Metal treatment – Having portions of differing metallurgical properties or... – Cutting tool
Patent
1988-04-08
1989-08-01
Yee, Deborah
Metal treatment
Having portions of differing metallurgical properties or...
Cutting tool
148902, 148324, 148321, C22C 3836
Patent
active
048530476
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to engineering of parts of machinery, such as parts and components of agricultural or farm machines, and more particularly it relates to engineering of the work-performing members of agricultural or farm machines.
The invention can be utilized to the utmost effect in the manufacture of grass rods and segments of the cutting units of various mowers and reapers for harvesting grain, grass and stem crops, of colters and blades of sheep shearers, and of other like parts and components.
Background of the Invention
The working conditions of the work-performing members of farm machines are characterized by the combined effect of various impact loads and intense abrasion wear of the cutting edges. Therefore, in order to avoid breakdowns of the work-performing members and prevent their cutting edges from getting blunt, more often than not such members are assembled of several components, e.g. of the main component made of either medium-carbon or low-alloy structural steels offering high mechanical properties, and of cutting elements made of high-carbon tool steels offering adequately high hardness, joined to the main component by riveting, welding, soldering or like techniques. However, this practice complicates the manufacture of a work-performing member and raises its production cost, to say nothing of the area of the joining of the components being prone to breakdowns. Thus, detachment of a riveted counter-cutting plate from the grass rods or fingers of a cutting unit is among the most frequent causes of cutting unit breakdowns.
For this reason the recently spreaded practice is to manufacture and use solid or integral work-performing members of farm machines. In most cases these work-performing members are made of medium-carbon steel grades by hot stamping or forging (see, for example U.S. Pats. Nos 2,719,353; Cl. 29-148, or 3,716,978; Int.Cl. A01d 55/10). After the forming of a part and its machining, the cutting edge is hardened by induction, hardening yielding a hardness of about HRC 50--55 (Rockwell Scale "C" hardness).
However, work-performing members thus manufactured have relatively low hardness and wear resistance of their cutting edges; furthermore, their manufacture involves the use of complicated forming equipment and labor-consuming operations, with production of serrated or toothed working edges being virtually impossible.
In some cases, to simplify the forming process, the work-performing members are made of low-carbon steel grades with subsequent carburizing or carbonitriding. However, this complicates the manufacturing technology and makes it more costly, while failing to adequately enhance the wear resistance of a cutting edge on account of the relatively small depth of the carburized layer.
There is also known the use of cast work-performing members of farm machines, made of malleable perlite cast iron (see, for example, U.S. Pat. No. 3,224,179; Cl. 56-310). Following the casting and annealing steps, the cutting edges of work-performing members are hardened by induction hardening. In this way the manufacturing process of such parts can be simplified and made less costly, and it is possible to produce serrated or toothed cutting edges.
However, the inadequate impact strength of the material has been found to lead to not infrequent cases of breakdowns of the work-performing members, while the relatively low hardness after the hardening (about HRC 50) would not ensure sufficient wear resistance of a cutting edge.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide the work-performing member for a farm machine, which would offer enhanced wear resistance of the cutting edge owing to the altered structure of the material, with the manufacturing technology of the work-performing member being simultaneously simplified.
This object is attained in a work-performing member for a farm machine, having its cutting edge made of a material which is basically a high-carbon steel which, in accordance with the invention, i
REFERENCES:
patent: 2204283 (1940-06-01), Potts et al.
patent: 2719353 (1955-10-01), Mills
patent: 3224179 (1965-12-01), Schuman
patent: 3716978 (1973-02-01), Haban
patent: 4711676 (1987-12-01), Kitaori et al.
Povyshenie Iznosostoilosti I Dolgovechnosti Rezhuschikh Elementov Selskokhozyaistvennykh Mashing.
Gajun Jury A.
Grigorov Petr K.
Perevozkin Jury L.
Samelik Boris V.
Zhurakovsky Vasily M.
Nauchno-Proizvodstvennoe Obiedinenie Po Tekhnologii Mashinostroe
Yee Deborah
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