ES2383492T3 - Phosphorous alloy of lead-free brass, easy machining and manufacturing method - Google Patents

Abstract

A phosphorous brass alloy, free of lead, easily machined, comprising: zinc, in an amount of at least 35% by weight; copper, in an amount such that the total amount of zinc and copper is between 97.0% and 99.5% by weight; 0.4 to 1.6% by weight of P; and other elements in an amount between 0.005 and 0.6% by weight, comprising at least two other elements selected from the group consisting of Al, Si, Sb, Sn, Re, Ti and B; the rest being unavoidable impurities, in which when Pb and Fe are unavoidable impurities, the content of Pb is less than 0.02% by weight, and the content of Fe is less than 0.05% by weight.

Description

Phosphorous alloy of lead-free brass, easy machining and manufacturing method.

Field of the Invention

The present invention relates, in general, to a phosphorous brass alloy, especially a lead-free brass phosphorous alloy, easy to machine, which is applicable in the forging and in the casting of water supply systems .

Background of the invention

It is well known that brass alloys containing lead, such as CuZn40PB1, C36000, C3604 and C3771, typically contain 1.0-3.7%, by weight, of Pb, to ensure excellent cutting capacity.

Brass alloys containing lead are still widely used in the manufacture of many products due to their excellent cutting capacity and low cost. However, the steam produced by the melting and casting process of the brass alloy containing lead, and the dust contaminated with Pb produced in the cutting and rectifying process of the brass alloy containing lead, are harmful to the body Human and the environment. If brass alloys containing lead are used in drinking water facilities such as faucets, valves and sleeves, contamination of drinking water by Pb is inevitable. In addition, toys that are produced by brass alloys that contain Pb are more harmful, since they are frequently touched, thereby increasing the potential exposure to Pb.

Ingestion of lead by humans is harmful, so the use of lead is strictly prohibited by law in many countries because it affects health and the environment. To solve this challenge, metalworkers and manufacturers of copper materials actively research and develop lead-free brass alloys that are easy to machine. Some of them use Si instead of Pb, but the cutting capacity noticeably does not improve and the cost increases due to the high amount of copper. Therefore, brass and silicon alloys are currently not commercially competitive. A type of lead-free brass alloy, easily used, commonly used, is a brass and bismuth alloy, which uses bismuth instead of Pb. Many kinds of brass and bismuth alloys have been developed, with high or low zinc content, and their formal alloy qualities have been registered in the United States. These kinds of brass alloys contain the valuable tin, nickel and selenium, as well as bismuth. Although its cutting capacities are 85% - 97% that of the C36000 brass alloy that contains lead, its costs are much higher than that of the C36000 alloy that contains lead. Therefore, these kinds of brass and bismuth alloys are not competitive in price. Brass and bismuth alloys have also been researched and developed in Japan and China, and applications have been filed at the Patent Offices. Considering that bismuth is expensive, low in reserves, and has a poor ability to work cold and hot, the use of a brass and bismuth alloy instead of a brass alloy that contains lead can be financially problematic. The invention of an easy-machining brass and antimony alloy that uses Sb instead of Pb has been patented in China (ZL200440045836.5). A corresponding application is currently pending in the US. (US2006 / 0289094). Japanese Patent Application published as JP 57044494, describes a brass and phosphorus alloy consisting of 1 ~ 9% by weight of phosphorus, 0.5 ~ 45% by weight of zinc, and the rest is copper. Japanese Patent Application published as JP 09143598 describes a composition of a brass alloy consisting of, in weight ratio, at least 47% of Cu, 15-45% of Zn, 0.3 to less than 3% of Al, and 0.1 to 5% Si.

Detailed description

An object of the present invention is to provide a phosphorous brass alloy that will solve the limitations of the conventional brass alloys discussed above, especially the problem of lead contamination.

An object of the present invention is to provide a phosphorous brass alloy that is excellent in its cutting capacity, casting capacity, hot and cold working capacity, and corrosion resistance, and that is not harmful to the environment. and the human body.

An object of the present invention is to provide an easily machinable lead-free brass phosphorous alloy, which is particularly applicable in the forging and casting of system components for water supply.

An object of the present invention is to provide a manufacturing method for a phosphorous brass alloy.

The objects of the present invention are achieved as follows.

The present invention is intended to provide a phosphorous alloy of lead-free brass, easy machining. Considering that the solubility, in solid state, of P in the copper matrix will decrease rapidly with the decrease in temperature, and will form the brittle intermetallic compounds of Cu3P with Cu, the present invention chooses P as one of the main elements to ensure The excellent cutting capacity of the alloy of the invention and solve the limitations of the conventional brass alloy discussed above, especially the environmental problem. The lead-free, easy-machining brass phosphorous alloy of the present invention comprises: zinc, in an amount of at least 35% by weight; copper, in an amount such that the total amount of zinc and copper is between 97.0% and 99.5% by weight; 0.4 to 1.6% by weight of P; and other elements in an amount between 0.005 and 0.6% by weight, comprising at least two other elements selected from the group consisting of Al, Si, Sb, Sn, Re, Ti and B; the rest being unavoidable impurities, in which when Pb and Fe are unavoidable impurities, the content of Pb is less than 0.02% by weight, and the content of Fe is less than 0.05% by weight.

The present invention is intended to provide a lead-free, easy-machining brass and phosphorus alloy, in which the P content is preferably ranging between 0.5 and 1.35% by weight, more preferably between 0.5 and 0.9% by weight, and most preferably between 0.5 and 0.8% by weight. The other said elements are preferably selected from Al, Si, Sb, Ti and B.

The lead-free, easy-machining brass-phosphorus alloy phase compositions mainly include alpha and beta phase, and a small amount of intermetallic compounds, Cu3P.

P is one of the main elements of the alloy of the invention. The beneficial effects of P include: ensuring the cutting capacity of the alloy of the invention by breaking the intermetallic, Cu3P, brittle compounds, which are formed by the elements P and Cu; improve the casting capacity and weldability of the alloys of the invention as deoxidants; and improve the corrosion resistance by desincado of the alloy of the invention. The negative effects of P include: decreasing the plasticity, at room temperature, of the alloy of the invention; If the intermetallic compounds, Cu3P, are dispersed in the crystalline grain limit, the negative influence on the plasticity will be greater.

The elements Re, Ti, and B, in the alloy, have effects on the deoxidation and refining of the grains. Re can still form intermetallic compounds with other elements, disperse the intermetallic compounds inside the crystalline grain and reduce the amount of the degree of aggregation of the intermetallic compounds, Cu3P, at the limit of the crystalline grain. The preferred content of Re, Ti and B is less than 0.02% by weight.

The elements Al and Si, in the alloy, have the effects of deoxidation, the reinforcement of the solid solution and the improvement of corrosion resistance. However, if the content of Al and Si is higher, the casting capacity will decrease due to the increase in the amount of oxidizing slag. Higher Si contents will also form a hard and brittle phase Ŭ, which will decrease the plasticity of the alloy of the invention. Therefore, the content of Al and Si is preferably ranging from 0.1 to 0.5% by weight. A small amount of Sn is added mainly to improve the corrosion resistance by desincado. The Sb can also improve the corrosion resistance by desincado, like the Sn, and in addition it is beneficial for the capacity of cutting.

Alloy features of the invention include: (a) the compositions of the alloy phases of the invention mainly include alpha phase, beta phase and intermetallic compounds, Cu3P; (b) P is one of the main elements to ensure the cutting capacity of the alloy of the invention; (c) Sb is complementary to the cutting capacity of the alloy of the invention through a small amount of brittle intermetallic compounds, Cu-Sb; and (d) multi-component alloy and grain refining tend to uniformly disperse intermetallic compounds inside and within the boundaries of crystalline grains, and improve the plasticity of the alloy.

The cost of the necessary metal materials of the alloy of the invention is lower than that of the brass and antimony alloy and that of the brass and bismuth alloy, free of lead and easy machining, and is equivalent to that of the alloy of brass containing lead, as a result of the selection of alloying elements, and the design of element content.

The alloy manufacturing process of the invention is as follows: when the alloy melt reaches a temperature of 980 to 1000 degrees Celsius, the melt is poured into ingot molds to form ingots for further treatment.

Optionally, the raw materials used in the alloy according to the invention include: electrolytic Cu, electrolytic Zn, brass scrap, Cu-P master alloy, Cu-Si master alloy, Cu-Ti master alloy, Cu- master alloy B and, optionally, pure Sb, Sn, Al and Re. The raw materials are combined in an electric induction furnace, of intermediate frequency, in which the vacuum has not been made, which has a quartz sand oven coating, in the following order:

First, electrolytic Cu, brass scrap, and a coating agent that increases the efficiency of slag removal are added to the furnace. These materials are heated until they melt. Then the Cu-Si master alloy, the Cu-Ti master alloy, and the Cu-B master alloy are added. After that, SB, Sn, Al and Re pure are optionally added. These materials are heated again until they melt, after that it is stirred. Then the electrolytic Zn is added. The molten mass is stirred, and the slag is separated by dragging the molten mass. The master alloy of Cu-P is then added, and the melt is further stirred. When the melt reaches a temperature of 980 to 1000 degrees Celsius, it is poured into ingot molds.

Alloy ingots can be treated in different ways according to the method of the invention. First, the ingot can be extruded at a temperature ranging from 550 to 700 degrees Celsius, for approximately 1 hour, with an elongation coefficient of more than 30 to be transformed, for example, into a bar. Second, the ingot can be forged at a temperature ranging from 570 to 680 degrees Celsius, so that it is transformed, for example, into a body of a valve, or to manufacture other system components for water supply. Third, the ingot can be re-melted and cast at a temperature ranging between 980 and 1010 degrees Celsius, at a pressure of 0.3 to 0.5 MPa, for example, to make taps.

Fusion is carried out in the atmosphere when it is protected with the coating agent. The laundry is carried out at a temperature that ranges between 980 and 1000 degrees Celsius. The ingot is extruded at a temperature that ranges between 550 and 700 degrees Celsius, with an elongation coefficient of more than 30, and is forged at a temperature that ranges between 570 and 710 degrees Celsius, or it is melted again to strain it at temperature ranging between 990 and 1010 degrees Celsius, by die casting at low pressure.

The advantages of this manufacturing process include the following. Casting ingots (instead of extrusion bars) are used directly for hot forging, and can thus reduce manufacturing costs. The new ingot fusion is favorable to control the addition of the content when a low pressure die casting is done. Extrusion with a higher elongation coefficient could further refine grain and intermetallic compounds such as Cu3P, and evenly disperse intermetallic compounds and, therefore, decrease the negative effect on plasticity.

The lead-free, easy-machining brass and phosphorus alloy of the invention uses P instead of Pb and has been improved in terms of cutting capacity, weldability and corrosion resistance. In addition, by means of the multicomponent alloy, the grain refining, the great degree of deformation, and the heat treatment, the intermetallic compounds, Cu3P, in granular form, are dispersed inside and at the limits of the crystalline grain, thereby improving Working capacity and mechanical properties of the alloy of the invention. The alloy of the invention is applicable in spare parts, forgings and castings that require cutting, and in particular in forgings and castings for a water supply system that require cutting, grinding (polishing), welding and electroplating. The ingot (Ԅ 37 mm, h 60 mm) can be forged at different temperatures ranging between 570 and 700 degrees Celsius, in valves with complex structures for water supply systems. The production yield by forging disposable molds is 98.6%. The results of the mold forging investigations indicate that the alloy of the invention has an excellent hot working capacity.

Brief description of the drawings

To understand the present invention, it will now be described, by way of example, in reference to the accompanying drawings in which:

Figure 1 shows the shapes of the cutting chips formed in Examples 1, 2, and 3.

Figure 2 shows the shapes of the cutting chips formed in Examples 4, 5, 6, 7, and 8.

Figure 3 shows the shapes of the cutting chips formed in Examples 9 and 10.

Figure 4 shows the shapes of the cutting chips formed in the C36000 brass alloy containing lead, for comparison.

Examples

The alloy compositions of Examples 1 to 10 are shown in Table 1. The alloy ingots are for applications that include forging, refusion and die casting at low pressure, and for extrusion to obtain a rod. The cutting capacity, the casting capacity, the corrosion resistance due to desiccation and the mechanical properties have been tested. The forging is done at a temperature of 570 to 700 degrees Celsius. The extrusion is performed at a temperature ranging from 560 to 680 degrees Celsius. Low pressure die casting is performed at a temperature that ranges between 980 and 1000 degrees Celsius. Annealing to relieve internal stresses is performed at a temperature that ranges between 350 and 450 degrees Celsius.

Table 1. Composition (% by weight) of brass and phosphorus alloy, lead free and easy machining

Examples

Cu P Sb Yes To the Sn You B Re Zn

one

60.13 0.42 0.20 0.24 <0.001 - - 0.005 0.003 The rest

2

60.11 0.59 0.10 0.25 <0.001 0.05 0.02 0.0008 - The rest

3

57.51 0.69 0.01 0.04 0.19 0.04 - 0.006 - The rest

4

59.18 0.99 0.01 0.33 0.05 0.05 0.01 0.0006 - The rest

5*

59.31 1.00 0.59 0.28 <0.02 - - 0.006 - The rest

6 *

57.10 0.96 0.54 0.43 0.21 - - 0.007 - The rest

7

57.94 0.92 0.01 0.27 0.16 - 0.01 0.0008 - The rest

8

58.87 0.90 0.11 0.26 0.05 0.03 - 0.004 - The rest

9

60.01 1.35 0.11 0.25 0.23 - - 0.004 0.004 The rest

10

57.53 1.57 0.01 0.28 0.10 0.06 0.001 0.0004 0.002 The rest

* Not part of the alloy of the invention

The lead-free brass and phosphorus alloy of the present invention has been tested with the following results:

5 Test of cutting capacity:

There are several indices and methods for checking the cutting capacity of the alloy. The present invention checks the cutting capacity by measuring the cutting resistance and comparing the shapes of the cutting chips. The samples for the tests are in semi-hard state. The same cutting tool, cutting speed and feed quantity (0.5 mm) are estimated. The relative cutting ratio is calculated by checking the resistance to

10 cut of the C36000 alloy, and that of the alloy of the invention:

The cutting ratio of the C36000 alloy is assumed to be 100%. Figure 4 shows the shapes of the cutting chips formed by cutting the C36000 brass containing lead. Then, the cutting ratio of Examples 1, 2

and 3 is ≥ 80%, by checking the shear strength of the C36000 alloy and Examples 1, 2 and 3 of

The alloy of the invention. Figure 1 shows the shapes of the cutting chips formed in Examples 1, 2 and 3.

The cutting ratio of Examples 4, 5, 6, 7 and 8 is ≥ 85%, by checking the shear strength

of the C36000 alloy and Examples 4, 5, 6, 7 and 8 of the alloy of the invention. Figure 2 shows the ways of

the cutting chips formed in Examples 4, 5, 6, 7 and 8. The cutting ratio of Examples 9 and 10 is ≥ 90%,

by checking the shear strength of the C36000 alloy and Examples 9 and 10 of the alloy of the invention. Figure 3 shows the shapes of the cutting chips formed in Examples 9 and 10.

Corrosion corrosion test:

Taking into account that the brass and phosphorus alloy of the invention is going to be mass produced to be cast by low pressure die casting, the test samples are in the molten state. C36000 alloy samples for testing are annealed to relieve internal stress. The essay of

The corrosion resistance due to de-icing is carried out according to the national standard of PRC GB10119-88. The results of the tests are shown in Table 2.

Table 2. The results show the corrosion resistance due to the removal of brass and phosphorus alloy, lead-free and easy machining.

Examples

one 2 3 4 5* 6 * 7 8 9 10 C36000

Descincado

90 100 120 120 fifty 60 110 120 140 180 610

* Not part of the alloy of the invention

Casting capacity test

Several indices can be used to measure the casting capacity of the alloy. The present invention uses standard samples in volume, cylindrical, strips and spiral contractions to check the pouring capacity of brass and phosphorus alloy, lead free and easy machining. For samples for volume contraction, as can be seen in Table 3, if the face of the cavity that concentrates the contraction is smooth and there is no visible porosity at the bottom of the cavity that concentrates the contraction, it indicates that the casting capacity is excellent and will be shown as “ο” in Table 3. If the face of the cavity that concentrates the contraction is smooth, but the height of the porosity by contraction, visible at the bottom of the cavity that concentrates the contraction, is less than 5 mm, indicates that the casting capacity is good, and will be shown as “∆” in Table 3. If the face of the cavity that concentrates the contraction is not smooth, and the height of the porosity by contraction, visible at the bottom of the cavity that concentrates the contraction, is greater than 5 mm, indicates that the casting capacity is poor, and will be shown as “x” in Table 3. For samples in the form of strips, the linear contraction rate is not greater than 1.5% For cylindrical samples, as can be seen in Table 3, if no visible fissure is shown by contraction, it indicates that the casting capacity is excellent and will be shown as “ο” in Table 3. If the visible fissure is shown by shrinkage indicates that the casting capacity is poor and will be shown as "x" in Table 3. The spiral samples are for measuring the fluidity of the alloy of the invention. The

pouring temperature of each alloy is approximately 1000 degrees Celsius. The results are shown in Table 3. It indicates that the casting capacity of the brass and phosphorus alloy is excellent.

Table 3. The results show the pouring capacity of the brass and phosphorus alloy, lead free and easy machining.

Examples

one 2 3 4 5* 6 * 7 8 9 10 C36000

Samples of volume shrinkage

Ο Ο Ο Ο Ο Ο Ο Ο Ο ∆ Ο

Cylindrical samples

Ο Ο Ο Ο Ο Ο Ο Ο Ο Ο Ο

Melt fluid length / mm

450 460 470 480 470 470 480 505 533 545 460

Linear Contraction Rate (%)

≤ 1.5 1.95 - 2.15

* Not part of the alloy of the invention Mechanical properties test

The samples for the test are in semi-hard state. The specification is a bar 6 mm The test results are shown in Table 4.

Table 4. The results show the mechanical properties of the brass and phosphorus alloy, lead free and easy machining.

Examples

one 2 3 4 5* 6 * 7 8 9 10 C36000

Tensile Strength / MPa

503 510 505 520 540 530 515 520 510 500 485

0.2% elastic limit / Mpa

360 360 350 370 395 385 380 390 385 380 340

Elongation/%

11.4 12.5 12.7 12.1 10.3 10.0 11.0 10.8 9.5 8.9 9

* Not part of the alloy of the invention

Tension corrosion test:

The samples for the test come from extruded bars, castings and forges. The stress corrosion test is carried out according to the national standard of PRC GB / T10567.2-1997, Ammonia Fumigation Test. The results show that no cracks appear on the face of the samples.

Claims (11)

one.

A phosphorous brass alloy, free of lead, easily machined, comprising: zinc, in an amount of at least 35% by weight; copper, in an amount such that the total amount of zinc and copper is between 97.0% and 99.5% by weight; 0.4 to 1.6% by weight of P; and other elements in an amount between 0.005 and 0.6% by weight, comprising at least two other elements selected from the group consisting of Al, Si, Sb, Sn, Re, Ti and B; the rest being unavoidable impurities, in which when Pb and Fe are unavoidable impurities, the content of Pb is less than 0.02% by weight, and the content of Fe is less than 0.05% by weight.

2.

The lead-free, easy-machining brass phosphorous alloy of claim 1, wherein the amount of P is ranging from 0.5 to 1.35% by weight.

3.

The lead-free, easy-machining brass phosphorous alloy of claim 2, wherein the amount of P is ranging from 0.5 to 0.8% by weight.

Four.

The lead-free, easy-machining brass phosphorous alloy of claim 1, wherein the other elements are selected from the group consisting of Al, Si, Sb, Ti or B.

5.

The lead-free, easily machinable brass phosphorous alloy of claim 2, wherein the amount of P is ranging from 0.5 to 0.9% by weight.

6.

The lead-free, easy-machining brass and phosphorus alloy of claim 1, wherein the content of Re, Ti and B is less than 0.02% by weight.

7.

The lead-free, easy-machining brass and phosphorus alloy of claim 1, wherein the content of Al and Si is ranging from 0.1 to 0.5% by weight.

8.

A method of manufacturing the phosphorous brass alloy, free of lead, easily machined, of any one of claims 1 to 7, wherein the melt of said alloy reaches a temperature of 980 to 1000 degrees Celsius, the mass Molten is poured into ingot molds to form ingots for further treatment.

9.

A method of manufacturing the lead-free, easy-machining brass phosphorous alloy of any one of claims 1 to 7, wherein the ingots are extruded at a temperature ranging between 550 and 700 degrees Celsius for about 1 hour, with an elongation coefficient greater than 30.

10.

A method of manufacturing the phosphorous brass alloy, free of lead, easily machined, of any one of claims 1 to 7, wherein the ingots are forged at a temperature ranging between 570 and 680 degrees Celsius.

eleven.

A method of manufacturing the phosphorous, lead-free, easily machinable brass alloy of any one of claims 1 to 7, wherein the ingots are re-melted and cast at a temperature ranging from 980 to 1010 degrees Celsius, at a pressure of 0.3 to 0.5 MPa.