KR20210035141A - Brass fabricated with stainless steel scrap for water supplyuynt and manufacturing method for the same - Google Patents

Abstract

The present invention relates to a brass alloy for drinking water including stainless steel precipitate and a manufacturing method thereof. More specifically, an objective of the present invention is to create an alloy from materials which can make up stainless steel among elements having a monotectic reaction with a brass alloy to selectively precipitate (separate) stainless steel spherically to promote property improvement of brass material and minimize the usage of lead which causes environmental problems. Moreover, economic efficiency was maximized by using scrap material instead of directly using relatively extensive elements making up stainless steel such as Cr and Ni. The brass alloy for drinking water developed through the present invention (1) is manufactured through scrap to have economic efficiency and (2) is eco-friendly by reducing the lead content. Nonetheless, the brass alloy for drinking water (3) has a second phase precipitate microstructure of spheres (separation) of conventional flexible brass to improve machinability. Moreover, (4) properties such as strength and corrosion resistance can also be improved through stainless steel precipitation which is high-strength/corrosion-resistant precipitate. Accordingly, a brass material with multifunctional properties overcoming the disadvantages of conventional flexible brass materials can be provided in a more economic manner.

Description

Brass alloy for drinking water manufactured by recycling stainless steel scrap and its manufacturing method {BRASS FABRICATED WITH STAINLESS STEEL SCRAP FOR WATER SUPPLYUYNT AND MANUFACTURING METHOD FOR THE SAME}

The present invention relates to a drinking water brass (Brass) alloy manufactured using stainless steel scrap (Scrap) and a method of manufacturing the same. In other words, this technology dissolves (1) the parent element (or scrap) constituting the brass and (2) the stainless steel (SUS) scrap at the same time, which will constitute the base composition of the material, thereby depositing stainless steel in the form of a second phase. By doing so, it relates to manufacturing a brass alloy for drinking water having multifunctional characteristics of high strength, high corrosion resistance, high workability and high cutting characteristics. The brass alloy described above has high strength and high corrosion resistance compared to conventional brass by depositing stainless steel in the mouth in the form of a second phase, and is manufactured by replacing the role of lead (Pb) precipitates with stainless steel precipitates to improve the existing processing characteristics and machinability. Therefore, it is environmentally friendly, and since it is manufactured using scrap instead of a high-purity parent element, there is an effect of having high economic efficiency.

Brass is an alloy of copper (Cu) and zinc (Zn), which is aesthetically beautiful, and due to its excellent electrical conductivity and workability, it is possible to implement a precise shape during processing such as extrusion and molding. In addition, since it has relatively high oxidation resistance compared to other alloys, it has been used for power reception and gas piping. In order to use brass as a desired part, one of the most important things is machinability. However, in the case of a pure brass material composed of only Cu and Zn, the ductility is too large, and there is a problem in processing the material into a desired shape. Conventionally, in order to solve such a problem, brass materials were used by alloying together alloying elements such as lead (Pb) and bismuth (Bi), which are alloying elements that easily form precipitates in copper. At this time, the alloyed additive elements precipitated in the grain (inside the grain), not in the grain boundary of the brass, and helped to improve the machinability by inducing the formation of a chip of an appropriate size between cutting operations. In order to form such a complex microstructure, it has a large positive (+) enthalpy of mixing (H _mix ) with (1) Cu, which is the main element of brass, and at the same time (2) has a large difference in melting point, resulting in a biased reaction. However, it must be easily separated from the liquid phase through a trapping reaction. In fact, Pb forms a monotectic reaction by liquid phase separation from brass, and it is known that most lead precipitates are formed inside the crystal grains rather than the grain boundaries because it is separated into a liquid state during solidification to form a final solidified microstructure .

However, as the demand for lead-free brass (Pb-free brass) that does not contain lead increases rapidly due to the increasing international environmental regulations, research and development of alternative materials are active. Therefore, in the present invention, in order to develop a new brass material for drinking water that does not necessarily contain Pb and has multifunctional characteristics of high strength, high corrosion resistance, and high cutting characteristics, a representative corrosion resistant alloy through various thermodynamic considerations through Calphad calculation, a thermodynamic simulation approach. A new alloy has been developed that has a unique complex microstructure between phosphorus brass and stainless steel.

[Document 1] Four others including Yun Eui-han. Brass alloy for unleaded drinking water. Registered Korean patent, KR-100225751B1, 1999-10-15 [Document 2] Park Ki-won and 3 others. Free grinding bronze alloy and its manufacturing method. Registered Korean patent, KR-100555854B1, 2006-03-03

The present invention is to solve the problems of the prior art described above, the parent element constituting the brass (or scrap having the same composition) and (2) the parent element (or scrap having the same composition) of stainless steel (Strainless steel, SUS) ) Simultaneously dissolving and depositing stainless steel in the brass base in the form of a second phase to develop a brass alloy for drinking water with multifunctional characteristics of high strength, high corrosion resistance, high workability, and high cutting characteristics.

Brass for drinking water according to the present invention is composed of a first phase of a matrix of Cu and Zn and a second phase of a stainless steel precipitate. In particular, the stainless steel precipitate at this time may be manufactured by recycling scrap. In addition, such a method for producing a brass alloy for drinking water comprises the steps of preparing a parent element or scrap to constitute a brass base; Preparing a stainless steel parent element or scrap to form a second phase precipitate; And it consists of a step of alloying by melting the prepared parent element or scrap at the same time.

Incidentally, in the "step of preparing a stainless steel parent element or scrap", it is necessary to prepare a stainless steel material that can be easily phase-separated by having a positive (+) mixed heat relationship with Cu constituting the first phase. In addition, in the "step of preparing the parent element or scrap to constitute the brass base", a master alloy or brass scrap material must be prepared in a specific Cu and Zn ratio to constitute the first phase of the brass base. Finally, in the "step of alloying by dissolving the prepared parent element or scrap at the same time", it is important to ensure that the alloying elements are homogeneously dissolved, and when dissolved, a sufficiently high temperature above the melting temperature so as to easily have a liquid phase separation phenomenon. It is important to dissolve in. In addition, even after the alloy is manufactured, a suitable microstructure can be secured through a post-treatment process including extrusion, rolling, and heat treatment processes.

As described above, in the case of the brass material according to the present invention, the precipitates of the stainless steel composition formed on the brass base of the first phase help to improve properties, such as high strength, high corrosion resistance, high processability, and high cutting properties, which were previously difficult to secure. It has the effect of securing the multifunctional characteristics of Incidentally, in the case of brass for drinking water developed through the present invention, (1) it is eco-friendly because it does not contain lead as a major alloying element, and (2) stainless steel precipitates play a role of lubrication for cutting in the mouth, thereby providing excellent workability and In addition to providing machinability, (3) excellent physical properties of high strength/corrosion resistance can be secured by forming a composite structure in which high strength/corrosion resistant precipitates are formed in the existing soft brass material. At the same time, (4) by using scrap, which is more than 10 times cheaper than the parent element, economic efficiency can be secured in the production of products.

1 is a binary state diagram between Cu and Zn.
_{2A and 2B are pseudo-binary phase diagrams between Cu 70} Zn ₃₀ (FCC single-phase material) and Cu ₆₀ Zn ₄₀ (FCC+BCC composite material) and Pb, which are representatively used brass compositions, respectively.
3 to 5 are stainless steel 201 (Comparative Example 1), stainless steel 304 (Comparative Example 5), and stainless steel 430 alloy (Comparative Example 11) and (a) representing 200 series, 300 series, and 400 series stainless steels, respectively. ) Comparative Examples 14 and (b) is a pseudo-binary phase diagram drawn through thermodynamic calculations between representative brass alloys of Comparative Example 15.
6 is a scanning electron microscope (SEM) image of a back scattered electron (BSE) observing the microstructures of (a) Comparative Examples 20 and (b) Example 30 according to the present invention.
7 shows the result of extrusion after casting the material of Example 30 according to the present invention.
8 shows the results of measuring the thickness at different locations as in (b), (c), and (d) by rolling the (a) extruded material of the composition of Example 30 according to the present invention.
9 is a scanning electron microscope image showing (a) a cutting surface of a material of Comparative Example 20 and (b) a cutting surface of the material of Example 30 according to the present invention, and (c) an image showing the shape of a cut sample of the material of Example 30. to be.
10 is a diagram showing the Vickers hardness of (a) Comparative Examples 20 and (b) Examples 30, (c) Examples 34, (d) Examples 31 and (e) Example 35 according to the present invention to be.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art can easily implement the embodiments of the present invention. The present invention may be implemented in various different forms and is not limited to the embodiments described herein. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and the same reference numerals are used for the same or similar components throughout the specification. In addition, in the case of well-known technologies, detailed descriptions thereof will be omitted.

On the other hand, when it is said that a certain part "includes" a certain component throughout the specification, it means that other components may be further included rather than excluding other components unless otherwise stated.

In addition, the "brass alloy" constituting the "first phase" of the material according to the present invention is an alloy of zinc (Zn) with copper (Cu), and constitutes the "alloy matrix" of the entire composite material. Therefore, the above three concepts should be understood as the same, and may be used interchangeably. In the same meaning, the "precipitate" or "post" constituting the "second phase" has a composition of "stainless steel", so the three concepts may also be used interchangeably.

Alloying strategy for classifying brass materials and improving machinability

Brass is a solid solution alloy in which Zn is dissolved in Cu and has a golden color and has excellent aesthetics, so it has been used in various fields. This brass material is a composite structure that includes a single-phase brass material based on a face centered cubic (FCC) crystal structure and a body centered cubic (BCC) crystal structure simultaneously. It is also used as a material. These materials are classified in various ways according to the content of Zn, and the criteria can be confirmed in the binary phase diagram between Cu and Zn shown in [Fig. 1]. (All state diagrams presented in the present invention were calculated using SSOL 6, a database for solid solution alloys, based on Thermo-Calc software capable of thermodynamic simulation. However, in the case of alloys containing stainless steel, the calculation accuracy was improved. It was calculated using TCFE 9, a database for iron-based alloys.) As shown in the figure, when the content of Zn exceeds 35 at.%, a phase of the BCC crystal structure begins to be formed, and in particular, Zn is 46.5 at. When it contains more than %, since the α phase of the FCC crystal structure is not formed at all, and other alloys such as the β top-tier alloy of the BCC crystal structure are formed, Zn is contained in 46.5 at.% or more compared to the base alloy of the first phase. Is not desirable. Therefore, as shown in the figure, the amount of Zn that can be included in brass is limited to a maximum of 46.5 at.%, and when an alloy composition that can be named "brass" is represented in a general formula, it is as follows [Chemical Formula 1].

(However, 0 <a ≤ 46.5 at.%)

However, since pure brass composed of only Cu and Zn as described above has too much ductility, flexible brass alloyed with Pb has been used to improve the machinability of such a material. Pb, which is alloyed with brass to form the second phase in the mouth, acts as a lubrication during cutting, thereby forming a cutting chip of an appropriate size, so that it has a smooth surface even after cutting. In fact, Pb has a large amount of mixing heat (+15 kJ/mol) with copper, which is known to influence its properties, among the components constituting the brass matrix, so it easily has a solubility gap in a high-temperature liquid phase. , It is known that when solidifying it, precipitates homogeneously distributed within the grain are formed.

[Fig. 2] (a) and (b) are _{pseudo-binary phase diagrams between Cu 70} Zn ₃₀ (FCC single-phase material) or Cu ₆₀ Zn ₄₀ (FCC+BCC composite material) and Pb, which are representatively used brass compositions, respectively. . As can be seen in the figure, it was found that both alloys had a wide liquid phase separation region at high temperature. That is, by adding Cu and Pb having a positive (+) heat of mixing relationship to brass and alloying it, it is possible to develop free-cutting brass evenly precipitated in the form of the second phase in the brass base. However, as the problem of environmental pollution caused by lead has recently emerged in the United States, the European Union, and around the world, the use of lead has been required to be restricted, and inevitably the use of leaded brass has also been restricted. Therefore, in the present invention, a new composition of brass material that can replace the material has been developed.

A plan to improve machinability using stainless steel precipitates

In order to solve this problem, the present invention has developed an alloying element and method for the development of brass for drinking water using a stainless steel material. Stainless steel is harmless to the human body compared to lead and has excellent corrosion resistance compared to general metal materials, so there is no shortage as a pipe material for drinking water.

At this time, [Table 1] is a table showing the composition of typical commercial stainless steel, and as shown in the table, stainless steel is known to have various properties according to its composition. Based on 300 series stainless steel, which is widely used as a commercial material, 200 series materials correspond to materials in which Ni is replaced with Mn to improve economic efficiency, and 400 series materials stabilize ferrite phase by extremely low Ni content. It is a high-strength material formed through.

division Composition (maximum, at.%) Remark
(Example classification) line AISI
standard Cr Ni Mn C Si P S Other (element) 200 series 201 16.0
-
18.0 3.50
-
5.50 5.50-7.50 0.15 1.00 0.06 0.03 - Comparative Example 1 202 17.0
-
19.0 4.00
-
6.00 7.50-10.0 0.15 1.00 0.06 0.03 - Comparative Example 2 204 15.5
-
17.5 1.5
-
3.5 6.50
9.0 0.15 0.50 0.04 - - Comparative Example 3 205 16.5
-
18.0 1.00
-
1.75 14.0-15.5 0.12-0.25 0.30
-
0.50 0.03 0.03 - Comparative Example 4 300 series 304 18.00-20.00 8.00
-10.50 2.00 0.08 1.00 0.040 0.030 - Comparative Example 5 309 22.00-24.00 12.00-15.00 2.00 0.08 1.00 0.040 0.030 - Comparative Example 6 316 16.00-18.00 10.00-14.00 2.00 0.08 1.00 0.040 0.030 3.00 (Mo) Comparative Example 7 321 17.00-19.00 9.00
-13.00 2.00 0.08 1.00 0.040 0.030 2.00 (Ti) Comparative Example 8 400 series 410 11.50-13.50 - 1.00 0.15 1.00 0.040 0.030 - Comparative Example 9 420 12.00-14.00 1.00 1.00 0.040 0.030 0.16-0.40 0.030 - Comparative Example 10 430 16.00-18.00 - 1.00 0.12 0.75 0.040 0.030 - Comparative Example 11

The chemical composition of the above-described various stainless steel materials can be expressed by a general formula such as [Chemical Formula 2] below.

(However, 11.50 ≤ b ≤ 24.00, 0 ≤ c ≤ 15, 1 ≤ d ≤ 15.5, 0 ≤ e ≤ 5 at.%, and X is selected from the group of additional elements including C, Si, P, Mo, and Ti. One or more alloying elements)

At this time, the most representative elements constituting stainless steel are Fe, Cr, Ni and Mn. In general, since these elements occupy 95 at.% or more of the total chemical composition, the properties of the entire material are also determined by the above elements. It can be said that it is done.

division Heat of mixing with Cu Melting point(℃) Remark
(Example classification) Brass and
Brass element Zn - 420 Comparative Example 12 Cu - 1080 Comparative Example 13 Cu ₇₀ Zn ₃₀ - 930 Comparative Example 14 Cu ₆₀ Zn ₄₀ - 890 Comparative Example 15 Stainless steel
Representative member Fe +13 kJ/mol 1538 Comparative Example 16 Cr +12 kJ/mol 1907 Comparative Example 17 Ni +4 kJ/mol 1455 Comparative Example 18 Mn +4 kJ/mol 1246 Comparative Example 19

At this time, the [Table 2] shows the characteristics of Fe, Cr, Ni and Mn constituting 95 at.% or more of the general stainless steel composition, along with typical brass compositions such as Cu and Zn constituting brass. As can be seen from the table, all elements constituting stainless steel have a large amount of mixing heat with Cu, a metal element that determines the properties of brass, and among them, Fe and Cr constituting most of the matrix composition are each + It was confirmed that it has a large heat of mixing of 13 and +12 kJ/mol. In addition, all the alloying elements constituting stainless steel showed a large difference in melting point from that of brass alloy, and through this, it could be expected that stainless steel could easily have a liquid phase separation region when alloyed with a brass matrix.

[Fig. 3] to [Fig. 5] are stainless steel 201 (Comparative Example 1), stainless steel 304 (Comparative Example 5), and stainless steel 430 alloy (Comparative Example 11) representing 200 series, 300 series, and 400 series stainless steels, respectively ) And (a) Comparative Examples 14 and (b) shows a pseudo-binary phase diagram drawn through thermodynamic calculations between representative brass alloys of Comparative Example 15. At this time, the calculation was performed using the TCFE 9 database to improve the calculation accuracy of the iron-based alloy.

In all the drawings, it can be seen that the shape of the liquid phase separation region did not change significantly depending on the amount of Zn, which is considered to be because Cu, a representative component of brass, influences the thermodynamic properties of brass. In addition, it can be seen that even though there is a difference in the composition and crystal structure of stainless steel, precipitates having the same FCC crystal structure are formed. This is because Fe, the main element constituting stainless steel, is separated into two types of FCC alloys during phase separation from Cu, which is the main element constituting brass. In particular, in the case of Cu, even if it has a heat of mixing positive (+) with most of the alloying elements constituting stainless steel, it can show a small solubility of about 1 at.%. In the present invention, since the fraction of the stainless steel alloy contained in the brass alloy is very small, 5 at.% or less, even if the stainless steel scrap of any composition is alloyed, precipitates in a specific composition region that are thermodynamically most stable can be formed. That is, if the stainless steel satisfies the conditions of [Chemical Formula 2], the same or similar microstructure can be expected. That is, by alloying stainless steel with brass, stainless steel precipitates can be easily formed, and it can be determined that the formed precipitates can help the processing characteristics and machinability.

Manufacture of brass for drinking water using stainless steel scrap

In this step, brass for drinking water according to the present invention was prepared and its microstructure was analyzed. The manufacturing method of such a drinking water brass alloy comprises the steps of preparing a parent element or scrap to constitute a brass base; Preparing a stainless steel parent element or scrap to form a second phase precipitate; And it consists of a step of alloying by melting the prepared parent element or scrap at the same time.

At this time, the brass for drinking water according to the present invention was prepared by melting and cooling through high frequency induction melting, which makes it easy to manufacture an alloy having a homogeneous microstructure due to an agitation effect by an electromagnetic field. In addition to the induction melting method, since high temperature can be achieved through arc plasma, it is possible to quickly produce a homogeneous solid solution in bulk form and to minimize impurities such as oxides and pores. It is possible to manufacture through a commercial casting process using a resistance heating method capable of temperature control and a rapid cooling and solidification method in which the formation of an electrifying solid solution is advantageous. In addition, not only the commercial casting method capable of dissolving the high melting point metal of the raw material, but also the high temperature using spark plasma sintering or hot isostatic pressing using powder metallurgy by making the raw material into powder, etc. / It can be manufactured by sintering at high pressure, and in the case of sintering, there are advantages of more precise microstructure control and easy manufacturing of parts having a desired shape. The alloy prepared as described above may be additionally subjected to a post-treatment process such as extrusion, cold rolling, hot rolling, or heat treatment for recrystallization in order to control the microstructure.

On the other hand, raw materials such as Cr and Ni constituting stainless steel have a price that is more than five times higher than lead used in the past. Therefore, when an alloy is manufactured using a raw material of stainless steel, it has no choice but to adversely affect the economics of the material. In order to solve this problem, the present invention considers a method of utilizing stainless steel scrap. In the case of scrap, since it has a price that is more than 10 times lower than that of a high-purity parent element, it can bring about an increase in economic efficiency. In the following, a method of manufacturing a free cutting copper using scrap and its results will be systematically described based on comparative examples and examples directly studied.

At this time, for comparison with the brass for drinking water developed in the present invention, conventional leaded brass was prepared and compared as shown in [Table 3] below. At this time, in the case of brass, it was confirmed that the same shape precipitates were found in both the case of scrap manufacturing (Comparative Example 20) and the case of preparing the master alloy (Comparative Example 21), which is the final case when the chemical composition is similar. The microstructure of the product means that there is no significant difference. Therefore, in the case of the first phase brass base, it can be seen that there is little difference in the microstructure of the case of manufacturing with the master alloy or the case of using scrap.

division Furtherance Microstructure Remark Comparative Example 20 (Cu ₆₅ Zn ₃₅ ) ₉₈ (Pb) ₂ Formation of spherical precipitates Leaded brass scrap Comparative Example 21 (Cu ₆₅ Zn ₃₅ ) ₉₈ (Pb) ₂ Formation of spherical precipitates Mother alloy manufacturing

(A) of FIG. 6 is an SEM photograph showing the microstructure of Comparative Example 20 in Table 3, and it can be seen that lead precipitates were formed in the brass matrix throughout the microstructure. That is, it can be seen that these second phase precipitates help improve machinability through the role of lubrication during cutting. Similarly , (b) of [Fig. 6] shows the microstructure of Example 30 in Table 4 below of the present invention, and it can be seen that stainless steel precipitates are distributed throughout the matrix. That is, it can be expected that the alloy of the present invention can also exhibit excellent machinability through having a microstructure similar to that of the existing flexible brass.

The following [Table 4] shows various embodiments according to the present invention confirmed by varying the stainless steel scrap fraction, the Zn fraction of brass, and the type of scrap forming the precipitated phase. In particular, for systematic confirmation, the scrap composition of stainless steel was also performed for four representative alloys (201, 304, 316 and 405) in each series.

division Alloy fraction (at.%)
(Brass) _x (SUS) _y Brass composition (at.%)
(Cu) _x (Zn) _y Scrap (SUS)
Kinds Microstructure x y x y Example 1 99 One 100 0 201 Spherical (separated) precipitate Example 2 304 Spherical (separated) precipitate Example 3 316 Spherical (separated) precipitate Example 4 430 Spherical (separated) precipitate Example 5 97 3 201 Spherical (separated) precipitate Example 6 304 Spherical (separated) precipitate Example 7 316 Spherical (separated) precipitate Example 8 430 Spherical (separated) precipitate Example 9 95 5 201 Spherical (separated) precipitate Example 10 304 Spherical (separated) precipitate Example 11 316 Spherical (separated) precipitate Example 12 430 Spherical (separated) precipitate Example 13 99 One 70 30 201 Spherical (separated) precipitate Example 14 304 Spherical (separated) precipitate Example 15 316 Spherical (separated) precipitate Example 16 430 Spherical (separated) precipitate Example 17 97 3 201 Spherical (separated) precipitate Example 18 304 Spherical (separated) precipitate Example 19 316 Spherical (separated) precipitate Example 20 430 Spherical (separated) precipitate Example 21 95 5 201 Spherical (separated) precipitate Example 22 304 Spherical (separated) precipitate Example 23 316 Spherical (separated) precipitate Example 24 430 Spherical (separated) precipitate Example 25 99 One 60 40 201 Spherical (separated) precipitate Example 26 304 Spherical (separated) precipitate Example 27 316 Spherical (separated) precipitate Example 28 430 Spherical (separated) precipitate Example 29 97 3 201 Spherical (separated) precipitate Example 30 304 Spherical (separated) precipitate Example 31 316 Spherical (separated) precipitate Example 32 430 Spherical (separated) precipitate Example 33 95 5 201 Spherical (separated) precipitate Example 34 304 Spherical (separated) precipitate Example 35 316 Spherical (separated) precipitate Example 36 430 Spherical (separated) precipitate

Looking at the table above, it can be seen that spherical precipitates that can be expected to improve machinability were formed in all of the various compositions prepared according to the present invention.Since the precipitates are not connected to each other and have a separate form, cracks along the interface during cutting It is expected that there will be less formation. In particular, the formation of such precipitates was made in a similar form regardless of the composition of the stainless steel scrap. This is believed to be due to the fact that stainless steel has only a slight difference in the fraction of constituent elements, and the overall types of constituent elements are similar. From this, it can be determined that all stainless steels satisfying the conditions of [Chemical Formula 2] can be accepted as a result of the present invention.

[Table 5] below shows the results of manufacturing an alloy having the same composition as Examples 17 to 20, which is a representative composition of the present invention, using a high-purity parent element instead of scrap. As can be seen in the table below, even if the alloy is prepared after configuring the same composition using the parent element of high purity, it can be seen that an alloy having a similar microstructure can be easily prepared.

division Alloy fraction (at.%)
(Brass) _x (SUS) _y Brass composition (at.%)
(Cu) _x (Zn) _y Composition of stainless steel master alloy Microstructure x y x y Example 37 97 3 70 30 201 Spherical (separated) precipitate Example 38 304 Spherical (separated) precipitate Example 39 316 Spherical (separated) precipitate Example 40 430 Spherical (separated) precipitate

On the other hand, the following [Table 6] is a result of the alloy group containing 10 at.% of the alloying element fraction of stainless steel. In this way, when the proportion of the stainless steel material is excessively high, each precipitate grows in a form connected to each other, or in a form of a dendritic branch with sufficient growth. The precipitates in such a connected form may cause cracks through the interface during cutting, and are preferably excluded from the scope of the claims.

division Alloy fraction (at.%)
(Brass) _x (SUS) _y Brass composition (at.%)
(Cu) _x (Zn) _y Type of scrap (SUS) Microstructure x y x y Comparative Example 22 90 10 70 30 201 Dendritic (linkage) precipitate Comparative Example 23 304 Dendritic (linkage) precipitate Comparative Example 24 316 Dendritic (linkage) precipitate Comparative Example 25 430 Dendritic (linkage) precipitate

When the results confirmed in this step are summarized as described above, the brass for drinking water in which the stainless steel according to the present invention is deposited as the second phase can be expressed as shown in [Chemical Formula 3] below.

(However, 0 ≤ x ≤ 5.00 at.%, Brass is a brass composition according to [Chemical Formula 1] , and SUS is a stainless steel composition according to [Chemical Formula 2])

On the other hand, Examples 41 to 49 shown in the following [Table 7] are for improving matrix machinability, Pb, Sn, Sb, As, Bi, Cd, P, Mg, which are known to improve machinability by adding a small amount to a brass material. And it shows the result that at least one alloy element selected from the alloy group consisting of Si and the like is contained in 2 at.% or more of the total alloy elements. The elements shown in the table below are substances that cannot be easily removed because they are included in brass scrap, or elements that can improve the machinability of the brass material itself, and may be included in the claims of the present development. In particular, the following materials are materials that can be included in a small amount in the existing brass scrap, and can inevitably be included in the material when manufactured using brass scrap.

division Alloy fraction (at.%)
(Brass) _x (SUS) _y (X)z Brass composition (at.%)
(Cu) _x (Zn) _y Type of scrap (SUS) Element added (X)
Kinds Microstructure x y z x y Example 41 68 30 2 70 30 304 Pb Precipitate formation Example 42 Sn Precipitate formation Example 43 Sb Precipitate formation Example 44 As Precipitate formation Example 45 Bi Precipitate formation Example 46 CD Precipitate formation Example 47 P Precipitate formation Example 48 Mg Precipitate formation Example 49 Si Precipitate formation

Analysis of processing characteristics of brass for drinking water manufactured from stainless steel scrap

In this step, processing characteristics and machinability of brass for drinking water in which the second phase of stainless steel made of stainless steel scrap is deposited are analyzed. To this end, various analyzes were performed based on Example 30 as a representative composition according to the present invention.

[Fig. 7] Silver For Example 30, which is a representative composition of the present invention, the shape of a specimen obtained by extruding a billet (175 mm diameter, 380-550 mm length) prepared through large-capacity casting (600 Kg) to a diameter of 19 mm is shown. This result means that even if the stainless steel second phase gives a large deformation to the deposited drinking water brass, cracks from the inside or outside do not easily occur.

At this time, [Fig. 8] shows the result of cold rolling the material extruded as described above. As shown in the figure, even if a material having a thickness of about 15 mm is rolled to 2.7 mm (80% or more), it can be seen that no large cracks occur. In addition, it can be seen that the thickness difference of 0.001 mm or less is observed even if the position is different and the thickness is measured in the rolled material as described above. This means that the brass for drinking water manufactured through the present invention can be precisely processed and molded.

[Fig. 9] shows the result of cutting the extruded specimen of [Fig. 7]. At this time, (a) shows the result of cutting the existing flexible brass. In the cutting surface of the leaded brass, a large-scale crack or shape deformation could not be confirmed. Likewise, it can be seen that very minute surface scratches were observed on the cutting surface of the specimen of Example 30 of the present invention, but it was found that no large-scale cracks or shape deformation occurred. This means that the material developed by the present invention can be applied as a commercial brass. In fact, as shown in (c), even if the overall shape of the processed specimen was checked, it was confirmed that a smooth and fluid shape could be confirmed without major cracks, and that the golden color peculiar to brass was maintained.

[Fig. 10] is a result of comparing the hardness of the brass material developed through the present invention and the conventional comparative example. The hardness measurement was analyzed through the Vickers hardness measurement method, and it was confirmed that the brass alloy of the present invention exhibited a hardness that was 2-3 times higher than that of the existing flexible brass. This means that the material developed through the present invention has high strength compared to the existing material through the precipitation of the stainless steel second phase, so that it can have durability as a structural material. In addition, the stainless steel precipitate included in the present invention has high oxidation resistance, and is expected to have excellent oxidation resistance compared to existing materials.

The present invention has been described above through preferred embodiments, but the above-described embodiments are merely illustrative of the technical idea of the present invention, and various changes are possible within the scope not departing from the technical idea of the present invention. Those of ordinary skill will understand. Therefore, the scope of protection of the present invention should be interpreted not by specific embodiments, but by the matters described in the claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

Claims (7)

The first phase of a brass alloy composed of Cu and Zn; And
The composition area of the brass alloy limited to have a second phase precipitate containing the constituent elements of stainless steel (SUS) is (Cu _100-a Zn _a ) _100-x (SUS) _x (however, 1 ≤ x ≤ 5 And 0 <a ≤ 46.5 at.%),
The composition ratio of SUS in the above formula is Fe _100-bcde Cr _b Ni _c Mn _d X _e (however, 11.50 ≤ b ≤ 24.00, 0 ≤ c ≤ 15, 1 ≤ d ≤ 15.5, 0 ≤ e ≤ 5 at.%, and ,
X is a brass alloy for drinking water, characterized in that represented by one or more alloying elements selected from the group of additional elements including C, Si, P, Mo, and Ti.
The method according to claim 1,
Brass alloy for drinking water, characterized in that the first phase of the brass alloy composed of Cu and Zn is manufactured by recycling scrap.
The method according to claim 1,
The second phase precipitate containing the constituent elements of the stainless steel (SUS),
Fe _100-bcde Cr _b Ni _c Mn _d X _e (However, 11.50 ≤ b ≤ 24.00, 0 ≤ c ≤ 15, 1 ≤ d ≤ 15.5, 0 ≤ e ≤ 5 at.%, and X is C, Si, P Brass alloy for drinking water, characterized in that produced by recycling commercial stainless steel scrap having a composition ratio of at least one alloy element selected from the group of additional elements including Mo and Ti.
The method according to claim 1,
In order to improve the machinability of the first phase of the brass alloy composed of Cu and Zn,
Brass for drinking water, characterized in that at least one alloy element selected from the alloy group consisting of Pb, Sn, Sb, As, Bi, Cd, P, Mg, and Si is alloyed to 2 at.% or less by replacing the brass alloy. alloy.
A brass article including a faucet article and a pipe, characterized in that it comprises the brass alloy for drinking water of claim 1.
Preparing a brass parent element or scrap to constitute a brass base in a ratio of Cu _100-x Zn _{x (however, 0<x≤45);}
Fe _100-bcde Cr _b Ni _c Mn _d X _e (However, 11.50 ≤ b ≤ 24.00, 0 ≤ c ≤ 15, 1 ≤ d ≤ 15.5, 0 ≤ e ≤ 5 at.%, and X is C, Si, P , Preparing a stainless steel parent element or scrap to form a second phase precipitate having a composition ratio of at least one alloy element selected from the group of additional elements including Mo and Ti;
Preparing the brass (Brass) parent element or scrap and the stainless steel (SUS) parent element or scrap prepared in the above steps at a ratio of (Brass) _100-x (SUS) _x (only 1 ≤ x ≤ 5);
A method for producing a brass alloy for drinking water, characterized in that the parent element or scrap prepared in the above steps is simultaneously dissolved to have a second phase precipitate containing a constituent element of stainless steel (SUS).
The method of claim 6,
To improve the machinability of the first phase of a brass alloy composed of Cu and Zn,
Brass for drinking water, characterized in that at least one alloy element selected from the alloy group consisting of Pb, Sn, Sb, As, Bi, Cd, P, Mg, and Si is alloyed to 2 at.% or less by replacing the brass alloy. Method of making the alloy.

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