COPPER-TIN CONTINUOUS CASTING ALLOY

Description

[0001] The invention relates to a copper-tin continuously cast alloy which is lead-free and which can be produced and cast well and economically and is easily machinable after casting and has good mechanical strength and load properties, which make it particularly suitable for the production of machine parts or gear parts, such as gears, worm gears, bushings or linear guide elements, or for the production of valve parts for the conduction of fluids.

[0002] With the present invention, which is based on copper-tin continuously cast alloys with higher tin contents, it was discovered that reducing the tin content to the initially specified range and partially substituting tin with zinc poses casting-related problems. A dendritic microstructure forms, which is difficult to feed during the casting process due to the large temperature interval between the solidus and liquidus curves of the system. As a result, cavities, so-called micro-shrinkages, form between the dendritically growing primary grains, which can lead to leaks in the casting and products manufactured from it. Use of the continuous cast alloy for the production of valve components would then be impossible.

[0003] The omission of lead also means that the machinability of the alloy does not meet the requirements.

[0004] EP 3 736 350 A1 relates to and discloses a multi-layer plain bearing element made of a composite material comprising a support metal layer and a further layer, in particular a sliding layer, and optionally an intermediate layer between the support metal layer and the further layer. The further layer is formed from a cast alloy, specifically a lead-free copper-based alloy containing sulfide precipitates. A composition for the lead-free copper-based alloy is claimed, comprising: Sulfur between 0.1 wt.% and 3 wt.%, in particular between 0.3 wt.% and 0.8 wt.%, iron between 0.01 wt.% and 4 wt.%, in particular between 0.2 wt.% and 2 wt.%, in particular between 0.3 wt.% and 1.5 wt.%, phosphorus between 0 wt.% and 2 wt.%, in particular between 0.001 wt.% and 2 wt.%, in particular between 0.01 wt.% and 0.5 wt.%, at least one element from a first group consisting of zinc, tin, aluminum, manganese, nickel, silicon, chromium, indium in total between 0.1 wt.% and 49 wt.%, wherein the proportion of zinc is between 0 wt.% and 45 wt.%, in particular between 0.01 wt.% and 5 wt.%, the proportion of tin is between 0 wt.% and 40 wt.%, in particular between 0.01 wt.% and 10 wt.%, the proportion of aluminum is between 0 wt.% and 15 wt.%, in particular between 0.01 wt.% and 7.5 wt.%, the proportion of manganese is between 0 wt.% and 10 wt.%, in particular between 0.01 wt.% and 5 wt.%, the proportion of nickel is between 0 wt.% and 10 wt.%, in particular between 0.01 wt.% and 2 wt.%, the proportion of silicon is between 0 wt.% and 10 wt.%. in particular between 0.01 wt.% and 3 wt.%, the proportion of chromium is between 0 wt.% and 2 wt.%, in particular between 0.01 wt.% and 1 wt.% and the proportion of indium is between 0 wt.% and 10 wt.%, and with at least one element from a second group consisting of silver, magnesium, indium, cobalt, titanium, zirconium, arsenic, lithium, yttrium, calcium, vanadium, molybdenum, tungsten, antimony, selenium, tellurium, bismuth, niobium, palladium in a proportion of between 0 wt.% and 1.5 wt.%, the total proportion of the elements of the second group being between 0 wt.% and 2 wt.%, and with the remainder being copper and impurities originating from the production of the elements. . Sulfur should preferably be present in a concentration of 0.2-1.5 wt.%, in particular 0.3-0.8 wt.%, and iron should preferably be present in a concentration of 0.2-2 wt.%, in particular 0.3-1.5 wt.%. Intermetallic FeS phases, which form alongside the copper sulfides, can reduce the tendency to seize. More preferably, the copper-based alloy should contain either zinc or tin. By avoiding the combination of both elements, a significant improvement in the casting properties of the alloy can be achieved through the resulting reduction in the solidification interval. There are 183 example compositions, of which 25 contain no indium or only 0.01 wt.% indium. Almost all of the other example compositions contain 3 or 7 wt.% indium and also relatively high proportions of aluminum and manganese; they also usually contain either tin or zinc.

[0005] EP 1 652 946 A1 discloses a copper alloy for producing components for medium-carrying gas or water pipes, which contains no more than 10 wt.% zinc, no more than 13 wt.% tin, no more than 3 wt.% manganese, and at least one element selected from the group consisting of aluminum and silicon in a proportion between 0.01 and 5 wt.%. The maximum nickel content of the alloy is set at 2.0 wt.%, preferably 0.6 wt.%. Phosphorus is present in a proportion of no more than 0.04 wt.%. The upper limit for the lead content is set at 3.0 wt.%. Iron is present in a proportion of no more than 0.5 wt.%, preferably no more than 0.3 wt.%. The sulfur content is no more than 0.04 wt.%. The antimony content is no more than 0.1 wt.%. The upper limit for the arsenic content is set at 0.03 wt.%. The alloy contains the remainder of copper and unavoidable impurities. The copper content is more than 80% by weight.To improve corrosion protection, the alloy may further contain at least one rare earth element in a proportion of up to 3 wt.%. Cerium (Ce) is considered a preferred alloying element.

[0006] JP 2004 300568 A discloses a copper-silver-palladium alloy with 18 - 48.5 wt% silver, with 1 - 8 wt% palladium and with 0.5 - 3 wt% indium and the remainder copper.

[0007] The present invention is based on the object of largely meeting the above-mentioned aspects in a copper-tin continuous casting alloy without adding lead to the starting material.

[0008] This object is achieved by a lead-free copper-tin continuous casting alloy having the features of claim 1.

[0009] If in this case a lead-free alloy is mentioned, this means that lead is not actively added as an alloying element and that an impurity-related residue of lead of at most 0.10 wt.%, in particular of at most 0.09 wt.%, in particular of at most 0.08 wt.%, in particular of at most 0.07, in particular of at most 0.06 and preferably of at most 0.05 wt.% is present.

[0010] It has now been discovered according to the invention that the addition of indium in the stressed range can significantly improve castability. It has been found that indium forms a low-melting phase with tin or copper, similar to a peritectic phase, and that this low-melting phase preferentially accumulates in the aforementioned micro-cavities and is thus able to seal and fill these cavities. This allows the problem of the poor feeding behavior of a zinc-containing copper-tin alloy to be solved in a more satisfactory manner. In contrast to the use of lead for dense feeding of the structure, the addition of indium in the stressed range does not adversely affect the strength properties of the copper-tin-zinc alloy. The elongation at break and the tensile strength are actually improved by the addition of indium in the stressed range.The yield strength is only slightly reduced and, at indium contents between 1.2 and 2.0 wt.%, is still close to 120 MPa, which is sufficient for most technical applications. Overall, the claimed composition of the continuous casting alloy according to the invention results in economical producibility while still maintaining good castability. The addition of indium, with the resulting quasi-peritectic phase(s), not only improves the feeding behavior and thus the castability, but also improves the machinability of the material, as the indium-containing phases act as chip breakers during machining. These phases are comparatively hard, but they have a lower melting point than the basic metallic matrix of the alloy.

[0011] The addition of nickel can improve the alloy's corrosion resistance and reduce the influence of wall thickness on mechanical strength. When nickel is added to the required extent, the resulting lattice can be further strained by tin in addition to solid solution strengthening. Nickel can also form intermetallic phases with other alloying elements, which serve as nuclei for microstructure refinement, such as nickel-iron phases.

[0012] From a casting technology perspective, it is also advantageous if the continuous casting alloy contains a maximum of 0.30 wt.%, in particular a maximum of 0.10 wt.%, in particular 0.03-0.08 wt.% phosphorus, a maximum of 0.20 wt.% iron, and a maximum of 0.30 wt.% antimony. Phosphorus can prove advantageous within the claimed continuous casting alloy because it can deoxidize the melt, while hydrogen can be effectively expelled by the tin. Iron can form advantageous phases with nickel, but on the other hand, it proves problematic from a casting technology perspective at amounts above 0.2 wt.%. Antimony settles at the grain boundaries and thereby somewhat embrittles the material, which is certainly advantageous with regard to the goal of good machinability through breaking chips.

[0013] Manganese can also be used to deoxidize the melt. During solidification, manganese, like nickel, can be incorporated into the metallic lattice. However, this reduces the solubility for the element tin, and solidification temperatures are generally lowered. The disadvantage is the relatively dense oxide skins, which can lead to uncontrolled strength losses. Therefore, the manganese content is limited to 0.5 wt.%.

[0014] In a further embodiment of the present invention, it proves to be advantageous if the copper-tin continuous casting alloy comprises at least 0.2 wt.%, in particular at least 0.3 wt.%, in particular at least 0.4 wt.%, in particular at least 0.5 wt.%, in particular at least 0.7 wt.%, in particular at least 1.0 wt.%, and / or at most 1.8 wt.%, in particular at most 1.7 wt.% of indium.

[0015] Furthermore, it proves to be advantageous if the copper-tin continuous casting alloy comprises at least 3.0 wt.%, in particular at least 4.0 wt.%, in particular at least 4.5, in particular at least 5.0 wt.%, in particular at least 5.5 wt.%, in particular at least 6.0 wt.% and / or at most 7.5 wt.%, in particular at most 7 wt.% tin.

[0016] Furthermore, it proves to be advantageous if the copper-tin continuous casting alloy comprises at least 2.0 wt.%, in particular at least 2.5 wt.%, in particular at least 3.0 wt.%, in particular at least 3.5, in particular at least 4.0 wt.% and / or in particular at most 5.5 wt.%, in particular at most 5.0 wt.% zinc.

[0017] A continuous casting alloy suitable for the production of drinking water fittings or drinking water piping comprises 3.0 to 5.0 wt% tin and 1.5 - 3.0 wt% zinc.

[0018] A continuous casting alloy suitable for the manufacture of other fittings, in particular sanitary fittings and sanitary piping, comprises 5.5 to 8.0 wt% tin and 2.0 - 5.0 wt% zinc, the sum of the weight percentages of tin and zinc being 8.0 - 12.0 wt%.

[0019] It also proves to be advantageous if the sum of the weight percentage of tin and zinc is at least 8.5 wt.%, in particular at least 9.0 wt.%, in particular at least 9.5 wt.%, in particular at least 10.0 wt.%, and / or at most 11.5 wt.%, in particular at most 11.0 wt.%.

[0020] The present invention relates to a continuous casting alloy of the claimed composition in the molten state. Furthermore, the present invention relates to a continuous casting alloy of the claimed composition in the cast state.

[0021] The present invention also relates to a continuous casting blank or a continuous casting intermediate product, in particular in strand form or tube form, produced by casting a continuous casting alloy of the claimed type and composition and having the same composition as this continuous casting alloy.

[0022] Furthermore, the invention relates to machined machine parts or gear parts, in particular gears, worm gears, bushings or linear guide parts, or machined fitting parts for the conduction of fluids, produced by machining a continuous casting blank or continuous casting intermediate product of the type claimed here.

Claims

1. Copper-tin continuous casting alloy which is lead-free, i.e. lead is not actively added as an alloying element and an impurity-related residual amount of lead of at most 0.10 wt.% is present, in particular for the production of machine parts or gear parts, such as in particular gear wheels, worm wheels, bushings or linear guide parts, or for the production of fittings for the conduction of fluids, comprising 3.0 - 8.0 wt.% tin, 1.5 - 6.0 wt.% zinc, 0.1 - 2.0 wt.% indium, wherein the sum of the weight percentage of tin and zinc is 5.0 - 12.0 wt.%, and further optionally comprising the following alloying elements up to 0.20 wt.% iron, up to 2.5 wt.% nickel, up to 0.30 wt.% antimony, up to 0.50 wt.% manganese, up to 0.3 wt.% phosphorus, up to 0.10 wt.% sulfur, and impurity-related elements in each case up to at most 0.10 wt.% and in total up to at most 0.5 wt.%, and the remainder copper.

2. Copper-tin continuous casting alloy according to claim 1, characterized in that it comprises at least 0.2 wt.%, in particular at least 0.3 wt.%, in particular at least 0.4 wt.%, in particular at least 0.5 wt.%, in particular at least 0.7 wt.%, in particular at least 1.0 wt.%, and / or at most 1.8 wt.%, in particular at most 1.7 wt.% indium.

3. Copper-tin continuous casting alloy according to claim 1 or 2, characterized in that it comprises at least 3.5 wt.%, in particular at least 4.0 wt.%, in particular at least 4.5 wt.%, in particular at least 5.0 wt.%, in particular at least 5.5 wt.%, in particular at least 6.0 wt.% and / or at most 7.5 wt.%, in particular at most 7 wt.% tin.

4. Copper-tin continuous casting alloy according to claim 1, 2 or 3, characterized in that it comprises at least 2.0 wt.%, in particular at least 2.5 wt.%, in particular at least 3.0 wt.%, in particular at least 3.5, in particular at least 4.0 wt.% and / or in particular at most 5.5 wt.%, in particular at most 5.0 wt.% zinc.

5. Copper-tin continuous casting alloy according to one or more of the preceding claims, characterized in that it comprises 3.0 to 5.0 wt.% tin and 1.5 - 3.0 wt.% zinc.

6. Copper-tin continuous casting alloy according to one or more of the preceding claims 1-4, characterized in that it comprises 5.5 to 8.0 wt.% tin and 2.0 - 5.0 wt.% zinc and in that the sum of the weight percentage of tin and zinc is 8.0 - 12.0 wt.%.

7. Copper-tin continuous casting alloy according to one or more of the preceding claims, characterized in that the sum of the weight percentage of tin and zinc is at least 8.5 wt.%, in particular at least 9.0 wt.%, in particular at least 9.5 wt.%, in particular at least 10.0 wt.%, and / or at most 11.5 wt.%, in particular at most 11.0 wt.%.

8. Continuous casting blank or continuous casting intermediate product, in particular in strand form or tubular form, produced by casting a continuous casting alloy according to one or more of the preceding claims, in a continuous casting process, wherein the continuous casting blank or the continuous casting intermediate product comprises: 3.0 - 8.0 wt.% tin, 1.5 - 6.0 wt.% zinc, 0.1 - 2.0 wt.% indium, wherein the sum of the weight percentage of tin and zinc is 5.0 - 12.0 wt.%, and further optionally the following alloying elements up to 0.20 wt.% iron, up to 2.5 wt.% nickel, up to 0.30 wt.% antimony, up to 0.50 wt.% manganese, up to 0.3 wt.% phosphorus, up to 0.10 wt.% sulfur, and impurity-related elements in each case up to at most 0.10 wt.% and in total up to at most 0.5 wt.%, and the remainder is copper.

9. Machine parts or gear parts manufactured by machining, in particular gear wheels, worm wheels, bushings or linear guide parts, or fittings manufactured by machining for the conduction of fluids, produced by machining a continuous casting blank or continuous casting intermediate product according to claim 8.