LEAD-FREE BRASS ALLOY AND METHOD OF USING THE LEAD-FREE BRASS ALLOY

Abstract

A lead-free brass alloy contains 57.0 to 60.0% wt. Cu, 1.0 to 2.0% wt. Al, 1.5 to 2.5% wt. Mn, 0.1 to 1.0% wt. Fe, at most 0.5% wt. Ni, at most 0.5% wt. Sn, 0.5 to 2.0% wt. Si, less than 0.1% wt. Pb, balance Zn and also unavoidable impurities. Wherein the copper equivalent (CuEq) is in the range from 52.0 to 58.0%.

Claims

1. A lead-free brass alloy, comprising: 57.0 to 60.0% wt. Cu, 1.0 to 2.0% wt. Al, 1.5 to 2.5% wt. Mn, 0.1 to 1.0% wt. Fe, at most 0.5% wt. Ni, at most 0.5% wt. Sn, 0.5 to 2.0% wt. Si, less than 0.1% wt. Pb, balance Zn; unavoidable impurities; and wherein a copper equivalent (CuEq) is in a range from 52.0 to 58.0%.

2. The lead-free brass alloy according to claim 1, wherein said Si is in an amount of at most 1.0% wt.

3. The lead-free brass alloy according to claim 1, wherein said Sn is in an amount of less than 0.2% wt.

4. The lead-free brass alloy according to claim 1, wherein said Ni is in an amount of at most 1.0% wt.

5. The lead-free brass alloy according to claim 1, wherein said Fe is in an amount of at most 0.5% wt.

6. The lead-free brass alloy according to claim 1, wherein said Mn is in an amount of at most 2.1% wt.

7. The lead-free brass alloy according to claim 1, wherein said Sn is in an amount of at most 0.1% wt.

8. The lead-free brass alloy according to claim 1, wherein said Sn is in an amount of less than 0.06% wt.

9. The lead-free brass alloy according to claim 1, wherein said Ni is in an amount of at most 0.5% wt.

10. The lead-free brass alloy according to claim 1, wherein said Fe is in an amount of at most 0.4% wt.

11. A method for producing goods, which comprises: producing parts for hydraulic pumps and hydraulic components using the lead-free brass alloy produced according to claim 1.

12. The method according to claim 11, which further comprises selecting the parts from the group consisting of: sliding blocks, distributor plates, retaining segments, and bearing bushes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0011] Proposed in accordance with the invention is a lead-free brass alloy containing 57.0 to 60.0% Cu, 1.0 to 2.0% Al, 1.5 to 2.5% Mn, 0.1 to 1.0% Fe, at most 0.5% Ni, at most 0.5% Sn, 0.5 to 2.0% Si, less than 0.1% Pb, balance Zn and also unavoidable impurities, wherein the copper equivalent (CuEq) is in the range from 52.0 to 58.0%.

[0012] The specified copper equivalent (CuEq) is calculated as follows:

If Si.SUB.free.=Si 3.26−(Fe+Mn)<0

[0013] a) then CuEq=Cu/{[100−Fe−Mn+(|Si.sub.free|.Math.0.7)−Al+(Al.Math.6)−Si)]/100}

If Si.SUB.free.=Si.Math.3.26−(Fe+Mn)>0

[0014] b) then CuEq=Cu/{[100−Fe−Mn−Al+(Al.Math.6)−Si+((Si.sub.free/3.26)10)]/100} [0015] c) Cu: % copper [0016] d) Fe: % iron [0017] e) Al: % aluminium [0018] f) Si: % silicon

[0019] For the purposes of the present description [%] is understood to be percent by weight.

[0020] In the above calculation of the copper equivalent CuEq, two cases, numbers 1 and 2, are distinguished. In case number 1 there is no free silicon Si.sub.free in the alloy. In this case, the silicon in the alloy bonds completely with Fe and/or Mn. Intermetallic Fe—Mn—Si compounds are formed.

[0021] In case number 2 there is free silicon Si.sub.free in the alloy. The distinction between the first and second cases is necessary because free silicon Si.sub.free in the alloy produces a strong shift in the phase diagram in the direction of the β-phase. In this case the shift in the phase diagram in the β-phase direction is stronger by a factor of about 10 than in the case of completely bonded silicon (see calculation above, case number 1).

[0022] It has emerged that the proposed brass alloy with a copper equivalent CuEq in the 52.0 to 58.0% range exhibits frictional properties comparable with those of conventional lead-containing alloys. The proposed lead-free brass alloy is notable additionally for good machinability, emergency operation properties, oil compatibility and the like.

[0023] According to one advantageous embodiment, Si is contained in an amount of at most 1.0%. In this way a particularly suitable β-phase content is established.

[0024] According to another embodiment, Sn is contained in an amount of at most 0.2%, preferably at most 0.1%, more preferably less than 0.06%. Sn increases the relaxation resistance of the alloy.

[0025] The lead-free brass alloy proposed may contain nickel in an amount of at most 1.0%, preferably at most 0.5%. Additionally, there may be Fe contained in an amount of at most 0.5%, preferably at most 0.4%. Mn may be contained in an amount of at most 2.1%. The aforesaid elements are added for the formation of intermetallic phases in the alloy. Intermetallic phases improve the wear resistance and the ductility of the alloy.

[0026] In further accordance with the invention, a use of the lead-free brass alloy of the invention is proposed, for producing parts for hydraulic pumps and hydraulic components. The parts may be selected in particular from the following group: sliding block, distributor plate, retaining segment, and bearing bush.

[0027] What makes the proposed brass alloy especially suitable for producing parts for hydraulic pumps and hydraulic components are its good frictional properties.

[0028] According to one exemplary embodiment of the invention, the alloy of the invention has for example the following composition:

TABLE-US-00001 Alloy constituent Wt % Cu 57.96 Al 1.56 Mn 1.94 Fe 0.36 Ni 0.06 Sn 0.01 Si 0.59 Pb 0.02

[0029] The alloy having the composition indicated above exhibits the properties identified in the following table:

TABLE-US-00002 Friction coefficient/ Properties wear Friction coefficient, lubricated 0.11 Splash lubrication in a Spirax/Fusus mixture in a ratio of 3 to 1 at 95° C. under a surface load of 52 N .Math. mm.sup.−2 and a rubbing velocity of 1.65 m/s in the pin-on-disc method Wear, lubricated, in km/g 226 km/g Splash lubrication in a Spirax/Fusus mixture in a ratio of 3 to 1 at 95° C. under a surface load of 52 N .Math. mm.sup.−2, a rubbing velocity of 1.65 m/s and a distance of 2500 m in the pin-on-disc method Friction coefficient, dry 0.20 under a surface load of 10 N .Math. mm.sup.−2 and a rubbing velocity of 0.55 m/s in the pin-on-disc method Wear, dry, in km/g 121 km/g under a surface load of 10 N .Math. mm.sup.−2 and a rubbing velocity of 0.55 m/s for 250 m in the pin-on-disc method

[0030] The good frictional properties of the alloy of the invention make it particularly suitable for producing hydraulic pumps and hydraulic components, more particularly sliding blocks, distributor plates, retaining segments and bearing bushes.