EP2625300B1 - Copper alloy - Google Patents

Description

The invention relates to a copper alloy, in particular a lead and tellurfreien copper alloy, as well as semi-finished products of such a copper alloy.

Due to its natural qualities, copper is an indispensable material in many areas of industry and technology. Particularly where materials of the highest electrical and thermal conductivity are required, copper and copper alloys are of great importance. However, the use of pure copper is difficult then if parts are to be machined. The high toughness of copper, which is particularly valued in chipless shaping, proves to be a disadvantageous material property here. Essential for this is the long chip formation, which inhibits the workflow during drilling and turning and leads to heavy wear of the tool cutting. On CNC-controlled, but also on conventional automatic lathes, pure copper can normally only be processed or processed with uneconomically high expenditure of time, personnel and tools.

Are known machinable copper materials with additions of lead, bismuth, sulfur and tellurium. Already in the US-A-1,959,509 the favorable influence of the addition of bismuth on the machinability of copper alloys was explained. The advantageous properties of tellurium in copper alloys go out of the US-A-2,027,807 out.

As chip breaker lead and bismuth act in metallic form, while sulfur and tellurium act as intermetallic phase in the form of copper sulfide (Cu ₂ S) or copper telluride (Cu ₂ Te). However, the low melting points of lead and bismuth limit the hot workability, for example by extrusion, considerably, so that an economic processability on conventional production facilities is not, or only limited. In addition, there are health and environmental concerns regarding lead in copper alloys.

In contrast, copper materials with additions of sulfur or tellurium in the form of CuSP or CuTeP are characterized by a favorable combination of good machinability and very high electrical and thermal conductivity. However, as a result of scarcity of raw materials, tellurium is limited in availability and comparatively expensive. With an increasing resource shortage of tellurium, therefore, an alternative is desirable.

From the DE 1 558 707 A1 For example, a sulfur-containing copper alloy is known in which the machinability, ductility, particularly by extrusion molding, while maintaining and / or increasing the high resistance to wear under stress on slip, friction and wear, is improved and which contains 0.005 to 2% sulfur.

In Elvira Moeller: "Handbuch Konstruktionswerkstoffe", 31 December 2008, pages 365 to 379 describes properties of copper wrought materials in terms of conductivity and processability. The effects of different alloying elements are highlighted.

Furthermore, the state of the art is the US 4,337,793A to name copper alloys for water pipes. These alloys may additionally contain up to 1.0% calcium to prevent the release of copper ions from the tubes, especially with stagnant and / or hot water.

The DE 30 43 833 A1 discloses a tube for transporting water and / or hot water from a copper material with 0.05 to 2.8% magnesium. The alloy may additionally contain aluminum and / or proportions of silicon and between 0.005 to 1.0% by weight of calcium. This copper alloy is also designed to prevent the deterioration of water quality.

The invention is therefore based on the prior art, based on the object to show a copper alloy, which has at least the same or better machinability and cold and hot workability over the known copper alloys CuTeP and CuSP.

A solution to this problem is according to the invention in a copper alloy according to claim 1.

According to the invention, a copper alloy based on copper with additions of manganese and sulfur as well as accompanying elements which does not require lead or tellurium but has good machinability is proposed.

The copper alloy is made of copper containing as alloying constituents 0.10 to 0.20% by weight of manganese (Mn), 0.10 to 0.80% by weight of sulfur (S), optionally one or more elements selected from among Selected from the group consisting of 0.002 to 0.05% by weight of phosphorus (P), 0.01 to 0.5% by weight of chromium (Cr), 0.01 to 0.5% by weight of aluminum (Al ), 0.01 to 0.5% by weight of magnesium (Mg), together with unavoidable impurities.

The chip breaker in the CuSMn alloy according to the invention is a mixed phase consisting of copper sulfide (Cu ₂ S) and manganese sulfide (MnS).

Particularly preferred is a sulfur content which is between 0.20 to 0.60 wt .-%.

Phosphorus serves as a deoxidizer, which binds to the dissolved in the melt free oxygen and thus prevents gas bubbles (hydrogen disease) and oxidation of alloying constituents. Furthermore, phosphorus added to improve the flow properties of the copper alloy during casting.

Manganese refines the grain and improves its machinability in combination with sulfur.

Aluminum increases hardness and mating limit without reducing toughness. Aluminum is an element that improves strength, machinability, and wear resistance as well as oxidation resistance at high temperatures.

Chromium and magnesium are used to improve the oxidation resistance at high temperatures. Particularly good results are achieved when mixed with aluminum to achieve a synergistic effect.

The inventively proposed copper material CuSMn has a machinability that is equal to or better than CuSP. In tests, a machinability index of 90% for CuSMn and 76 and 79% for the reference materials CuTeP and CuSP was determined.

The material has an electrical conductivity of between 35 to 55 MS / m, in particular in a range of 48 to 53 MS / m. Furthermore, the inventively proposed copper alloys is free of toxic alloying elements and cost, since the alloying elements are available at low cost. It should also be emphasized that the scraps are reusable. A particular criterion of the proposed copper alloy is that a processability with conventional manufacturing and processing machines is possible, in particular, the alloy has both a sufficient cold workability and a very good hot workability.

Semifinished products in the form of rolled products, pressed / drawn products, forged products or cast products can therefore be made available from the copper alloys proposed according to the invention.

• Anhand von 2 Ausführungsbeispielen seien die erfindungsgemäß vorteilhaften Eigenschaften der neuen blei- und tellurfreien Legierung im Vergleich zu den bekannten und genormten Werkstoffen CuTeP (= EN-Werkstoff CW118C, ASTM-Werkstoff C14500) und CuSP (= EN-Werkstoff CW114C, ASTM-Werkstoff C14700) erläutert.

Exemplary embodiments and comparative considerations:

• Based on two exemplary embodiments, the novel properties of the new lead-free and tellurium-free alloy compared to the known and standardized materials CuTeP (= EN material CW118C, ASTM material C14500) and CuSP (= EN material CW114C, ASTM material C14700 ) explained.

In a crucible induction furnace each CuSMn and the reference materials CuTeP and CuSP were melted and cast in a continuous casting process to extrusion billets. The composition of the materials is shown in Table 1. The composition of CuMnS complies with claims 1, 2 and 3. The composition of the reference materials meets the requirements of the EN and ASTM standards for the materials CuTeP and CuSP. The continuously cast round bolts were extruded without problems to press bars in an extrusion process with a heating temperature ≥ 850 ° C and then drawn with a cross-sectional decrease of 10 to 15% to the final dimension of φ 35 mm. With a 10% to 15% reduction in cross section, the most commonly used state of supply for machinable copper is R250 according to EN 12164 or H02 according to ASTM B301. Table 2 shows the mechanical-technological characteristics, Brinell hardness and spec. electrical conductivity of the thus finished drawn rods reproduced. As the test results show, the new materials according to the invention with the standard materials CuTeP or CuSP have comparable mechanical characteristics and an equally good electrical conductivity. Due to the even better strength / elongation at break compared to the standard material CuSP, the material CuSMn offers the advantage of a better cold formability (for example for the production of "hammered" burner nozzles).

Zerspanbarkeitsuntersuchungen:

Comparative machinability tests in the form of drilling tests were performed on the bars listed in Table 2. The machining by drilling was preferred to machining by turning or threading, because the production of small holes (eg in burner nozzles) is the most difficult machining shape. Shows a material here positive Results, the machining by turning or threading is also no problem.

• Bohrwerkzeug:
  • 2 mm Φ Vollhartmetallbohrer mit Innenkühlung
  • Spitze beschichtet mit AITIN
  • Typ Gühring WNRN15XD
• Bohrstrategie:
  • stirnseitig 45 Bohrungen in Stangenabschnitte einbringen:
  • Schnittgeschwindigkeit:100 m/min
  • Vorschub:0,04 mm/Umdrehung
  • Bohrtiefe:33 mm
  • Innenkühlung Bohrer:Emulsion 40 bar

For the drilling tests, the following parameters were used in modern CNC processing machines:

• drilling:
  • 2 mm Φ solid carbide drill with internal cooling
  • Tip coated with AITIN
  • Type Guhring WNRN15XD
• drilling strategy:
  • Insert 45 holes in rod sections on the front side:
  • Cutting speed: 100 m / min
  • Feed: 0.04 mm / revolution
  • Drilling depth: 33 mm
  • Internal cooling Drill: Emulsion 40 bar

• die Spanform in Anlehnung an das Stahleisenprüfblatt 1178-90
• die mittlere Spanmasse über Gewichtsmessung von jeweils 100 Spänen
• der Werkzeugverschluss als Freiflächenverschluss nach 270 Bohrungen
• die erforderliche mittlere Vorschubkraft
• die Bohrungsqualität anhand der Kriterien:
  • Zylindrizität (Konizität) der Bohrung über der Länge
  • Rundheit der Bohrung über den Umfang
  • Durchmesserabweichung über die Länge
  • Rauheit R_z der Bohrungsoberfläche

Rated:

• the chip shape based on the steel iron test sheet 1178-90
• the mean chip mass over weight measurement of 100 chips each
• the tool lock as an open space lock after 270 holes
• the required mean feed force
• the hole quality based on the criteria:
  • Cylindricity (conicity) of the hole over the length
  • Roundness of the hole over the circumference
  • Diameter deviation over the length
  • Roughness R _{z of} the bore surface

In order to allow a quantitative comparative evaluation of the material with the reference materials, the individual measurement results were evaluated with a points system of 0 to 10 points, where 0 points are extremely bad and 10 points are optimal = very good.

• CuSMn : 90 %
• CuTeP : 76 %
• CuSP : 79 %

The individual ratings have been added, with a maximum of 80 points are achievable. This overall assessment of machinability is here as a machinability index 80 points then correspond to a maximum achievable machinability index of 100%. The new material CuSMn according to the invention achieves the following machinability indices in comparison with the reference materials:

• CuSMn: 90%
• CuTeP: 76%
• CuSP: 79%

To illustrate the good short brittle machinability of all materials are in Fig. 1 the drill cuttings from the Zerspanbarkeitsuntersuchungen shown. The slightly longer Wendelspanstücke occur only occasionally. The very detailed and expensive Zerspanbarkeitsuntersuchungen have shown that the material according to the invention in the machinability of the previously available reference materials CuSP and CuTeP are at least equivalent or even have slight advantages.

• Zerspanbarkeit gleich oder besser als CuTeP/CuSP;
• Elektrische Leitfähigkeit ≥ 35 MS/m;
• Frei von toxischen Legierungselementen;
• Kostengünstige Verfügbarkeit der Legierungselemente;
• Wiederverwendbarkeit der Schrotte;
• Verarbeitbarkeit mit konventionellen Fertigungsschritten und -maschinen.

The inventors have carefully created a copper material that complements the current range of CuTeP and CuSP and has the following quality characteristics:

• Machinability equal to or better than CuTeP / CuSP;
• Electrical conductivity ≥ 35 MS / m;
• Free from toxic alloying elements;
• Cost-effective availability of alloying elements;
• Reusability of the scraps;
• Workability with conventional manufacturing steps and machines.

The alloying elements aluminum (Al), calcium (Ca), cobalt (Co), chromium (Cr), iron (Fe), magnesium (Mg), manganese (Mn), molybdenum (Mo), nickel (Ni) were investigated in each case. , Tin (Sn) and Zinc (Zn) in combination with Sulfur (S) and Calcium (Ca) as sole additive to copper, in terms of achievable electrical conductivity and machinability. The proven materials CuSP and CuTeP served as comparison samples for the machinability tests. Qualitatively, the chip shape was measured when drilling 3 mm holes and the occurrence of drill breaks.

The desired material properties or property combinations were achieved by the addition of manganese, to a proportion of 0.10 to 0.20 wt .-% and sulfur in a proportion of 0.10 to 0.80 wt .-%, in particular 0.20 to 0.60 wt .-%.

It has been found to be essential to the invention that the copper material CuSMn shown has the abovementioned independent chip-breaking phases, namely the mixed phase consisting of Cu ₂ S and MnS.

When processing and testing material samples of the copper alloys according to the invention, it was found that, in particular, the copper alloy CuSMn has a CuTeP-comparable or even slightly better hot and cold formability with the copper alloy CuSP or the copper alloy. <u> Table 1 </ u> Composition of the material according to the invention CuSMn and the reference materials CuTeP and CuSP material Composition in% by weight Cu Te S Mn Ca P unavoidable admixtures CuSMn 99.50 / 0.30 0.18 / 0,007 0.01 CuTeP 99.53 0.44 / / / 0,007 0.02 Setpoints EN -CW118C rest 0.4-0.7 / / / 0.003-0.012 ≤0,1 Setpoints ASTM -C14500 + Te ≥ 99.90 0.40-0.7 / / / 0.004-0.012 / CuSP 99.65 / 0.31 / / 0.005 0.03 Setpoints EN -CW114C rest / 0.2-0.7 / / 0.003-0.012 ≤ 0.1 Setpoints ASTM -C14700 + S ≥ 99.90 / from 0.20 to 0.50 / / 0.002 - 0.005 / Mechanical-technological characteristics of the material according to the invention CuSMn and the reference material CuTeP and CuSP in the drawn semi-hard state (R250 according to EN or 12164 HO2 according to ASTM B301) material tensile strenght 0.2% proof stress elongation Brinell hardness spec. el. Cond. in soft state at 20 ° C R _m (MPa) R _p0.2 (MPa) A (%) HBW2,5 / 62.5 (MS / m) (% IACS) CuSMn 265 245 20 85 53.0 91.5 CuTeP 286 257 18 88 53 91.5 CuSP 269 263 14 85 52.5 90.5 Setpoints for CuTeP + CuSP: EN 12164 R250 ≥250 ~200 ≥7 ~90 / / Setpoints for C14500 + C14700 ASTM B301 HO2 ≥260 ≥205 ^1)
1) 0.5% proof stress under load ≥ 12 / / CuTeP ≥85.0 CuSP ≥90.0 Results of the machinability studies ( including evaluation ) hole quality material chip shape average chip size Free area wear after 270 holes medium advance b-force Cylindricity (conicity of the bore) Roundness (diameter deviation over circumference) Diameter deviation over length Roughness R _z Gesamtbe-evaluation Machinability index x in% ug microns N microns microns microns microns Total points (80 P = 100%)
% CuSMn Spiral hairpins, spiral pieces Spirels panstück e (8 P) 90 (8P) 20 (8P) 40 (9p) 20 (9p) 5 (10 P) 0 (10p) 1 (10p) (72) 90 CuTeP Spiral saws Spiral pieces Pieces of bread (8 P) 110 (8P) 20 (8P) 35 (10 P) 50 (6P) 10 (5 points) 20 (6P) 1 (10p) (61) 76 CuSP Spiral saws Spiral pieces Pieces of bread (8 P) 90 (8P) 28 (4P) 50 (7 points) 30 (8P) 5 (10 P) 10 (8 points) 1 (10p) (63) 79

- no material breaks occurred on any material -

Claims (9)

1. Alloy based on copper, consisting of:

   0.10 to 0.20% by weight manganese (Mn),

   0.10 to 0.80% by weight sulphur (S),

   optionally, one or more elements which are selected from the group which consists of

   0.002 to 0.05% by weight phosphorus (P),

   0.01 to 0.5% by weight chromium (Cr),

   0.01 to 0.5% by weight aluminium (Al),

   0.01 to 0.5% by weight magnesium (Mg),

   and the remainder copper (Cu) and unavoidable impurities.
2. Alloy based on copper according to Claim 1, wherein the sulphur proportion is measured to be between 0.20 and 0.60% by weight.
3. Alloy based on copper according to Claim 1 or 2, wherein the electrical conductivity is 35 to 55 MS/m.
4. Alloy based on copper according to Claim 3, wherein the electrical conductivity is 48 to 53 MS/m.
5. Alloy based on copper according to any one of Claims 1 to 4, wherein the machinability rating is between 80% and 95%.
6. Semi-finished product consisting of an alloy according to any one of Claims 1 to 5 in the form of a rolled product.
7. Semi-finished product consisting of an alloy according to any one of Claims 1 to 5 in the form of a pressed/drawn product.
8. Semi-finished product consisting of an alloy according to any one of Claims 1 to 5 in the form of a forged product.
9. Semi-finished product consisting of an alloy according to any one of Claims 1 to 5 in the form of a cast product.

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