ES2271820T3 - MANUFACTURING PROCEDURE OF SEMIPRODUCTS BASED ON CUZNPBSN ALLOYS DESTINED FOR HOT DEFORMATION. - Google Patents

Abstract

The production of a semi-product of a CuZnPbSn alloy includes a spinning operation which does not include nor is it followed by a thermal treatment stage. Independent claims are also included for the following: (a) a finished product obtained fron the semi-product; and (b) the production of the finished product by deformation or machining, which does not include a thermal treatment stage.

Description

Semi-finished product manufacturing process a base of CuZnPbSn alloys intended for deformation in hot.

Field of the Invention

The present invention relates to the field of copper-based alloys for hot stamping, intended to the manufacture of parts used essentially in the drinking water distribution pipes (taps, valves, union fittings).

State of the art

Currently, the most commonly used alloys in This field are, according to the European nomenclature:

to)

Traditional stamping alloy: CW617N

b)

Alloys resistant to decincification, of which the most commonly used is Brass to arsenic: CW602N.

C)

A tin-plated brass alloy family, patented for its excellent hot plasticity (European Patent No. EP 1 029 935 A1, published on 23.08.2000).

In addition, it is known that the addition of tin to Brass can improve its corrosion resistance, as mentioned in the work Metals Handbook, 9th edition, volume 3, Corrosion (1987), and may present a character γ-tin gene in the brass traditional duplex α- \ beta ', as you mentions in the work of H. O. Hofmann "Metallurgy of copper", McGraw-Hill Book Company, Inc. (1924). The document of EP 0947592 A1 describes a family of alloys of tin brass and its manufacturing process, which comprises a stretching stage at temperatures between 480 and 650 ° C.

Issues raised

Among these alloys, the traditional alloy Stamping CW617N has the following drawbacks:

to)

extremely weak resistance to decincification;

b)

mechanization capacity median.

As for brass arsenic alloys, resistant to decincification, have the drawbacks following:

to)

evil machining (chip fragmentation);

b)

difficult manufacturing quality, which you need to perform a heat treatment before the delivery of the bars and other after stamping (taps, valves, fittings);

C)

rate of lead release in elevated water.

Finally, as regards the tin-plated brass alloys patented for their excellent hot plasticity, have the drawbacks following:

a) Difficulty of ability to flow very high in the recommended temperature range for stamping, with respect to the CW617N alloy (an order of different magnitude).

b) Important susceptibility in terms of stamping temperature; In other words, in order to ensure good hot malleability, the stamping temperature must be very stable (± 20 ° C), which requires the replacement of traditional heating modes with heating dies incorporated in the garments.
sas.

As a consequence of points a) and b) that just cited, the use of brass to tin, the object of previously mentioned patent, needs structural modification of existing printing presses.

Object of the invention

The alloys according to the invention are intended for the manufacture of parts used essentially in the drinking water distribution pipes (taps, valves, fittings) and are aimed at simultaneously satisfying the following conditions:

one)

Simple elaboration procedure and economic.

2)

Resistance to decincification very good

3)

Machining (chip fragmentation) very good.

4)

Very good forgeability (weak deformation resistance and good malleability in hot)

5)

Without harmful effects on the rate of release of lead in water potable.

This last condition is motivated by new regulations that refer to water quality potable.

Description of the invention

An object of the invention is constituted by the manufacturing process of a semi-manufactured according to the claim 1, method typically comprising stretching stage, not being followed by a stage of heat treatment. In this sense, the procedure according to the Invention is, therefore, especially economical.

The applicant has observed that the alloys from brass to tin according to the invention presented, with respect to the prior art alloys used for them applications, the optimal combination of features required Indeed, these alloys according to the invention are characterized by the simultaneous presence of the properties that are described below:

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Excellent resistance to decincification

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Machining (fragmentation of chips) very good.

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Excellent forgeability in hot.

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No harmful effects on the Lead release rate in drinking water.

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Simple manufacturing quality and economical (without the need for heat treatment or by the brass manufacturer or in the stammers after stamping of the pieces).

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Simple Recycling

The properties of the alloys according to the invention should be mainly due to the choice of composition and especially at the well chosen range of content in tin.

Within the framework of their work, the applicant has issued the following hypothesis to explain the beneficial effect of tin. The mechanism at stake would be as follows: once added tin, strongly "γ-geno", to brass, it would cause the formation of the new γ phase in the sine of the α-β 'duplex microstructure. This formation would be done to the detriment of the β 'phase, as illustrated in figure 1. Because of the high solubility of tin in the "γ" phase, its formation would be accompanied by a phenomenon, of very fast kinetics, of pumping the tin of the matrix (α and β 'phases), as illustrated in the figure 2.

Thus, the presence of tin within the "γ" phase would lead to:

- a decrease in the corrosion potential of "γ" which would result in an increase in Corrosion susceptibility of this phase. Consequently, in presence of a corrosive medium, the "γ" phase would be attacked with preference, (beginning of corrosion), protecting the rest of the matrix. In other words, the "γ" phase would play the role of "sacrificial" anode and protect the alloy rest;

- a slow corrosion kinetics (progression of the decincification front). Thus, because of this decrease in the kinetics (and despite the susceptibility to corrosion very high of the "γ" phase), the overall intensity of the decincification of tin containing alloys according to the invention, would be significantly diminished.

However, to obtain the properties sought according to the invention, the "γ" phase must, by a part, be present in a weak relative quantity, as illustrated in figure 1, and, on the other, must present a morphology fine and discontinuous, as shown in figure 2. Indeed, the Figure 2 shows that the "γ" phase is present in the grain joint between the α and β phases, in a weak thickness, and that is discontinuous, since it is absent in the other two junctions of the phases α and β ', (to the right and left), presented in figure 2.

In addition, within the framework of their investigations, the applicant has been able to demonstrate the disastrous role of arsenic in the Lead brass, in terms of lead release. In effect, although it is known that the arsenic present in the brass at lead is located in the area of the grain junctions, on the contrary, the applicant has found, as schematically illustrated in the Figure 4, that arsenic had a tendency to migrate to the surface and that, in an aqueous medium, being the arsenic more noble than lead (E_ {As} = 0.248 V; E_ {Pb} = -0.126 V), this led to the formation of electrochemical cells between arsenic and lead particles, so that the acceleration of the dissolution of lead in drinking water (release rate).

Description of the figures

Figure 1 is a diagram that gives the evolution of the percentages by weight of the phases α, β 'and γ as a function of the weight concentration of tin, being the CuZnPbSn alloys according to the invention those for which The amount of tin by weight is between 1.3 and 1.7%.

This diagram has been obtained from the six following alloys, of increasing content in Sn:

% weight of Sn % weight of Pb % weight of Fe % weight of Zn % Cu weight 0 2.16 0.19 38.6 Rest 0.59 2.06 0.20 39.9 Rest 1.13 2.12 0.19 39.1 Rest 1.71 2.19 0.17 38.5 Rest 2.19 2.08 0.20 38.1 Rest 2.73 2.02 0.18 37.5 Rest

Figure 2 is a diagram that gives the tin weight concentration of the α, β 'and phases γ of CuZnPbSn alloys according to the invention, concentration obtained in a micrographic section of a semiproduct obtained according to alloy number 2 by punctual analysis with a scanning microscope In ordinates, there is the weight content in tin and in abscissa is the distance in \ mum between the different analysis points, distance taken along a line straight from a point of origin taken in a phase α, line which successively cuts the phases from left to right ? /?? /? /?? /?. This diagram highlights a phenomenon of pumping the tin of the phases α, β 'by the γ phase.

Figure 3 is a photograph intended to put evidently the hot malleability of the alloys according to the invention (alloys 2 and 4) by crushing tests of 55% (upper disks) and 80% (lower disks), made at 700, 750 and 825 ° C.

Figure 4 is a scheme representing a cutting of a stamped part according to the invention, in contact with the water, explanation of the mechanism of accelerating action of arsenic on the rate of release of lead in drinking water.

Figure 5 is a scheme that takes up the Elements of the photograph in Figure 3.

Detailed description of the invention

According to the invention, the tin content of the CuZnPbSn alloy can be between 1.4 and 1.6%. He Lead content can be between 1.9 and 2.1%.

As regards the elements secondary or in a trace state, the iron content can be less than or equal to 0.2%.

Also, the arsenic content may be between 5 and 500 ppm.

The aluminum content can be comprised between 5 and 500 ppm.

The antimony content may be between 5 and 100 ppm.

The silicon content can be comprised between 5 and 500 ppm.

Another object of the invention comprises the semi-finished products obtained from the CuZnPbSn alloy according to the invention, in which the microstructure of the alloy is It consists of three intermetallic phases: α, β 'and γ.

Through image analysis of the microstructure, it has been observed that the percentage of surface area of the γ phase of these semiproducts can be comprised between 5 and 9% and that the percentage of surface area of the phase β 'can be between 25 and 40%.

As illustrated in Table 3 of Example 1, said CuZnPbSn alloy may have a composition chosen from so that, according to ISO 6509, said semiproduct obtained at from said alloy present an average depth of decincification less than 200 µm, and even typically less than 150 µm, such that said CuZnPbSn alloy, which It does not contain arsenic, it is far superior to CW617N alloy and even approximates the yields of the alloy with arsenic CW602N

As illustrated in Table 5 of Example 2, said CuZnPbSn alloy may have a composition chosen from so that the semiproduct obtained from this alloy present, for a drilling or drilling operation carried out in the usual machining conditions according to the NF standard E66-520-7 of the 2000 edition, a average chip size typically twice smaller than the obtained with the CW602N alloy which is arsenic brass.

As illustrated in Table 7 of Example 4 and in Figures 3 and 5, said CuZnPbSn alloy may have a composition chosen so that the compression test in hot according to ASTM E209-00 edition 2000, and performed in the range of 600ºC to 750ºC, do not cause no fissure of said semiproduct obtained from that alloy.

Thus, the semi-finished products according to the invention they have great freedom from hot deformation, both which refers to the temperature zone as to the rate of crushing, without cracks or cracks appearing, which is, in The practice, very advantageous.

As illustrated in Table 6 of Example 3, said CuZnPbSn alloy of said semiproduct can have a composition chosen in such a way that the lead release rate in drinking water is lower than the regulatory threshold according to the European Directive 98/83 / EC on the quality of the water destined to human consumption It is important to also note the very low rate of Zn release compared to that of alloys numbers 5 and 6.

As illustrated in Table 8 of Example 4, said CuZnPbSn alloy may have a composition chosen from such that said semiproduct has a malleability in high heat and so that its resistance to crushing is lower than that obtained with the CW602N alloy and, preferably, twice less than that of said CW602N alloy.

It goes without saying that the power installed in the machines or devices for manufacturing products finished, in particular when such manufacturing comprises a deformation of the semiproduct by crushing, will be less in the case of the semi-finished products of the invention that in the case of state-of-the-art semiproducts formed from the alloys numbers 5 and 6.

Another object of the invention is the finished product obtained from the semiproduct according to the invention, the semiproduct being typically chosen among: a tap, a valve, a fitting.

Another object of the invention is the manufacturing process of the finished product according to the invention, process in which said product is formed typically terminated by deformation or machining of said semi-finished product, said procedure not comprising the stage of heat treatment, which is very advantageous and economical in the practice regarding the comparable procedures of the state of technique.

Another object of the invention is the use of a CuZnPbSn alloy according to the invention, or a semi-finished product according to the invention or obtained according to the invention, for the manufacture of finished products or components used for distribution of sanitary water, such as taps, valves and fittings.

Examples of realization

Table 1 gives the chemical compositions of the alloys tested according to the invention (% by weight).

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TABLE 1 Chemical composition (% by weight) of the alloys tested according to the invention

Cu Pb Sn Faith Zn Alloy one 63.2 1.83 1.55 0.18 Rest Alloy 2 61.2 2.04 1.57 0.17 Rest Alloy 3 60.2 2.01 1.42 0.19 Rest Alloy 4 59.1 1.82 1.51 0.18 Rest

TABLE 1 (continued)

Cu Pb Sn Faith Zn Alloy 5 Alloy traditional 59.5 1.95 0.22 0.21 Rest from stamping CW617N Alloy 6 * Alloy resistant to the 61.2 2.20 0.06 0.01 Rest decincification CW602N * Alloy 6 contains 0.12% arsenic

The alloys in table 1 were made according to a conventional quality that includes the stages included in the table 2.

TABLE 2 Brass manufacturing operating conditions rehearsed

Casting temperature: T = 1060 ± 20 ° C, roller = 110 mm Inverse stretch: T = 700 ± 20 ° C, preheating time = 2 h, diameter bars = 26 mm Stretch ratio = 94%

Example 1

In this example, the influence has been studied of the composition of the alloy in decincification.

The decincification tests have been carried out in the longitudinal direction (stretch direction) according to the ISO standard 6509. The average depths of decincification have been measured with help of an image analysis system (average of twenty measurements).

Table 3 gathers the results of the measurements:

TABLE 3 Results of depth measurements of decincification

Deciphering Depth (\ mum) Half Typical deviation Alloy 1 750 27 Alloy 2 149 fifteen Alloy 3 135 13 Alloy 4 146 17 Alloy 5 1320 31 Alloy 6 80 10

The results of this table show the following points:

1) The reference alloy (alloy 6), is that is, the CW602N alloy shows the best resistance to decincification In effect, this resistance is the consequence, on the one hand, of the single-phase microstructure of this alloy (100% alpha) and, on the other hand, the presence of arsenic in the alloy.

However, it should be noted that the CW602N alloy You need two heat treatments (a ~ 500 ° C), one in the course of its manufacture (in the manufacturer of the alloy) and the other after the stamping operation.

2) Traditional stamping alloy (alloy 5), that is, CW617N alloy, shows resistance weaker to decincification.

3) The addition of tin according to the invention (alloys 2, 3 and 4) gives results close to those obtained for CW602N indescincifiable alloy. In other words, the addition of tin according to the invention significantly improves resistance to the decincification of stamping brass (comparison of alloys numbers 2, 3 and 4 with alloy number 5).

4) Since alloy number 1 has a copper content too high (out of range according to invention, that is, 59.5 to 61.5% by weight), has a depth of decincification almost five times higher than those obtained for the alloys numbers 2, 3 and 4.

Example 2

In this example, the aptitude for the mechanization of the alloys according to the invention in comparison, on the one hand, with that of the CW617N alloy and, on the other, with that of CW602N alloy.

Machining tests have been carried out in a Instrumented and automated drilling bench. The conditions Operatives used are the following:

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Cutting speed (Vc) = 280 m / min

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Feed per lap (f) = 0.56 mm / turn

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Drill:

\ circ

Carbide monobloc

\ circ

10 mm diameter

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Drilling Depth (pp) = 25 mm

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Lubrication: with the help of LACTUCUT 2, lubricant marketed by TOTAL®

The parameters measured were the axial force of drilling and the average chip size evaluated by a parameter called "medium chip" (VM).

The VM parameter has been calculated as follows shape:

The chips produced in the drilling are added to a series of 7 superimposed sieves, marked from 1 to 7. The table 4 gives the size (in mm) of the openings of the square meshes of each sieve, as well as an arbitrary index that refers to it (sieve index).

TABLE 4 Sieve characteristics used

No. of sieve Mesh opening (mm) Index of sieve one 2.5 7 2 2 6 3 1.6 5 4 1.25 4 5 0.9 3 6 0.56 2 7 0 (Bottom - no opening) one

The sieves are mounted on a vibrating support which is vibrated for five minutes for each operation of sifting

Then the content of each is weighed sieve. The "medium chip" (VM) parameter is then calculated with help from the following equation:

V.M. (dimensionless) = \ frac {\ sum \ limits ^ {7} _ {i = 1} (I_ {i} \ times m_ {i})} {\ sum \ limits ^ {7} _ {i = 1} (m_ {1})}

where: I_ {i} = sieve index number "i"; m_ {i} = weight of sieve shavings number "i".

The fragmentation of the chips obtained by Drilling an alloy is all the better the smaller VM is.

Table 5 gathers the results obtained. Every parameter is calculated using the average of the results of Five different measures.

TABLE 5 Results of machining tests (boring)

Force drilling (N) VM Alloy one 2739 ± 25 4.2 ± 0.2 Alloy 2 2940 ± 36 3.80 ± 0.2 Alloy 3 3082 ± pm 41 3.75 ± 0.1 Alloy 4 3193 ± 48 3.70 ± 0.2 Alloy 5 3232 ± 42 4.5 ± 0.2 Alloy 6 2642 ± pm 30 7.3 ± 0.2

The results in table 5 show that with respect to the alloy CW617N (nº 5), the alloys according to the invention (numbers 2, 3 and 4) have both a level of strength weaker and fragmentation of chips much better.

As for the comparison with the alloy arsenic, that is the CW602N alloy (nº 6), it is noted that the alloys according to the invention have more strength levels high. However, this difference is widely compensated. for the excellent fragmentation of the shavings of the brass with tin.

Example 3

In this example, release has been studied of lead, copper and zinc in drinking water. The essays of release have been made over a period of three weeks using the washing solution "Old-BSI 7766" (DD 201-1991 of the British Standard Institution).

The tests have been carried out on machined metal parts in the 26 mm diameter bars. The useful surface area of each piece (" godet ") is 1.90 dm 2 and contains 0.4 l of the washing solution previously mentioned.

In order to avoid the phenomenon of superficial contamination of godets by lead (formation of a thin film of this element on the machined surfaces), all of them have undergone a treatment surface (ECOWAVE® treatment from KME).

Samples of water were taken in the course of the third week of the essay, at the rate of a shot of Sample every 24 hours (of stagnation).

For each item, it has been considered for comparison the average of the 7 results obtained in the course of the third week of the essay.

Table 6 presents the results obtained. for lead, copper and zinc.

TABLE 6 Results of the trials of release

Average rate release (\ mug / dm2) Pb Cu Zn Alloy one 0.73 5.17 100.75 Alloy 4 1.15 5.31 93.8 Alloy 5 1.07 5.35 221.66. Alloy 6 2.03 7.98 160.05

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It is well noted that the alloy according to the invention (No. 4) produces less release (Pb, Cu and Zn) than CW602N alloy (alloy 6) and much less Zn release than CW617N alloy (alloy 5).

Example 4

In this example, forjability has been studied hot (hot stamping ability) of alloys according to the invention.

In order to assess forgeability, they have performed hot crush tests with the help of a traction machine The operating conditions used are the following:

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Sample Geometry: 15 mm diameter and 15 mm high cylinders.

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Lubrication with the help of a graphite bar

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Temperature: 600, 700, 750 and 825 ° C.

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Crush Rate * (ε): 55 and 80%

*

\ varepsilon = [(H_ {0} - h) / H_ {0}] 100%, where H_ {0} and h are, respectively, the heights of the sample before and after the crushing test.

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Deformation speed generalized: ε 0 = 34 s -1.

Forgeability It has been evaluated with the help of two parameters:

one)

The deformation resistance.

This has been measured directly with the traction machine. Reflects the power necessary for stamping the samples.

2)

The hot malleability.

It is evaluated "a eye ", observing the appearance of the compressed discs (fissures, orange peel, ...)

Table 7 gathers the test results visuals of hot smashed samples. Figure 3 shows the photo of a part of the crushed discs, while the Figure 5 is a schematic representation of the samples crushed appearing in figure 3.

TABLE 7 Result of hot crush tests (+: seamless; -: cracked)

T (ºC) Cup of No. of alloy crushing (%) one 2 3 4 5 6 600 55 + + + + + - 80 - + + + - - 700 55 + + + + + - 80 - + + + + + 750 55 + + + + + + 80 - + + + - - 825 55 + + + + - + 80 - - - - - -

It is appreciated that, unlike alloys CW617N and CW602N, the alloys according to the invention (numbers 2, 3 and 4), they are very well stamped between 600 and 750ºC and this for both rates crushing tested.

As for the resistance to deformation, (hot crush effort), table 8 summarizes the results obtained (expressed in kg) for a rate of 55% crush.

TABLE 8 Results of crushing efforts (kg)

T (ºC) Alloy number one 2 3 4 5 6 700 1725 1000 735 700 720 1650 750 1025 650 540 500 550 995 825 460 530 420 400 390 425

Table 8 shows that the alloys according to invention have lower crushing stress levels to those of alloy number 6 (CW602N) and close to those of the alloy number 5 (CW617N).

Advantages of the invention

As already indicated, the invention allows simultaneously solve numerous problems to the extent that allows to simultaneously satisfy the five conditions raised Previously, namely:

to)

simple elaboration procedure and economic;

b)

very good resistance to decincification;

C)

very good mechanization (chip fragmentation);

d)

very good forgeability (weak deformation resistance and good hot malleability);

and)

without harmful effects on the rate of lead release in water potable.

Thus, the comparison of the alloys according to the invention (alloys numbers 2 to 4) with state alloys Current technique (alloy number 5 = CW617N and alloy number 6 = CW602N) has clearly shown the overall superiority of the first with respect to the second.

Claims (19)

1. Procedure for manufacturing a semi-finished product in a CuZnPbSn alloy, in which said alloy It presents the following weight composition:

-

copper: from 59.5 to 61.5%;

-

lead: from 1.8 to 2.2%;

-

tin: from 1.3 to 1.7%;

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sum of other elements except Zn <0.3%;

-

zinc: rest;

characterized in that it comprises a stretching stage performed at a temperature of 700 ° C ± 20 ° C, which does not include or is not followed by a heat treatment stage. 2. Method according to claim 1, in which the content of tin is between 1.4 and 1.6% 3. Procedure according to any one of the claims 1 to 2, wherein the lead content is between 1.9 and 2.1%. 4. Procedure according to any one of the claims 1 to 3, wherein the iron content is less than or equal to 0.2%. 5. Procedure according to any one of the claims 1 to 4, wherein the arsenic content is between 5 and 500 ppm. 6. Procedure according to any one of the claims 1 to 5, wherein the aluminum content is between 5 and 500 ppm. 7. Procedure according to any one of the claims 1 to 6, wherein the antimony content is between 5 and 100 ppm. 8. Procedure according to any one of the claims 1 to 7, wherein the silicon content is between 5 and 500 ppm. 9. Procedure according to any one of the claims 1 to 8, wherein said semiproduct has a Alloy microstructure composed of three intermetallic phases: α, β 'and γ. 10. Method according to claim 9, in which the percentage of surface area of the γ phase is between 5 and 9%. 11. Procedure according to any one of the claims 9 to 10, wherein the percentage of area Superficial of the β 'phase is between 25 and 40%. 12. Procedure according to any one of the claims 9 to 11, wherein said CuZnPbSn alloy has a composition chosen in such a way that, according to ISO 6509, said semiproduct has an average depth of decincification less than 200 µm. 13. Procedure according to any one of the claims 9 to 12, wherein said CuZnPbSn alloy has a composition chosen in such a way that the semiproduct presents, for a drilling operation carried out under the conditions usual machining according to the NF standard E66-520-7 of the 2000 edition, a average chip size typically twice smaller than the obtained with the CW602N alloy, which is a brass with arsenic. 14. Procedure according to any one of the claims 9 to 13, wherein said CuZnPbSn alloy has a composition chosen in such a way that the compression test hot according to ASTM E209-00 of the 2000 edition, and carried out in the temperature range of 600 to 750 ° C, do not cause any cracks in said semiproduct. 15. Procedure according to any one of the claims 9 to 14, wherein said CuZnPbSn alloy has a composition chosen in such a way that the release rate of lead in drinking water is lower than the regulatory threshold according to European Directive 98/83 / EC on the quality of the water destined to human consumption 16. Procedure according to any one of the claims 9 to 15, wherein said CuZnPbSn alloy has a composition chosen in such a way that said semiproduct it has a high hot malleability, and so that its crush resistance is lower than that obtained with the CW602N alloy and, preferably, twice smaller than that of said CW602N alloy. 17. Finished product obtained from semiproduct obtained by the method according to any one of claims 1 to 16, said product being chosen finished between: a tap, a valve, a fitting. 18. Product manufacturing procedure finished according to claim 17, wherein said product typically terminated by deformation or machining of said semi-finished product, said procedure not comprising a stage of heat treatment. 19. Use of a CuZnPbSn alloy semi-finished product obtained by the procedure according to any one of the claims 1 to 16 for the manufacture of finished products or components used for the distribution of sanitary water, such as taps, valves and fittings.