WO2017009176A1

WO2017009176A1 - Brass alloy

Info

Publication number: WO2017009176A1
Application number: PCT/EP2016/066143
Authority: WO
Inventors: Karl Zeiger; Benjamin Cappi; Helge Lehmann; Daniel Lulinski
Original assignee: Aurubis Stolberg Gmbh & Co. Kg
Priority date: 2015-07-10
Filing date: 2016-07-07
Publication date: 2017-01-19
Also published as: RS61025B1; PT3320122T; ES2828578T3; EP3320122A1; EP3320122B1; DE102015212937A1

Abstract

The present invention relates to a brass alloy of copper and zinc, the brass alloy having an indium content.

Description

brass alloy

The invention relates to a brass alloy with the features of the preamble of claim 1.

Corresponding brass alloys are often produced as semi-finished products in strips, wire form, rods, sheets or plates and then further processed into finished products. The further processing takes place frequently by application of cutting operations.

When machining brass, it has proven advantageous in the past to add lead to the alloy in an amount of up to four percent by weight. The lead has a positive effect as a chipbreaker, extends the tool life and reduces the cutting forces. Important material parameters such as strength and corrosion resistance are not adversely affected by lead addition.

Despite the positive properties of lead, efforts are underpinned, inter alia, by EC Directive 2011/65 / EU (RoHS II) and its precursor 2002/95 / EC (RoHS I), Directive 2000/53 / EC on end-of life vehicles and Directive 2002/96 / EC on waste electrical and electronic equipment, replacing lead as a cutting element in brass.

However, the studies carried out so far with alternative alloy variants have not led to materials that meet the requirements. These are either significantly more expensive than leaded brass alloys lead to an excessive tool wear or also contain environmentally harmful alloying elements.

In the production of brass alloys, the aim is to achieve both good machinability and good ductility. A simultaneous optimal fulfillment of both requirements proves to be difficult, since usually all measures that support a desired property positive, lead to a deterioration of the second property. A compromise is typically chosen so as to impart high strength while maintaining sufficient deformability.

Object of the present invention is therefore to provide an alternative brass alloy, which has a good machinability, sufficient mechanical properties and causes the lowest possible wear on the cutting tools used.

According to the invention a brass alloy with the features of claim 1 is proposed to solve the problem. Further preferred embodiments of the invention can be found in the subclaims, the figures and the associated description.

In accordance with the spirit of the invention, it is proposed that the brass alloy has an indium content of 0.005 to 1.0 weight percent and an addition of at least one of FE, Sn, Ni or Mn of 0.01, 3.0 percent by weight and no bismuth added ,

It has been found that the addition of indium makes the chip breaking properties of the brass alloy positive can be influenced, so that the processability of the brass alloy can be improved. The indium virtually replaces the previously used lead while achieving the same advantages, so that the lead content in the brass alloy can be reduced to zero in extreme cases, and the brass alloy can still be machined very well.

The properties obtainable by the addition of indium are in particular:

-a good machinability,

-high strength but still good ductility,

-a very good hot and sufficient cold workability

-sufficient corrosion resistance.

In this case, the indium content is preferably 0.005 to 1.0 weight percent, whereby the benefits to be achieved can already be achieved. In particular, the indium content may be less than 0.25 weight percent, which already favorable structural properties can be achieved. In general, the indium content should be chosen rather low, since indium is a relatively expensive element. Thus, the indium content should be chosen as low as possible, and the favorable structural properties can still be achieved, to which an indium content of at least 0.05 and not more than 0.25 percent by weight has been found to be useful.

Further, the brass alloy contains a proportion of zinc of 36.0 to 46 weight percent and the proportion of copper is between 54 and 64 weight percent.

Furthermore, the alloy preferably has a mixed crystal with portions of an alpha microstructure or alpha / beta microstructure. In extreme cases, a brass alloy of 100% pha microstructure is conceivable if the zinc content is close to or equal to 36% by weight. However, preference is given to a mixed structure of alpha and beta microstructures, as a result of which, in particular, good machinability can be achieved. In particular, the proportion of copper may preferably be at most 60 percent by weight, and the zinc content may preferably be between 36 and 40 percent by weight, whereby a microstructure which is particularly favorable in terms of machinability can be achieved.

In this case, a mixed structure with particularly good properties can be realized by the weight fraction of the beta-structure 20 to 80 weight percent, preferably 50 weight percent, is.

In addition, at least one additional alloying component may be provided in a proportion of at most 3.0 percent by weight, the sum of the proportions of all additional alloying components being preferably at least 0.2 percent by weight.

The proportion of copper is preferably 54 to 64.0 percent by weight, and the proportion of zinc is preferably about 42 percent by weight.

The idea is based on the following approaches essential to the invention in order to achieve the desired material properties: a) The addition of indium has a positive effect on the chip-breaking properties. b) The microstructure is influenced by the proposed copper / zinc ratio such that an alpha / beta crystal mixture is present in which the proportion of beta phase is about 20 to 80%. Since the beta phase shows a brittle behavior under normal machining conditions, its increased proportion leads to a c) Further alloying elements serve to stabilize the alpha and beta phase, in particular during the production process of the semifinished product, d) In addition, the chipping behavior and the mechanical properties are positively influenced by the targeted addition of further precipitates of forming elements , On the one hand precipitates favor a short breaking chip, on the other hand a grain refinement is achieved, whereby an improved ductility at high strengths is achieved. E) A fourth advantage can be achieved by influencing the arrangement or orientation of the two phases alpha and beta and / or the precipitates, so as to adjust the processing properties specifically (eg by a combination of forming and heat treatment). Here, the chip-breaking properties are deliberately achieved by the alloying additives and in particular by the indium, so that an addition of bismuth is deliberately not provided. However, it can not be ruled out that small quantities of bismuth enter the alloy due to contaminated scrap, but this should not be understood as a deliberate addition of bismuth. Nevertheless, the solution according to the invention has the advantage that the chipbreaking own properties instead of the avoidable components lead and bismuth are now achieved with alloying additives, which are far more harmless in terms of possible health damage.

The precipitates contained in the microstructure support the machining behavior positively.

The alpha microstructure of the mixed crystal forms a cubic face-centered spatial structure. By contrast, the beta-mixed crystal structure forms a cubic-body-centered structure It proves to be particularly advantageous if the proportion of the beta structure is at least 50%. This is particularly supported by the fact that a zinc content of about 42 percent by weight is present.

The elements iron and nickel have a regulative influence on the grain growth of the alpha and beta phase, with nickel additionally promoting the stabilization of the alpha structure. Too high levels lead to embrittlement of the alloy.

The elements tin, silicon, manganese and iron stabilize and increase the proportion of the beta phase.

To improve the corrosion resistance, the addition of phosphorus may be provided. In particular, a maximum proportion of phosphorus in the range of 0.1% by weight is intended. According to a typical alloy composition, it is provided that the content of copper is 54 to 64.0% by weight.

A first additional alloying component is defined by the proportion of iron being from 0.05 to 0.5% by weight, preferably from 0.2 to 0.3% by weight. Iron is used to control the grain size of the alpha and beta hare. Contents less than 0.01% do not have a sufficient effect. Shares greater than 0.5% would lead to very large iron precipitates, which have a negative effect on the mechanical properties of the alloy.

A second additional alloying component is defined by the proportion of nickel being 0.05 to 0.5 weight percent, preferably 0.2 to 0.3 percent by weight, which advantageously stabilizes the alpha phase.

A third additional alloying component is defined by the proportion of silicon being from 0.01 to 0.20% by weight, preferably from 0.03 to 0.08% by weight. Silicon stabilizes the beta phase and, together with other elements, forms fine precipitates, which have a positive effect on the chipping behavior and are responsible for grain refining.

A fourth additional alloying component is defined by the proportion of manganese being 0.01 to 0.20% by weight, preferably 0.03 to 0.08% by weight. Manganese stabilizes the beta phase and, together with other elements, forms fine precipitates, which have a positive effect on the chipping behavior and are responsible for grain fines, similar to the proposed additional alloy component silicon.

A fifth additional alloy component is defined by the content of tin being 0.05 to 0.5% by weight, preferably 0.2 to 0.3% by weight.

A sixth additional alloying component is defined by the proportion of Cr being from 0.01 to 0.2% by weight.

Further, calcium and / or magnesium may be additionally provided in a proportion of 0.05 to 1.0% by weight, respectively Phosphor leads to an improved corrosion resistance of the alloy, in particular, P also acts against dezincification.

For an optimum composition of the alloy, it contributes that the proportion of elements other than copper, zinc, indium, iron, nickel, silicon, manganese, antimony, calcium, cadmium, selenium, magnesium, lead or tin is less than 0.2 Weight percent.

A preferred embodiment of the alloy preferably has the following percentages by weight with respect to its composition. Copper in the range of 54% to 64%, zinc in the range of 36% to 40.5%, iron in the range of 0.1% to 0.5%, nickel in the range of 0.1% to 0.5%, Silicon in the range of 0.01% to 0.2%, manganese in the range of 0.01% to 0.2%, antimony, calcium, cadmium, magnesium and selenium in the range to 0.1%, and tin in the range from 0.1% to 0.5% and lead with a maximum content of 0.1%. The content of indium preferably has 0.005 to 0.5%. The lead content of the alloy, also due to the use of scrap in the production of such alloys, is max. 0.1%.

According to the proportion of the above additives, components of copper and / or zinc are optionally reduced.

According to a particularly preferred embodiment, the proportion of copper is 57.0% to 57.5%, the proportion of zinc 41.9 to 42.5%, the proportion of nickel 0.2% to 0.3%, the proportion of Iron 0.2% to 0.3%, the proportion of silicon 0.03% to 0.08%, the proportion of manganese 0.03% to 0.08%, antimony, Kai cium, cadmium, magnesium and selenium in the Range up to 0.1% and the proportion of tin 0.2% to 0.3% and the proportion of Lead and indium less than 0.1% each. In addition, it is particularly conceived that the sum of the weight proportions of all other possible components is not more than 0.2%.

According to a further preferred embodiment, the proportion of copper is 54 to 58%, zinc 41 to 45%, nickel 0.2 to 0.3%, iron 0.2 to 0.3%, silicon 0.03 to 0.06% , Manganese 0.03 to 0.08%, calcium 0.3 to 0.5%, magnesium 0.6 to 0.9%, antimony <0.1%, cadmium <0.1%, selenium <0.1 %, the sum of lead and indium <0.1%, other components

<0.2%.

As for the above composition, it is basically possible to add only some of the listed elements to the alloy. According to a very particularly preferred embodiment, however, it is intended to add all the above-listed elements with a weight proportion within the respectively defined intervals in combination with one another to the alloy.

According to a typical embodiment, it is provided that the lead content is in an interval of 0.005% to 0.1%. The indium content should also be 0.005% to 0.5%. The inventive relationship between the alpha-mixed crystal and the beta-mixed crystal, the desired material properties can be achieved even at reduced lead or indium. The alpha-mixed crystal leads to a relatively good deformability of the alloy and gives this tough properties. The beta-mixed crystal, however, is relatively poorly deformable and brittle. These properties are desirable for good machinability. Due to the inventive relation of the alpha and beta shares become thus giving the alloy sufficient toughness to aid ductility and sufficient brittleness to aid machinability.

In addition to the pure relation between the alpha and the beta fractions, it also proves to be useful to influence the grain size of the mixed crystals. It has proven to be beneficial to support comparatively small and uniform particle sizes. By adding iron and silicon, iron silicides are formed which impede grain growth and thus have a positive effect on the microstructure. The addition of tin and / or iron promotes the formation of beta-mixed crystals.

It also turns out that the addition of manganese in combination with oxygen or phosphorus promotes the precipitation of oxides or phosphides and thereby leads to a finer grain structure. This in turn supports a good machinability. In small amounts, also proportions of phosphorus prove to be positive in terms of the formation of the microstructure.

With regard to the production of the alloy, a preferred production process can be carried out such that initially a hot working (eg hot rolling or extrusion) in a temperature range of 600 to 750 ° C is performed. It is thereby produced a structure having a proportion of the beta mixed crystal of about 50 weight percent. To support both good machinability and good ductility, it is possible to carry out an intermediate annealing. In this case, an intermediate annealing with a temperature of about 400 to 600 ° C. is carried out after a first forming step. The> intermediate annealing leads to a recrystallization tion and thus to a grain new formation. As a result, a fine-grained microstructure is supported.

By suitably performing the intermediate annealing, it is possible to realize a weight ratio of the beta mixed crystal of 30 to 60%. It is thereby achieved an increased formability of the semifinished product.

According to the invention, it is provided in particular to form the brass alloy of copper and zinc, with a lead content of 0.005 to 0.1%, an indium content of 0.005 to 0.5% and with at least one further alloying component. This additional alloying component influences the microstructure of the mixed crystal in order to achieve the respective desired material properties depending on the application.

According to a further preferred embodiment, it is provided to realize the following alloy in terms of weight percent.

Cu 55 to 56%, Fe 0.2 to 0.3%, Ni 0.1 to 0.2%, Si 0.01 to 0.03%, Mn 0.1 to 0.2%, Sn 0.3 to 0.5%, In 0.05 to 0.2%, Sb <0.1%, Ca <0.1%, Cd <0.1%, Se <0.1%, Pb <0.1% , Zn rest. This embodiment leads to a particularly high proportion of beta-mixed crystals between 55 and 70% beta-portion, which causes a particularly short-breaking chip.

Another preferred embodiment is provided in terms of weight percent by the following alloy.

Cu 57 to 57.5%, Fe 0.2 to 0.3%, Ni 0.2 to 0.3%, Si 0%, Mn 0%, Sn 0.2 to 0.3%, In 0.05 to 0.2%, Sb <0.1%, Ca <0.1%, Cd <0.1%, Se <0.1%, Pb <0.1%, Zn rest. The proposed composition here is to achieve a slightly increased alpha content and less hard precipitates.

Moreover, with regard to preferred embodiments, it is also intended to realize the following alloy in terms of weight percentages.

Cu 56 to 56.5%, Fe 0.4 to 0.5%, Ni 0.2 to 0.3%, Si 0%, Mn 0.1 to 0.2%, Sn 0.35 to 0.5 %, In 0.05-0.2%, Sb <0.1%, Ca <0.1%, Cd <0.1%, Se <0.1%, Pb <0.1%, Zn remainder. As a result, less hard precipitates are formed and promote the formation of the excretions of primarily excreted iron. The increased addition of manganese and tin results in an increased beta content compared to the previous embodiment.

The brass alloy according to the invention is used for the production of so-called semi-finished products which are subjected to at least one additional processing step. The semi-finished products are typically produced by a casting process. Typical embodiments of such semi-finished products are tapes, wires, profiles and / or rods. The further processing step includes at least one machining operation. Likewise, the further processing step may comprise a combination of shaping and machining. The shaping can be carried out both at room temperature and at an elevated temperature. At the elevated temperatures, a warm temperature of up to about 450 ° C and a hot working temperature in a range of 600 ° C to 850 ° C can be distinguished. The addition of the alloying elements iron, nickel, magnesium, calcium or chromium precipitates can be produced in the solid solution, which in turn favor the chip breaking in a subsequent mechanical processing, so that these alloying ingredients have a similar beneficial effect as previously used and where possible have avoiding lead. In this case, the chip breaking can be favorably influenced in particular by a specific ratio of the alloy constituents iron and tin, since the ratio of these two alloy constituents to one another particularly promotes the formation of the precipitates. Such a favorable ratio of iron to tin would be, for example, 1.0 to 1.2.

Furthermore, the formation of the precipitates or grain refining and thus chip breaking can be favorably influenced if the brass alloy contains chromium in an amount of 0.01 to 0.2 percent by weight and / or calcium and / or magnesium in an amount of 0 in each case , 0.05 to 1.0 percent by weight is added.

In the ideal case, the proportion of bismuth is equal to 0.0 percent, ie the brass alloy is free of bismuth. The chip-breaking properties are achieved solely by the indium content and the other alloying constituents, such as iron, tin, nickel, manganese, magnesium, calcium or chromium. This is desirable because bismuth should be avoided as far as possible on account of its health-damaging properties or should at least be used in the least possible amount. For this reason, the proportion of bismuth in the brass alloy according to the invention is already limited to a maximum value of 0.1 percent by weight, wherein it is desirable to keep the proportion of bismuth as low as possible. So it is possible, for example, that a small amount of bismuth through the use of contaminated scrap into the brass alloy. This proportion of actually unwanted bismuth is used by the inventive solution equal to the formation of precipitates and grain refining and thus to positively influence the Zerspanungsverhaltens, and it can be dispensed at least on the previously used also harmful lead in the alloy. If the proportion of bismuth can not be completely reduced to 0.0, for example due to impurities of added scrap, the proportion should preferably not exceed a maximum value of <0.003 percent by weight. Alternatively, however, a lead content of not more than 0.1 percent by weight may be provided in this case in order to set the desired chip breaking. In any case, no bismuth is actively added to the brass alloy according to the invention, but it is instead only accepted if it is unavoidable for technical reasons. However, as it may well have positive effects on the material properties of the brass alloy, despite its harmful properties, even very small quantities can be accepted.

Furthermore, it is possible to produce the structural properties, in particular the formation of the needle-like beta phase, by pressing or pulling or at least to reinforce the formation of the beta phase or to emboss it in a desired direction. Alternatively, by a combination of the pressing, annealing, and drawing operations in this order, or pressing, drawing, annealing, drawing, the appearance of a more globular morphology of the beta phase in the solid solution may be promoted, with the size of the grains and constituents of the beta phase passing through the selected process temperature can be adjusted during annealing, pressing or drawing. The higher the process temperature, the larger the grains and the coarser the microstructure.

Claims

Claims :

1. Brass alloy of 54 to 64 weight percent Cu and 36 to 46 weight percent Zn, characterized in that the alloy has an indium content of 0.005 to 1.0 weight percent, preferably 0.05 to 0.5 weight percent and an addition of at least one of Fe , Sn, Ni or Mn of 0.01 to 3.0 wt% and no addition of Bi.

2. brass alloy according to claim 1, characterized in that

the alloy has a mixed crystal with portions of an alpha-microstructure or of an alpha / beta microstructure with precipitates.

3. brass alloy according to claim 2, characterized in that

the weight fraction of the beta structure is 20 to 80% by weight, preferably 50% by weight.

4. brass alloy according to one of the preceding claims, characterized in that

the sum of the proportions of all alloying components in addition to Cu and Zn is at least 0.2% by weight.

5. brass alloy according to one of the preceding claims, characterized in that the proportion of Zn is 42 weight percent.

6. brass alloy according to any one of the preceding claims, characterized in that the proportion of Fe 0.05 to 0.5 Weight percent, preferably 0.2 to 0.3 weight percent, is.

7. brass alloy according to any one of the preceding claims, characterized in that the proportion of Ni 0.05 to 0.5 weight percent, preferably 0.3 weight percent, is.

8. Brass alloy according to one of the preceding claims, characterized in that the alloy has a content of Si of 0.01 to 0.20 weight percent, preferably 0.03 to 0.20 weight percent.

9. brass alloy according to any one of the preceding claims, characterized in that the proportion of Mn 0.01 to 0.20 weight percent, preferably 0.03 to 0.08 weight percent, is.

10. brass alloy according to any one of the preceding claims, characterized in that the proportion of Sn 0.05 to 0.5 weight percent, preferably 0.2 to 0.5 weight percent, is.

11. Brass alloy according to one of the preceding claims, characterized in that the proportion of Sb is up to 0.5 percent by weight.

12. Brass alloy according to one of the preceding claims, characterized in that the alloy has a proportion of cadmium of up to 0.5 weight percent.

13. brass alloy according to any one of the preceding claims, characterized in that the alloy to a share of Ca of up to 0.5, preferably up to 1.0 weight percent.

Brass alloy according to one of the preceding claims, characterized in that the alloy has a content of Mg of up to 0.5, preferably up to 1.0 weight percent.

15. Brass alloy according to one of the preceding claims, characterized in that the alloy has a proportion of Se of up to 0.5 weight percent.

16. brass alloy according to any one of the preceding claims, characterized in that the proportion of substances which are not Cu, Zn, Fe, In, Ni, Si, Mn, Sb, Ca, Cd, Se, Pb or Sn, less than 0 , 2 weight percent.

17. Brass alloy according to one of the preceding claims, characterized in that the brass alloy has the following percentages by weight: Cu 55 to 56%, Fe 0.2

to -0.3%, In 0.005 to 0.5%, Ni 0.1 to 0.2%, Si 0.01 to 0.03%, Mn 0.1 to 0.2%, Sn 0.3 to 0.5%, Sb <

0.1%, Ca <0.1%, Cd <0.1%, Se <0.1%, Pb <0.1%, Zn remainder.

Brass alloy according to any one of claims 1 to 16, characterized in that the brass alloy has the following percentages by weight: Cu 57 to 57.5%, Fe 0.2 to 0.3%, In 0.005 to 0.5%, Ni 0.2 to 0.3%, Sn 0.2 to 0.3%, Sb <0.1%, Ca <0.1%, Cd <0.1%, Se <0.1%, Pb <0.1% , Zn rest.

19. Brass alloy according to one of claims 1 to 16, characterized in that the following percentages by weight are realized: Cu 56 to 56.5%, Fe 0.4 to 0.5%, In 0.005 to 0.5%, Ni 0.2 to 0.3%, Si 0%, Mn 0.1 to

0.2%, Sn 0.35 to 0.5%, Sb <0.1%, Ca <0.1%, Cd <0.1%, Se <0.1%, Pb <0.1%, Zn rest.

20. Brass alloy according to one of claims 1 to 16,

characterized in that the following percentages by weight are realized: Cu 54 to 58%, Zn 41 to 45%, Ni 0.2 to 0.3%, Fe 0.2 to 0.3%, Si, 0.03 to 0.06 %, Mn 0.03 to 0.08%, Ca 0.3 to 0.5%, Mg 0.6 to 0.9%, Sb <0.1%, Cd <0.1%, Se <0, 1%, the sum of Pb and In <0.1%, other components <0.2%.

21. Brass alloy according to one of the preceding claims, characterized in that the brass alloy has a phosphorus content of at most 0.1 percent by weight.