - 18% chromium and / or 2.0% - 2.5% molybdenum and / or 10% - 14% nickel.

[0010] In a generally preferred embodiment, an article (e.g., a fastening element or a welding stud) is made of the proposed steel alloy. The steel alloy may be present in the bulk material of the article or added as a press-in element or a surface layer (such as a coating) to a semi-finished product to produce the article.

[0011] In another preferred embodiment, the article forms a fastening element, especially a welding stud.

[0012] According to another aspect, a method for welding a welding stud to a base material includes: providing a welding stud made of the proposed steel alloy; applying a welding current between the welding stud and the base material; liquefying a material portion of the welding stud and / or the base material; allowing the liquefied material of the welding stud and / or the base material to solidify; and sinking the welding stud into the liquefied material before the liquefied material of the welding stud and / or the base material solidifies. In a preferred embodiment, the amperage of the welding current is below 350 A.

[0013] Samples produced from the above materials show very good tolerance to carbon-induced cracking, especially the tolerance of the weld formed after a welding operation to carbon-induced cracking. Further, the embedding depth of the welding stud in the base material can be increased relative to welding studs made of common materials. Description of the Drawings

[0014] Further aspects and advantages of the steel alloy, the article, and the welding method will become more apparent from the following description given by way of example only and with reference to the accompanying drawings, in which: Figure 1 A welding device is schematically shown, Figure 2 The welding stud is shown in a longitudinal sectional view, and Figure 3 The welding stud is shown in a longitudinal sectional view. Detailed Description

[0015] Figure 1 A welding device 10 for welding a welding stud 20 to a base material 30 (such as structural steel) is schematically shown. The materials of the welding stud 20 and the base material 30 are electrically conductive. The welding device 10 includes: a welding gun 40 having a trigger switch 41 formed as a push-button switch, a welding unit 50, a first cable 61, a second cable 62 with a connection terminal 63, a power supply cable 64 formed as, for example, a power cable, a communication wire 65, a gas reservoir 70 formed as a gas cylinder, a tubular gas supply line 71, and a gas hose 72. The first cable 61 is used to supply current to the welding stud 20 through the welding unit 50. The second cable 62 is used to electrically connect the base material 30 to the welding unit 50 when the connection terminal 63 is clamped to the base material 30. When the welding stud 20 contacts the base material 30, the circuit is closed so that a welding current in the form of, for example, direct current or alternating current is applied to the welding stud 20 through the welding unit 50. The gas supply line 71 and the gas hose 72 are used to supply an inert gas from the gas reservoir 70 to the contact area between the welding stud 20 and the base material 30 to protect the contact area from oxidation by oxygen in the surrounding area during the welding operation. To control the gas flow to the contact area, the gas reservoir 70, the gas supply line 71, the welding unit 50, the gas hose 72, or the welding gun 40 includes a valve, particularly a controllable valve (not shown).

[0016] The welding unit 50 has an input device 51 with an actuating element 52, and an output device 53 with a visual display element 54 and a wireless transmission unit. The input device 51 is used for the user of the welding device 10 to input the parameters of the welding method to be performed using the welding device 10, such as voltage, current intensity of the welding current, power and duration, position and speed of the stud, etc. The output device 53 is used to output information to the user, such as information about the parameters of the welding method, information about the detected emissions or other variables of the welding method, information about the quality of the welding operation, information about measures for improving the welding operation, information about the detected characteristics of the welded stud, or information derived from the above variables, and / or recommendations or instructions for cleaning and / or maintaining the welding device 10 (especially the welding torch 40). The communication wire 65 is used for communication between the welding torch 40, especially the control device of the welding torch 40 ( Figure 1 not shown) and the welding unit 50, especially the control unit and / or the input device 51 and / or the output device 53. For example, through this communication, the exchange of information about the parameters of the welding operation is completed, so as to achieve or contribute to the synchronization of the welding current and the movement of the welding stud 20.

[0017] The welding torch 40 has a housing 42 with an opening 46, and a handle 43 with a trigger switch 41 extends from the housing. The welding torch 40 also has a stud holder 44, and the welding stud 20 is held on the stud holder during the welding operation. For this purpose, the stud holder includes, for example, two, three, four or more elastic arms (not shown in detail), and the welding stud 20 is inserted and held between these elastic arms by means of a clamping fit. In order to apply welding current to the welding stud 20, the welding torch 40 also has a welding current contact element integrated in the stud holder 44, for example, in the form of one or more of these elastic arms. The welding torch 40 also has a control device 99 for controlling the various components and devices of the welding torch and the welding unit 50. The control device 99 is designed to control one or more parameters of the welding operation. For this purpose, the control device 99 includes a variety of different electronic components, such as one or more microprocessors, one or more temporary or permanent data memories, etc.

[0018] The welding torch 40 also has a stud lifting device formed as a first lifting magnet, which, when enabled, causes a force away from the opening 46 to act backward ( Figure 1 upward in the middle) on the stud holder 44. Via a signal line (not shown), the control device 99 communicates with the stud lifting device to control the stud lifting device, especially to enable and disable it. The welding torch 40 also has a stud settling device formed as a spring element or a second lifting magnet, which, when enabled, applies a force towards the opening 46 forward ( Figure 1Acting (downward in the figure) on the stud holder 44. Via a signal line (not shown), the control device 99 communicates with the stud lowering device in order to control the stud lowering device, in particular to enable and disable it. If the stud lowering device is in the form of a spring element, then this spring element is preferably tensioned when the stud holder is moved backward by the stud lifting device, such that, once the stud lifting device is disabled, the spring element moves the stud holder forward.

[0019] During the welding process using the welding device 10, first the base material 30 and the stud 20 are provided. In a further step, the user inputs information via the input device, such as information about desired parameters for a subsequent welding operation. In a further step, the welding current between the welding stud 20 and the base material 30 is applied to the welding stud 20 by the welding unit 50 via the first cable 61 and the second cable 62. In a further step, the welding stud 20 is lifted from the base material by the stud lifting device while maintaining the welding current flowing between the welding stud 20 and the base material 30, forming an arc between the welding stud 20 and the base material 30. In particular, due to the heat generated by the arc, the material of the welding stud 20 and / or the base material 30 is then partially liquefied. In a further step, the welding stud 20 is lowered into the liquefied material of the welding stud 20 or the base material 30 by means of the stud lowering device. Then the liquefied material of the welding stud 20 or the base material 30 solidifies, such that the welding stud 20 is connected to the base material 30 in an integrally joined manner. The amount of electrical energy used for a single welding stud during the welding method can be as low as less than 3 kJ.

[0020] Figure 2 A welding assembly 200 is shown having an article or welding stud 220 and a stud holder 244. The welding stud 220 has: a shank 240 that defines a longitudinal direction 230 and is provided with an attachment device 250 designed as an external thread; a welding area 260 at the end that is provided for liquefying during the welding process; and a holding device 270 that is designed as a circumferentially extending recess, preferably a groove, and that is arranged along the longitudinal direction 230 between the welding area 260 and the attachment device 250. The stud holder 244 has a holding device 280 that is designed as a circumferentially extending protrusion, and the holding device 270 engages with the holding device in order to hold the welding stud 220 during a welding process, for example when using the welding device 10 ( Figure 1 )

[0021] The stud holder 244 is part of a welding gun (not specifically shown) for welding the welding stud 220 to a base material, for example the design of this welding gun is the same as that of the welding gun 40 ( Figure 1) Similar. The holding device 280 is arranged at the front end of the welding gun. As a result, for example, when the stud settling device moves the stud holder 244 forward, the welding stud 220 moves forward towards the substrate. Behind the holding device 280, the welding gun, especially the stud holder 244, has a socket 290 for the attachment device 250 of the welding stud, which is basically designed as a cavity. With this arrangement, on the one hand, the attachment device 250 is protected from being damaged by the holding device 280, and on the other hand, it is ensured that regardless of the length of its shank 240 and / or the attachment device 250, the holding device 280 holds the welding stud in the desired position. In addition, a single stud holder can be used for welding studs with different attachment devices, especially attachment devices of different sizes.

[0022] Figure 3 shows a second welding assembly 300 with a second welding stud 320 and Figure 2 a stud holder 244. The second welding stud 320 also has: a shank 340 that defines a longitudinal direction 330 and is provided with an attachment device 350 designed as an external thread; a welding area 360 at the end that is provided for liquefying during the welding process; and a second holding device 370 that is designed as a circumferentially extending recess, arranged along the longitudinal direction 330 between the welding area 360 and the attachment device 350 and has the same shape and the same size as the Figure 2 holding device 270 of the welding stud 220 shown.

[0023] The attachment device 350 of the welding stud 320 has a smaller diameter compared to the attachment device 250 of the welding stud 220 and is thus also received in the socket 290 when the welding stud 350 is held by the holding device 280 in engagement with the holding device 370. The welding stud 220 and the second welding stud 320 are thus part of the fastening system according to the present application. Here, the shape and size of the welding area 260 of the welding stud 220 are the same as those of the welding area 360 of the second welding stud 320. This makes it possible to weld welding studs with different attachment devices, especially attachment devices of different sizes, to the substrate using the same welding parameters (such as welding current intensity, voltage, welding current duration, etc.).

[0024] The article is made of a steel alloy consisting essentially of the following: 0 - 0.03% carbon, 0.5% - 0.75% silicon, 0 - 2% manganese, 0 - 0.045% phosphorus, 0 - 0.012% sulfur, 16% - 18% chromium, 2.0% - 2.5% molybdenum, 10% - 14% nickel, 0 - 0.1% nitrogen, 0.2% - 0.7% titanium, The balance is iron and impurities, as well as incidental amounts of residual elements. In particular, the entire welded studs 200, 300 can be composed of the steel alloy presented above. Alternatively, the welded areas 260, 360 can be composed of the steel alloy presented above, while the remainder of the welded studs 200, 300 can include different materials, such as steel containing less silicon and / or titanium. In another embodiment, particles or similar elements composed of the steel alloy can be added to the semi-finished welded studs composed of different materials, particularly in the welding area. In yet another embodiment, a surface layer (such as a coating) composed of the steel alloy can be added to the semi-finished welded studs composed of different materials, particularly in the welding area.

[0025] The above exemplary embodiments of the present invention have been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed, and modifications and variations are possible in light of the above teachings, or may be obtained from practice of the invention. The described functions may be distributed among modules different in number and distribution of functions from those described herein. Additionally, the order of performing functions may be altered in accordance with embodiments. The embodiments were chosen and described to explain the principles of the invention and as practical applications of the invention to enable one of ordinary skill in the art to utilize the invention in various embodiments with various modifications suitable for the particular purposes contemplated. The scope of the invention is intended to be defined by the appended claims and their equivalents.

Claims

1. A steel alloy, which consists essentially of the following: - 0 - 0.08% carbon, - 0 - 1% silicon, - 0 - 2% manganese, - 0 - 0.045% phosphorus, - 0 - 0.03% sulfur, - 16% - 20% chromium, - 2.0% - 3.0% molybdenum, - 8% - 14% nickel, - 0 - 0.1% nitrogen, - 0 - 0.7% titanium, - The balance being iron and impurities, and incidental amounts of residual elements.

2. The steel alloy according to claim 1, wherein the sum of the silicon content and the titanium content reaches at least 0.5%.

3. The steel alloy according to claim 2, wherein the sum of the silicon content and the titanium content is at least 0.5% more than the carbon content.

4. The steel alloy according to any one of the preceding claims, which contains 0 - 0.03% carbon.

5. The steel alloy according to any one of the preceding claims, which contains 0.5% - 0.75% silicon.

6. The steel alloy according to any one of the preceding claims, which contains 0 - 0.012% sulfur.

7. The steel alloy according to any one of the preceding claims, which contains 16% - 18% chromium.

8. The steel alloy according to any one of the preceding claims, which contains 2.0% - 2.5% molybdenum.

9. The steel alloy according to any one of the preceding claims, which contains 10% - 14% nickel.

10. The steel alloy according to any one of the preceding claims, which contains 0.2% - 0.7% titanium.

11. An article made of the steel alloy according to any one of the preceding claims.

12. The article according to claim 11, wherein the main body material of the article consists of the steel alloy.

13. The article according to any one of claims 11 to 12, wherein the surface layer or coating of the article consists of the steel alloy.

14. The article according to any one of claims 11 to 13, wherein the article is a fastening element or a welding stud.

15. A method for welding a welding stud to a base material, the method comprising: a) providing a welding stud according to claim 14, b) applying a welding current between the welding stud and the base material to the welding stud; c) liquefying a material portion of the welding stud and / or the base material; d) allowing the liquefied material of the welding stud and / or the base material to solidify; e) sinking the welding stud into the liquefied material before the liquefied material of the welding stud and / or the base material solidifies.

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