Weld seam for joining cast iron materials

Abstract

Weld for joining two cast iron materials, wherein an iron-based filler material is added to the weld, the filler material having less than 0.5 wt% carbon and the carbon content in the weld is between 1 wt.% and 2 wt.%, characterized by the fact that The weld width is between 0.5 mm and 2 mm, where two different cast iron materials are welded together.

Description

[0001] The invention relates to a weld seam for joining cast iron materials according to the preamble of claim 1.

[0002] When cast iron materials are to be joined by welding in a composite component, this generally leads to a limitation in the choice of materials, which is determined by the carbon content of the iron materials. The limit for materials that can be welded easily and reliably is approximately 0.2 wt% to 0.3 wt% carbon, with the carbon content of cast iron materials always being above this limit. Steels and cast iron materials with a higher carbon content harden under normal welding processes such as electric arc, MIG, or MAG welding, which leads to increased cracking and a resulting loss of weld strength.

[0003] In DE 10 2005 057 317 A1, a method for welding ferrous materials with different carbon contents is described, which is advantageous in itself.

[0004] Furthermore, US patent 2006 / 0237412 A1 discloses a welding composition made from a coated welding electrode for use in welding cast iron. US patent 4,534,793 A also discloses a welding composition for use in submerged arc welding of cast iron. Additionally, DE patent 10 2005 057 317 A1 discloses a method for laser welding of metallic materials.

[0005] The object of the invention is to improve the mechanical properties of a weld seam when welding cast iron material, while simultaneously reducing process costs.

[0006] The solution to the problem consists of a weld seam with the features of claim 1.

[0007] The weld according to claim 1 is located between two cast iron materials, wherein a filler material containing less than 0.5 wt.% carbon is added to the weld. It has been found that a targeted adjustment of the carbon content in the weld to a value between 1 wt.% and 2 wt.% achieves a particularly good compromise between, on the one hand, the lowest possible hardness and, on the other hand, the highest possible ductility. The carbon content in the weld is preferably between 1.25 wt.% and 1.75 wt.%, and more preferably between 1.4 wt.% and 1.6 wt.%, and most preferably at 1.5 wt.%, whereby a technical inaccuracy of 0.2 wt.% in the representation of the weld must be taken into account.

[0008] To achieve these values ​​when welding cast iron materials, it is necessary to use an iron-based filler material with as little carbon as possible; ideally, it is desirable to reduce the carbon content, apart from impurities, to almost 0%.

[0009] Compared to special welding processes (e.g. hybrid processes), the weld described by claim 1 can be produced with low energy expenditure, it is environmentally friendly because nickel-containing filler materials can be dispensed with, and it can be represented by a technically relatively simple process control.

[0010] The weld seam is relatively narrow, namely 0.5 mm and 2 mm, preferably up to 1.1 mm. Such a narrow weld seam compensates for the often increased hardness in a transition zone between the material and the weld seam.

[0011] Furthermore, two different cast iron materials are welded together.

[0012] In a preferred embodiment, the weld seam exhibits at least a partial austenitic or retained austenitic microstructure. Austenitic microstructures are defined as γ-solid solutions in the iron-carbon phase diagram. These solid solutions form, for example, when the material is quenched from a temperature above 1000°C. Austenitic microstructures have a low yield strength but also high toughness. Preferably, at least remnants of an austenitic microstructure (retained austenite) are present in the weld seam, which contributes to its high toughness.

[0013] Further advantageous embodiments result from the remaining dependent claims.

[0014] The invention further relates to an arrangement of two components that can be joined via a weld seam as described above. It is provided that one edge of each component in the joint area between the components, i.e., where the weld seam between the components is to be applied, is chamfered at an angle of 45°. The width of the chamfered area is ideally 0.2 to 0.4 mm. It is also particularly advantageous to insert an additive material in the form of a film into this joint area between the first and second components, wherein this additive material in the form of a film projects 0.4 to 0.6 mm beyond a surface of at least one component and 0.6 to 1 mm from a lower edge of a chamfered area of ​​at least one component. Such an arrangement enables the use of the device for controlling welding parameters in laser beam welding, as disclosed in DE 19716293 A1.The aforementioned patent application shall be deemed fully disclosed herein. The specified values ​​for the protrusion of the foil-shaped filler material are limited by the detectability of the material in the aforementioned control method. The lower limit is determined by the detectability of the filler material, and the upper limit by possible droplet formation due to heat buildup. In particular, this enables focus position control as well as penetration control.

[0015] The following section will examine individual, exemplary embodiments of the invention in more detail. These will demonstrate: Fig. 1 a cross-section through a weld seam, Fig. 2 a cross-section through a weld seam using a film as filler material and Fig. 3 a cross-section through an arrangement of two components with a foil-shaped additive material inserted in the joint area, which can be joined via a weld seam according to the invention. Example 1:

[0016] When welding two identical cast iron materials 4, 4' according to Fig. 1 with a weld seam 2, for example, the following carbon contents in wt.% are present in the materials: Cast iron, GGG 60: 3.2 wt.% carbon (C) Additive material as foil 10 (Fig. 2): 0 wt.% C

[0017] This yields an arithmetic mean carbon content (wt%) in the weld seam, of (3.2%+0%) / 2=1.6%.

[0018] (In this and the following calculations of the carbon content, it is always ideally assumed that the same volume of each material enters the weld.)

[0019] The weld seam 2 is very narrow; according to Fig. 1. The weld seam is approximately 0.5 mm thick in a lower section and approximately 1.1 mm thick in an upper section. It tapers from an upper end 6 to a lower end 8. Such a weld seam can preferably be achieved by a laser welding process. Other possible welding processes include electron beam welding, plasma welding, as well as hybrid welding processes and MAG, MIG, or TIG processes.

[0020] After welding, the weld is rapidly quenched from a temperature above 1000°C, which preserves at least a partial austenitic microstructure within the weld. This retained austenite, with a carbon content of approximately 1.5 wt%, exhibits high ductility for a microstructure with this carbon content, while its hardness is comparatively low. The weld microstructure is inhomogeneous because martensite is also incorporated within the retained austenite. The combination of low hardness and high ductility, along with the very narrow weld seam, enables the weld to withstand dynamic stresses effectively.

[0021] Example 2, welding of different cast iron materials: This example is essentially the same as Example 1. The only difference is that it involves two different cast iron materials with different carbon contents. The resulting carbon concentrations in the weld are as follows: Cast iron, GGG 60: 3.2 wt.% carbon (C) Cast iron 2: 3.0 wt.% C Additive material: 0% carbon.

[0022] This yields an arithmetic mean carbon content (wt%) in the weld seam, of ((((3.2%+3.0%) / 2)+0%) / 2)=1.55%.

[0023] Here too, quenching is carried out to achieve the advantageous austenitic microstructure. The mechanical properties of this weld are analogous to those in Example 1 and are based on the same mechanical properties.

[0024] To achieve the previously mentioned preferred carbon content of 1.5 wt.%, it is advantageous to offset the weld seam into the area of ​​the cast iron material with the lower carbon content. This results in the weld metal receiving less than 50 by volume of higher-carbon cast iron material and more than 50 by volume of lower-carbon cast iron material, thus reducing the carbon content in the weld. Such a technique is already described in the aforementioned document.

[0025] Furthermore, the weld seam according to Example 2 corresponds to the weld seam according to Example 1. Here, too, rapid quenching is achieved with the same mechanical results, leading to at least a partially austenitic microstructure. The effect of this microstructure was already explained in more detail in Example 1. The same applies to the welding processes, which were also already mentioned in Example 1.

[0026] In this example, according to Fig. 2. The use of foil 10 as filler material is described. Here, foil 10, with the lowest possible carbon content specified above, is placed between the cast iron materials 4, 4' to be welded. During welding, the foil melts and fuses with the locally melted areas of the cast iron materials. Due to the minimal carbon content of the foil, the carbon content of the weld is reduced to the desired level of approximately 1.5 wt.%. The amount of filler material, and thus the carbon concentration in the weld, is adjusted by the thickness of the foil and therefore its volume.

[0027] However, it is also advantageous to apply the filler material in another form, for example, by means of a spray coating (plasma spray coating or arc wire spray coating) applied to the workpieces beforehand. Furthermore, for various workpieces, it is advantageous to continuously add the filler material to the welding process using a wire with the desired carbon content. The same can also be achieved by adding an ice powder precisely calibrated to the required carbon content.

[0028] Fig. Figure 3 shows an arrangement of a first component 100 and a second component 102, which can be joined via a weld seam as described above. In the joint area 104 between the first component 100 and the second component 102, a filler material 106 in the form of a foil is inserted. The thickness d1 of the filler material, and thus the gap between the components 100 and 102, is d1 = 0.4 mm. The edge area 108 of the first component 100 and the edge area 110 of the second component 102 are chamfered at an angle α = 45°. The width d4 of the chamfered area of ​​the first component 100 is 0.2 mm, and the width d5 ​​of the chamfered area 110 of the second component 102 is 0.4 mm.

[0029] The foil 106 extends beyond the surface 112 of the second component 102 by a length d2, with this overhang ideally being 0.4 to 0.6 mm. The overhang d3 of the foil 106 beyond the lower edge 114 of the chamfered area 110 of component 102, i.e., the deeper chamfered part, ideally ranges in length from 0.6 to 1 mm.

[0030] Such a workpiece geometry, as already described at the beginning, enables the use of a device for controlling welding parameters according to DE 19716293 A1. This is achieved by using a CCT camera and evaluating the weld pool geometry during welding of the... Fig. In the arrangement shown in Figure 3, such a device makes it possible to monitor and, if necessary, control the weld quality, in particular the weld position, the focus position of a laser beam, and the penetration depth.

[0031] Suitable components for welding include, among others, gearbox parts, shafts such as camshafts or crankshafts, as well as chassis components, engine parts and body parts.

Claims

[1] Weld for joining two cast iron materials, wherein an iron-based filler material is supplied to the weld, wherein the filler material has less than 0.5 wt% carbon and the carbon content in the weld is between 1 wt.% and 2 wt.%, characterized by , that The weld width is between 0.5 mm and 2 mm, where two different cast iron materials are welded together. [2] Weld according to claim 1, characterized by that the weld seam contains an austenitic microstructure. [3] Weld according to claim 1 or 2, characterized by that the carbon content of the weld is between 1.25 wt.% and 1.75 wt.%. [4] Weld according to claim 3, characterized by , that the carbon content of the weld is between 1.4 wt.% and 1.6 wt.%, in particular 1.5 wt.%. [5] Weld according to any one of the preceding claims, characterized by that the additive material contains less than 0.2 wt% carbon. [6] Weld according to any one of the preceding claims, characterized by that the additive material is added in the form of a thermal spray coating, a film, a continuously fed wire or a powder. [7] Arrangement of two metallic components (100, 102) which can be joined by a weld (2) according to one of the preceding claims, wherein in a joint area (104) between the first (100) and the second component (102) an additional material (106) in the form of a film is inserted between the first (100) and the second component (102), wherein the first (100) and the second component (102) each have at least one edge (108, 110) in the joint area (104) which is chamfered at an angle of 45°, wherein the chamfered area extends over a length of 0.2 to 0.4 mm. [8] Arrangement according to claim 7, characterized by, that the filler material (106) in the form of a foil protrudes by 0.4 to 0.6 mm beyond a surface (112) of the first and / or the second component, and protrudes by a distance of 0.6 to 1 mm beyond a lower edge (114) of a chamfered area of ​​at least one of the components.

Images