JP5345316B2 - High hardness wear resistance Corrosion resistance cast iron - Google Patents

Description

  The present invention relates to a cast iron material, particularly a piston ring having this cast iron material as a base. In particular, the present invention relates to a new cast iron material containing acicular ferrite having a specific blending ratio of austenite, martensite and / or pearlite.

  The cast iron material can exist in a variety of microscopic structures that can be adjusted through the use of special compositional parameters and / or method parameters.

  A cast iron material having a bainite basic structure to a martensite basic structure manufactured by heat treatment is described in, for example, German Patent DE 2428821A. This basic structure contains flaky to bone-like graphite deposits in order to ensure fail-safe properties (Notlaufeigenschaften).

  A method for producing pearlite cast iron and / or ferrite cast iron is described in US Pat. No. 3,565,698. Here, the raw materials are mixed with the alloy in a molten state and cast into a raw cast product (Rohling). After casting, the raw cast product is heated to a temperature in the range of 900 ° C. to 1050 ° C. to dissolve the cementite and produce black malleable cast iron. The heating time can be shortened by adding a significant amount of sulfur to the feedstock as described in US Pat. No. 3,0007,070.

  Cast iron materials or cast iron alloys are typically used to produce high stressed parts of internal combustion engines, such as piston rings. Piston rings are under high stress in engines that are under increasing stress, such as compression pressure, combustion temperature, lubricant film reduction, etc., which is critical to functional properties such as wear, burn marks, microwelds, and corrosion resistance Has a significant impact.

  The piston ring seals a gap existing between the piston head and the cylinder wall from the combustion chamber. During the up and down movement of the piston, the piston ring, on the one hand, always slides against the cylinder wall with a resilient design, and on the other hand, the piston ring moves into the piston ring groove due to the tilting movement of the piston. The side surface of the piston ring groove is alternately adjacent to the upper side surface and the lower side surface of the piston ring groove. In the sliding parts that slide against each other, some strong wear occurs depending on the material, which may lead to so-called scratches, nicks, and finally engine damage when dry sliding occurs. . In order to improve the sliding behavior of the piston ring relative to the cylinder wall, the piston ring was provided with a coating of various materials on its peripheral surface.

  Compression rings in high stress engines, such as diesel engines or two-cycle engines, for example, are preferably sliding such as, for example, chrome ceramic coatings, thermal spray layers (thermische spritzschicht), PVD layers, or abradable layers (Einlaufschicht) Designed as a cast piston ring with face coating.

  Further, European Patent EP 1 384 794 A1 describes a cast iron material for a piston ring which exhibits a specific chemical composition and is subjected to a heat treatment including an austenitizing treatment followed by an isothermal quenching method. The spherical granular material is retained by the addition of the spherical graphite forming additive. In the case of a piston ring, this cast iron material has a matrix of pearlite containing a small amount of ferrite share to receive an optimum heat treatment. This type of heat treatment improves the mechanical properties of the cast iron material, but the cost of the heat treatment makes the product expensive.

  The object of the present invention is to provide a cast iron material which has high wear resistance and corrosion resistance, and does not increase the manufacturing cost, and has a reduced risk of breakage, and has a high mechanical dynamic load. Even in this case, it is to provide a piston ring whose functional behavior is guaranteed over a long service life.

  According to the invention, this object is achieved by a cast iron material according to claim 1 and a piston ring according to claim 11. The dependent claims contain advantageous embodiments of the invention.

  According to the present invention, there is provided a cast iron material showing a matrix (matrix) containing acicular ferrite and / or martensite with a portion made of austenite and / or pearlite. In particular, this matrix contains> 50% acicular ferrite, <20% austenite, <30% martensite, <50% pearlite, and <15% carbide in the matrix structure. In a preferred embodiment, the proportion of each phase is as follows:> 65% acicular ferrite, <5% austenite, <10% martense. Sites, <10% pearlite, and <7% carbide, where the ferrite can be acicular ferrite without cementite, or acicular ferrite with cementite, and mixtures thereof.

  The cast iron material according to the present invention preferably exhibits the following chemical composition (% by weight). That is, carbon: 3.0 to 4.2, silicon: 1.0 to 3.5, manganese: 1.0 at maximum, phosphorus at most 0.4%, sulfur: 0.1 at maximum, chromium: at most 0.5, copper: maximum 3.0, magnesium: maximum 0.08, tin: maximum 0.3, molybdenum: maximum 3.0, vanadium: maximum 1.0, nickel: 1.0 ~ 6.0, the rest is iron and contaminants from manufacturing conditions. This cast iron material is particularly excellent in terms of high corrosion resistance, wear resistance, and bending strength. At the same time, the cast iron material according to the present invention can utilize excellent toughness which has a particularly advantageous influence on the fracture tendency.

  In a preferred embodiment, the cast iron material has the following composition (% by weight): That is, carbon: 3.0-4.0, silicon: 1.0-3.0, manganese: maximum 1.0, phosphorus: maximum 0.3%, sulfur: maximum 0.05, chromium: maximum 0.5, copper: 0.5 to 3.0, magnesium: 0.08 at the maximum, tin: 0.25 at the maximum, vanadium: 0.1 at the maximum, molybdenum: 0.08 at the maximum, nickel 1. 0-4.0, the remainder is iron and contaminants due to manufacturing conditions.

  The cast iron material according to the invention can be further controlled in particular so that the type of graphite formation present in the material varies in the form of sphaerolitisch and / or vermicullar, or lamellar. it can.

  Worm-like graphite is “wurmfoermiger” graphite, which is morphologically between thin-layered graphite and spherical graphite and is generally abbreviated as GJV (worm-like graphite cast iron). Due to the formation of worm-like graphite, its properties essentially deviate from the ferrite / pearlite ratio of the basic structure and the attendant proportion of spheroidal graphite in the graphite. As a rule, in this case, worm-like graphite is 80-90% and the remainder consists of spherical graphite. Therefore, GJV is suitable for a component such as a piston ring that is subjected to thermal stress and particularly subjected to temperature change stress.

  Cast iron with spherical or “spherical” graphite formation is also known as GJS. In the case of this material, the main part of carbon in the cast state is deposited in the form of spherical graphite.

  In the case of a cast iron material having a thin layered graphite formation, the main part of the carbon in the cast state is deposited in the form of a thin layer. This type of material is also known as GJL.

  Laminar graphite cast iron exhibits a very good heat transfer coefficient and very good damping (Daemphung), while spherical cast iron has a clearly reduced notch effect (Kerbwirkung) and a clearly high tensile strength. Shows advantages such as strength and ductility. Worm-like graphite cast iron material exhibits higher strength properties than other graphite formations. Of course, it is possible to prepare one cast iron material alone or as a mixture from various graphite configurations. Methods known to those skilled in the art can be used for the method. Graphite conversion to cast iron material containing worm-like graphite structures (GJV) or spherical granular graphite structures (GJS) can be achieved, for example by Mg treatment, as is well known from the state of the art. Examples of the reforming method include a GF (Gerog-Fischer) converter, a sandwich method, a flow method (Durchfluss), and a cored wire injection processing method (Fulldraht-Injektionsbehandlung).

  The cast iron material further contains an element selected from the group consisting of titanium, niobium, tantalum, tungsten, boron, tellurium, and bismuth, and combinations of two or more thereof, particularly in an amount of up to 0.1% by weight. be able to. This type of element tends to form carbides, thus improving wear resistance. Further, the cast iron material is preferably an additive material selected from the group consisting of cobalt, antimony, calcium, strontium, aluminum, lanthanum, cerium, rare earth elements, and combinations of two or more thereof, preferably up to 0.1% by weight. Can contain only the amount. These elements and additive materials can be contaminants mixed in depending on the production conditions, or can be added to the melt during the production of the cast iron material according to the invention.

  Further, the cast iron material can contain lead, zinc, nitrogen, and further unspecified components up to 0.1% by weight. The ratio of the above-mentioned raw materials, components, unspecified components, elements, and additive materials can be adjusted by various methods well known to those skilled in the art. The chemical composition is adjusted in particular according to the casting module (Gussstueckmodul).

  Furthermore, the cast iron material according to the invention is particularly suitable for the production of piston rings. In order to improve the wear resistance, the piston ring can likewise be dielectrically inducted, nitrated or coated partially or fully on its sliding surface and / or side. The contents of nickel, copper, tin and chromium have a positive effect on the corrosion resistance of the material. This is especially important in the case of a two-cycle engine. This is because the piston ring is now exposed to a noxious medium and thus the cast iron material according to the invention is most suitable as a basic structure for the piston ring.

  In the method for producing a cast iron material according to the present invention, first, a molten metal (Schmelze) is produced. It is preferable that this molten metal shows the following composition as weight%. That is, carbon: 3.0-4.2, silicon: 1.0-3.5, manganese: maximum 1.0, phosphorus: maximum 0.4%, sulfur: maximum 0.1, chromium: maximum 5.0, copper: at most 3.0, magnesium: at most 0.08, tin: at most 0.3, vanadium: at most 1.0, molybdenum: at most 3.0, nickel: 1.0- 6.0, including the balance iron and contaminants from manufacturing conditions. Subsequently, the molten metal is solidified to produce a raw cast product.

  The raw casting can then be further processed into piston rings by methods well known in the state of the art.

  The cast iron manufacturing method does not proceed to further heat treatment. Larger dimensions (Mo 1.5 cm) do not require additional heat treatment. Smaller dimensions may require additional tempering, but quenching is no longer necessary. In this case, tempering is optionally carried out at a temperature of <700 ° C.

  FIG. 1 is a 500x magnified view showing a cast iron cast structure according to the present invention etched with 2% Nital.

  The following examples illustrate the invention, but the invention is not limited thereto.

Casting module M: 1.5cm
Chemical composition The basic structure consists of about 60% cement-rich acicular ferrite without cementite, about 20% pearlite, about 10% martensite, <3% austenite, and <7% carbide. The mechanical properties of the piston ring are as follows. The hardness was 320 HB 2.5 and the bending strength was> 1100 MPa, in which case the exact bending strength was difficult to investigate due to the high ductility of the material.

  The cast structure of the cast material illustrated in the example etched with 2% nital is shown in an enlarged view of 500 times in FIG.

FIG. 5 is an enlarged view 500 times the cast structure of the cast material illustrated in the example etched with 2% night.

Claims (8)

Having a matrix comprising > 65% acicular ferrite, <5% austenite, <10% martensite, <10% pearlite, and <7% carbide;
As weight%
C: 3.0-4.2
Si: 1.0 to 3.5
Mn: 1.0 at most
P: 0.4 at most
S: 0.1 at most
Cr: 5.0 at maximum
Cu: 3.0 at most
Mg: 0.08 at the maximum
Sn: 0.3 at most
Mo: 0.08 at the maximum
V: 1.0 at most
Ni: 1.0-6.0
The rest: a cast iron material characterized by having a composition of contaminants due to Fe and production conditions. As weight%
C: 3.0-4.0
Si: 1.0 to 3.0
Mn: 1.0 at most
P: 0.3 at most
S: 0.05 at the maximum
Cr: 0.5 at maximum
Cu: 0.5 to 3.0
Mg: 0.08 at the maximum
Sn: up to 0.25
V: 1.0 at most
Mo: 0.08 at the maximum
Ni: 1.0-4.0
The cast iron material according to claim 1, characterized by the composition of the remaining: Fe and contaminants due to manufacturing conditions.   The cast iron material according to claim 1 or 2, wherein the ferrite contains acicular ferrite containing no cementite, acicular ferrite containing cementite, or a mixture thereof. The cast iron material according to any one of claims 1 to 3, wherein the graphite present in the cast iron material has a spherical shape and / or a worm shape or a thin layer shape. The element selected from the group consisting of Ti, Nb, Ta, W, B, or a combination of two or more thereof is included in an amount of up to 0.1% by weight . Cast iron material according to one item . An additive material selected from the group consisting of Co, Sb, Ca, Sr, Al, La, Ce, rare earth elements, or a combination of two or more thereof is included in an amount of up to 0.1% by weight. The cast iron material according to any one of claims 1 to 5 . The piston ring which contains the cast iron material as described in any one of Claim 1 to 6 as a base | substrate. The piston ring according to claim 7 , further comprising a coating on a side surface and / or a sliding surface.

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