TWI387656B - Preparation of Low Lead Brass Alloy and Its - Google Patents

Description

Low-lead brass alloy and its preparation method

The present invention relates to a method for producing an environmentally-friendly cast brass alloy and articles thereof. In particular, the present invention relates to a method for producing a low-lead brass alloy and articles thereof.

The main components of brass are copper and zinc, which are usually about 7:3 or 6:4, and usually contain small amounts of impurities. In order to improve the properties of brass, conventional brass is lead-containing (up to 1-3% by weight) to achieve the desired mechanical properties of the industry, and thus has become an important industrial material, which is widely used in pipelines, faucets, water supply/drainage systems. Products such as metal devices or metal valves.

However, with the rise of environmental awareness, the impact of heavy metals on human health and the problem of environmental pollution are gradually being taken seriously. Therefore, limiting the use of lead-containing alloys is the current trend, and countries such as Japan and the United States have successively revised relevant regulations to promote Reducing the lead content in the environment, including lead-containing alloy materials used in household appliances, automobiles, and water peripheral products, in particular, it is not allowed to dissolve lead to drinking water from the product, and lead pollution must be avoided in the processing. Therefore, the industry is eager to develop lead-free brass materials, looking for alloy formulations that can replace lead-containing brass, but still have to take into account casting properties, machinability, corrosion resistance, and mechanical properties.

A number of lead-free copper alloy formulations have been reported, such as bismuth (Si) as a major component, instead of lead, which is added to brass alloys, such as TW421674, US7354489, US20070062615, US20060078458, US2004023441, etc. A disadvantage of these prior art techniques is poor machinability. In addition, lead-free copper alloy formulations such as CN10144045 disclose aluminum, bismuth and phosphorus as main alloying elements. Although they can be used for casting, they have poor machinability and processing efficiency is much lower than that of lead brass, which is not suitable for mass production; CN101285138 and CN101285137 disclose Phosphorus is the main alloying element, but it is prone to cracks and slag inclusions when it is used for casting.

Or, there is also a literature in which bismuth (Bi) is used as a main component instead of lead added to a brass alloy, for example, US Pat. No. 7,729,215, US Pat. No. 6,974,509, US Pat. No. 6,955,378, US Pat. No. 6,149,739, US Pat. No. 5, 092, 056, US Pat. No. 5, 565, 827, US Pat. No. 5, 487, 867, US Pat. The cerium content of the alloy formulation covers a range of from about 0.5% by weight to about 7% by weight, and each has a different elemental composition and a specific ratio in addition to cerium. Moreover, US6413330 discloses a lead-free copper alloy formulation containing bismuth, antimony and other components, and CN101440444 also discloses a high-zinc antimony-free brass alloy. However, due to its high strontium content, the copper content is low, and the alloy melt flow Poor performance, it is more difficult to refill the cavity in the metal mold, and it is easy to produce casting defects such as insufficient pouring. CN101403056 discloses a lead-free brass alloy in which lead and manganese are replaced by lead. However, the high bismuth content is liable to cause defects such as cracks and slag inclusions, while the low Mn is high in hardness, is not easy to be broken, and has poor machinability.

Because of the scarce resources and high price of bismuth, replacing lead with a higher amount of lead will cause the manufacturing cost of lead-free brass to be too high, which is not conducive to commercialization. Moreover, the above brass alloy formulations still have poor casting properties and material embrittlement cannot be effectively improved.

In addition, there are also literatures on the improvement of lead-free copper alloy processes or lead-washing processes. For example, US 5,904,783 discloses the treatment of brass alloys at high temperatures with sodium and potassium metals to reduce lead filtration to the feed solution; TW491897 reveals 1 - 2.6% by weight of the brass alloy; however, the conventional lead-washing process can only reduce lead precipitation on the surface of the water contact when the lead-containing product is immersed in water, and can not reduce the lead content in the raw material component to 0.3 wt% or less.

In view of this, the object of the present invention is to develop a low-lead brass alloy material and to improve the process.

To achieve the above and other objects, the present invention provides a low lead environmentally friendly brass alloy comprising: 0.05 to 0.3% by weight (wt%) of lead (Pb); 0.3 to 0.8% by weight of aluminum (Al); 0.01 to 0.4% by weight of bismuth (Bi); 0.1 to 0.15% by weight of trace elements; and more than 97.5% by weight of copper (Cu) and zinc (Zn), wherein the content of copper in the low-lead brass alloy is 58 Up to 70% by weight.

In one aspect, the total content of copper and zinc contained in the low-lead brass alloy of the present invention is from 97.5 to 99.54% by weight, preferably 98% by weight or more. In one aspect, the copper content is from 58 to 70% by weight based on the total weight of the low-lead brass alloy. The copper in this range provides good toughness of the alloy and good processability. In a preferred embodiment, the copper content is preferably from 62 to 65 wt%.

In the low-lead brass alloy of the present invention, the lead content is 0.05 to 0.3% by weight. In a preferred embodiment, the lead content is from 0.1 to 0.25 wt%, more preferably from 0.15 to 0.25%.

In the low-lead brass alloy of the present invention, the aluminum content is from 0.3 to 0.8% by weight. In a preferred embodiment, the aluminum content is from 0.4 to 0.7% by weight, more preferably from 0.5 to 0.65% by weight. Adding an appropriate amount of aluminum increases the fluidity of the copper water and improves the casting properties of the alloy material.

In the low-lead brass alloy of the present invention, the content of the cerium is 0.4% by weight or less. In a preferred embodiment, the cerium content is from 0.01 to 0.4% by weight, preferably from 0.05 to 0.3% by weight, more preferably from 0.1 to 0.2% by weight.

0.1-0.15 wt% of the trace element contained in the low-lead brass alloy of the present invention may be a rare earth element and/or an unavoidable impurity, wherein the rare earth element includes lanthanum, cerium, lanthanum, lanthanoid, and the like. The rare earth elements may be used singly or in combination. The addition of an appropriate amount of a rare earth element (for example, cerium (Ce)) can strongly refine the as-cast microstructure of the alloy material, and can change the relative amounts of the α and β phases and the crystal morphology after recrystallization annealing, and It can form particulate impurities with elements such as lead, thereby improving the distribution of impurities in the alloy material and improving the physical properties and processing properties of the alloy. In one aspect, the rare earth element is cerium and its content is from 0.1 to 0.15 wt%.

The low-lead brass alloy of the present invention comprises a phosphorus (P) of 0.8% by weight or less. In a preferred embodiment, the phosphorus content is from 0.4 to 0.8% by weight. Adding an appropriate amount of phosphorus can improve the fluidity of the melt and improve the welding performance of copper and alloy. Phosphorus has a large solid solubility in copper, and the surface energy of CuP is low, so that the surface tension of copper can be lowered, and the ruthenium is precipitated in the form of particles.

In the present invention, Bi is substituted for Bi in order to maintain the machinability of brass. The Pb phase is a face-centered cubic lattice with a lattice constant of 4.949×10 ^-10 m. The solid solubility of Pb in Cu is extremely small. Therefore, Pb is often present as a simple phase in Cu alloy. The Bi phase is a rhombohedral lattice with a lattice constant of 4.7457×10 ^-10 m and an angle between the crystal axes a=57°14.2'. Cu is substantially immiscible in the solid state, so a small amount of Bi will be in the structure. A separate Bi phase appears. Bi is often a continuous brittle film distributed on the grain boundaries of brass, which produces both hot brittleness and cold brittleness. Bi is the mechanism of segregation in the grain boundary, as shown in Figure 8.

The mechanism that causes Bi to segregate at the grain boundary is explained by two mathematical models. The 8A map is explained by the McLean model and the Hofmann-Ertewein Model. Figure 8A is a model of volumetric diffusion. The principle is that Bi atoms diffuse from the bulk to the grain boundary, which is the general cognitive Fick's Law; the 8B map can be dislocated-pipe diffusion. Model) to explain its mechanism, the principle is that the liquid Bi first flows into the difference row, and the difference is like the conveying tube sends the liquid Bi into the grain boundary, which is a diffusion mechanism. These two diffusion mechanisms, the latter diffusion rate is 105 times that of the former. When Bi precipitation is dominated by the differential diffusion mechanism, this mechanism leads to the (Cu) solid solution + L (liquid Bi) two-phase region, resulting in the so-called film-like Bi generation, and the brittleness of the material is greatly improved. In order to improve the situation, when the temperature drops below 750 ° C, the accelerated diffusion is used to make the difference between the two-phase regions disappear, and Bi does not segregate to the grain boundary, which will avoid the occurrence of brittle cracking of the material.

In the present invention, the surface tension of the brass alloy is reduced by further adding a phosphorus element to the brass alloy formulation. The ratio of the surface tension between the opposite phases of the brass alloy to the surface tension between the in-phase angles is close to 0.5, and if the dihedral angle is greater than 60 degrees, the Bi in the brass alloy formulation is formed. Granular Bi precipitates. Thereby, the machinability of the alloy material is improved, and casting defects are not generated.

In one aspect, the low-lead brass alloy of the present invention comprises: 0.05 to 0.3% by weight of lead; 0.3 to 0.8% by weight of aluminum; 0.01 to 0.4% by weight of bismuth; and 0.1 to 0.15% by weight of trace elements ( That is, a rare earth element and/or an unavoidable impurity); 0.8% by weight or less of phosphorus; and 98 to 99.54% by weight of copper and zinc, wherein the copper is contained in the low-lead brass alloy in an amount of 58 to 70% by weight. %.

In one aspect, the low-lead brass alloy of the present invention comprises 62-65 wt% copper, 0.05-0.25 wt% lead, 0.5-0.75 wt% aluminum, 0.2-0.3 wt% bismuth, 0.8 wt%. The following phosphorus (and the total content of aluminum and phosphorus is 1.4 wt% or less), 0.1-0.15 wt% of rhodium and the balance zinc, and the unavoidable impurity content is 0.1 wt% or less.

In accordance with the purpose of the present invention, the present invention provides a method of manufacturing a low lead brass alloy article comprising the following steps:

(a) preheating the low-lead brass alloy and the reheating material to 400 ° C to 500 ° C;

(b) melting the low-lead brass alloy and the recycled material to boiling to form a molten copper liquid;

(c) after preheating the mold to 200 ° C, placing the sand core in the mold;

(d) casting the molten copper liquid into the mold, wherein the casting temperature is between 1010 and 1060 ° C;

(e) demolding the resulting casting.

The method of the present invention may further comprise the step of preparing the sand core, which is one or more round sands and resins selected from the group consisting of round sands having a particle diameter of 40 to 70 mesh, 50 to 100 mesh, and 70 to 140 mesh. And the curing agent is mixed to prepare a sand core, wherein the resin is a urea resin and/or a furan resin. The sand core used in the method of the present invention must be sufficiently dried to reduce porosity defects.

In one aspect, the recycled material is subjected to sand washing before preheating to remove sand and iron wire.

In one aspect, the weight ratio of the lead-free copper ingot and the recycled material in the step (b) of the present invention is from 6:1 to 9:1, and preferably the weight ratio of the lead-free copper ingot to the recycled material is from 6:1 to 8: 1, better at 7:1.

The step (b) of the present invention may further comprise adding a refining slag agent, wherein the refining slag agent is preheated to above 400 ° C before being added. In one embodiment, the refining slag agent is added in an amount of 0.1 to 0.5% by weight, preferably 0.15 to 0.3% by weight, more preferably 0.2% by weight, based on the total weight of the lead-free copper ingot and the recycled material. In the step (b), the refining slag agent may be added once or in portions.

In the step (d) of the present invention, the casting of the molten copper liquid may be gravity casting. The casting temperature for step (d) needs to be maintained at 1010-1060 °C. For the casting step, the casting is carried out in batches, and the casting amount of the casting is about 1 to 2 kg each time, and the casting time is 3 to 8 seconds.

In the method of the present invention, the demolding is carried out 10 to 15 seconds after the completion of the casting, or the casting is not in a red hot state. In the preferred embodiment, the casting that completes the demolding is cooled by natural cooling.

The method of the present invention may be further included in the step (e), cooling the mold to maintain the temperature of the mold between 180 and 220 ° C; and cleaning the mold (for example, blowing the mold surface with compressed air), a little graphite water Spray on the surface of the mold (for example, spray with a sprayer) for the next casting.

In one aspect, the mold is cooled with graphite water by immersing the mold in the graphite water for 3 to 8 seconds. The temperature of the graphite water is preferably maintained between 25 and 40 ° C, and the specific gravity of the graphite water is between 1.02 and 1.10.

The embodiments of the present invention are described by way of specific examples, and those skilled in the art can understand the advantages and advantages of the present invention as disclosed in the present disclosure.

In the present specification, unless otherwise stated, the components contained in the low-lead brass alloy are based on the total weight of the alloy and are expressed in weight percent (wt%).

The inventors of the present invention have found that when a high content of cerium (1 wt% or more) is added to a brass alloy, microscopically, a liquid film of bismuth is easily formed in the crystal grains of the brass alloy, and finally segregated at the grain boundary to produce The continuous sheet-like enamel obscures the grain boundary, causing the mechanical strength of the alloy to collapse, which increases the hot brittleness and cold brittleness of the alloy, causing cracking of the material. However, according to the low-lead brass alloy formulation of the present invention, only 0.4% by weight or less of bismuth is required, which not only solves the defects of material cracking but also can reach the material of lead brass (such as the conventional H59 lead brass). Characteristics (such as machinability, etc.), and are not susceptible to product defects such as cracks or inclusions. Therefore, the low-lead brass alloy of the present invention can greatly reduce the amount of bismuth, and effectively reduce the production cost of the low-lead brass alloy, and has great advantages for commercial mass production and application.

In addition, the low lead brass alloy formulation according to the present invention can reduce the lead content of the alloy to 0.05-0.3 wt%, in accordance with international regulations for lead content in pipeline materials in contact with water. Therefore, the low-lead brass alloy according to the present invention is advantageous for the manufacture of faucets and sanitary components, water pipes, water supply systems and the like.

In an embodiment, the low-lead brass alloy of the present invention comprises: 0.05 to 0.3% by weight of lead; 0.3 to 0.8% by weight of aluminum; 0.01 to 0.4% by weight of bismuth; 0.1 to 0.15% by weight of trace elements (ie, a rare earth element and/or an unavoidable impurity) a rare earth element and an unavoidable impurity; and 97.5 to 99.54% by weight of copper and zinc, wherein the copper is contained in the low-lead brass alloy in an amount of 58 to 70% by weight.

Hereinafter, the present invention will be described in detail by way of illustrative embodiments.

Example 1:

In the preferred embodiment 1, the composition (in weight percent) of the low-lead brass alloy of the present invention is as follows:

Cu: 62.51

Zn: 35.72

Pb: 0.177

Bi: 0.154

Al: 0.478

P: 0.52

Sn: 0.183

Ce: 0.114

Scanning electron microscopy (SEM) and X-ray energy dispersive spectrometer (EDS) were used to analyze the morphology, composition and formation mechanism of the environmentally-friendly cast brass test piece. Figure 1, Figure 2 and Table 1. In the electric map of Fig. 2, point A is α phase, copper content is high, and there is a small amount of ruthenium inside the grain; point B is β phase, zinc content is high, generally does not contain bismuth; and point C is At the grain boundary, there are more defects deposited here, which form a soft point that is easy to break and can improve the cutting performance of the material. The composition analysis of points A, B, and C of the low-lead lead-free brass test piece is shown in Table 1.

Test Example 1:

Under the same process and the same operating conditions, the low lead brass alloy of the present invention (Example 2-4), bismuth-free lead brass (Comparative Example 1-4), and H59 lead brass (Comparative Example 5-6) And high-phosphorus lead brass (Comparative Example 7) is the material, the same product is cast, and the processing characteristics of each alloy and the process yield of each stage are compared. The process yield is defined as follows:

Production yield = number of good products / total number of products x 100%

The production yield of the process reflects the quality stability of the production process, and the higher the quality stability, the normal production can be guaranteed.

It can be seen from Table 2 that when the product is cast with lead-free tantalum brass as a material, the resulting product has many casting defects, so the total production yield of the product is less than 70%, and the higher the niobium content, the lower the yield. The main defects of the castings which are made of completely lead-free bismuth brass are: pores, slag inclusions, cracks, insufficient filling, shrinkage, and defective products with such defects account for 72% of all defective products. Specifically, the molten copper of the lead-free bismuth brass has poor fluidity, and the filling property of the mold is poor, and the casting is prone to underfilling; the casting is prone to cracking, and some microcracks can be found until the final polishing stage; The phenomenon of slag inclusion and pores occurs; and the lead-free bismuth brass has poor machinability, and is prone to problems such as vibrating knives and sticking knives, resulting in low yield of subsequent machining.

According to the low-lead brass of the present invention, the yield is the best (up to 90%), and the material fluidity is close to the conventional H59 lead brass. After the casting process is optimized, when the casting is solidified. The formation of equiaxed dendritic crystal structure with low brittle fracture sensitivity, while ensuring machinability, is not easy to produce cracks and other defects, so that the material can fully meet the needs of production. Among them, since the high content of phosphorus easily causes casting defects in the brass alloy and lowers the yield, the phosphorus content of the low-lead brass of the present invention should not exceed 0.8%. In addition, the corrosion resistance of the low-lead brass of the present invention was also significantly improved as compared with the high-grade lead-free copper of Comparative Examples 1 and 2.

Test Example 2:

The test piece of the brass material was examined under an optical metallographic microscope for the tissue distribution of the material, and the result of magnification was 100 times as shown in Fig. 3.

The composition of the low lead brass of Example 1 was found to be Cu: 63.35 wt%, Al: 0.515 wt%, Pb: 0.182 wt%, Bi: 0.117 wt%, and P: 0.435 wt%. Its tissue distribution, as shown in Figure 3A, will form an equiaxed dendritic phase structure. Because the grains are dendritic, the material will be easier to break and provide good machinability; and it has low brittle fracture sensitivity. Therefore, defects such as cracks are less likely to occur.

3B is the tissue distribution of Comparative Example 1, and the main components of the lead-free brass are: Cu: 62.48 wt%, Al: 0.513 wt%, Pb: 0.0075 wt%, Bi: 0.762 wt%, P: 0.0024 wt%. . When the content of strontium is high, the heterogeneous nucleation sites are many and the nucleation rate is fast, while the α phase composition is too cold, and the formed crystal grains are mostly in the shape of a branch arm and are rarely in a block shape. Therefore, the niobium segregates at the grain boundary to produce a continuous sheet-like flaw, which causes the mechanical strength of the material to be broken, the hot brittleness and the cold brittleness to be improved, and the material is easily cracked.

The 3C figure is the tissue distribution of Comparative Example 6, and the measured values of the main components of H59 lead brass are: Cu: 61.1 wt%, Al: 0.589 wt%, Pb: 1.54 wt%, Bi: 0.0089% wt%, P: 0.0002 Wt%. The alloy α phase has a round granular shape, has good toughness, and is less prone to cracks and the like.

Among them, the sorghum lead-free brass test piece of Comparative Example 1 naturally cracked after casting, and the cracking of the test piece was as shown in Fig. 4A, and the observation under the stereo microscope was as shown in Fig. 4B, and the bismuth content was compared. The higher ones tend to produce larger cracks along the grain boundary direction and lower the mechanical strength.

Test Example 3:

Dezincification tests were carried out using the brass alloys of Example 3 and Comparative Example 4 to detect the corrosion resistance of brass. The dezincification test is carried out in accordance with the Australian AS2345-2006 "copper alloy anti-dezincification" standard. Before the corrosion test, the phenolic wax was used to mount ‧ so that the exposed area was 100 mm ² . All the test pieces were ground and smoothed by 600# metallographic sandpaper, and washed and dried with distilled water. The test solution was a 1% CuCl ₂ solution, and the test temperature was 75 ± 2 °C. The test piece and the CuCl ₂ solution were placed in a constant temperature water bath for 24±0.5 hours, and then taken out and cut longitudinally. After the cross section of the test piece was polished, the corrosion depth was measured and observed by a digital metallographic electron microscope. The result was as shown in the fifth. The figure shows.

The average dezincification depth of the low bismuth-free brass (Bi: 0.147%) of Comparative Example 4 was 324.08 mm, as shown in Fig. 5A. The low lead brass of the present invention (Bi: 0.149%) has an average dezincification depth of 125.36 mm as shown in Fig. 5B. The above results confirmed that the low lead brass of the present invention is more resistant to dezincification corrosion.

Test Example 4:

The mechanical properties of the brass alloy were tested in accordance with ISO 6998-1998 "Standard tensile test of metallic materials at room temperature". The results are shown in Table 3 below:

As can be seen from Table 3, the tensile strength and elongation of the low-lead brass alloy of the present invention are comparable to those of H59 lead brass, indicating that the low-lead brass alloy of the present invention has mechanical properties equivalent to that of H59 lead brass and can indeed be substituted. H59 lead brass is used in the manufacture of products.

Test Example 5:

According to the NSF 61-2007a SPAC single product metal allowable precipitation standard test, the test results of the metal precipitation of the brass alloy in the environment in contact with water are shown in Table 4 below:

As shown in Table 4, the precipitation amount of each metal of the low-lead brass of the present invention is lower than the upper limit standard value, and meets the requirements of NSF 61-2007a SPAC. Moreover, the precipitation of heavy lead in the low-lead brass of the present invention is significantly lower than that of the H59 lead brass, and is also lower than that of the lead-treated H59 lead brass, which is more environmentally friendly and beneficial to human health.

Test Example 6:

Machinability tests were carried out on a lathe with the low lead brass of Example 1, the lead-free brass of Comparative Example 1, and the H59 lead brass of Comparative Example 5, respectively. The machinability test conditions were set such that the feed amount was 2 mm, the number of revolutions was 950 rpm, and the feed amount was 0.21 mm/rev. The results are shown in Fig. 6 and Table 5. .

In the machinability test, the cutting resistance in the axial (Ff), radial (Fp), and normal (Fc) directions is the largest in the lead-free brass, while the low-lead brass of the present invention and the conventional H59 lead Brass is closer. The cutting energy is also the largest with lead-free brass, while the low-lead brass of the present invention is relatively close to the conventional H59 lead brass.

In addition, as can be seen from Fig. 6, H59 lead brass is dispersed in the form of soft dots on the brass base, so that the chips are broken or granulated, and the machinability is good (Fig. 6B); Low-lead brass chips (Fig. 6C) are similar to H59 lead brass chips; while 铋 lead-free brass (Fig. 6A) chips are flaky and have poor machinability.

It can be confirmed from the above test cases that the machinability of the lead-free brass material is inferior to that of the conventional H59 lead brass, and it is easy to cause problems such as vibrating knives and sticking knives, resulting in low yield of subsequent machining, and is not suitable as a substitute for lead yellow. Copper alloy. When the product is made of lead-free brass material, the casting is prone to slag inclusion, pores and cracks, and the crack is often found until the polishing stage, and the production cost is high, so it is not suitable for industrial application.

The low-lead brass alloy of the present invention has mechanical properties (such as machinability) comparable to those of H59 lead brass, and is even better than the conventional H59 lead brass (for example, tensile strength and depth); The rate and the mechanical processing yield are also good; and the low-lead brass alloy of the present invention greatly reduces the amount of lead precipitation, and is highly suitable as an alloy material for replacing the conventional lead brass.

Test Example 7:

The process for preparing a faucet from the environmentally-friendly cast brass of the present invention is shown in Fig. 7.

Firstly, 40-70 mesh, 50-100 mesh and 70-140 mesh round sand, urine aldehyde resin, furan resin and curing agent are used as raw materials to prepare sand cores by core shooting machine, and the gas generating capacity of the resin is measured by a gas generating tester. . The obtained sand core must be used within 5 hours, otherwise it needs to be dried in an oven.

The low-lead brass alloy and the reheating material of the present invention are preheated for 15 minutes to make the temperature reach 400 ° C or higher, and then the two are smelted in an induction furnace at a weight ratio of 7:1 until the brass alloy reaches a certain level. The molten state (hereinafter referred to as melting copper solution), analysis and sampling of the copper alloy test block, and component analysis using a direct reading spectroscopy instrument, confirming that the chemical composition of the copper alloy meets the requirements, using a metal gravity casting machine with a sand core and recasting The mold is cast and controlled by a temperature monitoring system to maintain the casting temperature between 1010-1060 °C.

In the casting process, in order to avoid excessive temperature change, the amount of feed is 1-2kg per feed, and the casting time is controlled within 3-8 seconds, thus reducing casting defects. After each feeding, clean the surface of the molten copper and the pouring spoon, visually inspect the surface of the molten copper to avoid excessive impurities floating, and check the pouring spoon to avoid excessive oxide adhesion. If the casting is a steel mold, the slag cleaning operation is performed once after casting the 5-8 mold, and if it is a copper mold casting, the 20 mold is used once.

After each molded part is taken out, the mold is cleaned with an air gun to ensure that the position of the core is clean, and the graphite is sprayed on the surface of the mold and then immersed in water for cooling. The temperature of the graphite water used to cool the mold is preferably maintained at 30-36 ° C, and the graphite water concentration is measured by a hydrometer before each casting to control the specific gravity between 1.05 and 1.06, and the water tank must be cleaned. Impurities to reduce the appearance defects of castings. The graphite water system is centrally cooled by a central cooling system, and the cooling water is distributed to the gravity casting machine water tank through a pipeline, and the mold is immersed in the water tank to achieve a cooling effect.

After the mold is cooled and solidified, the mold is unloaded to clean the pouring riser, the mold temperature is monitored, the mold temperature is controlled at 200-220 ° C and the casting is formed, and then the casting is demolded. The casting was damaged in red hot.

After the molten copper solution in the induction furnace is completely cast, the cooled castings are self-tested and sent to the sand cleaning machine for cleaning. Next, the blank processing (heat treatment of the cast blank (clearing stress annealing) is performed to eliminate the internal stress generated by the casting). The blank is subsequently machined and polished so that the interior of the casting is free of sand, metal shavings or other impurities. The blank is then completely closed and the seal of the casing and the seal of the separator are tested in water. Finally, it is classified into the warehouse through quality inspection analysis and inspection.

Through this process, the lead-free copper gravity casting production is fully considered from the perspective of 6M (Man, Machine, Material, Method, Measurement, Mother Nature), and the production conditions such as temperature and time are strictly regulated, so that the various variation factors are Get effective control. Minimize the adverse conditions of the product.

In summary, the low-lead brass alloy of the invention can improve the casting property of the material, has good toughness, has good machinability, does not cause casting defects, can achieve the material characteristics of the conventional lead brass, and is beneficial to the alloy material. Follow-up process. Moreover, the low-lead brass alloy material of the invention is less prone to defects such as cracks or inclusions, and can greatly reduce the amount of antimony, and effectively reduce the production cost of the low-lead brass alloy, and has great advantages for commercial mass production and application.

In addition, the process and process of the present invention can increase the yield and yield of lead-free brass products.

The above examples are merely illustrative of the preparation method of the low-lead brass alloy of the present invention and its articles, and are not intended to limit the present invention. Modifications and variations of the above-described embodiments can be made by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is set forth in the appended claims.

Figure 1 is a schematic view showing the liquid solidification of the low-lead brass self-melting solution of the present invention;

Figure 2 is a micromorphology of a low-lead brass test piece of the present invention under a scanning electron microscope (SEM) and quantitative analysis of elemental components in a microscopic region by an X-ray spectrometer (EDS).

Figure 3A is a metallographic structure distribution of the low lead brass test piece of the present invention;

Figure 3B shows the metallographic structure of the lead-free brass test piece;

Figure 3C shows the metallographic structure of the H59 lead brass test piece;

Figure 4A shows the cracking of the material of the lead-free brass test piece;

Figure 4B is an enlarged view of the crack of the lead-free brass test piece;

Figure 5A is the metallographic structure of the anti-dezincification test of the lead-free brass test piece;

Figure 5B is a metallographic structure distribution of the anti-dezincification corrosion test of the low lead brass test piece of the present invention;

Figure 6A is a swarf of lead-free brass;

Figure 6B is the chip of H59 lead brass;

Figure 6C is a chip of the low lead brass of the present invention;

Figure 7 is a schematic view showing the process of manufacturing the low lead brass product of the present invention;

Figures 8A and 8B illustrate the mechanism by which the ruthenium in the alloy segregates at the grain boundaries.

Claims (24)

A low-lead brass alloy comprising: 0.05 to 0.3% by weight of lead; 0.3 to 0.8% by weight of aluminum; 0.01 to 0.4% by weight of bismuth; 0.1 to 0.15% by weight of trace elements; and more than 97.5% by weight of copper and Zinc, wherein the copper is present in the low-lead brass alloy in an amount of from 58 to 70% by weight. A low-lead brass alloy according to claim 1, wherein the lead content is from 0.15 to 0.25% by weight. A low-lead brass alloy according to claim 1 wherein the aluminum content is from 0.5 to 0.65% by weight. A low-lead brass alloy according to claim 1, wherein the content of the bismuth is from 0.1 to 0.2% by weight. A low-lead brass alloy according to claim 1, wherein the copper is present in the low-lead brass alloy in an amount of 62 to 65 wt%. For example, the low-lead brass alloy of claim 1 includes a phosphorus content of 0.8% by weight or less. A low-lead brass alloy according to claim 6 wherein the phosphorus content is from 0.4 to 0.8% by weight. For example, the low-lead brass alloy of claim 1 is a rare earth element and/or an unavoidable impurity. A method of manufacturing an article comprising a low-lead brass alloy according to claim 1 of the patent application, comprising the steps of: (a) preheating the low-lead brass alloy and the recycled material to 400 ° C to 500 ° C; (b) The low-lead brass alloy and the recycled material are melted to boiling to form a molten copper liquid; (c) the mold is preheated to 200 ° C, and the sand core is placed in the mold; (d) the molten copper liquid is cast To the mold, wherein the casting temperature is between 1010 and 1060 ° C; and (e) demolding the resulting casting. The method of claim 9, further comprising the step of preparing the sand core, wherein the step of preparing the sand core is selected from the group consisting of round sands of 40 to 70 mesh, 50 to 100 mesh, and 70 to 140 mesh. One or more round sands, resins, and curing agents of the group are mixed. The method of claim 9, wherein the recycled material is subjected to sand washing before preheating to remove sand and iron wire. The method of claim 9, wherein the weight ratio of the low-lead brass alloy to the recycled material is between 6:1 and 9:1. The method of claim 9, wherein the step (b) comprises adding a refining slag. The method of claim 13, wherein the refining slag is preheated to above 400 ° C before being added. The method of claim 13, wherein the refining slag agent is added in an amount of 0.10 to 0.15% of the total weight of the low-lead brass alloy and the recycled material. The method of claim 9, wherein the casting step is performed for 3 to 8 seconds. The method of claim 9, wherein the casting step is carried out in batches, and the casting amount of the casting is about 1 to 2 kg each time. The method of claim 9, wherein the demolding step is performed 10 to 15 seconds after the casting is completed or the casting is not in a red hot state. For example, in the method of claim 9, after the step (e), a cooling step is performed to cool the mold so that the temperature of the mold is maintained between 180 and 220 °C. The method of claim 19, wherein the cooling step cools the mold with graphite water. The method of claim 20, wherein the mold is immersed in the graphite water for 3 to 8 seconds. The method of claim 20, wherein the graphite water has a specific gravity of between 1.02 and 1.10. The method of claim 20, wherein the temperature of the graphite water is between 25 and 45 °C. The method of claim 9 is further included in the step (e), after the step of cleaning the mold and spraying the surface of the mold with graphite water.