BRASS ALLOY

Abstract

A brass alloy is formed from 54 to 64% Cu, 0.05 to 0.15% Al, 0.005 to 0.5% In, at least one of the components of Fe, Sn and Ni in an amount of 0.01 to 3.0%, balance Zn and also unavoidable impurities. The combination of these materials provides a brass alloy that has improved machinability.

Description

FIELD AND BACKGROUND OF THE INVENTION

The invention relates to a brass alloy. It relates more particularly to a brass alloy to which neither lead (Pb) nor bismuth (Bi) have been added.

One such brass alloy is known from European patent EP 3 320 122 B1. The known brass alloy consists of 54 to 64% Cu and 36 to 46% Zn, and the alloy has an In content of 0.005 to 1.0% and an addition of at least one of the components Fe, Sn, Ni or Mn of together 0.01 to 3.0%. No Bi is added to the alloy.

In the past, the machinability of brass alloys was improved by adding Pb to an extent of up to 4 wt %. The addition of Pb is greatly restricted owing to statutory stipulations, according to application.

It has been found that the addition of Pb may be replaced by an addition of Bi. It has emerged, however, that the addition of Bi leads to hot embrittlement of the brass alloy. Brass alloys of this kind have only limited amenability to hot forming. Consequently, such brass alloys are not used for parts shaped by pressing.

The above-referenced EP 3 320 122 B1 discloses a brass alloy with neither Pb nor Bi added. To improve the machinability, the addition to the brass alloy of 0.005 to 1.0% In is proposed. The proposed addition of In does indeed improve the machinability. Machining, however, produces relatively long spiral chips, which can lead to blockages as they are transported away, and to tool breakage.

SUMMARY OF THE INVENTION

It is an object of the invention to eliminate the disadvantages according to the prior art. The intention more particularly is to specify a brass alloy of improved machinability. According to a further objective of the invention, the brass alloy is to exhibit low hot embrittlement, so allowing it to be processed by hot forming.

This object is achieved by the features of the independent claim. Judicious embodiments are apparent from the features of the dependent claims.

In accordance with the invention, a brass alloy is proposed with

• • 54 to 64% Cu,
  • 0.15% Al,
  • 0.5% In,
  • at least one of the components Fe, Sn and Ni in an amount collectively of 0.01 to 3.0%,
  • balance Zn and also
  • unavoidable impurities.

For the purposes of the present description, [%] is understood to be percent by weight.

It has surprisingly emerged that through the addition of 0.05 to 0.15% Al, as proposed in the invention, to a brass alloy which contains 0.005 to 0.5% In, improved chip breaking can be achieved. The proposed brass alloy is notable for low hot embrittlement. It may be processed by hot forming.

To produce the proposed brass alloy, neither Pb nor Bi are added. The aforesaid elements are included in the proposed brass alloy, if at all, only as unavoidable impurities.

According to one advantageous embodiment, at least one of the components Fe, Sn and Ni is present in an amount of 0.05 to 0.4%, preferably in an amount of 0.1 to 0.3%. With particular preference, the components Fe, Sn and Ni are present in an amount of in each case 0.1 to 0.3%. The proposed addition of Fe and Ni influences the grain growth of the alpha and beta solid solutions. Sn stabilizes the beta solid solution. Accordingly, through the fractions of Fe, Sn and Ni, it is possible to adjust the ratio between the alpha and the beta solid solution or between the alpha and beta phases.

According to a further embodiment, the brass alloy contains Si in an amount of up to 0.01%. Si likewise acts to stabilize the beta phase.

According to a further embodiment, Mn is present in an amount of up to 0.2%. Mn as well stabilizes the beta phase and with other elements contributes to the formation of precipitates which have beneficial consequences for the machining behavior.

It has proven advantageous, furthermore, for the Zn content to be to 44%, preferably more than 41% and less than 43%. A brass alloy having the proposed Zn content comprises relatively little Cu and is consequently inexpensive to produce.

According to a further particularly advantageous embodiment, the only components added for producing the proposed brass alloy are the following: Cu, Fe, Ni, Sn, In, Al and Zn. Accordingly, the following composition has proven particularly advantageous:

• • 56.0 to 58.0% Cu,
  • to 0.3% Fe,
  • to 0.3% Ni,
  • to 0.3% Sn,
  • 0.005 to 0.25% In,
  • 0.05 to 0.15% Al,
  • balance Zn and also
  • unavoidable impurities.

The proposed brass alloy is notable for very good machinability. It can be deformed by hot forming.

The brass alloy advantageously comprises a matrix composed of a beta solid solution with fractions of an alpha solid solution. The fraction of alpha solid solution is advantageously at least 28%, preferably at least 30%. The proposed brass alloy is notable for particularly favorable machine behavior.

The proposed brass alloy may further comprise one or more of the following components.

Sb and/or Cd and/or Se in an amount of in each case up to 0.5%. It has emerged that higher contents of Sb and/or Cd and/or Se are detrimental to the properties of the brass alloy.

Ca and/or Mg in an amount of in each case up to 1.0%. Ca and/or Mg contribute to the formation of precipitates in the solid solution. Such precipitates favor the machinability of the brass alloy.

P in an amount of up to 0.1%. P contributes to improve corrosion resistance of the brass alloy. In particular, P counteracts removal of zinc.

Cr in an amount of up to 0.2%. Cr may in turn contribute to the formation of precipitates in the solid solution that favor the machinability of the brass alloy.

Illustrative examples of the invention are elucidated below.

The table below shows the composition of a reference alloy and also of an alloy according to the invention.

TABLE I
	Cu	Fe	Ni	Si	Mn	Sn	In	Al	Zn
Reference alloy	56.51	0 23	0 24	0.03	0.02	0 26	0 24	—	Balance
alloy of the invention	56.45	0.19	0.19	0.001	0.01	0.21	0.10	0.09	Balance

The numerical values reported in the table above are [%] or [wt %].

The microstructure of the reference alloy consists of a matrix composed of a beta solid solution with 39% alpha solid solution.

The microstructure of the alloy of the invention consists of a matrix composed of a beta solid solution with 32% alpha solid solution.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described herein as embodied in a brass alloy, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an illustration showing chips after a machining trial on the reference alloy (prior art); and

FIG. 2 is an illustration showing chips after a machining trial with the alloy of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Trial parameters used for performing the machining trials were as follows:

• • Rotary speed n of the spindles: 1600 min-1,
  • Advance velocity f: 0.1 mm/revolution,
  • Cutting depth a: 1.25 mm, and
  • Tool used: indexable cutting insert VBMT 160408-UR.

The machining trials were carried out in each case on specimens having an identical geometry.

FIG. 1 shows the result of the machining trial using the reference alloy. The chips formed are relatively long spiral chips. Their mean first length is approximately in the range from 15 to 20 mm.

FIG. 2 shows the result of the machining trial using the alloy of the invention. The chips formed are short, broken chips. Their mean second length is approximately in the range from 5 to 10 mm.

Claims

1. A brass alloy, comprising: 54 to 64 wt % Cu;0.05 to 0.15 wt % AI;0.005 to 0.5 wt % In;at least one component selected from the group consisting of Fe, Sn and Ni in an amount collectively of 0.01 to 3.0 wt %;balance Zn; andunavoidable impurities.

2. The brass alloy according to claim 1, wherein the at least one component selected from the group consisting of Fe, Sn and Ni is present in the amount of to 0.4 wt %.

3. The brass alloy according to claim 2, wherein the at least one component selected from the group consisting of Fe, Sn and Ni is present in the amount of to 0.3 wt %.

4. The brass alloy according to claim 3, wherein each of Fe, Sn and Ni is present as three components each being present in an amount of in each case of 0.1 to 0.3 wt %.

5. The brass alloy according to claim 1, further comprising Si in an amount of up to 0.01 wt %.

6. The brass alloy according to claim 1, further comprising Mn in an amount of up to 0.2 wt %.

7. The brass alloy according to claim 1, wherein the Zn content is 40 to 44 wt %.

8. The brass alloy according to claim 1, wherein only the following components have been added: Cu, Fe, Ni, Sn, In, Al and Zn.

9. The brass alloy according to claim 8, wherein: 56.0 to 58.0 wt % Cu;0.1 to 0.3 wt % Fe;0.1 to 0.3 wt % Ni;0.1 to 0.3 wt % Sn;0.005 to 0.25 wt % In;0.05 to 0.15 wt % AI;balance Zn; andunavoidable impurities.

10. The brass alloy according to claim 1, further comprising a microstructure having a matrix of a beta solid solution with fractions of an alpha solid solution.

11. The brass alloy of claim 10, wherein a fraction of the alpha solid solution is at least 28 wt %.

12. The brass alloy of claim 10, wherein the fraction of the alpha solid solution is at least 30 wt %.

13. The brass alloy according to claim 1, wherein the Zn content is more than 41 wt % and less than 43 wt %.