US2035392A - Copper steel alloys - Google Patents

Description

Patented Mar. 24,

UNITED STATES PATENT OFFICE aoaam COPPER swam. more Russell H. McCarroll and Gosta Vennerholm, I i

Dear-born, Mich, asslgnors to Ford Motor Company, Dearborn, Mlcln, a corporation of Delaware No Drawing. Application April 13, 1888; Serial No. 685,9

Claims. (Ul- 75-125) This invention relates to the production of copper-alloys of steel and articles thereof.

Although copper is widely used in industry alloyed with tin and zinc for the production of brass, bronze and the like, it has not heretofore been considered practical to attempt to alloy it with iron or steel except in very small proportions, not in excess 01' 1%, because of the limited gether different purpose than the use contemplated by the present invention in which the object is to produce a steel of high physical properties to enable the steel to be used with highly satisfactory results for the manufacture of machine, engine or automotive parts where great strength, wear and fatigue resistance and good bearing properties are desired.

The principal object oi the present invention is to produce a new and improved steel containing a copper content in an amount suiilcient to produce supersaturation thereof, or, in other words, so that the internal pressure is equalized just before the point is reached where precipitation would occur. The equalization of the internal pressure just before the precipitation point is reachedcan only be secured by the maintenance of a proper balancing within comparatively narrow limits of the carbon, silicon and copper contents, as hereinafter more fully set forth. The invention relates primarily, as above pointed out, to the production of alloy steels of high physical properties, and in order to obtain such proper--v ties, it is necessary that the balancing referred to, of the respective proportions of the three elements, carbon, silicon and copper, be maintained or the desired results would not be secured. In addition to the proper balancing of carbon, silicon and copper, it is highly desirable to employ a carbide forming element, the'proportion of which must also benicely balanced to that of the other elements. Although the use of chromium is preferred as the carbide forming element, it will be understood that the invention is not limited to the use of this particular element but that other elements having known similar physical and metallurgical properties may be employed.

Considered from another standpoint one of the. principal objects of the invention may be said to be the production of a copper-alloy steel in which a high silicon content is. employed to insure complete solubility of the copper. 5

The invention briefly consists in the production of a copper-alloy steel in which a high copper,

'high silicon analysis is used, the analysis also including a high carbon content together with smaller proportions of other metals such as 10 chromium and manganese, and in which the entire copper content goes into solution while such of the carbon as is not in solution, is in the form of small particles of iron-chrome carbides and iron'carbides uniformly distributed throughout 15 the matrix thereby to produce articles having high physical properties, excellent foundry prop-. erties, and possessing marked advantages from the standpoint of machinability as well as furnishing an exceptionally good material for bear- 2o ing surfaces with a low coeilicient of friction and relatively high Brinell hardness.

In accordance with the present invention, highly satisfactory results have been obtained by using a material of which the analysis preferably 25 falls within the following limits:

Percent Carbon 1.10 to 1.30 Manganese", 0.50 to 0.75 so Silicon 1.60 to 2.10 Chromi m 0.75 to 1.00 Copper 2.00 to 3.00 Iron Balance The invention may, however, be practiced with 35 analyses within the wider limits as below: 7

' 4 Percent Carbon .75 to 1.70 Manganese 0.40 to 2.00 0 Silicon 1.00 to 2.50 Chr m 0.30 to 2.00 Copper 1.00 to 4.00 Iron Balance The carbon content should not be above the within approximately the same limits as in the analyses heretofore given, and when molybdenum is employed separately in substitution for chromm the same limits also apply.

As the result of extensive laboratory and practical tests we have found that precipitation of copper can be entirely prevented by the use of a high silicon content, the silicon increasing the solubility of copper and preventing precipitation upto4% copper. v

As the use of copper decreases shrinkage, increases fluidity and lowers the melting point the metal has excellent foundry properties. high carbon and silicon contents also contribute to improve the foundry properties.

In addition the copper produces an age hardening eifect, insures remarkably easy machinability of articles of relatively high Brinnell hardness and permits the production of a metal having high physical properties without the necessity of resorting to complex heat treatments. A typical analysis, from the use of which a highly satisfactory product has been obtained, is as fol-' lows:

- Percent Carbon 1.17 Manganese 0.69 Silicon 1.95 Chromium 0.96 Copper 2.55 Phosphorus 0.04 Sulphur 0.04

It will be understood that the inclusion of phosphorus and sulphur forms no part of the present invention but that they are present merely as impurities. For certain uses it may be found desirable to normalize the product obtained from the above analysis at a sufliciently high temperature at about 1425 F.1650 F. depending on properties desired, for a cycle of one and one-half hours for castings having a crosssectional area of approximately one and one-half square inches; the heat cycle consisting merely of bringing up to the normalizing temperature and cooling, but such .normalizing or other heat treatment is not essential and may bedispensed with.

In the cast state the metal has a Brinell hardness of from 364 to 418 which is brought down by normalizing to an average of about 340, at which hardness the product can readily be machined and has excellent physical properties. It will, however, be understood that the metal is machinable m the cast state at a Brinell of approximately 400.

All of the copper enters into solid solution with the iron. The matrix is sorbitic, partly pearlitic, with excess carbon in the form of small particles oi iron-chrome carbides and iron carbides uni-.

formly distributed throughout the matrix, so that the final product is completely homogeneous with a fine close grained structure. As hereinbefore pointed out, it is essential that a proper balancing of the carbon, silicon, copper and chromium contents beyond relatively narrow limits be main- .tained. The amount of the carbon content, as

pointed out, should be slightly in excess of the carbon content required for forming solid solu- The tions with iron in the matrix, and when such a carbon content is employed, together with the copper, the eifect is for the copper to restrict materially the size of the grain formations. The grain refining properties of the copper tend materially to restrict .the size of the carbon particles which are formed as very fine particles of temper carbon uniformly distributed throughout the entire matrix. By using the proper proportion of silicon to carbon substantially complete solubility of the copper is secured and the precipitation is prevented of particles of free carbon, the forto the skilled metallurgist, such changes are included within the scope of the claims hereunto appended.

We claim:

1. An article of manufacture comprising a readily machinable copper-alloy steel having an analysis within the following limits:

Percent Car 1.10 to 1.30 Manganese 0.50 to 0.75 Silicon 1.60 to 2.10

, Chromium 0.75 to 1.00 Copper 2.00 to 3.00 Iron Balance and having a tough matrix in which the entire copper content is in solution, and said matrix having imbedded in it extremely hard particles of iron chromium carbides and free carbon uniformly distributed throughout said matrix.

2. An article of manufacture comprising a readily macbineable copper-alloy steel having an analysis substantially within the following limits:

Percent Car 0.75 to 1.70 Manganese 0.40 to 2.00 Silicon 1.00 to 2.50 Chromium 0.30 to 2.00 Copper 1.00 to 4.00 Iron Balance Percent Carbon 0.75 to 1.70 Manganese 0.40 to 2.00 Silicon 1.00 to 2.50 Chromium 0.30 to 2.00 Copper 1.00 to 4.00 Iron Balance the silicon and copper being inbalanced proportions with suflicient silicon relatively to the amount of copper employed to insure solubility of 75 Percent Carb 0.75 to 1.70 Manganese 0.40 to 2.00 Silicon 1.00 to 2.50 Chromiu 0.30 to 2.00 Copper 1.00 to 4.00 Iron Balance 3 the ratio of the carbon, silicon, chromium and copper contents being substantially in the pro-- portions, carbon 1. silicon 1 chromium and copper 2, with the balance substantially iron.

5. An article of manufacture comprising high carbon alloy steel having an analysis substantially within the following limits:

Percent Car 1.10 to 1.30 Manganese 0.50 to 0.75 Silicon 1.60 to 2.10 Chromium 0.75'to,1.00 Copper 2.00 to 3.00 Iron Balance and in which the ratio of carbon, silicon, chromium and copper is substantially as 1 to 1% to A to 2 respectively.

- RUSSELL H. MCCARROIL.

. GOSTA VENNERHOLM.