METHOD FOR PRODUCING METAL COMPONENTS AND METAL COMPONENT PRODUCED IN THIS WAY

Abstract

The invention relates to a method for producing metal components, consisting at least partially of a copper alloy, comprising the following alloy components in wt. %: 0 wt. %<Sn≤8 wt. %; 0 wt. %<Zn≤6 wt. %; 0.1 wt. %≤S≤0.7 wt. %; optionally no more than 0.2 wt. % phosphorus; optionally no more than 0.1 wt. % antimony; and optionally iron, zirconium and/or boron alone or in a combination of two or more of said elements of no more than 0.3 wt. %; and unavoidable impurities, and the rest being copper. The method comprises the following stages: (a) melting the copper alloy: (b) producing press blanks from the copper alloy; and (c) pressing the press blanks at a suitable pressing temperature to form the metal components. The invention also relates to a metal component which has been produced according to a method of this type.

Claims

1. A method for producing metal components which consist at least in part of a copper alloy that comprises the following alloy components in wt. %:
0 wt. %<Sn<8 wt. %;
0 wt. %<Zn<6 wt. %;
0.1 wt. %<S<0.7 wt. %; optionally no more than 0.2 wt. % phosphorus; optionally no more than 0.1 wt. % antimony; and optionally iron, zirconium and/or boron alone or in a combination of two or more of said elements no more than 0.3 wt. %; and unavoidable impurities, and copper for the remainder; wherein the method comprises the following steps: (a) melting the copper alloy; (b) producing press blanks from the copper alloy; and (c) pressing the press blanks at a suitable pressing temperature to form the metal components.

2. The method according to claim 1, characterized in that the proportion of sulfur in the alloy is 0.20 wt. %<S<0.65 wt. %, in particular 0.23 wt. %<S<0.45 wt. %, and preferably 0.25 wt. %<S<0.35 wt. %.

3. The method according to claim 1, characterized in that the proportion of zinc in the alloy is 1.3 wt. %<Zn<3.5 wt. %, preferably 1.5 wt. %<Zn<3.3 wt. %, and particularly preferably 2.0 wt. %<Zn<3.0 wt. %.

4. The method according to claim 1, characterized in that the proportion of phosphorus in the alloy is 0.015 wt. %<P<0.1 wt. %, in particular 0.02 wt. %<P<0.08 wt. %, and preferably 0.04 wt. %<P<0.06 wt. %.

5. The method according to claim 1, characterized in that the content of the proportion of tin in the alloy is 3.0 wt. %<Sn<4.8 wt. %, preferably 3.0 wt. % to 4.5 wt. %, and particularly preferably 3.5 wt. % to 4.0 wt. %.

6. The method according to claim 1, characterized in that copper is contained in the lead-free copper alloy in a quantity of greater than 90 wt. %.

7. The method according to claim 1, characterized in that the pressing temperature in step (c) is in a range of from 750° C. to 900° C., preferably in a range of from 800° C. to 880° C., and particularly preferably in a range of from 815° C. to 850° C.

8. The method according to claim 1, characterized in that the press blanks are heated to the pressing temperature before step (c) and are kept at the pressing temperature over a period of time of from 0.1 seconds to 60 minutes, preferably of from 2 seconds to 10 minutes.

9. The method according to claim 1, characterized in that the copper alloy in the component has a structure having an average grain size of less than 100 μm in a region close to the surface after the pressing process.

10. A metal component, produced according to a method according to claim 1.

11. The metal component according to claim 10, characterized in that the copper alloy in the component has a structure having an average grain size of less than 100 μm in a region close to the surface after the pressing process.

12. The metal component according to claim 10, characterized in that the component has a wall thickness at least in portions in the range of from 0.5 mm to 6.0 mm, preferably in the range of from 1.0 mm to 4.0 mm.

13. The metal component according to claim 9, characterized in that the metal component is a component for media-carrying gas or water pipes, in particular a fitting or valve for drinking water pipes.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG. 1 shows a cross-sectional image of the structure of a formed test body made of alloy 1;

[0034] FIG. 2 shows a cross-sectional image of the structure of another formed test body made of alloy 1;

[0035] FIG. 3 is a photograph of an embodiment of a metal component according to the invention formed as a wall bracket, made of alloy 2;

[0036] FIG. 4 is a photograph of an overview of the cross section of the structure of the metal component according to the invention shown in FIG. 3, made of alloy 2;

[0037] FIG. 5 shows an enlarged detail of the overview of the metal component according to the invention shown in FIG. 4, made of alloy 2;

[0038] FIG. 6 shows another enlarged detail of the overview of the metal component according to the invention shown in FIG. 4, made of alloy 2;

[0039] FIG. 7 shows another enlarged detail of the overview of the metal component according to the invention shown in FIG. 4, made of alloy 2;

[0040] FIG. 8 shows another enlarged detail of the overview of the metal component according to the invention shown in FIG. 4, made of alloy 2;

[0041] FIG. 9 is a photograph of a component that has been cast and therefore is not according to the invention, made of alloy 22 according to table 5, showing an example of a possible shrink hole and the deeper attack point in the artificial-ageing test (based on Turner, with a chloride content of 250 mg/l and a carbonate hardness of 5.5° dH);

[0042] FIG. 10 is a photograph of a metal component produced according to the invention, made of alloy 22 according to table 5, showing an example of a homogeneous surface having a protective-layer structure in the artificial-ageing test (based on Turner, with a chloride content of 250 mg/l and a carbonate hardness of 5.5° dH).

LABORATORY TEST OF THE FORMING BEHAVIOR

[0043] In order to simulate the forming behavior, closed-die-forging tests were carried out on a laboratory scale. A pipe having the dimensions 23 mm×8 mm was used as the starting material. The semi-finished product was produced from a copper alloy in a continuous casting process, with the proportions of the components in the copper alloy being stated in wt. % in table 1 below.

TABLE-US-00001 TABLE 1 Alloy composition Alloy Cu Zn Pb Sn P S Fe Ni Si Sb Al 1 94.2 1.4 0.02 3.87 0.04 0.42 0.01 0.01 0.01 0.01 0.01

[0044] The half-moon-shaped test bodies were produced by slices having a thickness of approximately 5 mm being cut from the pipe and the slices being cut through the center. The test bodies thus obtained were placed into the die with the round side at the top. The die is a cube-shaped tool made of solid steel. It has a cross-shaped cut-out on the upper face, and the test body to be tested was placed into this cut-out.

[0045] The test body received in the die was placed into a furnace for the heating time stated in table 2 and was heated therein to the forming temperature also stated in table 2. For the forming, the test body received in the die was removed from the furnace, placed on an anvil, and was formed by being struck with a sledgehammer having a mass of 5 kg. The number of hammer strikes is stated in table 2. Owing to the half-moon-shaped geometry and the cut-out in the internal diameter of the pipe, forming took place in every case. After the forming, the sample was cooled with water in order to conserve and evaluate the resulting state of the structure. The formed samples were then metallographically prepared and evaluated in the region of the forming. The grain sizes were determined in accordance with DIN EN ISO 2624 using the linear intercept method.

[0046] The test conditions are summarized in table 2 below:

TABLE-US-00002 TABLE 2 Test conditions Forming Heating Number Sample temperature time of strikes number [° C.] [min] (deformation) 1 800 90 2 2 800 30 1 3 830 75 1 4 830 75 1 5 860 65 1 6 860 65 — 7 800 60 — 8 800 60 — 9 830 60 — 10 830 60 — 11 860 60 — 12 860 60 — 13 600 60 — 14 600 60 — 15 600 60 1 16 600 60 1 17 700 60 1 18 700 60 1 19 700 60 — 20 700 60 — 21 950 60 1 22 950 60 1 23 950 60 1 24 950 60 —

[0047] In the tests, it was possible to establish that very positive forming properties became apparent in the range between 800 and 860° C. and that the described fine-grain formation took place. If the temperatures were in a lower range, hardly any further forming would be obtained. If they were in a higher range, fused points and reticulated sulfide agglomerates would be visible. FIG. 1 shows a cross-sectional image of the structure of a test body that was formed at 830° C. in the laboratory test (sample 3). The formed structure has a reduced average grain size of approximately 45 μm. The grain size of the test body before the forming corresponds to that of a cast component, approximately 540 μm.

[0048] FIG. 2 (sample 21) shows a cross-sectional image of the structure of another formed test body that was formed by a hammer strike at approximately 950° C. As FIG. 2 shows, the structure of the test body has fused regions in the structure, which can be attributed to the high forming temperature of approximately 950° C. The average grain size is approximately 140 μm here. The present component exhibits hot cracks and sulfide particles that are unfavorably distributed in the structure. This is a state that cannot be used in the actual component.

Investigation of a Pressed Component with Regard to the Grain-Size Distribution

[0049] In order to simulate the producibility of a pressed component in an actual manufacturing process, some typical components of a drinking water installation were manufactured. Inter alia, a wall bracket was produced, which is shown in the photograph according to FIG. 3.

[0050] The copper alloy used for pressing the wall bracket had the proportions of the components stated in wt. % in table 3 and table 4 below.

TABLE-US-00003 TABLE 3 Alloy composition Alloy Cu Zn Pb Sn P S Fe Ni Si Sb Al 2 94.9 1.6 0.05 3.2 0.01 0.19 0.01 0.02 0.01 0.00 0.01

TABLE-US-00004 TABLE 4 Other alloy compositions Alloy Cu Zn Pb Sn P S Fe Ni Remainde 3 95.1 1.5 0.01 3.1 0.00 0.26 0.01 0.01 0.03 4 95.1 1.6 0.01 3.0 0.04 0.25 0.02 0.01 0.04 5 95.2 1.6 0.01 2.9 0.03 0.24 0.02 0.01 0.03 6 95.1 1.6 0.01 3.0 0.02 0.25 0.01 0.01 0.04 7 93.6 1.6 0.02 4.5 0.01 0.24 0.02 0.01 0.04 8 93.8 1.6 0.01 4.0 0.03 0.43 0.01 0.01 0.04 9 95.4 1.3 0.01 3.0 0.01 0.16 0.01 0.01 0.03 10 95.5 1.3 0.01 3.0 0.01 0.14 0.01 0.01 0.03 11 94.5 1.3 0.01 3.9 0.02 0.15 0.01 0.00 0.03 12 94.7 1.2 0.01 3.9 0.01 0.15 0.01 0.00 0.03 13 94.3 1.5 0.01 3.9 0.03 0.15 0.01 0.00 0.04 14 93.9 1.5 0.02 4.1 0.04 0.46 0.01 0.00 0.03 15 93.9 1.5 0.02 4.0 0.02 0.46 0.01 0.00 0.03 16 94.0 1.5 0.02 4.0 0.02 0.46 0.01 0.00 0.02 17 92.4 3.1 0.02 4.0 0.04 0.43 0.02 0.00 0.03 18 92.4 3.0 0.02 4.0 0.04 0.43 0.02 0.00 0.03 19 94.9 1.6 0.01 3.0 0.05 0.44 0.01 0.00 0.02 20 95.3 1.3 0.01 2.9 0.02 0.46 0.01 0.00 0.03 21 95.4 1.2 0.01 2.9 0.01 0.45 0.01 0.00 0.02

[0051] For the production of the wall bracket, continuously cast bars were produced from the above-mentioned material and were cut to length to form press blanks. The press blanks were then heated to a pressing temperature of approximately 830° C. in a preheating furnace. From the preheating furnace, the heated blanks were then slid into a preheated die in which the components were produced by closing the die.

[0052] The pressed parts thus obtained were then cooled. In a final step, the components underwent final processing and were provided with a through-hole and a thread.

[0053] FIG. 4 shows an overview of the cross section of the structure through the pressed wall bracket shown in FIG. 3, produced from alloy 2. The different positions in this figure show critical regions of the formed part. In FIG. 5 (position 1), the threaded region having a particularly fine-grained structure can be seen. The lower part of the image shows the inside coming into contact with the medium, which, when the component according to the invention is used as intended, comes into contact with the medium, in particular with water. The increased strength of the pressure-tight structure in the threaded region comes into effect here. As a result, less deformation occurs in the highly loaded thread region and the component has better sealing. FIG. 6 (position 2) shows the inner region behind the threaded ridge from FIG. 4. The grain size increases at this point, such that greater toughness is provided. FIG. 7 (position 3) also shows this type of structure formation in another region. This is positioned at the base of the thread, at the transition to the tapered portion of the component. The average grain size is approximately 25 μm here. Particularly in order to prevent erosive wear, the surface hardness, which is increased due to the low average grain size, is advantageous in this region. FIG. 8 (position 4) illustrates the region in which the component according to the invention has been drilled out for the transition to the outlet. Essentially, the press blank is still in the original state of the alloy here, i.e. before the pressing process, which can absorb any mechanical forces that occur here in the form of offsets, where necessary. These may constitute a particularly highly loaded region during on-site assembly, primarily when aligning the wall bracket for a valve, with the tough core thereof being highly advantageous.

[0054] This demonstrates that the material hardness in the deformed regions can be significantly increased as a rule. In the present example, in the collar region (see position 1 in FIG. 3) the hardness was able to be significantly increased to a hardness of 78 HBW 2.5/62.5 in accordance with DIN EN ISO 6506-1 compared with a structurally identical wall bracket made in a sand-casting process.

[0055] For the other lead-free copper alloys from table 4, components pressed according to the invention having likewise improved properties, such as the material hardness in the deformed regions, are obtained.

Determining the Corrosive Behavior of a Copper Alloy in Contact with an Aqueous Medium of Components Produced in a Closed-Die-Forging Process

[0056] In order to evaluate the corrosion resistance, components produced using closed die forging were subjected to an artificial-ageing test, as described in the laid-open publication DE 10 2017 100896 A1.

[0057] For these artificial-ageing tests, a lead-free copper alloy was used, inter alia, with the proportions of the individual alloy components being stated in wt. % in table 5 below.

TABLE-US-00005 TABLE 5 Alloy composition Alloy Cu Zn Pb Sn P S Fe Ni Si Sb Al 22 94.78 1.66 0.00 3.27 0.01 0.20 0.01 0.02 0.00 0.01 0.00

[0058] In order to produce test bodies, a 16 Rp ½ wall bracket for on-site use was manufactured from the alloy. The mechanical processing of the components took place under near-series conditions. To do this, the surfaces were manufactured to have comparable roughness depths, for example. In order to obtain the test bodies, the components were then cut in half. The surface of the test bodies was cleaned with acetone. In order to generate a zero level for the measurement, the components were then coated on the underside and were cleaned once more in the uncoated test region. The test bodies were then inserted into a test container so as to hang freely. The test containers were then placed into a heating cabinet at 90° C. for five months, with the test medium being changed at intervals of seven days.

[0059] Twenty-one different aqueous test media or test waters having different pHs and acid capacities were used as test media. Furthermore, different contents of chloride ions and/or sulfate ions were set by the addition of sodium chloride and/or sodium sulfate. The contents can be found in table 6.

TABLE-US-00006 TABLE 6 Carbonate Water hardness Chloride Sulfate number pH in °dH in mg/l in mg/l 1 9 0.5 10 — 2 9 0.5 100 — 3 9 0.5 250 — 4 9 0.5 1000 — 5 8 1.5 15 — 6 8 1.5 60 — 7 8 1.5 140 — 8 8 3.0 30 — 9 8 3.0 100 — 10 8 5.5 80 — 11 8 5.5 120 — 12 8 5.5 250 — 13 7 9.0 100 — 14 7 9.0 160 — 15 7 14.0 140 — 16 7 18.0 40 — 17 7 18.0 100 — 18 7 18.0 250 — 19 9 0.5 250 250 20 8 5.5 250 250 21 7 18.0 250 250

[0060] After the five-month test period, the test containers were removed from the heating cabinet and cooled to room temperature, the test bodies were removed from the respective test containers, were dried and cut open, and the cut surface was inspected with a light microscope after corresponding processing.

[0061] By comparison with a component cast from alloy 22, a component hot-pressed from alloy 22 exhibits yet further improved attack resistance. This is primarily justified by the denser structure. Because there are no shrink holes and no porosity, the medium acts on the hot-pressed component from the surface in a planar manner and very quickly forms a protective, adhering, closed cover layer. As in the cast component, this layer is virtually free of faults or defects and therefore imparts its full protection by preventing any attack at the bottom of any porosity.

[0062] FIG. 9 shows a component conventionally cast from alloy 22 that has undergone attacks that continue into the depth along pores, which component was tested at a carbonate hardness of 5.5° dH and a chloride content of 250 mg/l in the artificial-ageing test. By comparison therewith, FIG. 10 shows a component made of alloy 22 hot-pressed according to the invention, which component was tested with an identical material composition under the same test conditions during the artificial-ageing test. By contrast with the component from FIG. 9, there are no pores at all in the hot-pressed component. The medium therefore attacks the surface homogeneously and the attacks are therefore considerably less pronounced. The corrosive behavior is positively influenced by the hot pressing, as shown in FIG. 10.

[0063] In the above, the present invention has been described with reference to examples and comparative examples; however, it is clear to a person skilled in the art that the invention is not restricted to these examples, but instead the scope of the present invention results from the accompanying claims.