Anti-abrasive and anti-corrosive alloy

Abstract

An anti-abrasive and anti-corrosive alloy capable of being finished by cutting process in a condition where it has been built on the surface of a base metal. The anti-abrasive and anti-corrosive alloy contains, as main component, Co, Cr, Mo and Ni mixed at the following weight ratio:

Description

BACKGROUND OF THE INVETION

[0001] 1. Field of the Invention

[0002] The present invention relates to an anti-abrasive and anti-corrosive alloy containing, as main components, Co, Cr, Mo and Ni.

[0003] 2. Discussion of the Prior Art

[0004] In a thrust bearing metal, a cylindrical bushing or the like, it is required to enhance anti-abrasiveness and anti-corrosiveness of a surface of one of the component parts or surfaces of both the component parts assembled in a sliding contact relationship. To satisfy the requirement, a layer of anti-abrasive and anti-corrosive alloy is formed on the surfaces of the component parts. The layer of anti-abrasive and anti-corrosive alloy is built up on the surface of a base metal by plasma-arc welding such as plasma-transfer-arc welding or plasma-jet welding of a powder of anti-abrasive and anti-corrosive alloy and is subjected to finish machining. In Japanese Patent Publication No. 52(1977)-38807, an anti-abrasive and anti-corrosive alloy containing, as main components, Co, Cr and Mo has been proposed for use in manufacture of a thrust bearing.

[0005] Although the anti-abrasive and anti-corrosive alloy containing, as main components, Co, Cr and Mo is superior in anti-abrasiveness and anti-corrosiveness, the built-up portion of the alloy on the surface of the base metal may not be finished by cutting process due to extremely high hardness (about 750 Hv in Vickers hardness) of the alloy. For this reason, the built-up portion of the alloy must be finished by grinding process. During the grinding process, however, a mother material (for example, stainless steel) of the base metal is ground together with the built-up portion of the alloy. When the mother material relatively high in viscosity and the high hardness alloy are simultaneously ground, the grinding wheel is plugged in a short time and defaced at one side thereof.

SUMMARY OF THE INVENTION

[0006] It is, therefore, a primary object of the present invention is to provide an anti-abrasive and anti-corrosive alloy capable of being finished by cutting process in a condition where it has been built up on the surface of the base metal.

[0007] According to the present invention, the object is accomplished by providing an anti-abrasive and anti-corrosive alloy containing, as main components, by weight 16% -18% Cr, 28% -32% Mo and 46% -48.5% Co+Ni.

[0008] In a practical embodiment of the present invention, it is preferable that the component ratio of Co and Ni in the anti-abrasive and anti-corrosive alloy is determined in such a manner that Co is more than or equal to 8 wt. % and less than or equal to 18 wt. % and that Ni is more than or equal to 30 wt. % and less than 40 wt. %. Alternatively, the component ratio of Co and Ni in the anti-abrasive and anti-corrosive alloy may be determined in such a manner that Co is more than or equal to 23 wt. % and less than or equal to 25 wt. % and that Ni is more than or equal to 23 wt. % and less than or equal to 25 wt. % . The component ratio of Co and Ni in the anti-abrasive and anti-corrosive alloy may be also determined in such a manner that Co is more than or equal to 34 wt. % and less than or equal to 36 wt. % and that Ni is more than or equal to 12 wt. % and less than or equal to 14 wt. % . In the anti-abrasive and anti-corrosive alloy, it is desirable that an average value of the Vickers hardness of the alloy is in an extent of 540-680 Hv.

[0009] In the anti-abrasive and anti-corrosive alloy, less than 1.0 wt. % Fe and less than 0.03 wt. % C are contained as impurities, and 3 wt. % -3.5 wt. % Si may be contained in necessity.

[0010] The hardness and characteristic of the anti-abrasive and anti-corrosive alloy are influenced by a mixture amount of Co, Cr and Mo. It is, therefore, required that the total amount of the components is more than 55 wt. %. As the base metal is, in general, made of austenitic stainless steel such as SUS 304 or SUS 316, it is preferable that the amount of Cr is determined in an extent of 16 wt. % -18 wt. %. Even if the amount of Mo was more than 32 wt. %, an influence of Mo to the hardness of the alloy would be small. It is, therefore, preferable that taking into account the hardness and anti-corrosiveness of the alloy, the amount of Mo is determined in an extent of 28 wt. % -32 wt. %. Accordingly, the amount of Co+Ni is determined in an extent of 46 wt. % -48.5 wt %.

[0011] In the anti-abrasive and anti-corrosive alloy, it is indispensable that the hardness of the built up portion of the alloy is less than 700 Hv in Vickers hardness for cutting of the built-up portion and is more than 540 Hv in Vickers hardness for anti-abrasiveness.

[0012] In the case that Co is more than or equal to 8 wt. % and less than or equal to 18 wt. % and that Ni is more than or equal to 30 wt. % and less than or equal to 40 wt. %, the Vickers hardness of the anti-abrasive and anti-corrosive alloy becomes 600-700 Hv. In the case that Co is determined more than or equal to 23 wt. % and less than or equal to 25 wt. % and that Ni is more than or equal to 23 wt. % and less than or equal to 25 wt. %, the Vickers hardness of the anti-abrasive and anti-corrosive alloy becomes 540-650 Hv. In the case that Co is more than or equal to 34 wt. % and less than or equal to 36 wt. % and that Ni is more than or equal to 12 wt. % and less than or equal to 14 wt. %, the Vickers hardness of the anti-abrasive and anti-corrosive alloy becomes 600-700 Hv. In the case that the component weight ratio of Co and Ni is determined in these extents, the built-up portion of the alloy can be finished by cutting. Particularly, in the case that the Vickers hardness is in an extent of 540-680 Hv, the built-up portion of the alloy can be finished by cutting in a good condition.

[0013] The main components of the anti-abrasive and anti-corrosive alloy are mixed at the predetermined ratio and molten at a high temperature of 1200° C.-1900° C. The alloy is powdered in an appropriate manner and used in the form of powder. The powder of the anti-abrasive and anti-corrosive alloy is built up on a surface of a base metal by plasma-arc welding such as plasma-transfer-arc welding or plasma-jet welding. In this instance, the built-up portion of the alloy can be finished by cutting in a good condition without subjected to any grinding process.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In the drawings:

[0015] FIG. 1 is a side view of an auger the journal portions of which are formed with an anti-abrasive and anti-corrosive alloy of the present invention;

[0016] FIG. 2 is an enlarged side view of a journal portion of the auger shown in FIG. 1; and

[0017] FIG. 3 is an enlarged side view of a built-up condition of the alloy on the journal portion of the auger.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0018] In a preferred embodiment of the present invention, plural kinds of alloys containing, as main components, Co, Cr, Mo and Ni mixed at various ratios were prepared and used to form a layer of anti-abrasive and anti-corrosive alloy on a surface of a journal portion of an auger 10 shown in FIG. 1, as in Examples 1-4 and Comparative Examples 1-3 described later.

[0019] The auger 10 is adapted for use in an auger-type ice making machine. The auger 10 has an auger body 11 integrally formed at its opposite ends with shaft portions 12 and 13. The shaft positions 12 and 13 are formed with journal portions 14 and 15, respectively. The auger 10 is coaxially mounted at its journal portions 14 and 15 for rotary movement within an ice making cylinder (not shown) forming an ice making chamber of the ice making machine. The base metal of the auger 10 was made of austenitic stainless steel, and a layer of anti-abrasive and anti-corrosive alloy was formed on each peripheral surface of the journal portions 14, 15 of auger 10 as described later.

[0020] FIG. 2 illustrates each shaft portion 12, 13 of auger 10 to be formed thereon with the journal portions 14 and 15. FIG. 3 illustrates an anti-abrasive and anti-corrosive alloy built up on the respective shaft portions 12 and 13 by plasma-transfer-arc welding. The shaft portions 12 and 13 of auger 10 each were preliminarily formed with annular recesses 12a, 13a. The anti-abrasive and anti-corrosive alloy was prepared to contain, as main components, Co, Cr, Mo and Ni respectively mixed at weight ratios shown in the following table 1. Each mixture of the components Co, Cr, Mo and Ni was melted in a furnace-at 1200° C.-1900° C. and prepared in the form of plural kinds of alloy powder. These alloy powders were built up in the annular recesses 12a, 13a of shaft portions 12, 13 by plasma-transfer-arc welding, and each built-up portion 12b, 13b of the alloy was finished by cutting process to form the journal portions 14, 15 of auger 10. The hardness and machinability of the respective built-up portions 12b, 13b of the alloy are shown in the following table 1. 1 TABLE 1 Experiment Example Comparative Example Components 1 2 3 4 1 2 3 Components C 0.01 0.01 0.01 0.01 0.01 0.01 0.01 Co 24.10 12.25 35.90 6.30 41.85 47.79 40.29 Cr 16.96 16.44 17.48 16.18 17.74 18.00 18.00 Fe 0.71 0.56 0.85 0.48 0.93 1.00 0.00 Mn 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Mo 30.74 31.75 29.70 32.26 29.20 28.70 23.00 Ni 23.87 35.20 12.50 40.86 6.85 1.20 16.00 P 0.00 0.00 0.00 0.00 0.00 0.00 0.00 S 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Si 3.63 3.80 3.50 3.88 3.40 3.30 2.70 Average 597 552 672 549 689 720 520 hardness(Hv) Machinability Good Good Enable Good Limit Unable Good

[0021] Listed in the table 1 is each average value of Vickers hardness (Hv) measured at equally spaced twenty positions of each of the built-up portions 12b and 13b of the alloy. In the case that each surface of the built-up portions of the alloy is finished by cutting process, it is desirable that the Vickers hardness of the built-up portions 12b, 13b of the alloy is less than 700 Hv, particularly 680 Hv. Taking into account a lower limit of the Vickers hardness caused by anti-abrasiveness and corrosiveness, it is desirable that the Vickers hardness is in an extent of 540-680 Hv.

[0022] In the preferred embodiment, it has been found that the desired Vickers hardness is obtainable by an alloy containing, as main components, Co, Cr, Mo and Ni mixed at the component ratios described below.

[0023] In the case that Cr is in an extent of 16 wt. %-18 wt. % and that Mo is in an extent of 28 wt. %-32 wt. %, Co+Ni is determined in an extent of 46 wt. %-48.5 wt. %. In addition, the component weight ratio of Co and Ni is deternined in such a manner that Co is more than or equal to 8 wt. % and less than or equal to 18 wt. % and that Ni is more than or equal to 30 wt. % and less than or equal to 40 wt. %. The component weight ratio of Co and Ni may be determined in such a manner that Co is more than or equal to 23 wt. % and less than or equal to 25 wt. % and that Ni is more than or equal to 23 wt. % and less than or equal to 25 wt. %. Alternatively, the component weight ratio of Co and Ni may be determined in such a manner that Co is more than or equal to 34 wt. % and less than or equal to 36 wt. % and that Ni is more than or equal to 12 wt. % and less than or equal to 14 wt. %.

Claims

1. An anti-abrasive and anti-corrosive alloy containing, as main components, Co, Cr, Mo and Ni mixed at the following weight ratio:

Cr 16 wt. %-18 wt. %

Mo: 28 wt. %-32 wt. %

Co+Ni: 46 wt. %-48.5 wt. %

2. An anti-abrasive and anti-corrosive alloy as claimed in claim 1, wherein the component ratio of Co and Ni is determined in such a manner that Co is more than or equal to 8 wt. % and less than or equal to 18 wt. % and that Ni is more than or equal to 30 wt. % and less than or equal to 40 wt. %.

3. An anti-abrasive and anti-corrosive alloy as claimed in claim 1, wherein the component ratio of Co and Ni is determined in such a manner that Co is more than or equal to 23 wt. % and less than or equal to 25 wt. % and that Ni is more than or equal to 23 wt. % and less than or equal to 25 wt. %.

4. An anti-abrasive and anti-corrosive alloy as claimed in claim 1, wherein the component ratio of Co and Ni is determined in such a manner that Co is more than or equal to 34 wt. % and less than equal to 36 wt. % and that Ni is more than or equal to 12 wt. % and less than or equal to 14 wt. %

5. An anti-abrasive and anti-corrosive alloy as claimed in claim 1, wherein an average value of Vicker s hardness of the alloy is in an extent of 540-680 Hv.