EP2312063B1 - Cover with wear-resistant surface and method for its production - Google Patents

Description

The invention relates to a cover made of cast iron with at least one surface subject to abrasion according to the preamble of claim 1 and to a method for producing such a cover.

Covers, attachments, other items for line and point drainage as well as tree protection grates and tree protection systems have long been used in road construction. Preferably, these components are made of cast iron, since sometimes act on the covers high traffic loads.

For reasons of traffic safety, these objects additionally require slip-resistant behavior. One possibility for producing the required slip resistance is influencing the surface roughness by using composite materials. For this purpose, the top of the cover is coated with a concrete or resin-bonded granules. The manufacturing method for such covers is expensive, since after the casting process further process steps for the production of such a cover are necessary. The problem with the known from the prior art covers is often the durability of the surface design. Vehicles or pedestrians that move over the covers lead to the surface of the covers to a not insignificant material removal, which can endanger the safety of the traffic.

Out US 2,004,335 A is a manhole cover consisting of a frame and a cover known. In this case, an upper frame edge and the horizontally aligned contact surfaces between the frame and the cover are hardened by means of a white solidification of the cast iron. For this purpose, annular iron inserts are provided in the mold, whereby metal filled in the mold rapidly cools down in the contact zone with the iron inserts.

In US 4,003,425 A there is described a method of producing white solidified cast iron when casting metal into a mold. For this purpose, the mold is coated at least in places with tellurium or bismuth. In addition, a material with chemically bound water or loosely attached water of crystallization is incorporated into the coating. The water is released during the filling of the hot metal and cools the metal quickly. As a result, in cooperation with the tellurium or bismuth-containing coating, white solidification of the cast iron occurs.

US 2,250,489 A shows a method for the production of white solidified cast iron. For this purpose, a variety of materials is described, which can cause a white solidification of cast iron, including silicon, carbon, sulfur, chromium, vanadium and tellurium. In particular, according to D1, the coating of a mold with tellurium for the production of white-solidified cast iron is described. Also, the addition of tellurium in the form of powder, tellurium salt solution or powder of tellurium alloys to molten iron is described, thereby causing crystallization or solidification of the cast iron. As a method, spraying, brushing and dusting of the respective tellurium-containing substances are disclosed.

Further, DATABASE WPI, Week 198910, Thomson Scientific, London, GB; AN 1989-074884 and JP S64 8045 B known to remove an iron part immediately after casting from a mold to quench the still hot, but already dimensionally stable material at least partially with water. The surface of such a quenched portion of the casting acquires a harder and thus more resistant surface.

It is an object of the invention to provide a cover with a traffic or a contact surface, which withstands the abovementioned abrasion stresses. Furthermore, it should be inexpensive and easy to manufacture.

Main features of the invention are specified in claim 1 and in claim 3. Embodiments are the subject of claims 2, 4 and 5.

In a cover of cast iron with at least one upper-side abrasion-loaded traffic surface, the invention provides that the abrasion-loaded traffic surface has a slip resistance, which is formed by a fine structuring in cast iron, wherein the structuring has a boot height of 2 to 8 mm, and that the Traffic surface at least partially has a wear layer and the wear layer is partially formed by a white solidification of the cast iron.

With the cover according to the invention, it makes no difference whether it is a manhole cover, an inlet grate, an attachment for road entrances or a tree protection system. By forming a comparatively thin wear layer formed by white-solidified cast iron, the durability of such covers can be significantly increased. The solidification of iron-carbon alloys after the metastable system ensures that the wear layer is made harder than the rest of the cast iron, which is gray solidified.

It does not have the full wear surface made of white solidified cast iron. Rather, only a portion of the wear surface may consist of white-solidified cast iron. Melted cast iron, which contains white and gray solidified structural areas next to each other, is therefore also suitable.

The formation of a white-frozen microstructure zone (white radiation) ensures that the cover according to the invention can thus withstand the abrasion loads significantly better than a conventional cast iron cover. In addition, such a cover is inexpensive to manufacture. The abrasion-loaded surface need not necessarily be at the top of the cover. For example, the contact surface of the cover to the frame is also exposed to increased abrasion stress.

Particularly advantageous is the formation of the wear layer such that it has a Brinell hardness greater than 275 HBW and less than 350 HBW. In this hardness range, surface abrasion is already best prevented. A hardness above 350 HBW makes the wear layer brittle. Fast pulse loads then gradually destroy them, negatively affecting the life of the entire cover.

According to the invention, it is also provided that the traffic area has an anti-slip, which is formed by a fine structuring in cast iron. In combination with the white-solidified wear layer, it is thus possible to produce the surface roughness directly in the casting process. The structuring is well protected on the surface in cast iron from abrasion and still provides after years of use in an anti-skid on the surface of the cover.

The structuring has a boot height of 2 to 8 mm. In a cover with a preferably selected boot height, it is possible to produce the entire structuring of white solidified cast iron. This further improves the durability of the cover.

1. 1. Herstellen eines Formkörpers für die Abdeckung, wobei beim Herstellen des Formkörpers ein Formkasten mit einem Oberkasten und einem Unterkasten ausgebildet wird;
2. 2. Ausbilden einer Aktivierungsschicht im Formkörper, wobei die Aktivierungsschicht an einer Formkörperhälfte des Formkörpers ausgebildet ist;
3. 3. Einfüllen von Gusseisen, wobei die Aktivierungsschicht aus chemischen Elementen oder chemischen Verbindungen hergestellt ist, die die kristalline Ausbildung von Eisencarbid, Ledeburit oder anderen verschleißfesten Gefügebestandteilen an der Kontaktfläche zum Gusseisen sicherstellt, wobei die oberseitige Verkehrsfläche teilweise durch weißerstarrtes Gusseisen gebildet wird und eine Rutschhemmung aufweist, welche durch eine feine Strukturierung im Gusseisen ausgebildet wird, wobei die Strukturierung eine Riefelhöhe von 2 bis 8 mm aufweist.

An inventive method for producing a cover made of cast iron comprises the following steps:

1. 1. producing a molded article for the cover, wherein in the manufacture of the molded article, a molding box is formed with a top box and a bottom box;
2. 2. forming an activation layer in the shaped body, wherein the activation layer is formed on a shaped body half of the shaped body;
3. 3. filling of cast iron, wherein the activation layer is made of chemical elements or chemical compounds, which ensures the crystalline formation of iron carbide, ledeburite or other wear-resistant structural components at the contact surface to the cast iron, wherein the top traffic area is partially formed by white solidified cast iron and slip resistance which is formed by a fine structuring in the cast iron, wherein the structuring has a boot height of 2 to 8 mm.

The method according to the invention provides the prerequisites for producing a cover made of cast iron alone, which has a durable, abrasion-resistant wearing layer on its traffic surface or on the contact surface between cover and frame.

In a first debris to a molded body is made, which often consists of clay-bonded molding sand. The main constituents of the foundry sand are quartz sand, foundry clay, various carbon carriers and water. About a suitable model, which is surrounded by a frame, the so-called molding box, the molding sand is compacted into a mold ready to form and thus forms the molding.

Within the shaped body, an activation layer is then formed. Subsequently, the cast iron is filled in such a way that it becomes white solid at the contact surface to the activation layer. The white solidification does not take place through the entire casting, but only on the activation layer facing surface. In this case, the wear-resistant structural constituents in the cast iron, such as Iron carbide or Ledeburit, crystalline formed. This layer can then serve as a wear layer and ideally has a thickness of up to 5 mm. The wear layer thus formed has the necessary hardness to withstand the traffic loads of daily use over many years.

The activation layer can be made, for example, from chemical elements or chemical compounds that ensure the crystalline formation of iron carbide, ledeburite or other wear-resistant structural constituents at the contact surface with the cast iron. As an example of such a chemical element is called tellurium. An advantage of this embodiment of the invention is that a uniform surface of the activation layer can be achieved. The small particles of the chemical compounds can be distributed as desired fine in the molding.

Particularly preferred are the chemical elements or chemical compounds in the molding by inserting, spraying, soaking, tamponing or spreading applied. As a result, almost all usable chemical compounds and chemical elements can be easily applied in the molding. The activation layer is thereby adaptable to any surface of the molding. Thus, according to the invention covers with complicated geometries can be produced by the method.

Another, not less advantageous embodiment of the invention provides that the activation layer is formed in the molding by inserted heat sink or inserted molds. The white solidification can also be formed by a rapid cooling of the filled cast iron. Through the heat sink or molds a rapid cooling is achieved at the activation layer, it also comes there to white solidification. An advantage of this process variant is that no expensive chemicals such. Tellurium will be needed. Also, the preparation of the molding sand is easier and thus cheaper, since no chemical residues must be removed from this.

The molded body is formed in a molding box consisting of an upper box and a lower box. For the production of the molded body, the upper box and the lower box are filled separately with molding sand. In the next step, a press head moves over the top or bottom box and compacts the foundry sand into a hard, mold-ready half-mold. Upper and lower box are then stacked and secured with a clamping device against buoyancy forces during casting. The molded body is now ready to pour in the closed mold box.

After the casting process, the halves can be easily taken apart and the blank removed.

It is also advantageous that the activation layer is formed in the molding on a respective mold half. Upper and lower case are not connected at this stage of the process.

The preparation of the activation layer in this way has the advantage that the shaped body halves can be checked directly with respect to errors with a trained activation layer. Expensive misses are thus avoided, the production of the activation layer is facilitated.

Fig. 1

eine Abdeckung mit einer durchgehenden Verschleißschicht;

Fig. 2

eine Abdeckung mit einer Verschleißzone;

Fig. 3

eine erfindungsgemäße Abdeckung im Formkasten.

Further features, details and advantages of the invention will become apparent from the wording of the claims and from the following description of exemplary embodiments with reference to the drawings. Show it:

Fig. 1

a cover with a continuous wear layer;

Fig. 2

a cover with a wear zone;

Fig. 3

a cover according to the invention in the molding box.

Fig. 1 shows a cover 10 according to the invention with associated frame 18. It can be seen on the traffic surface 20, a wear layer 30 is formed. It can be seen that the wear layer 30 is not formed over the entire component thickness. The edge supports 12 and the ribs 14 of the cover 10 are also coated on their upper side only with a constant, thin wear layer 30. The white-solidified wear layer 30 has over the entire surface curve approximately a constant thickness. This applies equally to the areas of the Riefeltäler RT and the areas of the Riefelkuppen RK. The boot height RH defined between Riefeltal RT and Riefelkuppe RK has no influence on the thickness of the wear layer 30. Further shows Fig. 1 in that a wear layer 30 can likewise be formed on a contact surface 16 of the cover 10 relative to the frame 18.

Fig. 2 shows a similar embodiment of the invention. In contrast to FIG. 1 Here, however, only the wear layer 30 is formed in a wear region VB. The complex production of the wear layer 30 can thus be omitted for areas that are exposed to less high abrasion loads. The support areas (contact surfaces 16) of the cover 10 are also formed here with a wear layer 30.

Fig. 3 shows a cover 10 according to the invention, which is still in the molding box 40. The cover 10 with the wear layer 30 in the lower case 44. The edge support 12 and the ribs 14 extend into the upper box 42. The molding box 40 surrounds with its molding sand 48 the entire Cover 10. In the lower case 44, an activation layer 50 is formed. At the contact surface 60 of the activation layer 50 to the later traffic area, the wear layer 30 is whitened. The cast iron passes through a pouring funnel 49 and a running and gate system 46 in the molding. After solidification of the cast iron top box 42 and lower box 44 can be separated from each other on the axis A for model division. The cover 10 can then be removed from the molding box 40.

The invention is not limited to one of the above-described embodiments, but can be modified in many ways. For example, upper and lower box can be reversed in the casting process. Also, the location of the activation layer can be varied.

All of the claims, the description and the drawings resulting features and advantages, including design details, spatial arrangements and method steps may be essential to the invention both in itself and in various combinations.

LIST OF REFERENCE NUMBERS

10

cover

12

Randauflager

14

ribs

16

contact area

18

frame

20

traffic area

30

wearing course

40

molding box

42

top box

44

lower box

46

Running and gate system

48

molding sand

49

sprue

50

activation layer

60

contact area

RT

Riefeltal

RK

Riefelkuppe

RH

Riefelhöhe

VB

wear range

A

Axis for model division

Claims (5)

1. Cover (10) made of cast iron with at least one upper traffic surface (20) subjected to wear, the traffic surface (20) subjected to wear having an anti-slip property produced by fine structuring in the cast iron, the structuring having a groove height (RH) of 2 to 8 mm, and the traffic surface (20) having a wear layer (30) at least in parts and the wear layer (30) being partially formed by chilling of the cast iron.
2. Cover (10) according to claim 1, characterised in that the wear layer (30) has a Brinell hardness of more than 275 HBW and less than 350 HBW.
3. Method for the production of a cover (10) made of cast iron with an upper traffic surface, comprising the following steps:

   i. producing a mould for the cover (10), whereby, during the production of the mould, a moulding box (40) is formed having an upper box (42) and a lower box (44);

   ii. forming an activation layer (50) in the mould, the activation layer (50) being formed on one half of the mould;

   iii. pouring in cast iron, the activation layer (50) being produced from chemical elements or chemical compounds and ensuring the crystalline formation of iron carbide, ledeburite or other wear-resistant structural constituents on the surface which is to come into contact with the cast iron, the upper traffic surface being partly formed by chilled cast iron and having an anti-slip property produced by fine structuring in the cast iron, the structuring having a groove height (RH) of 2 to 8 mm.
4. Method according to claim 3, characterised in that the chemical elements or chemical compounds in the mould are introduced by placing, spraying on, impregnating, dabbing or sprinkling on.
5. Method according to one of claims 3 or 4, characterised in that the activation layer (50) is formed at least partly in the mould by inserting cooling elements or by inserting denseners.

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