COPPER-TIN CONTINUOUS CASTING ALLOY

Description

[0001] The invention relates to a copper-tin continuous casting alloy, which is lead-free and can be produced and cast well and economically, and which is easily machinable after casting and has good mechanical strength and load-bearing properties, making 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 fitting parts for conveying fluids.

[0002] The present invention reveals that a dendritic structure forms which is difficult to feed during the casting process due to the large temperature range between the solidus and liquidus curves of the system. As a result, cavities, known as micro-shrinkage cavities, form between the dendritically growing primary grains. These cavities can lead to leaks in the casting and in products manufactured from it. Consequently, the continuous casting alloy could not be used for the production of valve components.

[0003] Furthermore, the omission of lead 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 sliding 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.%.

[0005] 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 a total of 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.%, and 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.%, wherein the total proportion of the elements of the second group is between 0 wt.% and 2 wt.%, and with the remainder being copper and impurities originating from the manufacture of the elements.

[0006] Preferably, sulfur should be present in a concentration of 0.2–1.5 wt.%, particularly 0.3–0.8 wt.%, and preferably iron in a concentration of 0.2–2 wt.%, particularly 0.3–1.5 wt.%. Intermetallic FeS phases, which form alongside the copper sulfides, can reduce the tendency to corrode. The copper-based alloy should preferably contain either zinc or tin. By avoiding the combination of these two elements, a significant improvement in the casting properties of the alloy can be achieved through the resulting reduction in the solidification range. There are 183 example compositions, 25 of which contain no indium or only 0.01 wt.% indium. Almost all of the remaining example compositions contain 3 or 7 wt.% indium and also relatively high proportions of aluminum and manganese; they also mostly contain either 10 wt.% tin or 5 wt.% zinc.

[0007] CN 101 806 324 A discloses a lead-free copper-tin alloy for roll cladding as a bearing metal layer on a substrate layer containing 5–12 wt.% tin, 1–2 wt.% nickel, 0.05–0.20 wt.% indium, and the remainder copper and unavoidable impurities. An embodiment of the alloy comprises 12 wt.% tin, 0.18 wt.% indium, 1.2 wt.% nickel, and the remainder copper and unavoidable impurities.

[0008] US 4,130,421 A discloses a copper-nickel-tin alloy suitable for machining with low contents of tellurium, selenium, lead, or manganese sulfide (MnS). One embodiment contains 0.5–1.5 wt.% MnS.

[0009] The present invention is based on the objective of largely meeting the aforementioned aspects in a copper-tin continuous casting alloy without adding lead to the starting material.

[0010] This problem is solved by a lead-free copper-tin continuous casting alloy having the features of claim 1.

[0011] When a lead-free alloy is mentioned in this context, this means that lead is not actively added as an alloying element and that a residual amount of lead due to impurities of at most 0.10 wt.%, in particular at most 0.09 wt.%, in particular at most 0.08 wt.%, in particular at most 0.07 wt.%, in particular at most 0.06 wt.% and preferably at most 0.05 wt.% may be present.

[0012] It has now been found according to the invention that the addition of indium in the claimed area 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 micropores and is thus able to seal and fill these cavities. This allows the problem of the sometimes poor feeding properties of the copper-tin alloy to be solved more satisfactorily. Overall, the claimed composition of the continuous casting alloy according to the invention results in economical manufacturability and yet 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 enhances the machinability of the material. This is because the indium-containing phases act as chip breakers during machining. These phases are comparatively hard, yet they have a lower melting point than the metallic matrix of the alloy. Furthermore, it has been found according to the invention that a portion of the indium can be replaced by adding sulfur, which is less expensive than indium, and that an improvement in dense feeding and machinability can still be achieved. However, a combination of indium and sulfur can lead to wetting and adhesion to the mold, which is undesirable. Therefore, the combined proportion of indium and sulfur is limited to 2.0 wt.%.

[0013] The addition of nickel improves the corrosion resistance of the alloy and reduces the influence of wall thickness on mechanical strength. When nickel is added to the required extent, the resulting lattice can be further strained in addition to the solid solution strengthening caused by tin. Nickel can also form intermetallic phases with other alloying elements, which serve as nuclei for microstructure refinement, for example, nickel-iron phases.

[0014] From a casting perspective, it is further advantageous if the continuous casting alloy comprises at most 0.30 wt.%, in particular at most 0.10 wt.%, in particular 0.03–0.08 wt.% phosphorus, at most 0.20 wt.% iron, and at most 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 driven off by the tin. Iron can form advantageous phases with nickel, but on the other hand, it proves problematic from a casting perspective at amounts above 0.2 wt.%. Antimony is deposited at the grain boundaries and thus slightly embrittles the material, which proves quite advantageous with regard to the goal of good machinability through brittle chips.

[0015] Manganese can also be used to deoxidize the melt. During solidification, manganese, similar to nickel, can be incorporated into the metallic lattice. However, this reduces the solubility of tin, and solidification temperatures are generally lowered. A disadvantage is the relatively dense oxide layers, which can lead to uncontrolled reductions in strength. Therefore, the manganese content is limited to 0.5 wt.%. It is advantageous if the sum of the weight percent indium and sulfur content is at least 0.6 wt.%, in particular at least 0.7 wt.%, in particular at least 0.8 wt.%, in particular at least 0.9 wt.%, in particular at least 1.0 wt.%, in particular at least 1.1 wt.%, in particular at least 1.2 wt.%, and / or in particular at most 1.9 wt.%, in particular at most 1.8 wt.%, in particular at most 1.7 wt.%.

[0016] It is further advantageous if the copper-tin continuous casting alloy comprises at least 0.3 wt.%, in particular at least 0.4 wt.% and / or in particular at most 0.7 wt.%, in particular at most 0.6 wt.% sulfur.

[0017] In a further embodiment of the present invention, it proves advantageous if the copper-tin continuous casting alloy comprises at least 9.5, in particular at least 10.0 wt.%, in particular at least 10.5 wt.%, and / or at most 14.0 wt.%, in particular at most 13.0 wt.%, in particular at most 12.0 wt.%, in particular at most 11.5 wt.%, in particular at most 11.0 wt.% tin.

[0018] Furthermore, it proves 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.% indium.

[0019] The present invention relates to a continuously cast alloy of the claimed composition in the molten state. Furthermore, the present invention relates to a continuously cast alloy of the claimed composition in the cast state.

[0020] The present invention also relates to a continuously cast blank or a continuously cast intermediate product, in particular in strand form or tube form, produced by casting a continuously cast alloy of the claimed type and composition and with the same composition as this continuously cast alloy.

[0021] Furthermore, the invention relates to machined machine parts or transmission parts, in particular gears, worm gears, bushings or linear guide parts, or machined fitting parts for the conveyance of fluids, manufactured by machining a continuous cast blank or continuous cast intermediate product of the type claimed herein.

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 9.0 - 15.0 wt.% tin, 0.1 - 2.0 wt.% indium, 0.2 - 0.8 wt.% sulfur, wherein the sum of the weight percentage of indium and sulfur is 0.5 - 2.0 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 0.5 wt.% zinc, 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 the sum of the weight percentage of indium and sulfur is at least 0.6 wt.%, in particular at least 0.7 wt.%, in particular at least 0.8 wt.%, in particular at least 0.9 wt.%, in particular at least 1.0 wt.%, in particular at least 1.1 wt.%, particularly at least 1.2 wt.% and / or in particular at most 1.9 wt.%, in particular at most 1.8 wt.%, in particular at most 1.7 wt. %.

3. Copper-tin continuous casting alloy according to claim 1 or claim 2, characterized in that it comprises at least 0.3 wt.%, in particular at least 0.4 wt.% and / or in particular at most 0.7 wt.%, in particular at most 0.6 wt.% sulfur.

4. Copper-tin continuous casting alloy according to claim 1, claim 2 or claim 3, characterized in that it comprises at least 9.5, in particular at least 10.0 wt.%, in particular at least 10.5 wt.% and / or at most 14.0 wt.%, in particular at most 13.0 wt.%, in particular at most 12.0 wt.%, in particular at most 11.5 wt.%, in particular at most 11.0 wt.% tin.

5. Copper-tin continuous casting alloy according to claim 1 or claim 2, 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 1.7 wt.% indium.

6. 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: 9.0 - 15.0 wt.% tin, 0.1 - 2.0 wt.% indium, 0.2 - 0.8 wt.% sulfur, wherein the sum of the weight percentage of indium and sulfur is 0.5 - 2.0 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 0.5 wt.% zinc, 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.

7. Machine parts or gear parts manufactured by machining, in particular gearwheels, wormwheels, bushings or linear guide parts, or fitting parts manufactured by machining for the conduction of fluids, produced by machining a continuous casting blank or continuous casting intermediate product according to claim 6.