JP2602029B2 - Method for producing abrasion resistant composite casting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a technique relating to a wear-resistant body having strong resistance to abrasion wear in which severe wear conditions, particularly, wear particles collide with a surface or flow by abrasion.

[Prior art] Conventionally, in a place that is attached to a mechanical device and falls under severe wear conditions, a material having high wear resistance itself, for example,
We have responded by manufacturing components using 12% Mn steel (Hadfield steel) or 27% Cr cast iron.

However, users have demanded that the mechanical device withstand continuous operation for a longer period of time, and development of better wear-resistant parts has been promoted. Some publications of composites can be seen as a promising means, and a typical example thereof is “composite composed of a sintered carbide alloy and cast iron” (Japanese Patent Publication No. 60-11096).

This technology consists of a composite consisting of a sintered carbide alloy and cast iron, the feature of which is that the cast iron itself is a graphite cast iron having low wear resistance and hardness, and that the carbon equivalent has been adjusted to 2.5 to 6.0, An intermediate alloy phase or a transition zone is formed between the two, and 20 to
80% is in the transition zone. Several examples are given as the optimum use conditions of this composite, but it is applied to a liner of a coal pulverizer, a bit body for a rock drill, a bit gripper for a rock drill, a cold head die, and the like. , Compared with conventional hard martensitic cast iron, wear-resistant material such as manganese steel, conventional bit or steel bit itself with a high quality fatigue-resistant steel gripper, or conventional die made of ball bearing steel Each showed significant advantages.

As a cause of this excellent result, for such high impact services, this prior art favors the intervening transitions and continuous changes between hard sintered carbide and soft graphite cast iron. To do. For example, when used for the bit body of a rock drill, good results remain in order to avoid the impact load which is reduced due to the mechanical distortion due to the low Young's modulus and large damping capacity of graphite cast iron and is dispersed and concentrated It is assumed.

It can be guessed that the prior art cited here shows better durability than conventional products, for example, on rock bits and cold head dies with severe impact. FIG. 1 is a micrograph of the metal structure of the prior art which was additionally tested by the applicant. The photo is magnified 50 times, and it is adjacent to the spheroidal graphite cast iron, the intermediate layer, and the cemented carbide alloy in the order of layers from the left consisting of three phases. Obviously, this intermediate layer absorbs the violent impact and prevents breakage and delamination.

However, it is impossible for the cemented carbide alloy, which is super-hard, to completely cover the entire surface that falls due to wear, and when the cast iron penetrating the surface is graphite-based, its low hardness,
There is a concern that the low abrasion resistance may lead to the inferior deterioration depending on the use conditions. The most problematic is when faced with so-called abrasion wear, which is attacked by hard particles, scratching, impacting and rubbing the surface. Graphite cast iron that penetrates the cemented carbide alloy interface and withstands severe impacts and bites it is also inexhaustibly worn away by abrasion wear. It peels off quickly without exhibiting excellent wear resistance, greatly disappointing.

On the other hand, for abrasion wear, a "joining method of chrome cast iron and cemented carbide" (JP-A-59-199165) has been proposed. Or, after forming a nickel-boron alloy film, the main idea is to cast chromium cast iron, specify the alloy of the film, and conduct various tests with different chrome contents. This is shown in the embodiment.

By controlling the chromium content of the film-forming component and the matrix phase in this way, the formation of the η phase in the conventional film and cast-in method is prevented, and the gap and crack between the cemented carbide and the chromium cast iron are prevented. ing.

Further, in the prior art proposed in Japanese Patent Application Laid-Open No. Sho 60-206557, a super-hard carbide such as WC, 3-5% by weight of C and Cr
Of a cast iron binder having a eutectic composition close to the eutectic composition containing 5 to 30% by weight of a cast iron material having the same component as the binder. It is stated that since a cast material having properties similar to those of the cermet binder is used, wettability with the binder is good, mutual diffusion between the cermet and the cast-in material is sufficiently performed, and the cermet is completely integrated.

[Problems to be Solved by the Invention] Although it is possible to enlarge the layer of the cemented carbide alloy to obtain a long service life, the cost is greatly increased, and there is a technical difficulty in penetrating the casting layer throughout the particle layer. Not practical with gender.

Also, as described above, the large amount of the intermediate layer in the first prior art relieves the low hardness of graphite cast iron, but reduces the high hardness of the sintered carbide alloy itself, resulting in a loss of excellent wear resistance. In addition, there is a concern that iron in cast iron and cobalt frequently used in sintered carbide may be substituted to form a brittle layer, and a problem remains as a member mainly composed of abrasion wear.

The prior art disclosed in Japanese Patent Application Laid-Open No. 59-199165 has the effect of improving the wettability with a cast-in material, preventing the generation of a brittle phase (η), and preventing cracks and oxidation. As a result, it is necessary to form a nickel, phosphorus alloy, nickel or boron film, and the equipment, labor, time, cost, and the like required for passing through the process impose an extremely large burden on the cost structure of the cast product. Moreover, when the particles are coated with a thin film of an alloy belonging to the series of nickel, phosphorus, etc. and come into contact with high chromium cast iron at high temperatures, there is a high concern about the generation of embrittlement phase (η). You have to add restrictions. Therefore, the wear resistance of the base metal itself is also restricted, and a grudge that does not reach the most desirable wear resistance as chrome cast iron remains.

Further, according to the prior art disclosed in Japanese Patent Application Laid-Open No. 60-206557, as a specific manufacturing process,
A small amount of powder is blended, pressed in a mold, and pre-sintered in vacuum to produce a skeleton with a porosity of 40%. The skeleton is placed on a carbon board and immersed in molten chrome cast iron maintained at 1300 ° C. in vacuum and held for 30 minutes to obtain a cermet bonded by chrome cast iron. The cermet is placed in a mold, and chrome cast iron at 1450 ° C. is poured and poured. However, it cannot be denied that this configuration has at least the following three problems.

The process of making the cermet is too cumbersome, and the cost of the process is lost too expensive. As is well known, a wear-resistant material is a consumable part, and since it has the essence of replacement after wear and disposable, the adoption or rejection is determined based on a combination of a service life and a price. In addition to the fact that hard alloys are much more expensive than ordinary metallic materials, such a time and labor intensive method is already disqualified by itself.

Since this conventional technology does not particularly limit what the product is applied to, it is judged that it aimed at general-purpose products such as civil engineering and construction machinery, chemical machinery, and iron making machinery as described by himself, but the cermet itself Is press-formed from a powder state, and thus is specified by the shape of the mold. If versatility is required, it is meaningless unless it can be applied to any of a variety of differently shaped wear-resistant members, but in reality the part of the wear-resistant member that faces wear is not limited to a flat surface. However, in many cases, the cermet is formed by grinding a surface that matches the shape of the worn curved surface from the cermet in order to widely implement the present invention. In spite of the fact that it is originally a material that was born with a high level of wear resistance, but it is necessary to grind it to achieve the desired wear surface, it can be considered impractical if it is considered impractical. .

There is no description of the field test in the embodiment, and it is doubtful that the device is actually used as a wear-resistant member. Although there is a description of the individual hardness of cermet and chromium cast iron, what is actually required is the abrasion resistance and the service life of a composite of the two. Cermet has an intermediate product skeleton with a porosity of 40 during the manufacturing process.
%, Which means that the chromium cast iron as a binder was impregnated and filled into a spongy porous skeleton. If the chromium cast iron replaced (as much as about 40% capacity) is not significantly deducted and evaluated, then there is no point. Therefore, even with regard to the important abrasion resistance, which is the subject, it is generally possible to expect a considerably discounted result.

SUMMARY OF THE INVENTION An object of the present invention is to provide a composite having strong abrasion resistance particularly against abrasion wear in order to solve the problems described above.

[Means for Solving the Problems] The method for producing an abrasion-resistant composite cast according to the present invention provides a crushed body and a granular body of a sintered carbide alloy on a desired mold surface in a mold having a desired shape. Alternatively, one of the compression molded bodies or a phase body having a desired thickness Tcm made of a mixture thereof is fixed and locked, and the carbon content of the mold is 2.5% to 3.5%.
% High chromium cast iron with a chromium content in the range of 23% to 35% and a chrome / carbon (Cr / C%) in the range of 5 to 12 magnifications, 120 × (0.75 + T) above its melting point
By pouring at a pouring temperature selected in consideration of the total pouring amount and the layer thickness Tcm within a high temperature range of ℃ to 180 × (1.50 + T) ° C., it completely penetrates the layered body to the mold surface. The above-mentioned problem was solved by densely forming the wear surfaces which are impregnated with each other and bite each other.

[Action] Cast iron with a white iron structure is an extremely hard material consisting of iron carbide and martensite, compared to graphite cast iron. However, in order to further improve wear resistance, alloy elements, most commonly,
It is well known that iron-chromium composite carbide is precipitated on a matrix (mother phase) as a structure after solidification by adding Cr and solidifying, and also increases the hardness of the matrix itself.

However, according to the present application, high chromium cast iron, which is evaluated to be the most resistant to abrasion wear among iron-chrome alloys, has a carbon content of 2.5% to 3.5%.
%, Limited to the highest wear resistant materials with a chromium content of 23% to 35%.

This material is roughly equivalent to 25% Cr cast iron of Class III according to the American standard (ASTMA532), and is also one of the representative wear-resistant materials in Japan as a so-called 27% Cr cast iron. However, when using such a cast-in material, it is necessary to overcome the problems of familiarity, oxidation and cracking of hot water. In this application, the cemented carbide layer is composed of a stack of strips, so that the high chromium cast iron quickly and completely penetrates into the layer to reach the mold surface, and by this rapid impregnation, between the strips and the strips Was completely filled with the base material, and a solid liquid sintering action was developed such that the strips, the base material, and the strips bite each other after solidification and do not easily peel off.

To this end, the ratio of chromium to carbon was kept in the range of 5 to 12 and the fluidity of the molten metal in the mold and the alloy layer was set within the maximum range in combination with the limitation of the total amount of carbon and chromium. Originally, the oxidation of the as-cast portion during casting is almost crucially governed by the passing speed of the tip, which propagates through the gaps between the as-cast particle layers. It is not a problem that can never be solved with sufficient research.

Therefore, regarding the properties of the particles, if the particle size is too small, the interval between the sintered carbide alloys becomes too small, and even if the casting temperature is increased, the white cast iron does not sufficiently penetrate between the particles. If the particle size is too coarse, not only does the volume ratio of the sintered carbide decrease, but also the mean free path cut by the abrasive particles of the intergranular white cast iron base material increases, and the wear resistance deteriorates.
Therefore, a configuration in which 2 mm to 15 mm particles account for 70% or more of the whole is optimal.

Another way to improve the flowability is at the casting temperature of the melt. In ancient times, the choice of casting temperature is a very important requirement in order to obtain a sound casting, but in this application it will serve its purpose without other limitations which cannot be controlled by ordinary casting techniques for the reasons already mentioned. Can not do.

The higher the casting temperature, the higher the fluidity and the above-mentioned conditions are met, but if it is too high, there is a limit because the particles of the sintered carbide alloy themselves are melted from the interface. In addition, as long as the reason for enhancing the fluidity is rapid complete impregnation into the alloy layer and prevention of oxidation, it is reasonable to consider the relationship between the total amount of pouring and the layer thickness.

The present invention has completed a casting temperature calculation formula that is uniformly expressed as a linear function of the alloy layer thickness through a valuable physical test that builds a heap of defective products.

According to this equation, the casting temperature when the thickness of the alloy layer is 1 cm is determined by the melting point of high chromium cast iron (27% Cr).
Since it is 1290 ° C, it is calculated as 1500 ° C at the minimum and 1740 ° C at the maximum.

The choice within this range is set mutatis mutandis using the usual casting axioms such as the relationship between the elements other than the thickness T of the alloy layer of the casting, that is, the relationship between the overall shape and thickness and the total amount of pouring. do it.

For reference, it is considered appropriate that the casting temperature of a normal product of 27% Cr cast iron is about 1450 ° C. to 1390 ° C.

Regarding the properties of the particles, if the particle size is too small, the interval between the sintered carbide alloys becomes too small, and even if the casting temperature is increased, white cast iron does not sufficiently penetrate between the particles. On the other hand, if the temperature is too high, the amount of the sintered carbide alloy melted in the white cast iron increases significantly. If the particle size is too coarse, not only does the volume fraction of the sintered carbide decrease, but also the mean free path cut by the abrasive particles of the intergranular white cast iron base material increases, and the wear resistance deteriorates. Therefore 2mm ~ 15mm particles are 70% of the whole
The configuration described above is optimal.

[Examples] 1. Spheroidal graphite having a 2.6% C-26% Cr white cast iron, an alumina sintered plate, and a 10 mm thick sintered carbide particle layer as a shoot liner of a sinter ore conveyor line at an ironworks. Three comparison examples of composite liner using cast iron as base material, and 6m
2.8% C-24% Cr-Ni-
An actual product of the present invention using Mo as a base material was used. The life of each liner is shown below.

(1) 2.6-26% Cr white cast iron liner 30 days (2) Alumina sintered plate liner 40 days (3) Spheroidal graphite base material sintered carbide composite liner 150 days (4) Inventive product 500 days More expensive Even when the amount of the sintered carbide is reduced by half compared to the prior art (3), the effect of improving the wear resistance of the matrix between the carbide particles is clearly seen.

2. 5.5% C-22 as a liner for blast furnace skip cars
Hardening material having composition of 8% Cr-7% Mo-8% Ni-2% W, 8mm thick sintered carbide with alumina sintered plate 2.6% C-27% Cr-Ni-Mo as base material The product of the present invention having a particle layer was used. The life of each liner is shown below.

(1) Hardened overlay material 270 days (2) Alumina sintered plate 90 days (3) Inventive product 720 days or more 3. As a chute liner at the inlet of the sintering raw material drum mixer, 3.0% C-26% Cr white cast iron The product of the present invention having a sintered carbide particle layer having a thickness of 8 mm and using 2.7% C-25% Cr-Mo as a base material was used. The life of each liner is shown below.

(1) 3.0% C-26% Cr white cast iron 45 days (2) The present invention product 650 days or more 4. 3.2% C-1 as a side liner for sinter transport line
5% Cr-3% Mo white cast iron and 8mm thick sintered carbide layer
The product of the present invention using 2.8% C-25% Cr white cast iron as a base material was used. The life of each liner is shown below.

(1) 3.2% C-15% Cr-3% Mo white cast iron 90 days (2) Inventive product 980 days or more [Effect of the Invention] As described above, the composite casting of the present invention is non-impact or low-impact. It exhibits excellent resistance to impact wear, especially abrasion wear accompanied by scratching, sliding and abrasion on the surface by hard particles (minerals, coal, coke, abrasive grains, earth and sand, etc.). While maintaining the excellent wear resistance of the cemented carbide alloy, which is the original cemented carbide, the base metal is a high chromium cast iron, which is a representative of abrasion-resistant wear materials, particularly, a so-called 27-35% chrome content of 23% to 35%. The choice of% Cr cast iron guarantees the highest durability over the long term. And C
% And Cr%, as well as the ratio of Cr / C and the casting temperature, which is governed by the grain size and thickness of the alloy layer, are comprehensively and mechanically limited.
The cast-in portion of the cast product adheres to the base as a densely integrated sintered body, and can have an outstanding service life as illustrated in the four examples without peeling off easily.

[Brief description of the drawings]

 FIG. 1 is a micrograph of a conventional metal structure.

Claims (1)

(57) [Claims] 1. A desired thickness Tcm of any one of a broken body, a granular body, a compression molded body or a mixture thereof of a sintered carbide alloy on a desired mold surface in a mold having a desired shape. The layered body is fixedly locked, and the mold has a carbon content of 2.5% to 3.5%, a chromium content of 23% to 35%,
A high chromium cast iron having a chrome / carbon (Cr / C%) in a magnification range of 5 to 12 is heated to 120 × (0.75
+ T) ° C. to 180 × (1.50 + T) ° C. In a higher temperature range, pouring is performed at a pouring temperature selected in consideration of the total pouring amount and the layer thickness Tcm, so that the mold surface penetrates the layered body. A method for producing an abrasion-resistant composite casting, characterized in that the abrasion surfaces that are completely impregnated with each other and bite each other are densely formed.