Abstract:
A wear resistant copper alloy composition which includes: 
     
       ______________________________________ 
     
     Component           (% by weight)______________________________________Zn                  20 to 40Al                  2 to 11at least one iron family metal               1 to 5selected from Fe, Ni, and CoTi                  0.1 to 4Component X, which is at least one               Mn = 0.01 to less than 0.1of Mn or S, in the amounts               S = 0.0005 to 0.01indicatedCu (with unavoidable impurities)               balance.______________________________________ 
     The copper alloy, which contains as an optional component Mg (from 0.01 to 0.5% by weight), is particularly suitable for manufacturing synchronizer rings in automatic transmissions for internal combustion engines.

Description:
BACKGROUND OF THE INVENTION 
     Synchronizer rings for automatic transmissions for internal combustion engines are required to withstand severe conditions and have wear resistance. Copper alloys have been used for such synchronizer rings. For example, Japanese Laid-Open Patent Application No. 64-55347 discloses the following composition: 
     
         ______________________________________Component          (% by weight)______________________________________Zn                 17 to 40Al                  2 to 11at least one of Fe, Ni, Co              0.02 to 3at least one of Ti, Zr, V              0.1 to 3.5at least one of P, Mg, Ca              0.003 to 0.3Mn                 0.1 to 4Cu (with unavoidable impurities)              balance.______________________________________ 
    
     With the advent of more powerful internal combustion engines recently, synchronizer rings made of known copper alloys do not possess sufficient wear resistance to withstand the higher load and higher rotation speed in these engines. Therefore, the lifetimes of known synchronizer rings when used in those engines were not adequate. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to develop a copper alloy having improved wear resistance, which is suitable for synchronizer rings. The copper alloy of the invention has the following composition: 
     
         ______________________________________Component            (% by weight)______________________________________Zn                   20 to 40Al                    2 to 11at least one of Fe, Ni, Co                1 to 5Ti                   0.1 to 4Component X, which is at least one                Mn = 0.01 to less than 0.1of Mn, S, in the amounts indicated                S = 0.0005 to 0.01Cu (with unavoidable impurities)                balance.______________________________________ 
    
     Another object of the invention is to develop a copper alloy composition having improved wear resistance and characterized by improved hardness, particularly at high temperatures. The copper alloy having those characteristics has the same composition as shown immediately above, but also contains Mg in the following amounts (% by weight): 
     
         ______________________________________Additional component            (% by weight)______________________________________Mg               0.01 to 0.5______________________________________ 
    
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a drawing illustrating a wear resistance test method. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In conducting research to obtain a copper alloy having increased wear resistance suitable for synchronizer rings, the inventors have determined that the use of an Mn content which is smaller than in known copper alloy compositions for synchronizer rings helps to increase the wear resistance. Thus, the copper alloy of the invention has the following composition: 
     
         ______________________________________Component            (% by weight)______________________________________Zn                   20 to 40Al                    2 to 11at least one of Fe, Ni, Co                1 to 5Ti                   0.1 to 4Component X, which is at least one                Mn = 0.01 to less than 0.1of Mn, S, in the amounts indicated                S = 0.0005 to 0.01Cu (with unavoidable impurities)                balance.______________________________________ 
    
     Synchronizer rings made of the copper alloy of the invention have excellent wear resistance exceeding the resistance of known synchronizer rings, and have longer lifetimes. 
     In another aspect of the invention, the copper alloy contains in addition to the above-recited components in the above recited ranges the following additional component: 
     
         ______________________________________Additional component            (% by weight)______________________________________Mg               0.01 to 0.5______________________________________ 
    
     The copper alloy of the invention which contains Mg in the above-recited amount has significantly improved hardness, in particular hardness at high temperatures. 
     The composition of the copper alloy of the invention is further described below in terms of its components. All proportions recited hereinafter are in percent by weight. 
     (1) Zn and Al 
     Zn and Al, when present in combination, have the effect of improving the strength and toughness of the alloy. Strength and toughness cannot be achieved when the Zn content becomes less than 20% or the Al content becomes less than 2%. On the other hand, when the Zn content exceeds 40% or the Al content exceeds 11%, there is an undesirable decrease in toughness. Accordingly, the Zn content should be from 20 to 40%, and the Al content should be from 2 to 40%. The preferable ranges are: 
     
         ______________________________________Component     (% by weight)______________________________________Zn            25-40Al            2-7______________________________________ 
    
     (2) Fe, Ni, Co in combination with Ti 
     Ti forms intermetallic compounds with the iron family metals, namely Fe, Ni and Co. Therefore, when Ti is present with at least one element selected from the group consisting of Fe, Ni and Co, the wear resistance is enhanced to due to dispersion of the intermetallic compounds into the matrix. When the iron family metal content is less than 1%, or Ti is less than 0.1%, the desired effects cannot be achieved. On the other hand, when the iron family metal content exceeds 5% or the Ti content exceeds 4%, there is an undesirable reduction in toughness. Accordingly, the iron family content should be from 1 to 5%, and the Ti content should be 0.1 to 4%. The preferable ranges are: 
     
         ______________________________________Component       (% by weight)______________________________________Iron family metals           2-4Ti              0.5-3______________________________________ 
    
     (3) Mn 
     The use of Mn in smaller amounts than in known copper alloy compositions improves the wear resistance of the copper alloy of the invention. The Mn content should be from 0.01 to less than 0.1%, the preferred range being 0.03 to 0.07%. The wear resistance is not satisfactory when the Mn content is less than 0.01%. On the other hand, an Mn content of more than 0.1% reduces the wear resistance and further impairs workability. 
     (4) S 
     S has the effect of improving wear resistance in the copper alloy of the invention. The S content should be from 0.0005 to 0.01%. An S content of less than 0.0005% is not sufficient to improve the wear resistance. On the other hand, an S content of more than 0.01% undesirably hinders hot workability. A preferred range for S is 0.001 to 0.005%. 
     (5) Mg 
     Mg improves the hardness of the copper alloy of the invention, in particular hardness at high temperatures. Therefore, it is desirable to include Mg in the copper alloy of the invention for manufacturing synchronizer rings to be used under operating conditions of high load and/or high speed revolution. The Mg content should be from 0.01 to 0.5%, more preferably from 0.05 to 0.35%. An Mg content of less than 0.01% does not achieve the desired effect, and an Mg content of more than 0.5% causes undesirable lowering of the toughness. 
     The invention is further illustrated in the following examples, to which the invention is not limited. 
     EXAMPLES 
     Copper alloys having the compositions shown in Tables 1-3 were prepared in a high-frequency melting furnace, and then ingots of 65 mm in diameter and 220 mm in length were made by die casting. These ingots were hot forged at 750° C. to prepare synchronizer rings blanks of 15 mm in thickness, 100 mm in width, and 300 mm in length. The thus made synchronizer ring blanks were cut to prepare test pieces 1-30 for the synchronizer ring of the invention (hereinafter designated as &#34;test pieces of the invention&#34;) and to prepare test pieces 1-3 of known synchronizer rings (hereinafter designated as &#34;conventional test pieces&#34;) . Further, a circular carburizing and quenching steel counter member (surface roughness: 2.0 to 2.5 Rz) was used as a counterpart member. A surface roughness of 2.0 to 2.5 Rz means that the average surface roughness of the ten points of the curved area, as defined in JIS B 0601- 1982, is 2.0 to 2.5 μ. 
     The test piece 1 and the counterpart member 2 were positioned as shown in FIG. 1, the counterpart member 2 being immersed in oil 3. Thereafter, the counterpart member 2 was subject to rotation under the following conditions as the test piece 1 was pressed with the load 4 of 50 kg as shown in FIG. 1: 
     sliding velocity: 5 m/s 
     oil: transmission oil 
     sliding distance: 10 km 
     oil temperature: 80° C. 
     The wear depth of the test pieces was measured to evaluate the wear resistance. The results are shown in Table 1 through Table 3. 
     
                                           TABLE 1__________________________________________________________________________    COMPOSITION (Weight %): Cu contains                             WEARTEST    unavoidable impurities        DEPTHPIECE    Zn Al Ni Fe Co Ti Mn S  Mg Cu (μm)__________________________________________________________________________S I   1    20.5  4.6     2.6        -- -- 1.6                 0.05                    -- -- BAL.                             75   2    31.5  4.6     2.5        -- -- 1.5                 0.06                    -- -- BAL.                             70   3    38.5  4.6     2.4        -- -- 1.6                 0.06                    -- -- BAL.                             72   4    31.2  2.1     2.4        -- -- 1.6                 0.05                    -- -- BAL.                             74   5    30.5  10.5     2.4        -- -- 1.4                 0.06                    -- -- BAL.                             72   6    31.1  4.7     1.1        -- -- 1.5                 0.06                    -- -- BAL.                             86   7    31.2  4.7     4.8        -- -- 1.5                 0.07                    -- -- BAL.                             65   8    31.7  4.5     -- 2.5           -- 1.6                 0.05                    -- -- BAL.                             71   9    30.8  4.6     -- -- 2.6              1.7                 0.05                    -- -- BAL.                             70  10    30.9  4.6     1.2        1.3           -- 1.6                 0.06                    -- -- BAL.                             72  11    31.0  4.7     1.3        -- 1.3              1.7                 0.06                    -- -- BAL.                             70__________________________________________________________________________ S I: THE INVENTION&#39;S TEST PIECES S II: CONVENTIONAL TEST PIECES 
    
     
                                           TABLE 2__________________________________________________________________________    COMPOSITION (Weight %): Cu contains                              WEARTEST    unavoidable impurities         DEPTHPIECE    Zn Al Ni Fe Co Ti Mn S   Mg Cu (μm)__________________________________________________________________________S I  12    31.3  4.7     -- 1.2           1.6              1.6                 0.06                    --  -- BAL.                              68  13    30.7  4.8     1.0        0.8           1.4              1.4                 0.06                    --  -- BAL.                              71  14    31.2  4.6     2.5        --  0.12               0.12                 0.06                    --  -- BAL.                              83  15    31.5  4.6     2.4        -- 3.8              3.8                 0.05                    --  -- BAL.                              78  16    31.5  4.5     2.4        -- 1.6              1.6                 0.02                    --  -- BAL.                              88  17    31.2  4.8     2.5        -- 1.6              1.6                 0.09                    --  -- BAL                              65  18    31.2  4.6     2.4        -- 1.6              1.6                 --  0.0007                        -- BAL.                              77  19    31.5  4.6     2.5        -- 1.7              1.7                 -- 0.001                        -- BAL.                              75  20    31.3  4.8     2.4        -- 1.7              1.7                 -- 0.002                        -- BAL.                              72  21    30.7  4.6     2.5        -- 1.6              1.6                 -- 0.003                        -- BAL.                              71  22    30.8  4.7     2.4        -- 1.6              1.6                 -- 0.005                        -- BAL.                              68__________________________________________________________________________ S I: THE INVENTION&#39;S TEST PIECES S II: CONVENTIONAL TEST PIECES 
    
     
                                           TABLE 3__________________________________________________________________________COMPOSITION (Weight %): Cu contains                              WEARTEST unavoidable impurities        DEPTHPIECEZn Al Ni Fe Co Ti Mn S  Mg Cu (μm)__________________________________________________________________________S I   2330.9   4.6      2.4         -- -- 1.7                  -- 0.009                        -- BAL.                              65   2430.6   4.6      2.6         -- -- 1.6                  0.07                     0.001                        -- BAL.                              55   2531.2   4.7      2.4         -- -- 1.6                  0.05                     0.002                        -- BAL.                              50   2631.2   4.6      2.5         -- -- 1.6                  0.08                     -- 0.02                           BAL.                              60   2730.5   4.7      2.4         -- -- 1.7                  0.08                     -- 0.48                           BAL.                              55   2830.6   4.6      2.5         -- -- 1.6                  -- 0.001                        0.21                           BAL.                              70   2931.2   4.6      2.5         -- -- 1.6                  -- 0.002                        0.15                           BAL.                              68   3031.3   4.6      2.4         -- -- 1.7                  0.08                     0.001                        0.18                           BAL.                              47S II    131.5   4.6      2.5         -- -- 1.6                  -- -- 0.15                           BAL.                              125    231.1   4.7      2.4         -- -- 1.7                  0.15                     -- 0.16                           BAL.                              95    331.2   4.6      2.5         -- -- 1.6                  3.8                     -- 0.15                           BAL.                              230__________________________________________________________________________ S I: THE INVENTION&#39;S TEST PIECES S II: CONVENTIONAL TEST PIECES 
    
     The results in Table 1 through Table 3 show that the test pieces 1-30 of the invention are much more superior in wear resistance (i.e., exhibit less wear) than the conventional test pieces 1-3. 
     In addition to their use in synchronizer rings, the copper alloys of the invention can be used in other applications requiring high wear resistance under severe conditions.