RU2695402C2 - High-strength cast iron plane parts manufacturing method - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: invention relates to the machine building, in particular to the field of metal forming, and can be used in the flat parts from high-strength cast iron manufacturing for the stamped products further manufacturing from them. Preheated tubular billet is upset on the press by the flat strikers in the transverse direction with double flat billet production. Then, at the resulting double billet cutting the bending zones. Heating is carried out to a temperature T₁, satisfying the 950 °C<T₁<T_C inequality. Flat strikers are heated to temperature T₂, satisfying the T_Mn<T₂<T₁ inequality. T_C is the high-strength cast iron solidus temperature, T_Mn is the austenite to martensite in the high-strength cast iron phase transformations onset temperature.

EFFECT: result is enabling increase in the flat parts from high-strength cast iron manufacturing method productivity by reduction in the transitions number.

1 cl, 3 dwg, 1 ex

Description

The invention relates to mechanical engineering, in particular, to the field of metal forming and can be used in the manufacture of flat parts from ductile iron for the further manufacture of stamped products from them.

High-strength cast iron is characterized by increased casting properties, a denser structure, high heat resistance, cold resistance, and corrosion resistance. It can be welded and autogenously cut and has high wear resistance. High-strength cast iron is used to make such products as machine tool beds, presses and rolling mills, gear housings, sleeves of internal combustion engines and compressors, camshafts and crankshafts, track fingers of tracked vehicles, large-modular gears, gear wheels. Due to the above complex of technological and operational properties, ductile iron products are in high demand in the production of conveyors, as well as in agricultural machinery for the production of combines, seeders, mowers and other harvesting machines in which chain gears are widespread. The traditional technology for manufacturing cast-iron parts is casting with subsequent machining, the disadvantages of which are gas porosity, which reduces the mechanical characteristics, in addition, it is not economically feasible to obtain products of small size by casting.

The most vulnerable parts of a chain drive are the chain itself and the sprockets. According to GOST 592-81 "Asterisks for plate chains. Methods for calculating and constructing a tooth profile. Limit deviations "one-way sprockets are flat parts that are expedient to produce using the separating operations of sheet stamping: cutting the outer contour with a gear rim and punching a central hole for mounting on the shaft. For this purpose, flat blanks in the form of strips or sheets are used as the starting metal.

The search showed that at present, sheet blanks of cast iron of the required thickness are not produced by industry.

Flat parts can be obtained by the technology proposed in NITU MISiS [Kobelev OA Modeling and improvement of a wedge tool for developing forged large diameter pipes // Forging and stamping. Metal forming. 2010. No. 7. S. 27-29], according to which the forged large hollow billet is cut and deployed with a wedge shaped tool. The disadvantage of the technology is that it is implemented using a large number of transitions (9-10) and is mainly suitable for producing large-sized flat plates (up to 5000 mm).

There is another method for producing large-sized plates of aluminum alloys [Burkin SP, Razinkin A.V., Iskhakov R.V., Babailov N.A. Analysis of a new technology for forging large-sized plates from aluminum alloys. Metallophysics, mechanics of materials, nanostructures and deformation processes: In 2 volumes. T. 2.P. 38-49. Proceedings of the international scientific and technical conference. Metalldeform-2009 (Samara, June 3-5, 2009). Samara: SSAU, publishing house. literature, 2009. 366 s], which consists in a transverse draft previously cut in 2 places forged pipe billet in several stages. The disadvantage of this method is the high complexity of the method, including 8-10 transitions.

The prior art method for rolling sheet metal blanks with spheroidal graphite [Patent No. 2137560 RU. Method for the production of sheet metal from cast iron. Publ. 09/20/1999]. The disadvantages of the known method of rolling are the multi-transition process (more than 5) with the need to rotate a long workpiece by 90 ° and subsequent rolling for 4-5 transitions, as well as an unacceptably large spread in temperature and speed modes of rolling.

Among the few known, adopted as a prototype, is a method of manufacturing flat parts from ductile iron, according to which a pre-heated to 900 ... 1100 ° C pipe blank is deposited on the press in the transverse direction for two transitions without heating the tool to obtain a double flat workpiece and then cutting inflection zones [Ponomarev A.S., Sosenushkin E.N. Investigation of the technological capabilities of separation operations for the production of semi-finished products from ductile iron with spherical graphite // Status, problems and prospects for the development of forge-and-press machine-building and forge-stamping industries: Sat. reports and materials of the X Congress "Smith-2010". Ryazan, 2010. S. 226-229].

The disadvantages of the prototype include low productivity due to the number of transitions (two) of the formation of a double flat workpiece.

The objective of the invention is to reduce the number of transitions without reducing stable guaranteed physical and operational performance.

The technical result is an increase in the productivity of the method of manufacturing flat parts from ductile iron by reducing the number of transitions.

The problem is solved, and the claimed technical result is achieved by the fact that in the method of manufacturing flat parts of high ductile iron, according to which a preheated tube billet is deposited on the press with flat drills in the transverse direction to obtain a double billet and then cutting off the bending zones, the tube billet is heated ₁ to a temperature T satisfying the inequality 950 ° c <T ₁ <T _C, and the flat die is heated to a temperature of T ₂ satisfying the inequality _MN T <T ₂ <T _1, g e T _C - the solidus temperature of ductile iron, and T _MH - onset temperature of the phase transformation of austenite to martensite in ductile cast iron.

The invention is based on the following.

It has been experimentally established that high-strength cast iron (in the definition and nomenclature in force in the Russian Federation at the time of filing GOST 7293-85. Spheroidal cast iron for castings. Grades) has ductility sufficient for its plastic deformation into the product while maintaining the continuity of the material and its physical the mechanical characteristics of the product are not worse than in the molded product, in the temperature range of hot stamping (GS) from 950 ° C to a temperature of solidus. In this case, experiments show that attempts to stamp above solidus temperature lead to the destruction of the workpiece and / or its elements due to collective recrystallization and / or fusion along the grain boundaries. At temperatures below 950 ° C, the resistance to deformation of ductile iron increases sharply with a simultaneous decrease in ductility, which leads to the appearance of cracks and other types of damage in the product.

In this case, the contact of the workpiece with the tool (flat die strikers) having a temperature lower than the temperature at which the phase transformations of austenite to martensite begin in high-strength cast iron initiates the appearance of a thermally stressed zone, a stress concentrator, and a source of cracking at the point of contact. Moreover, experiments have shown that heating the tool (flat die strikers) above the temperature of the onset of phase transformations of austenite to martensite in high-strength cast iron completely eliminates the occurrence of the indicated stress zone, which allows the pipe billet to be precipitated to a double flat billet in one transition.

The upper limit of the heating of the tool (flat press heads) is determined by the heat resistance of the tool itself and the solidus temperature of ductile iron, heating of the workpiece above which leads to the destruction of the workpiece and / or its elements due to collective recrystallization and / or fusion along the grain boundaries.

The invention is illustrated by the images:

FIG. 1 - the product is a one-way chain sprocket with a gear;

FIG. 2 - microsection of a high-quality separation surface (without cracks) subject to temperature conditions;

FIG. 3 - microsection of the separation surface in violation of temperature conditions (with cracks).

An example of the method of manufacturing flat parts of ductile iron.

In the technological process of stamping a flat part made of high-strength cast iron, such as a one-way chain sprocket, having a complex outer contour with a gear rim, according to which a preheated tube billet is deposited in the press with flat drills in the transverse direction to obtain a double billet and then cutting off the bending zones, heating the tube billets are carried out to a temperature T ₁ satisfying the inequality 950 ° C <Ti <T _C , and flat strikers are heated to a temperature T ₂ satisfying the inequality The temperature T _Mn <T ₂ <T ₁ , where T _C is the solidus temperature of ductile iron, T _Mn is the temperature of the onset of phase transformations of austenite to martensite in ductile iron.

Next, the obtained flat billet is heated to a temperature T ₁ satisfying the inequality 950 ° C <T ₁ <T _C , and the working parts of the stamp — the punch and die are heated to a temperature T ₂ satisfying the inequality T _Mn <T ₂ <T ₁ . Then, in a stamp for separating operations, a flat product with a complex external contour is obtained from cutting a blank from a flat blank. The cutting operation was carried out on a P3234A hydraulic press with standard technological force P _n = 2 MN and a deformation rate of 4 mm / s.

Experimental studies have shown that if the specified temperature ranges for heating the workpiece and tool are strictly maintained, then cracks do not occur on the separation surface in the product, which is confirmed by microstructural analysis (Fig. 2). Conversely, if these temperature ranges are not maintained, then on the separation surface unwanted cracks appear (Fig. 3), propagating deep into the product and leading to marriage.

From the examples considered, it follows that, subject to the parameters stated in the claims, the quality of the obtained billet fully meets the general requirements of high-strength cast iron billets (GOST 7293-85), and going beyond the declared ranges leads to the appearance of marriage.

The foregoing allows us to conclude that when implementing the invention, the task - reducing the number of transitions without reducing stable guaranteed physical and operational indicators - is solved, and the claimed technical result - increasing the productivity of the method of manufacturing flat parts from ductile iron by reducing the number of transitions - is achieved.

The analysis of the claimed technical solution for compliance with the conditions of patentability showed that the characteristics indicated in the claims are essential and interconnected with the formation of a stable set of necessary features, unknown at the priority date from the prior art and sufficient to obtain the desired technical result.

Thus, the above information indicates the fulfillment of the following set of conditions when using the claimed technical solution:

- the object embodying the claimed technical solution, when it is implemented, relates to mechanical engineering, in particular, to the field of metal forming and can be used to obtain flat parts from ductile iron;

- for the claimed object in the form described in the claims, the possibility of its implementation using the methods and methods described above or known from the prior art on the priority date is confirmed;

- the object embodying the claimed technical solution, when implemented, is able to ensure the achievement of the technical result perceived by the applicant.

Therefore, the claimed object meets the criteria of patentability "novelty" and "industrial applicability" under applicable law.

Claims (6)

A method of manufacturing flat billets from ductile iron, including the upsetting of a preheated tube billet on the press with flat dies in the transverse direction to obtain a double flat billet and subsequent cutting of the inflection zones, characterized in that the flat billets are heated, while the tube billet is heated to a temperature T ₁ satisfying the inequality: 950 ° C <T ₁ <T _C , and flat strikers are heated to a temperature T ₂ satisfying the inequality: T _Mn <T ₂ <T ₁ , where T _C is the solidus temperature of ductile iron; T _Mn is the temperature of the onset of phase transformations of austenite to martensite in ductile iron.

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