CN113073230A

CN113073230A - Lead-free-cutting brass alloy having excellent fusion castability, and method for producing and use thereof

Info

Publication number: CN113073230A
Application number: CN202110322871.5A
Authority: CN
Inventors: 陈金龙; 陈贞光; 洪启捷; 叶斐钦
Original assignee: Fortune Mfg Co ltd
Current assignee: Fortune Mfg Co ltd
Priority date: 2016-01-21
Filing date: 2016-01-21
Publication date: 2021-07-06
Also published as: CN106987737A

Abstract

The invention relates to a lead-free-cutting brass alloy with excellent fusion castability, and a manufacturing method and application thereof, the lead-free-cutting brass has good air leakage sealing property, casting meltback property and mechanical property, and the brass alloy comprises: 65 to 75 wt% copper, 22.5 to 32.5 wt% zinc, 0.5 to 2.0 wt% silicon, and other unavoidable impurities; wherein the total copper and zinc content of the brass alloy is 97.5 wt% or more.

Description

Lead-free-cutting brass alloy having excellent fusion castability, and method for producing and use thereof

The present application is a divisional application of 'a lead-free-cutting brass alloy having excellent melt castability and a method for producing the same and use thereof', which was filed 2016, 21/1/2016 and application No. 201610041118.8.

Technical Field

The invention relates to a leadless free-cutting brass; in particular to a lead-free-cutting brass which has good air leakage sealing performance, casting meltback performance and mechanical property.

Background

Conventional lead-containing copper alloys have good machinability and mechanical properties and are widely used as various industrial materials, for example: the civil industrial application of water valves and hardware parts is an important industrial base material. At present, the copper alloy valve material is widely used in pipeline parts, but good turning performance is necessary for turning parts such as valves, ball valves and the like. Besides the requirement for corrosion resistance, another important additive element of these cast copper alloys, which are commonly used for valves, plumbing equipment and ship parts, is lead, which plays the role of embrittling turning chips during the turning of the parts, making the turning easier. However, under the recent environmental awareness, it is necessary to consider the role of adding other alloying elements instead of lead in the free-cutting copper alloy. Lead-containing copper alloy can generate lead vapor which is released to cause physical harm to human bodies and lead pollution to environment as heavy metal in the production and use processes. In recent years, advanced countries attach more importance to the issue of environmental protection, and with the passing of the specification of north american NSF drinking water, the directive of european union ROHS2.0 and the lead-free law of california, strict limitations on the lead content in copper alloys and the amount of lead leached from drinking water are worried out.

Traditional lead-containing copper alloys are lead-free, mainly replacing lead with bismuth to enhance the free-cutting effect, and chinese patents CN102828064B and CN102071336B disclose that the machinability of high-bismuth brass with 0.3 to 3.5 wt% bismuth content is quite close to that of lead brass. However, bismuth has a melting point of only 271 ℃, is prone to heat cracking during casting solidification, and high bismuth brass is not an ideal material for valve members for welding applications because the high bismuth brass-based castings suffer from hot shortness defects once the welding temperature is above the melting point of bismuth, thereby causing leakage of the valve members carrying high pressure gas and fluid.

To reduce the use of bismuth, it is a new trend to replace bismuth with silicon, which is relatively inexpensive and readily available. The alloy elements added in the lead-free brass alloy in the prior art comprise elements such as silicon, bismuth, graphite, tin, iron, calcium and the like, wherein a proper amount of silicon element is added in the brass, so that the solid solution strengthening effect can be generated, and the casting fluidity and the weldability of the alloy are improved. Therefore, the preparation of the lead-free brass alloy by using the silicon element as an additive element becomes the key point for developing the environment-friendly silicon brass alloy. Such as: prior art ASTM C87800 silicon brass alloy, by adding silicon in an amount of 3.8 to 4.2 wt% to brass, results in a high silicon lead free brass alloy with excellent mechanical strength, corrosion resistance; however, the prior art ASTM C87800 alloy has a greatly expanded mushy zone due to the increase of silicon content in the alloy, and is summarized as an alloy with a wide solidification zone (the solidification zone temperature is 95 ℃, see the Copper alloy section for casting of "Copper and Copper alloys" published by American Society for Metals) in the handbook of materials, which easily causes loose defects in the casting formed by the ASTM C87800 alloy during the solidification process, thereby causing poor airtightness of the casting and leakage.

On the other hand, the prior art C87800 silicon bronze alloy is a ternary alloy consisting of Cu-14Zn-4Si, which has excellent dezincification corrosion resistance similar to red copper because the alloy is added with silicon element and has a zinc content of less than 15 wt%; however, the alloy composition can significantly affect the solidification characteristic, the silicon content is as high as 4 wt%, the silicon bronze solidification interval is enlarged, the solidification process is in a congelation-shaped solidification state, and the casting method is more suitable for a metal permanent mold with low heat storage coefficient of a casting mold, and a casting process for guiding the casting to generate directional solidification is carried out by utilizing a die casting method and a proper flow path design scheme. At present, most copper alloy manufacturers mainly utilize a sand mold casting method to produce valve products, and the prior art can not meet practical requirements.

The patent nos. TW577931 and TW421674 disclose that the addition of 2 to 4 wt% of silicon element as a main alloy strengthening element of the lead-free brass alloy, although the melt flow ability can be improved to improve castability; however, the silicon element produces wear-resistant kappa and gamma hard precipitated phases which affect the service life of the tool, and the addition of trace lead (less than 0.4 wt%) is still required to further obtain the preferable machinability.

Taha et Al [ Ain Shams Engineering Journal, vol.3, 2012, pp.383-392 ] developed on the basis of a prior art lead-containing silicon brass (60 wt.% Cu, 0.25 to 5.5 wt.% Si, and 0.15 to 0.5 wt.% Pb), modified with a hexa-brass alloy base, with 1-4 wt.% Si and 0.5 wt.% Al substituted for lead, and found that silicon content of 3-4 wt.% Si produces η -Cu8ZnSi and χ -Cu8ZnSi precipitates, making the structure finer and stronger, while also possessing preferred fluidity, but increasing the fraction of cast porosity. Puathawee et al (Advanced Materials Research, vol.802, 2013, pp. 169-173) found that as the silicon content increased, the γ phase precipitated from equiaxed β phase grain boundaries to form a network structure, and that after addition of tin, the β and γ phases were more uniformly dispersed than before addition, while increasing the alloy hardness to HV398, the generation of the γ phase facilitated turning chip breaking, and the hard and brittle characteristic of the γ phase also caused tool wear to become severe.

It is thus clear that since the effect of solid solution strengthening of silicon is remarkable, it is necessary to adjust the amount of silicon added to an appropriate amount to prevent the generation of excessive γ hard phase and to deteriorate the mechanical properties, Oishi et al, Sanbao copper industries, Japan [ Materials transformations, vol.67, 2003, pp.219-225] invented a leadless silicon brass alloy containing 75.5Cu-3Si-0.1P-Zn, which is a composition of α + γ + κ phase, and in which the precipitation of residual β phase and equilibrium stable phase μ is not observed, and which has excellent forgeability, ease of casting, dezincification resistance and easy-cutting properties.

Since the wide solidification interval affects the ability of the liquid phase to perform replenishment shrinkage, when the liquid phase cannot effectively replenish the complicated and staggered dendritic crystals, the casting is caused to generate fine shrinkage cavities, so that it is very important to know the solidification interval of the alloy. The fact that the lead-free CAC403(Cu-10Sn-2Zn) has a wider solidification interval than the lead-containing CAC406(Cu-5Sn-5Pb-5Zn) as measured by a thermocouple by the Japanese academy of sciences Xiaolin and Wanshan [ journal of the Japanese society of metals, volume 43, 2004, p.647-650 ], indicates that the removal of lead has an influence on the casting characteristics of the alloy, and thus, the conditions for melting and casting the copper alloy need to be strictly controlled.

Therefore, there is a need for a new lead-free brass alloy material that can meet the lead-free specification and has the manufacturing process convenience to replace the traditional lead-containing copper alloy, such as a lead-free brass with the advantages of convenient casting and easy machining, no loose structure generated during the casting process, and the casting with air tightness, even dezincification corrosion resistance, and the performance required by high-quality valve parts for gas and fluid transportation.

The invention improves the characteristic of wide solidification interval of silicon bronze by a component adjustment mode, aims at the alloy component design suitable for sand mold casting production, reduces the tendency of casting loose, shrinkage cavity and other solidification defects caused by congelation, and improves the soundness of the casting.

Disclosure of Invention

The invention meets the requirements of environmental continuous development and industrial application, follows the lead-free idea and has the characteristics of mechanical strength and easy casting, so that the alloy characteristics of the lead-free silicon brass are improved by selecting the seven-three brass as a base material in the prior art, adding silicon as a main alloy element and adding a trace amount of alloy elements such as aluminum, antimony, tin, manganese, nickel, boron and the like in a compounding way.

The invention aims to provide a lead-free-cutting brass alloy, which overcomes the defect that in the prior art, in an ASTM C87800 high-silicon brass alloy, the solidification process is overlong due to a wide solidification temperature range, so that a casting is fully distributed with nest-shaped loose shrinkage cavities, and the poor sealing property of the casting is caused to cause leakage; on the other hand, the alloys disclosed in the patent nos. TW577931 and TW421674, which contain high amounts of si elements added to brass alloys, cause hard phases such as κ and γ, which deteriorate tool life and increase time required for cutting, are also solved by the present invention.

Another object of the present invention is to provide a silicon-containing lead-free brass which is easily cast and has low working time and weldability, and which comprises: 65 to 75% by weight of copper, 22.5 to 32.5% by weight of zinc, 0.5 to 2.0% by weight of silicon and other unavoidable impurities. The alloy composition range is capable of meeting the material manufacturing characteristics required for producing high quality valve members.

The addition of the silicon element can form a small amount of alloy precipitates among dendrites to become a starting source of turning chip fracture during turning, and overcomes the defects that the high-silicon brass alloy is difficult to cast and cut.

It has surprisingly been found that by adjusting the zinc content of a brass alloy to 22.5 to 32.5% by weight and the silicon content to 0.5 to 2.0% by weight, and wherein the total of the copper and zinc contents of said brass alloy is 97.5% by weight or more, preferably 97.5 to 98.5% by weight, a brass alloy comprising a total of 97.5% by weight of copper and zinc, in which the liquid phase does not crystallize α -Cu between the two phases, is obtained, while releasing the latent heat of solidification to prevent the internal temperature of the alloy from dropping. Therefore, under the non-equilibrium solidification condition, once the zinc atoms in the residual liquid phase reach the concentration required by the peritectic reaction, the beta phase consumes the residual liquid phase rich in solute, and starts nucleation growth from the surface of primary crystal alpha-Cu, so that the transformation of the peritectic reaction of L + d-Cu → beta occurs, and as can be seen from a cooling curve, the peritectic reaction platform after being lower than the liquidus inclines slightly, and finally the peritectic reaction is finished at 859.7 ℃, and the temperature of a two-phase interval of 31.7 ℃ is still maintained. The solidification range of the brass alloy can be reduced. Specifically, the lead-free-cutting brass alloy of the invention can significantly reduce the liquidus temperature of the alloy by increasing the zinc content; however, with the addition of other alloying elements except copper and zinc, the proportion of the alpha and beta phases of the brass alloy is increased, and the temperature between the two phases of the alloy can be increased to 50 ℃ or higher; it has surprisingly been found that the brass alloy according to the invention, wherein the total amount of copper and zinc is 97.5 wt.% or more, preferably in the range of 97.5 and 98.5 wt.%, has a substantially reduced temperature range between the two phases of about 30 ℃ compared to brass alloys disclosed in the prior art.

In another aspect, the invention comprises a brass alloy comprising copper and zinc in a total amount of 97.5% by weight or more, preferably 97.5 and 98.5% by weight, and silicon in an amount of 0.5 to 2.0% by weight, the structural alloy composition being composed of an α + β phase; as can be understood by those skilled in the art, considering the property of high ductility of the alloy alpha phase, the mutual balance of the property of chip breaking can be improved by the phenomenon that the excessive silicon-rich gamma phase is enriched in the grain boundary; the present invention has surprisingly found that, by controlling the above-mentioned component ratio, in addition to the α phase ratio having proper ductility, the γ phase of the lead-free-cutting brass alloy of the present invention can occupy proper fraction, and the γ phase of the lead-free-cutting brass alloy of the present invention can be generated at the α and β phase boundary, and the precipitation amount is significantly reduced, and at the same time, the network precipitate of the γ phase along the β phase boundary is greatly reduced, and the γ phase is transformed into granular form and uniformly dispersed between the α phase and the β phase. Therefore, the composition of the lead-free-cutting brass alloy has mechanical properties with proper strength and achieves the effect of easy chip breaking.

The lead-free-cutting brass alloy of the present invention, wherein said brass alloy may further comprise at least one element selected from the group consisting of aluminum, tin, manganese, nickel, antimony, and boron, wherein the total content of said elements is 2.5 wt% or less.

The lead-free-cutting brass alloy of the present invention, wherein said brass alloy further comprises at least one element selected from the group consisting of tin, manganese, nickel and antimony, each of said elements being 0.01 to 0.55% by weight or nickel being 0.01 to 0.8% by weight, and wherein the total content of said elements is 2.5% by weight or less.

The lead-free-cutting brass alloy of the present invention, wherein the brass alloy further comprises at least one element selected from the group consisting of 0.1 to 1.0 wt% of aluminum, 0.01 to 0.55 wt% of tin, 0.01 to 0.55 wt% of manganese, 0.01 to 0.8 wt% of nickel, 0.01 to 0.55 wt% of antimony, and 0.001 to 0.1 wt% of boron, wherein the total content of the said elements is 2.5 wt% or less.

The lead-free-cutting brass alloy of the present invention, wherein the total copper and zinc content of the brass alloy is 97.5 wt% or more, preferably the total copper and zinc content is between 97.5 and 98.5.

The lead-free-cutting brass alloy of the present invention has a lower limit value of 65 wt%, 67 wt%, or 68 wt% of copper and an upper limit value of 70 wt%, 73 wt%, or 75 wt% of copper. The copper content may range between any combination of the aforementioned lower and upper values, for example, preferably 68 to 70 weight percent.

The lead-free-cutting brass alloy of the present invention has a lower limit value of silicon content of 0.5 wt%, 0.75 wt%, 1 wt%, 1.1 wt%, 1.15 wt%, 1.3 wt%, or 1.45 wt%, and an upper limit value of silicon content of 1.35 wt%, 1.5 wt%, 1.75 wt%, or 2.0 wt%. The silicon content may range between any combination of the aforementioned lower and upper values, and is preferably, for example, 1.0 to 1.5 wt%, 1.1 to 1.35 wt%.

The lead-free-cutting brass alloy of the present invention, wherein the brass alloy further comprises aluminum in an amount having a lower limit of 0.1 wt%, 0.15 wt%, 0.2 wt%, or 0.25 wt% and an upper limit of 0.30 wt%, 0.45 wt%, 0.5 wt%, 0.6 wt%, or 1.0 wt%. The aluminum content may range between any combination of the foregoing lower and upper values, for example, 0.1 to 1.0 weight percent, preferably 0.2 to 0.5 weight percent, and more preferably 0.15 to 0.30 weight percent.

The lead-free-cutting brass alloy of the present invention as set forth above, wherein said brass alloy further comprises 0.01 to 0.55% by weight of tin. The lower limit of the tin content is 0.01 wt%, 0.05 wt%, 0.075 wt%, 0.10 wt%, 0.20 wt%, or 0.25 wt%, and the upper limit is 0.10 wt%, 0.20 wt%, 0.25 wt%, 0.3 wt%, 0.40 wt%, 0.45 wt%, or 0.55 wt%. The tin content may range between any combination of the foregoing lower and upper values, and is preferably, for example, 0.01 to 0.2 wt.%, 0.1 wt.%, or less.

The lead-free-cutting brass alloy of the present invention, wherein said brass alloy further comprises 0.01 to 0.55% by weight of manganese. The lower limit of the manganese content is 0.01 wt%, 0.05 wt%, 0.075 wt%, 0.10 wt%, 0.20 wt%, or 0.25 wt%, and the upper limit is 0.10 wt%, 0.20 wt%, 0.25 wt%, 0.3 wt%, 0.40 wt%, 0.45 wt%, or 0.55 wt%. The manganese content may range between any combination of the foregoing lower and upper values, for example, preferably from 0.01 to 0.25 wt.%, more preferably from 0.10 to 0.20 wt.%.

The lead-free-cutting brass alloy of the present invention, wherein said brass alloy further comprises 0.8% by weight or less of nickel. The lower limit of the nickel content is 0.01 wt%, 0.05 wt%, 0.075 wt%, 0.10 wt%, 0.20 wt%, or 0.25 wt%, and the upper limit is 0.10 wt%, 0.20 wt%, 0.25 wt%, 0.3 wt%, 0.40 wt%, 0.45 wt%, or 0.55 wt%, 0.65 wt%, 0.78 wt%, or 0.80 wt%. The nickel content may range between any combination of the aforementioned lower and upper values, for example, 0.01 to 0.55 weight percent, preferably 0.01 to 0.25 weight percent, and more preferably 0.10 to 0.20 weight percent.

The lead-free-cutting brass alloy of the present invention, wherein said brass alloy further comprises 0.01 to 0.55% by weight of antimony. The lower limit of the antimony content is 0.01 wt%, 0.05 wt%, 0.075 wt%, 0.10 wt%, 0.20 wt%, or 0.25 wt%, and the upper limit is 0.10 wt%, 0.20 wt%, 0.25 wt%, 0.3 wt%, 0.40 wt%, 0.45 wt%, or 0.55 wt%. The amount of antimony can range between any combination of the foregoing lower and upper values, e.g., from 0.1% to 0.45%, preferably from 0.15% to 0.45%, and more preferably from 0.20% to 0.45% by weight.

The lead-free-cutting brass alloy of the present invention as set forth above, wherein the brass alloy further comprises 0.001 to 0.1 wt% of boron, the lower limit of the boron content being 0.001 wt%, 0.005 wt%, 0.01 wt%, 0.02 wt%, 0.03 wt%, 0.04 wt%, 0.05 wt%, 0.06 wt%, 0.07 wt%, 0.08 wt%, or 0.09 wt%, and the upper limit of the boron content being 0.005 wt%, 0.01 wt%, 0.015 wt%, 0.025 wt%, 0.035 wt%, 0.045 wt%, 0.055 wt%, 0.065 wt%, 0.075 wt%, 0.085 wt%, 0.095 wt%, or 0.1 wt%. The boron content may range between any combination of the lower and upper values, preferably between 0.001 and 0.05 wt.%, more preferably between 0.001 and 0.02 wt.%.

The lead-free-cutting brass alloy of the present invention as set forth above, wherein the inevitable lead content of said brass alloy is 0.15% by weight or less, preferably 0.1% by weight or less.

The lead-free-cutting brass alloy of the present invention as set forth above, wherein the inevitable iron content of said brass alloy is 0.15% by weight or less.

The lead-free-cutting brass alloy according to the present invention as described above, wherein the brass alloy contains other unavoidable impurities, such as but not limited to at least one selected from the group consisting of bismuth, lead, iron, sulfur, phosphorus, selenium, etc., in a total amount of 0.5% or less, such as preferably 0.3% or less.

In a preferred aspect of the lead-free-cutting brass alloy of the present invention, the brass alloy further comprises at least one element selected from the group consisting of 0.2 to 0.5 wt% of aluminum, 0.01 to 0.2 wt% of tin, 0.01 to 0.25 wt% of manganese, 0.01 to 0.55 wt% of nickel, 0.1 to 0.45 wt% of antimony, and 0.001 to 0.05 wt% of boron, wherein the total content of the elements is 2.5 wt% or less, and wherein the total content of zinc and copper in the brass alloy is 97.5 wt% or more.

The present invention further relates to a casting method, which utilizes the molten liquid of the brass alloy as described above to cast in a wet sand mold, a furan sand mold or a metal mold to form a casting.

The casting method of the present invention as described above, wherein the casting is carried out at a casting temperature of 1000 to 1050 ℃.

The casting method according to the present invention as set forth above, wherein the casting is further cut by a machining tool to produce a work piece and machining chips thereof.

The casting method according to the present invention as described above, wherein the molten soup of brass alloy further comprises a melt-back of the workpiece or the machining chips thereof produced by the method according to the present invention as described above.

The lead-free-cutting brass alloy of the present invention has excellent fusion castability as described above, and is suitable for various cast products such as: casting products obtained by sand casting, gravity casting and metal mold casting processes; a marine component; hardware for water; pipeline parts and fittings thereof; valves, such as: ball valves, gate valves, check valves, non-rising stem gate valves, butterfly valves; filters, such as: a Y-type filter; pumping; or complex shaped parts (such as bearings, screws, nuts, bushings, gears, oil hydraulic members, etc.). The lead-free-cutting brass alloy is particularly suitable for various pressure-resistant products, such as high-pressure valves, nozzles, high-pressure pipes, pressure pumps and the like.

The final and most important desired characteristic of the lead-free-cutting brass alloy of the present invention is the leak-tightness associated with the material casting. Accordingly, the invention further relates to a lead-free brass alloy cast article, such as: valve components (e.g., ball valves, gate valves, check valves, non-rising stem gate valves, or butterfly valves), plumbing components, or filters (e.g., Y-filters), etc., comprising the lead-free-cutting brass alloy of the present invention as described above.

As lead free brass alloy cast articles according to the present invention, such as: valves (e.g., ball valves, gate valves, check valves, non-rising stem gate valves, or butterfly valves), plumbing components, or filters (e.g., Y-filters), etc., that do not leak at pressures of 900psi or greater.

As lead free brass alloy cast articles according to the present invention, such as: the lower limit of the tensile strength of a valve member (e.g., a ball valve, a gate valve, a check valve, a non-rising stem gate valve, a rising stem gate valve, or a butterfly valve), a piping component, or a filter (e.g., a Y-type filter), etc., is 280MPa or more, 331 MPa or more, 355MPa or more, 409MPa or more, 450MPa or more.

As lead free brass alloy cast articles according to the present invention, such as: a valve member (e.g., a ball valve, a gate valve, a check valve, a non-rising stem gate valve, a rising stem gate valve, or a butterfly valve), a piping component, or a filter (e.g., a Y-type filter), etc., having a lower limit of breaking elongation of 8% or more, 9% or more, 16% or more, 20% or more, 25% or more, or 32% or more.

The lead-free-cutting brass alloy has the following characteristics and advantages: 1. compared with lead-containing brass, the brass has approximate easy-cutting characteristics; 2. the casting alloy has excellent meltback performance and melting convenience; 3. excellent in mechanical strength and applicable to welding use, free from the concern of thermal embrittlement of a brass alloy containing bismuth and excellent in sealing property; 4. the high-temperature-resistant high-corrosion-resistant high-temperature-resistant high-corrosion-resistant.

The solidification interval of the lead-free-cutting brass alloy

In one aspect of the present invention, when the lead-free-cutting brass alloy of the present invention is further compounded with aluminum in an amount of 0.1 to 1.0 wt% and tin in an amount of 0.01 to 0.55 wt%, respectively, the aluminum and tin elements added in trace amounts are low-melting point elements compared to copper, and thus the low-melting point solute in the liquid phase continuously releases latent heat with solidification until the solidification is completed, so that the low-melting point solute in the liquid phase completely enters the solid phase region at a lower temperature, and the temperature range of the two phase region of the brass alloy after the compound addition of aluminum and tin is about 60 ℃.

In one aspect of the present invention, the lead-free-cutting brass alloy of the present invention may further comprise aluminum in an amount of 0.1 to 1.0 wt%, wherein the two-phase interval is maintained at 35 ℃; the invention increases the adding amount of aluminum element to 1.0 wt%, which can further reduce the solidus temperature and relatively lower the temperature for completing the peritectic reaction.

In one aspect of the invention, the lead-free-cutting brass alloy of the present invention may further comprise manganese in an elemental content of 0.01 to 0.55 wt%, said brass alloy having a narrower two-phase range of about 30 ℃.

In another aspect, the lead-free-cutting brass alloy of the present invention can remove the harmful gases from the melt by adding at least one element selected from the group consisting of silicon, aluminum, tin and manganese to purify the melt and reduce the sources of the evolved gases during solidification, such as: in addition, compared with the silicon brass alloy in the prior art of ASTM C87800, the solidification range of the lead-free-cutting brass alloy disclosed by the invention has a narrower solidification temperature range and can also improve the mold filling capacity of molten soup.

Mechanical properties of the lead-free-cutting brass alloy of the invention

The lead-free-cutting brass alloy composition is further modified according to the silicon content, the silicon content is reduced to 0.5 to 2.0 weight percent, preferably 1.1 to 1.35 weight percent, so as to prevent excessive gamma phase from precipitating on grain boundaries to cause negative influence on mechanical properties, and 0.1 to 1.0 weight percent of aluminum element can be further added as a solid solution strengthening element of the alloy.

The lead-free-cutting brass alloy of the present invention has a silicon content adjusted to 0.5 to 2.0% by weight, preferably 1.1 to 1.35% by weight, which shows from X-ray diffraction analysis that the lead-free-cutting brass alloy of the present invention is mainly composed of an α + β two-phase structure; in addition, in one aspect of the lead-free-cutting brass alloy of the present invention, 0.1 to 1.0 wt% of aluminum element may be further added, and after x-ray diffraction analysis, the beta phase diffraction peak signal at 43.4 ° is significantly higher, which is consistent with the higher beta phase fraction observed in the microstructure.

As for the observation of the as-cast strength of the leadless free-cutting brass alloy of the present invention, although the leadless free-cutting brass alloy of the present invention reduces the content of silicon to 0.5 to 2.0 wt%, preferably 1.1 to 1.35 wt%, by increasing the content of zinc to 22.5 to 32.5 wt%, or further adding 0.1 to 1.0 wt% of aluminum, it can complement the solution strengthening effect brought by the original silicon element, so that the leadless free-cutting brass alloy of the present invention is quite close to the mechanical strength of commercial C87800 silicon bronze.

Machinability of the lead-free-cutting brass alloy of the present invention

The prior art achieves the purposes of prolonging the service life of a cutter, reducing the turning cost, generating discontinuous turning chips and the like by adding elements of easy-cutting lead and bismuth and changing cutting parameters, can also achieve the purposes of increasing the zinc content of 22.5 to 32.5 weight percent of the brass alloy, and can also achieve the purpose of increasing the total content of copper and zinc by 97.5 weight percent or more, the increase of the zinc content can ensure that the lead-free-cutting brass alloy has higher hardness and a beta-phase structure with poor ductility and can also provide the source position of cutting chip cutting fracture, and meanwhile, in the design of the lead-free-cutting brass alloy, hard and brittle gamma and kappa phases generated by silicon added to 0.5 to 2.0 weight percent, preferably 1.1 to 1.35 weight percent have the effect of increasing the cutting chips.

In one aspect of the present invention, the pb-free-cutting brass alloy of the present invention may further comprise 0.001 to 0.1 wt% of b, preferably 0.001 to 0.05 wt%, more preferably 0.001 to 0.02 wt% of b or 0.01 to 0.8 wt% of ni, wherein the addition of ni in the pb-free-cutting brass alloy changes the α -phase form, and converts from acicular fidman into a dendritic structure, and the γ phase of the pb-free or ni-free alloy is distributed in a form of particles between α + β phases, compared to the structure of pb-free-cutting brass alloy without the addition of b or ni; and when boron is added, the gamma phase precipitates especially along the phase boundary; on the other hand, the addition of nickel allows the silicon-rich solute liquid to be drained from the dendrites of the solidified alpha phase; therefore, further addition of 0.001 to 0.1 wt% of boron or 0.01 to 0.8 wt% of nickel can generate a metal compound between the β phase and the γ phase at the interdendritic sites, and it can be further confirmed from the EDS analysis that the concentrations of zinc and silicon in the γ phase are indeed higher than those of the mother phase.

Although the aforementioned gamma phase generated by further adding 0.001 to 0.1 wt% of boron or 0.01 to 0.8 wt% of nickel may have a negative influence on the ductility of the alloy; however, the lead-free-cutting brass alloy of the present invention lacks the addition of the conventional easy-cutting elements of lead or bismuth, and therefore, the present invention needs to rely on the generation of a compound phase with hard and brittle characteristics in the microstructure to achieve the purpose of breaking the continuity of the microstructure, so as to induce the cutting chip breaking effect in the copper alloy similar to lead, and at the same time, the mechanical properties of the alloy are not greatly reduced, which is essential. According to the lead-free-cutting brass alloy, the gamma phase plays a role in influencing the mechanical property and the cutting capability of the alloy in the alloy structure; when 0.001 to 0.1 wt% of boron or 0.01 to 0.8 wt% of nickel is further added to produce a gamma phase uniformly dispersed in a granular form between an alpha phase and a beta phase, it is desirable for the precipitation form.

Dezincification corrosivity of the lead-free-cutting brass alloy of the invention

The lead-free-cutting brass alloy has 22.5 to 32.5 weight percent of zinc content, the beta phase fraction in the structure of the lead-free-cutting brass alloy is increased along with the increase of the zinc content, the selective dissolution problem of zinc is obviously generated when the zinc content is higher than 15 weight percent, and a porous and loose pure copper is remained on a dezincification layer subjected to corrosion, namely, the dezincification corrosion phenomenon is the phenomenon.

The invention provides a lead-free-cutting brass alloy with dezincification corrosion resistance, and the brass alloy can further contain trace boron, nickel or antimony so as to improve the dezincification resistance of the brass alloy.

In one aspect of the lead-free-cutting brass alloy of the present invention, the alloy further comprises 0.001 to 0.1 wt% of boron, preferably 0.02 wt% or less of elemental boron and/or 0.01 to 0.8 wt%, preferably 0.01 to 0.55 wt% of nickel, in order to improve dezincification corrosion resistance. The lead-free-cutting brass alloy can also be further added with 0.01 to 0.55 weight percent of antimony, preferably 0.15 to 0.45 weight percent of antimony, more preferably 0.25 to 0.45 weight percent of antimony, has dezincification corrosion resistance effect, meets the standard that the specification of ISO 6509-1: 2014 is lower than 100 mu m of corrosion, and greatly improves the dezincification corrosion resistance of the brass alloy. The alloy composition of the lead-free brass alloy not only meets the lead-free standard, but also has the preferable dezincification resistance, and the phenomenon of dezincification corrosion is obviously generated when the zinc content of the conventional brass alloy is higher than 15 weight percent.

Alloy remelting characteristic of the lead-free-cutting brass alloy

Good and convenient material casting meltback is an object of the invention. The lead-free-cutting brass alloy can form a narrow solidification range, and is beneficial to the rapid passing through a porridge-shaped area in the solidification stage; therefore, the lead-free-cutting brass alloy also has high melting casting convenience. The convenience of casting here means that the alloy raw materials equivalent to the composition range of the lead-free-cutting brass alloy of the present invention are charged, and include: the turning scraps, the flow channel and the secondary scrap returning material can reduce the time required by melting due to the characteristic of low melting point, thereby achieving the purpose of reducing the power consumption during casting, and the alloy of the free-cutting brass alloy does not need to be degassed and refined by additional physical machinery and chemical agents during remelting; the molten soup has excellent fluidity and cleanliness, and the casting method of the lead-free-cutting brass alloy can effectively recycle the turning scraps and the returned materials and reduce the recovery and treatment cost. From the comparative example of fig. 1(a), it is clear that the casting after remelting the conventional copper alloy is covered with the hole defects, and the casting after remelting and casting the lead-free-cutting brass alloy of the present invention has good solidification shrinkage state, high tissue density and no solidification porosity defects, as shown in fig. 1 (B). Compared with the material disclosed in ASTM C87800 high-silicon brass or the TW577931 patent, the leadless free-cutting brass alloy of the present invention has the advantages of lower copper content and reduced material cost, and provides a novel leadless brass alloy to solve the problems caused by the solidification defect of silicon brass in the prior art, and further solve the leakage problem when the conventional silicon brass alloy is applied to cast high-pressure valves.

The lead-free-cutting brass alloy is added with boron and nickel elements, the solidification range of the alloy is still maintained at 35 ℃, and the two-phase region is not influenced by expansion.

In another aspect of the lead-free-cutting brass alloy of the present invention, which further comprises 0.01 to 0.8 wt%, preferably 0.01 to 0.55 wt% of nickel, the addition of the nickel of the present invention can cause a change in solidification form, the lead-free-cutting brass alloy of the present invention crystallizes α -Cu at 903 ℃, the β -phase crystallizes at 888 ℃, and the temperature drops to 869 ℃ which is the solidus temperature of the alloy, indicating that the peritectic reaction of the β -phase and the liquid phase has been completed. Two exothermic peaks are clearly distinguished from the DSC curve and respectively correspond to the crystallization of alpha phase and beta phase in sequence, and the crystallization temperature of the alpha phase is increased because nickel is an alpha phase stabilizing element and has high melting point.

In a preferred aspect of the lead-free-cutting brass alloy of the present invention, wherein the copper content is between 65 wt.% and 75 wt.% and the sum of the copper and zinc contents is between 97.5 and 98.5, the aforementioned silicon element exerts good solid solution strengthening effect to provide the alloy with preferable mechanical strength and ductility, so that the content of the added element silicon is 1.0 to 1.5 wt.%; the content of aluminum is 0.1 to 0.6 wt%; and comprises at least one selected from the group consisting of: 0.01 to 0.2 wt.% tin, 0.15 to 0.45 wt.% antimony and 0.01 to 0.25 wt.% manganese.

In a preferred aspect of the lead-free-cutting brass alloy of the present invention, the copper content is between 65 wt% and 75 wt%, the silicon content is between 1.0 wt% and 1.5 wt%, and antimony content is between 0.01 wt% and 0.55 wt%, so as to obtain a lead-free-cutting brass alloy having both easy-cutting property and mechanical strength. The invention separates out copper-silicon-antimony compound between alpha-Cu solid solution phases evenly, so that the lead-free-cutting brass alloy has the easy-cutting effect similar to that of lead and bismuth added in the brass alloy in the turning process, and the lead-free-cutting brass alloy has the advantage of simple phase structure, and the temperature of the two-phase interval is only 30-35 ℃.

The principle of adding a high content of solid solution strengthening manganese to form an intermetallic compound is also applied to the lead-free-cutting brass alloy of the present invention, and with respect to the lead-free-cutting brass alloy of the present invention, a preferred embodiment is one in which the copper content is 65 to 75% by weight, the zinc content is 22.5 to 32.5% by weight, the silicon content is 0.5 to 2.0% by weight, and the manganese content is 0.1 to 0.55% by weight, wherein the total of the copper and zinc contents in said alloy is 97.5% by weight or more. It has surprisingly been found that the lead-free-cutting brass alloy according to the invention, which further comprises between 0.1 and 0.55% by weight of manganese, forms a structure with an alpha phase matrix and a small amount of beta phase interspersed with Mn₅Si₃High hardness of the intermetallic compound, thereby providing good wear characteristics, and at the same time a narrow two-phase interval, which is about 30 to 35 ℃.

Drawings

FIG. 1: comparison of sections of slugs cast by remelting, (a) comparative example of ASTM C87800 prior art silicon brass; (b) the lead-free-cutting brass alloy S73M5 shows excellent compact and contracted structure.

FIG. 2: the optical microscope image of the as-cast microstructure of the lead-free-cutting brass alloy T73M of the invention: (a) T73M5, (b) T73M5B, (c) T73M 5N.

FIG. 3: the lead-free-cutting brass alloy of the invention presents short C-shaped and discontinuous machining turning scraps: (a) T73M5, (b) T73M5B, (c) T73M 5N.

FIG. 4: a valve member cast from the lead-free-cutting brass alloy of the present invention (T73M5B) was joined by argon welding to provide a weld bead with a consistent appearance of no cracking.

Detailed Description

In the following detailed description of the preferred embodiments, which is made in conjunction with the drawings, the advantages and features of the lead-free-cutting brass alloy of the present invention will be clearly disclosed, compared with the prior art materials.

The embodiments of the present invention are illustrated by the following examples:

example 1: production of leadless free-cutting brass alloy

The material of this example used C1100 pure copper, a C87800 silicon bronze master alloy ingot, heptatribrass as the melting material, and additionally required pure aluminum (99.9%), pure tin (99.8%), pure antimony (99.8%), boron copper, a 99% pure manganin master alloy containing 30 to 70 wt% manganese, or C7541 foreign copper (copper-zinc-15% nickel master alloy) before tapping. The melting materials are weighed and mixed according to the design of alloy components, and then are sequentially put into a high-frequency melting furnace for melting operation according to the melting point of the materials from high to low, wherein the crucible is made of graphite. In order to reduce the melting loss of zinc, pure zinc was added at 930 ℃, the temperature was raised to 1050 ℃. + -. 25 ℃ to obtain a melt, the oxide slag on the surface of the melt was removed, the melt was cast into a pre-prepared green sand mold at 950 ℃, the components were analyzed by a spectrometer (brand: SPECTROMAXX, Germany), and the results of the measurements are shown in Table 1.

The melting materials exemplified in this example can be adjusted and selected as required by those skilled in the art, and the elements other than copper, zinc and silicon, such as aluminum or manganese, are not essential elements for achieving the present invention.

Table 1: chemical composition (weight percent) of the lead-free-cutting brass alloy

Example 2: influence of silicon content

The brass alloy of comparative example 73M4 (Si > 2.0%) was composed mainly of the α + β + γ phase. The gamma phase precipitation is concentrated on beta phase grain boundary and inside, and because the gamma phase is hard and brittle, when the gamma phase is precipitated excessively, the alloy strength is too high, and the extensibility is greatly reduced. According to the EDS analysis result, the gamma phase is a zinc-rich and silicon element compound phase. Since a large amount of coarsened γ phase precipitates at β phase grain boundaries, mechanical properties may be negatively affected. In order to improve the phenomenon that excessive silicon-rich gamma phase is enriched in grain boundaries when the silicon content exceeds 2.0 wt%, the lead-free-cutting brass alloys S73M5 and SA73M5 of the present invention surprisingly found that when the silicon content is adjusted to 2.0 wt% or less (about 1.24 to 1.25 wt%), diffraction analysis showed that the lead-free-cutting brass alloys S73M5 and SA73M5 of the present invention are mainly composed of an alpha + beta dual-phase structure; in addition, the diffraction pattern shows that the beta-phase diffraction peak signal of SA73M5 at 43.4 ℃ is higher, which is consistent with the higher beta-phase fraction observed in the microstructure.

On the other hand, from the microscopic structure observation of S73M5 and SA73M5, it was confirmed that the α phase was a needle-like Ferdman structure, and the remaining β phase was consistent with the diffraction analysis result. In addition, the SEM image shows that the gamma phase is mainly generated from the phase boundary between alpha and beta, the precipitation amount is obviously reduced, the reticular precipitates precipitated from the gamma phase along the phase boundary are greatly reduced, and the gamma phase is converted into a form uniformly distributed in the phase boundary in a granular shape, which shows that the lead-free-cutting brass alloy reduces the silicon content and reduces the amount of the gamma phase. Therefore, the lead-free-cutting brass alloy of the present invention can improve the strength and ductility of the alloy through a design strategy of reducing the silicon content to 2.0 wt% or less, so that the copper alloy material has proper mechanical properties.

Example 3: turning performance test

In the example, the conventional lathe turning material is used for testing the chip breaking capacity of copper alloy materials with different components under the same processing conditions. The turning tool material is a commercially available disposable tungsten carbide blade, the R angle of the tool nose is 0.4mm, the turning conditions are that the depth of feed is 1mm, the feed speed is 0.09mm/rev and the rotation speed of the lathe is 550r.p.m, so that the turning test is carried out, after turning is finished, 20 turning chips are randomly collected, weighed and the length of the turning chips is measured, and the turning chip type classification standard specified by ISO 3685 is combined to be used as the quality for judging the machinability of the copper alloy.

The typical C36000 lead-containing free-cutting brass structure is composed of an alpha + beta dual-phase structure and pure lead scattered in alpha and beta crystal boundaries, so as to meet the requirements on machinability and strength of materials, and simultaneously, the free-cutting brass structure is a standard product with 100% machinability, and in order to meet the requirements of environmental protection laws, the microstructure of three alloys exemplified by the lead-free-cutting brass alloys T73M5, T73M5B and T73M5N of the invention forms gamma-phase precipitates with chip breaking promoting effect, and fig. 3 shows that the chips of the alloys T73M5, T73M5B and T73M5N are in C-shaped discontinuity.

The present invention selects an alloy design strategy with low influence on mechanical strength in terms of two contradictory properties of mechanical properties and turning properties, controls the distribution of hard and brittle gamma phases in the form of particles on the phase boundary through the adjustment of silicon content, and reduces the negative influence of hard and brittle precipitates on the alloy strength, thereby obtaining machinability (machinability degree of 90%) equivalent to that of C84400 lead-containing brass, and remarkably has a mass production advantage over other two kinds of silicon brasses in comparison with the processing time required for conventional lead-containing brasses, as shown in Table 2. The turning chips of the lead-free-cutting brass alloy are C-shaped discontinuous as shown in FIG. 3, namely T73M5, T73M5B and T73M5N alloys, so that the chip breaking capacity in the turning process is excellent, and the chip adhesion phenomenon with a turning tool is not easy to occur, and the time required by processing is greatly shortened compared with the wear-resistant kappa and gamma in the structure.

Table 2: equal-size valve machining time

Example 4: dezincification corrosion resistance test for copper alloy

This example was tested according to the dezincification corrosion resistance test method for copper alloys (ISO 6509-1: 2014) established by the International organization for standardization, which is suitable for the evaluation of dezincification corrosion resistance of copper alloys having a zinc content higher than 15% by weight. Carried out in 12.7g of aqueous copper chloride (CuCl)₂·2H₂O) in 1000ml of deionized water (< 20. mu.S/cm), heating the aqueous solution of copper chloride to 75 ℃. + -. 5 ℃ by heating over water and maintaining the temperature, cutting the sample to a size of 10X 5mm (the exposed area of the sample in contact with the test solution is 100 mm)²) After embedding, grinding the surface of the test piece by using #1000 abrasive paper, placing the test piece into a test solution for keeping for 24h +/-30 min, taking out the test piece, cleaning the surface of the test piece by using deionized water, cutting the test piece in a direction vertical to the bottom surface of a beaker, slightly grinding and polishing the test piece by using #2500 abrasive paper to prevent a dezincification layer on the test surface from falling off, so that the dezincification layer can be clearly distinguished from a non-corroded base material of the test piece, and measuring the thickness and the uniform corrosion depth of the dezincification layer.

The total thickness of the local dezincification layer of the comparative example heptatribrass is 332 μm; comparative example C87800 copper chloride acid etch produced mainly uniform etch depth of 174 μm, but no local dezincification occurred; comparative example C87850 copper chloride acid etching solution uniformly etched to a depth of 133 μm, and partially dezincified layer 72 μm, the total depth of penetration into the test piece was 205 μm.

The thickness of the local dezincification layer of the lead-free-cutting brass alloy T73M5B is 181 mu M; BS73M, uniform etch depth of 45 μm, plus a local dezincification layer of 9 μm, resulted in a total etch depth of only 54 μm. Compared with the heptatribrass of the comparative example, the T73M5B has a great reduction in the local dezincification layer thickness of 332 mu M of the copper chloride acid etching solution; whereas BS73M showed a lower etch depth of 174 μm for the cupric chloride etching solution than comparative example C87800. The BS73M alloy of the present invention has better uniform corrosion resistance than the alloy of comparative example C87800, but the local dezincification property is slightly worse than that of C87800, and the total corrosion thickness is better than that of comparative example C87800. In contrast, the BS73M alloy of the present invention exhibited better uniform corrosion and localized dezincification corrosion performance than comparative example C87850, which is better in rain than comparative example C87850.

Comparing the prior art heptatribrass alloy of comparative example 70 wt% copper to 30 wt% zinc with the T73M5B and BS73M alloy of this example, the localized dezincification corrosion depth can be further reduced from 332 μ M to a considerable extent, indicating that the lead-free-cutting brass alloy of the present invention has utility against dezincification corrosion. In conclusion, the lead-free-cutting brass alloy of the present invention can meet the standard set by AS2345 and ISO6509 for the dezincification resistance of brass alloys.

Example 5: alloy remelting Property test

The macroscopic structure of the alloy of comparative example C87800 before remelting is mainly columnar crystal structure, and loose pores which are not fully supplemented appear among dendrites, which can be observed in the alloy of comparative example C87800, comparative example C87850, and the T73M5N alloy of the present invention. After the alloy is remelted, the cast ingot of the comparative example C87800 has no sign of solidification shrinkage, the cast ingot is bulged on the upside, and meanwhile, the generation of a large amount of loose defects in the cast ingot can be clearly seen, which is presumed to be caused by the fact that the solidification range of the alloy of the comparative example C87800 is wider, and simultaneously, the returned material and the turning scraps which are adhered with water and cutting oil are remelted to cause the increase of the gas content of the alloy liquid, so that the porosity of the cast is increased, and the castability is reduced, and the original mechanical property of the C87800 alloy cannot be achieved. It has surprisingly been found that the lead-free-cutting brass alloy of the present invention has a normal solidification shrinkage after remelting. The macrostructures of the examples T73M5 and T73M5B show that the macrostructures before and after remelting are both composed of relatively dense equiaxed crystals, no holes are observed, and the T73M5 and T73M5B alloy has preferable casting remelting properties and excellent mechanical strength.

The lead-free-cutting brass alloy can be directly fed during recovery and smelting through repeatedly melting and casting a flow channel and processing copper scraps and machined parts which are stained with cutting fluid, and chemical degassing treatment or cooling degassing treatment is carried out by reduction reaction in molten soup without adding refined agent or degasifier. The lead-free-cutting brass alloy is recovered and smelted, reaches the temperature of and is directly discharged at ; and the casting operation is carried out at the casting temperature of 1000-1050 ℃, preferably at the casting temperature of 1000-1020 ℃, the soup after the sand mold is filled with the molten steel is normal in solidification and shrinkage, the castability, the casting convenience and the forming rate are good, and the lead-free-cutting brass alloy has good casting meltback property and the forming rate.

Example 6: tensile Property test

Although the lead-free-cutting brass alloy T73M5 of the present invention reduces the silicon content to about 1.3 wt.%, the solid solution strengthening effect of silicon element is compensated by increasing the zinc content, so that the strength of T73M5 is close to that of the silicon bronze of comparative example C87800.

Because the T73M alloy is designed to have higher zinc content, the amount of the silicon element which can be dissolved in solid solution in the alpha phase and the beta phase is lower and lower, and the observation of the structure and the fracture surface shows that the added silicon element can not be completely dissolved in solid solution in the alpha phase and the beta phase; therefore, when the silicon concentration is higher than the maximum solid solution limit of the matrix phase, a γ phase which is hard and brittle and rich in zinc and silicon elements is generated. The dimple microstructure left by the tensile deformation of the alpha phase can be observed from the fracture surface of example T73M5, wherein the gamma phase particles are found in the finer dimple microstructure, which shows that the gamma phase particles are uniformly distributed on the alpha and beta phase boundary, which is helpful to obtain the preferred ductility of the alloy. Surprisingly, it is found that the elongation of the lead-free-cutting brass alloy of the invention is reduced obviously after adding boron (T73M5B) and nickel (T73M5N), and the section system of the lead-free-cutting brass alloy of the invention is damaged along the interface of alpha phase and gamma phase; in addition, because the addition of nickel causes the fracture surface to spread along the dendritic crystal with poor toughness, the fracture traces of beta and gamma phases on the surface of the dendritic crystal can be observed, and meanwhile, no obvious alpha-phase slip band is generated.

Example 7: application example-lead-free brass alloy valve member

One of the purposes for which the lead-free-cutting brass alloy of the present invention is applied, namely, the leakage-resistant sealing property of the material. The lead-free-cutting brass alloys T73M5B, T73M5N and BS73M of the present invention were cast and processed under the above conditions, and thenFormed as a valve element, such as: ball valves, gate valves, check valves, non-rising stem gate valves, or butterfly valves, piping components, Y-filters, or valve covers. The casting formed by the lead-free-cutting brass alloy has no material pores or no material pores except for slag pores and sand pores on the appearance of the casting caused by casting factors

Flaw of the crack. Castings formed from the lead-free-cutting brass alloys of the present invention, T73M5B, T73M5N, and BS73M, all meet the air pressure test at 88psi or greater, and the high pressure water pressure test at 900psi or greater (actual test water pressure is about 1150psi to 1450psi), (MSS SP-110Ball Valves, Threaded, Socket Welding, Solder Joint, ground and curved Ends standards). Therefore, the lead-free-cutting brass alloy material has the structure characteristics, and can be suitable for valve products with the pressure requirement of 900psi or higher.

This example further utilized sand castings made from the reflow of the lead-free-cutting brass alloys of the present invention, T73M5B, T73M5N, and BS73M, which contained 40% turnings and 60% scrap returns with the same alloy composition, which were cast, worked and argon welded to form a valve member. FIG. 4 shows the appearance of a valve element cast using the lead-free-cutting brass alloy T73M5B of the present invention, joined using argon welding, without any cracking around the weld bead; this example also shows that the valves made from the back-melted castings of the lead-free-cutting brass alloys T73M5B, T73M5N, and BS73M of the present invention can pass the high pressure leak test standard without crack marks in the structure, and therefore, the valves made from the lead-free-cutting brass alloys of the present invention have exhibited sufficient leak-proof sealing characteristics. The comparison of the properties of the present example with those of other conventional alloys is summarized in Table 3 below.

Specifically, the lead-free-cutting brass alloys T73M5B, T73M5N, and BS73M of the present invention were formed into valve members by reflow casting, which had tensile strengths of 355MPa or more, 411MPa or more, and 450MPa or more, and breaking elongations of 25% or more, 20% or more, and 16% or more, respectively. The foregoing mechanical properties are further fully demonstrated by the ability of the lead-free-cutting brass alloys of the present invention to exhibit a combination of high tensile strength and good elongation properties by adding appropriate amounts of alloying elements, while valves cast from the lead-free-cutting brass alloys of the present invention are all verified to be leak-free by pressure testing at 900psi or greater, preferably 1150psi or greater, and more preferably 1500psi or greater.

In summary, the present invention differs from other conventional copper alloy features in terms of alloy element control microstructure, machinability, reflow castability, mechanical properties, dezincification corrosion resistance, weldability, and casting gas tightness, and although the above embodiments only disclose valve components for fluid transport but are not limited to other extended applications, the scope of the claims of the present invention shall be determined by the claims and not limited to the above embodiments.

Claims

1. A lead-free-cutting brass alloy comprising

Copper: from 65 to 75% by weight of a water-soluble polymer,

zinc: from 22.5 to 32.5% by weight,

silicon: 1.0 to 1.35% by weight,

at least one element selected from the group consisting of 0.01 to 0.8 wt% nickel and 0.01 to 0.55 wt% antimony, and

unavoidable impurities;

wherein the total content of copper and zinc in the brass alloy is 97.5 wt% or more, and the gamma phase of the brass alloy is in a granular state and is uniformly dispersed between the alpha phase and the beta phase.

2. A brass alloy in accordance with claim 1, wherein the copper content is from 68.369% to 75% by weight.

3. A brass alloy as claimed in claim 1, in which the sum of the copper and zinc contents is in the range 97.5 to 98.5% by weight.

4. A brass alloy in any of claims 1-3, wherein the silicon content is from 1.1 to 1.35 percent by weight.

5. A brass alloy in any of claims 1-3, comprising a copper-silicon-antimony compound distributed in a solid solution of α -Cu.

6. A brass alloy in accordance with any of claims 1-3, further comprising 0.01 to 0.55 wt.% manganese.

7. A brass alloy in accordance with any of claims 1-3, further comprising 0.001 to 0.1 wt% boron.

8. A brass alloy in accordance with any of claims 1-3, further comprising 0.01 to 1.0% by weight aluminum.

9. A brass alloy in accordance with any of claims 1-3, further comprising 0.01 to 0.55 wt.% tin.

10. A brass alloy in accordance with claim 8, further comprising 0.01 to 0.55% by weight tin.

11. A casting method using the molten soup of a brass alloy according to any one of claims 1 to 10, in a wet sand mold, a furan sand mold, or a metal mold to form a casting.

12. The casting method according to claim 11, wherein the casting is performed at a casting temperature of 1000 to 1050 ℃.

13. The casting method according to claim 11 or 12, wherein the casting is further cut by a machining tool to produce a work piece and machining chips thereof.

14. Casting method according to claim 13, wherein the molten soup of a brass alloy further comprises a melt-back of the work piece or its processing chips produced by the method according to claim 13.

15. A lead-free brass alloy cast article comprising a brass alloy according to any of claims 1 to 10.

16. The lead-free brass alloy cast product of claim 15, comprising a valve element, a piping component, or a filter.

17. The lead-free brass alloy cast article of claim 15, comprising a ball valve, gate valve, check valve, non-lift gate valve, butterfly valve, or Y-filter.

18. The lead-free brass alloy cast article in accordance with any one of claims 15 to 17, which does not produce leakage at a pressure of 900psi or more.

19. The lead-free brass alloy cast product according to any one of claims 15 to 17, which has a tensile strength of 280MPa or more.

20. The lead-free brass alloy cast product according to any one of claims 15 to 17, which has an elongation at break of 8% or more.