HU203586B - Process for treating rolled stell for improving corrosion-resistance - Google Patents

Description

The present invention relates to a process for the treatment of corrosion resistance of rolled steel, in particular concrete or prestressed steel, and the like, from a non-ferrous metal, e.g. an anhydrous coating, first removing the roll formed at the roll from the rolled steel and then applying the desired coating to the hot rolled steel to prevent re-forming of the roll.

Rolled steel products are widely used, including as structural steel at construction sites, in particular in the form of reinforcing steel, prestressed steel, ashore and rock anchors, etc. feszítőiként.

When used as reinforcement in concrete building elements - whether loose reinforcement for reinforced concrete, prestressed reinforcement, or as a tensile member for shore and rock anchors - there is always some form of bonding, but a bond is created between the reinforcing steel and the concrete. In the case of reinforced concrete and prestressed concrete, this bonding is achieved by immediate bonding, without further ado, by embedding the reinforcing elements in the concrete, which encapsulates them. In the case of prestressed concrete, the joint is formed retrospectively by injection of the prestressing grooves required to maintain the longitudinal movement of the prestressing members with cement mortar.

In the production of concrete, the dissolution of the limestone particles in the cement produces an alkaline solution having a pH above 12. As a result, an iron oxide overcoat is formed on the surface of the reinforcing elements, which passivates the surface of the steel and protects it from surface corrosion. However, from a statistical and structural point of view, the reinforcing elements are usually located in the extreme ranges of the building blocks and are located at a certain minimum distance from the external surface, the so-called concrete cover. Due to air pollution and the increasing use of salting in melting heat and ice on bridge structures, the less satisfactory, but often adequate concrete cover, has the potential for chlorides dissolved in these chemicals to penetrate to the steel, where so they can attack steel directly. The same applies to the tension members of coastal and rock anchors, where soil moisture, water and acidic components of the soil can exert a destructive corrosive effect on steel structures. For this reason, there is a growing need for additional corrosion protection measures for such rolled steel products used in architecture.

It is generally known that metals, especially ferrous metals, are coated with a thin layer of zinc to protect against rust. Various methods are known for this. For hot dip galvanizing or hot dip galvanizing, the parts to be protected are immersed in a molten zinc dip, which may optionally be alloyed with aluminum. Acidic sulphate, sulphate chloride, or cyanide-alkaline baths are used for electrolytic or galvanic galvanization.

It is also known to apply a metal coating by spraying a liquid metal, wherein the metal is fed into a spray gun in a wire or powder form, where it is melted with a mixture of oxygen and combustible gas and sprayed with compressed air.

The disadvantage of all these known processes is that they are very expensive and can be used to handle bulk products, such as reinforcing steels and prestressed steels, in a continuous continuous process, or only at very high labor and cost. Added to this is the fact that the products to be coated must always be cleaned before applying such a layer, and this is especially true for rolled steel products, which already have a rolling layer which needs to be removed before the coating is applied. In practice, this is done by sandblasting, etching or other similar treatment.

It is also known in the case of continuous process rolled steel products that rolled goods after rolling - directly from rolling! In connection with the operation - decolorization and utilization of the rolling temperature by preventing corrosion re-formation with a corrosion-resistant coating -pl. with anchor - they are provided. Such a process is known from U.S. Patent No. 2,442,485. patent. In the known process, the deburring takes place in the last roll, as a result of an elongation causing a strong cross-section, whereby the brittle rib breaks, so that the rolled article leaves the roll in a substantially loose manner. In order to maintain this status, approx. Rolled goods at a temperature of 980-760 ° C are passed through a closed chamber filled with deoxidizing gas, preferably carbon monoxide, after leaving the roll, where the carbon monoxide burns to form carbon dioxide. Immediately thereafter, the rolled article passes through another chamber, preferably coated with powdered zinc, which melts on the surface due to the heat content of the rolled article. Bearing in mind that the coated rolled product is still about one hour away from the last compartment. Temperatures of 700-600 ° C require immediate cooling of the article immediately after coating in order to prevent zinc oxide from burning zinc powder.

The disadvantage of this known process is that it is relatively costly since maintaining the bleached surface of the rolled article by means of a deoxidizing gas atmosphere not only requires this gas to be introduced but also requires a suitably sealed chamber and an appropriate temperature to maintain the deoxidizing atmosphere. before the rolled article is rapidly cooled with other media after coating.

Against this background, it is an object of the present invention to provide a process which allows rolling steel products to be coated with a continuous operation directly connected to the rolling operation, utilizing the rolling temperature, so that the required operating and

EN 203 586 Β should be as low as possible.

The object of the present invention is achieved by a process wherein the rolled steel is defrosted with pressurized water during continuous rolling, the surface of the steel is rapidly cooled to below 600 ° C with water immediately after defrosting and finally a corrosion resistant coating is formed on the steel surface.

The present invention is based on the discovery that only one medium, namely water, is used for both decalcification, rupture, and cooling, so that the cooling can be controlled by rolling. heat can be used optimally for coating. This ensures that all process steps or treatment processes can be carried out as a direct continuation of the rolling process, i.e. rolling at speed, so that the finished coated product can leave the production line in the same way as a normal non-post-rolled product.

In treating the steel surface with high pressure pressurized water to deflate, we use the phenomenon that the rolling process results in the loosening of the adhesive to the rolled steel, which when loosened in the last rolling mill, e.g. rolled goods left the roll chair, relatively easy to remove.

In a preferred embodiment of the process according to the invention, the pressurized water pressure is above 200 bar, preferably from 300 to 400 bar; note that, if necessary, the pressure is approx. Can be increased up to 1000 bar. However, this requires only a very short treatment, namely, that the rolled article passes through a nozzle which causes only a slight decrease in temperature of the rolled article.

While the de-frosting with pressurized water is carried out at 900-1000 ° C due to heat, the treatment of this water according to the invention is carried out continuously, that is, by using the same medium for cooling, in such a way that the frosting temperature is reached. - which approx. 600 'C - we move down quickly so that no new revs can be formed, and we reach temperatures where coatings can be applied.

This is done according to the process of the invention by passing the rolled steel through a water bath or by spraying with water. Temperatures suitable for the application of corrosion-resistant coatings are, for example, in the range of 560 to 570 ° C for pure aluminum and approx. 415 'C is the temperature; in the case of alloys intermediate stages may be incorporated. Thus, in the process according to the invention, it is possible to use any of the alloys as a coating, since the rolling can be carried out from a temperature ranging from heat to complete cooling.

The coating may be applied in any manner, so in another preferred embodiment of the process of the invention, the non-ferrous metal which is to be coated is sprayed in the form of a powder; but the coating may also be formed by passing the rolled steel through a liquid non-metallic bath.

After descaling, rolled steel is protected from re-formation by water treatment; this protection also applies to the coating after the coating has been applied until the rolled steel has cooled down completely. It is noted that in some cases it is desirable that, for example, an additional resin, e.g. a layer of epoxy resin is also applied. This process can also be carried out without any further delay by the process of the invention, utilizing the residual heat.

In accordance with the process of the invention, the rolled steel is cooled by treatment with water after decontamination, which treatment can be carried out in the form of a process known in the art using water. For example, a process known as "Tempcore" for low-carbon and therefore weldable reinforcing steels, in which water is treated by forming a flange of martensite and bainite in the rolled steel immediately after hardening, while the residual heat content of the steel core is the next time it cools, it will not cause the edge zone to defrost outside the bainite stage. In the case of higher carbon steels which can be used as prestressing steels, the water treatment is carried out by hardening the steels from a final temperature of 860 to 1060 ° C so that the fringing zone is completely martensitic and the temperature of the fringing zone begins. equilibrate to 40Q-500C over a period of one second. In this way, the cooling performed according to the invention is particularly advantageous for improving the strength of steels.

A preferred embodiment of the process of the present invention will be described with reference to the following examples.

Example 1

The example illustrates the galvanizing of a 0 16 mm diameter rolled wire which is an "endless" roll of merchandise wire and is wound into bundles of appropriate diameter. If the rolled product is subsequently used as reinforcing steel, it is cut and used as rod steel.

This example illustrates the coating of rolled steel with a zinc layer. The rolled product leaves the last roll chair at a speed of 7.5 m / sec and a temperature of 960 ° C. After removing the last roll, the rake is removed with pressurized water at 290 bar, after which the wire is cooled to a temperature of 410 'C, where the zinc coating can be applied.

The surface of the zinc layer is known in the art, in which the metal is added to the spray gun in the form of a wire, in which it is melted by the light arc and sprayed by compressed air.

Parameters used for galvanizing:

HU 203 586 Β. 2 zinc wires (99%): 0 2 mm (1/8 ”) luminous energy: 4x550 A Drying with air nozzle: 6.5 bar.

Layer Thickness: 23-36 gm The zinc layer applied is resistant to weather-induced como.

Example 2

Forming a zinc-aluminum alloy coating on a 16 mm diameter rolled wire; before the coating is formed, the flake is removed with pressurized water at 290 bar after leaving the last mill. The rolling speed is 8 m / sec and the wire temperature when leaving the mill is 960 'C. After cooling rapidly, the temperature is achieved by using a jet of water at 520 C.

Zinc-aluminum alloy wire with a diameter of 0 to 2 mm is used for coating.

Coating parameters, sheet metal energy: 4x550 Air drying with nozzle: 6.5 bar

The resulting film thickness is approx. 30 gm, which is very resistant to the weather.

An advantage of the process according to the invention is that each session can be performed in a continuous through process directly connected to the rolling operation for each treatment station located after the last rolling mill. While the rolling of the ingots necessarily interrupts the rolling process until it leaves the last roll stand, of course, the process according to the invention also offers particular advantages when the welding process of the ingot has been converted to an endless roll. This is particularly advantageously achieved by the butt welding of the smelting known per se, in the range between leaving the furnace or a trio of rolling mills and first piercing the fine roll.

Claims (8)

PATENT CLAIMS A process for treating corrosion resistance of rolled steel, in particular concrete or prestressed steel, and the like, from a non-ferrous metal, e.g. for applying a zinc coating, first removing the roll formed from the rolled steel at the rolling temperature and then applying the desired coating to the hot rolled steel to prevent the roll from forming, characterized in that the steel surface is cooled rapidly to less than 600 ° C with water immediately after descaling to prevent the formation of a rupture and finally 15 are provided with a corrosion resistant coating on steel surfaces. Method according to Claim 1, characterized in that the surface descaling is carried out with pressurized water at a pressure of 200-1000 bar, preferably 300-400 bar. 20th The process according to claim 1 or 2, wherein the rolled steel is passed through a water bath. Method according to claim 1 or 2, characterized in that the rolled steel is sprayed with water. 5. The process according to any one of claims 1 to 25, wherein the cooling of the rolled steel is carried out by hardening, whereby a roll zone consisting of martensitic and bainite is formed in the rolled steel immediately after the hardening, while the remaining heat content of the steel core 30 defrost zones. 6. A process according to any one of claims 1 to 4, characterized in that the coating is carried out by spraying the non-ferrous metal powder. 7. A method according to any one of claims 1 to 3, characterized in that the coating on the rolled steel is carried out by passing it through a molten non-ferrous metal bath. 8. A process according to any one of claims 1 to 3, characterized in that the coating comprises an additional synthetic resin, e.g. an epoxy resin layer is also provided.