US2826371A

US2826371A - Manganese steel crusher wearing plate

Info

Publication number: US2826371A
Application number: US484708A
Authority: US
Inventors: Forrest E Smith
Original assignee: Frog Switch & Manufacturing Co
Current assignee: Frog Switch & Manufacturing Co
Priority date: 1955-01-28
Filing date: 1955-01-28
Publication date: 1958-03-11
Anticipated expiration: 1975-03-11

Description

. March 11, 1958 1;. E. SMITH 2,826,371

MANGANESE STEEL CRUSHER WEARING PLATE Filed Jan. 28, 1955 po y-re s? b gam a-1 M, #umwAe L .in structure, and extremely strong and tough.

States Forrest E. Smith, Ashevilie, N. (3., assignor to The Frog,

Switch & Manufacturing Co., Carlisle, Pa, a corporation of Pennsylvania Application January 28, 1955, Serial No. 484,708 2 Claims. (Cl. Tam-2M) The present invention relates to a manganese steel wearing plate, and more particularly to jaw plates and breaker plates for rock and ore crushers.

The material from which jaw crusher plates should be made must possess the quality of toughness, hardness, strength and durability which is required to withstand the impact and abrasion to which such wearing plates are subjected. It has been found in practice that Hadfields standard manganese steel is best adapted for this purpose. Because of its comparatively high carbon content, the microstructure of this steel before heat treatment consists of austenite plus a considerable amount of free carbide or cementite. The carbide is hard and brittle, and, by breaking up the continuity of the austenite ground mass, the presence of the carbide results in a brittle metal.

As a consequence, it has been found that a drastic heat treatment is necessary in order to retain the carbide of manganese steel in solution in the austenite. To dissolve such carbide in the austenite, manganese steel articles must be heated to about 1830 degrees F. and quenched in cold water, which results in a steel wholly austenitic As a result, certain limits to the use of this steel have been set in industry. Because of the high coefficient of thermal expansion (about one and one-half times that of pure iron) of Hadfields manganese steel, and the low heat conductivity (about one-seventh that of carbon steel) of this steel, there is a great difference in the cooling rates of the exterior and interior of a manganese steel piece in quenching. The lag of the inside of the metal in cooling, coupled with the high coefficient of expansion, sets up stresses of such magnitude that sections of manganese steel over some four and three-quarters to five inches thick cannot be quenched without producing cracks, which generally start within the body of the piece and work toward the surface.

Such behavior of manganese steel during heat treatment has presented the industry with a serious problem since large heavy-duty crushing machinery requires jaw plates and impact plates to be thicker than four and three-quarter or five inches in order to withstand the heavy pressure and impact received in crushing rocks and ore particles and to still allow for wear.

In obedience to these requirements, it is the conventional practice to provide wearing plates having panelled- V out back surfaces for maintaining the above-mentioned maximum metal thickness. Although such panelling is restricted to the back surface of such a plate and thus permits retention of a flat front crushing surface, still this construction is not satisfactory for use in modern rock crushers. The panelling gives rise to irregular metal sections in the plate due to the presence on the back surface of ribs which must be employed to define the panelled-out portions. Such irregularly sized metal sections cause internal stresses to be set up in the metal during heat treatment thereof because of the phenomena discussed above, i. e., the high coeflicient of thermal expansion of manganese steel and its relatively low heat conductivity. Another serious disadvantage of the presently used panelled-out plate construction is that the effective thickness of the plate is limited to approximately 4%5 inches, so that such plates must be replaced after, only atent l atented Mar. 11, 1958 two or three inches of metal has been worn from their front faces. A further disadvantage of this type plate is that the ribs defining panelled-out portions on the back surface of the plate tend to frictionally wear against a rock crusher frame which receives and grips the back of the plate.

Accordingly, it is a general object of the present invention to overcome the aforementioned disadvantages by forming a wearing plate cast from manganese steel or the like with a plurality of carefully spaced slots across the front surface of the plate so as to define a series of parallel, alined beams rigidly connected by an integral back sheet, which slots facilitate proper heat treatment :of all portions of the metal and yet permit a plate of any across the face of a crusher wearing plate so that every portion of solid metal is a maximum of 2 /2 inches from a slot or other cooling surface that the metal can be effectively heat treated in 'a uniform fashion.

It is a further object of the present invention to provide a wearing :plate having a smooth, solid back surface for reception within a rock crusher frame so that the back surface does not frictionally wear into such frame. An ancillary object is to provide a wearing plate having a smooth back surface which is solid and which is strong enough to resist bending, even after the front or face surface of the plate has been worn down.

Other objects and advantages will become apparent upon reading the attached detailed description and upon reference to a drawing in which:

Figure 1 is a plan view of a crusher wearing plate employed in practicing the present invention.

Fig. 2 is an elevation of the wearing plate shown in Fig. 1.

Fig. 3 is a perspective of the wearing plate shown in Figs. 1 and 2.

While the invention has been described in connection with the preferred embodiment, it will be understood that it is not intended to limit the invention thereto, but it is intended to cover all modifications and alternative constructions and methods falling within the spirit and scope of the invention as expressed in the appended claims.

Turning now to the drawings, the finished product, as

shown in the drawings, will be first described and then 'four corners of the plate for alinement with corresponding holes in the crusher frame (not shown) and for reception of suitable fastening elements (not shown), such as bolts. In order that such fastening elements will not protrude above the front surface 12 of the plate 10, square recesses 20 are provided in the front surface at each hole 18. Thus each fastener head rests in one of the recesses 2i) when such fastener has been inserted through one of holes 18 and the head cannot interfere with the crushing action exerted by the front surface 12 of the plate It).

In effect, the slots 22 define a series of parallel, alined 'hearns rigidly connected by a substantially flat, relatively thin, integral'sheet. These beams bear the crushing loads when the :plate :is in operation and remain effective even after substantial wear has occurred. ,t ince the plate ltlispreferablycast from manganese steel, a plurality of spaced longitudinal slots 22 are arranged in parallel fashion across the front surface 12 of the cast plate so as to facilitate rapid cooling of the plate after heat treatment, thereby tempering and toughening the metal for use in crushing rock and ore. More specifically, the cooling slots 22 are carefully spaced and sized for arrangement with the

plate surfaces

12 and 14 so that there is no portion of metal between cooling surfaces which is greater than 2 /2 inches from a cooling surface, this having been found to be the maximum allowable thickness for effecting adequate heat treating of the metal.

Thus, it will be noted that the slots 22 are a maximum of five inches apart, and the bottom portion 23 of the slots is a maximum of five inches from any point on the back surface 14 of the plate 10. It will be seen that the slots 22 in the plate present wall surfaces 24 for a coolant, such as water, used in the process of toughenmg and tempering the plate, to enter the interior of the mass of the plate and thus render positively every portion of the plate structure tough and homogeneous.

The method of making a plate of the present invention is practiced by forming a mold (not shown in the drawings) having a recess therein corresponding to the configuration of the plate 10. The slots 22 of the plate 10 are formed in the casting by employing a plurality of parallel mold ribs which are provided in the mold wall opposite the front surface 12 of the plate 10. The holes 18 and the square recesses 20 are formed in the plate 10 by employing ordinary molding cores. It is important that the slots 22 be arranged across the front surface or face 12 of the plate 10 in an evenly spaced fashion so that there is no portion of metal between such slots which is more than 2 /2 inches from one of the slot walls 24 or from the back surface 14. The invention also contemplates a regulation of the depth of the slots 22 within the plate 10 so that no portion of metal is situated more than 2 /2 inches from the bottom portion 23 of each slot. In this way the slots 22 are provided so that the bottoms 23 of the slots are a maximum of 5 inches from the back surface 14 of the plate.

In practicing the method, manganese steel having the proper metallurgical characteristics, i. e. Hadfields manganese steel, is heated above its melting temperature to the molten state. The molten metal is then introduced into the mold described above, which mold provides a cavity corresponding to the configuration of the plate 10 and includes mold ribs and cores inserted within the mold to form the slots 22, holes 18 and recesses 20. The

resulting manganese steel casting is then allowed to solidify by cooling within the mold. Upon such solidification, the carbide within the casting is hard and brittle. Such characteristics are undesirable and at this point it is necessary to cause a metallurgical solution of the carbide within the austenite. To dissolve such carbide in the austenite, the plate 10 is then heated to above 1830 degrees F. The heat treatment of the plate 10 is then completed by suddenly plunging the plate into a coolant, such as cold water or the like, which quenching action jells the grain structure of the metal and results in a steel wholly austenitic in nature and extremely durable and strong.

Upon plunging the plate 10 into the coolant, it will be seen that the inventive method of forming the above described accurately sized and spaced slots 22 in the front surface 12 of the plate 10 enables the coolant to rapidly contact the inner walls 24 of the slots 22 and thus to effect immediate cooling of all internal portions of the plate quickly and efficiently.

One of the advantages of the present invention is that the provision of the regularly spaced slots 22 in the front surface 12 of the plate 10 effects an even spacing of the metal sections between such slots and thus eliminates internal stresses in the metal due to uneven cooling of the central portions of the plate as compared with edge portions thereof. One of the further advantages of the invention is inherent in the predetermined 5 inch maximum spacing between the slots 22 which spacing has been found in practice to be essential for insuring rapid cooling of every portion of the metal in order that complete solution of the carbide in the austenite is effected and a resulting tough and durable wearing plate is produced.

It is another of the features of the invention that the wearing plate 10 may be formed of any thickness metal desired. since in all cases the depth of the slots 22 formed in the front surface 12 is variable to maintain a minimum metal thickness of 5 inches between cooling surfaces. Thus the effective thickness of the inventive wearing plate is not limited to 4 or 5 inches, but can be set at 8 or 10 or more inches. Needless to say replacements of worn out plates is necessary only infrequently as compared with the conventional type of wearing plate.

Yet another advantage of the present invention is that a wearing plate is provided having a smooth back surface with no outstanding ribs thereon so that there is no frictional wear between such surface and a rock crushing frame which grips this surface.

I claim as my invention:

1. A cast manganese steel wearing plate for mounting in a crushing mechanism and having a front crushing face and a back mounting surface, comprising a plurality of parallel, alined beams rigidly connected by a substantially flat, relatively thin, sheet formed integrally with said beams and defining a non-recessed back mounting surface, said beams having opposed parallel side walls spaced apart so as to permit free circulation of a liquid coolant therebetween when heat treating said plate, and said beams and said sheet being sized and proportioned so that (1) all internal metal portions are a maximum of 2 /2 inches from the closest metal surface and (2) each of said beams present substantially uniform cross sections, thus permitting positive and uniform heat treatment of all of the manganese steel making up said plate.

2. A cast manganese steel wearing plate for mounting in a crushing mechanism and having a front crushing face and a back mounting surface, comprising a plurality of parallel, alined beams rigidly connected by a substantially flat, relatively thin, sheet formed integrally with said beams and defining a back mounting surface, said beams having a uniform, substantially rectangular cross section and being spaced apart so as to permit free circulation of a liquid coolant therebetween when heat treating said plate, and said beams having a maximum thickness of 5 inches so that all internal metal parts are a maximum of 2 /2 inches from the closest metal surface, said uniform cross section and said beam size permitting positive and uniform heat treatment of all of the manganese steel making up said plate.

References Cited in the file of this patent UNITED STATES PATENTS 36,424 Seely Sept. 9, 1862 816,709 Brinton Apr. 3, 1906 888,253 Nichols May 19, 1908 1,187,161 McKee et a1 June 13, 1916 1,608,561 Larsson Nov. 30, 1926 2,210,357 Beament Aug. 6, 1940 2,609,154 Baker Sept. 2, 1952 FOREIGN PATENTS 1,258 Great Britain of 1899 666,161 Germany Oct. 11, 1938 776,752 France Nov. 8, 1934 OTHER REFERENCES Bullens: Steel and Its Heat Treatment, published by John Wiley and Sons, New York, 1939, volume II, pages 6 and 7.

Metals Handbook, American Society for Metals, Cleveland, 1939, page 568.

Claims

1. A CAST MANGANESE STEEL WEARING PLATE FOR MOUNTING IN A CRUSHING MECHANISM AND HAVING A FRONT CRUSHING FACE AND A BACK MOUNTING SURFACE, COMPRISING A PLURALITY OF PARALLEL, ALINED BEAMS RIGIDLY CONNECTED BY A SUBSTANTIALLY FLAT, RELATIVELY THIN, SHEET FORMED INEGRALLY WITH SAID BEAMS AND DEFINING A NON-RECESSED BACK MOUNTING SURFACE, SAID BEAMS HAVING OPPOSED PARALLEL SIDE WALLS SPACED APART SO AS TO PERMIT FREE CIRCULATION OF A LIQUID COOLANT THEREBETWEEN WHEN HEAT TREATING SAID PLATE, AND SAID BEAMS AND SAID SHEET BEING SIZED AND PROPORTIONED SO THAT (1) ALL INTERNAL METAL PORTIONS ARE A MAXIMUM OF 2 1/2 INCHES FROM THE CLOSEST METAL SURFACE AND (2) EACH OF SAID BEAMS PRESENT SUBSTANTIALLY INIFORM CROSS SECTION, THUS PERMITTING POSITIVE AND UNIFORM HEAT TREATMENT OF ALL OF THE MANGANESE STEEL MAKING UP SAID PLATE.