RU2721730C1 - Steel element with modified surface, formed by impregnation with nickel and zinc, and method of production thereof - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: disclosed group of inventions relates to a steel element with a modified surface with anticorrosive properties and to a method for production thereof. Said steel element comprises, in the direction from the outside to the inside, an alloy deposition layer and a metal diffusion layer, wherein the alloy deposition layer with thickness of 60 micron to 110 micron contains zinc and iron alloys, and metal diffusion layer with thickness of 30 micron to 120 micron contains perlite crystals and ferrite crystals. Method of anticorrosion modification of steel element surface includes the following stages. Stage S1, where steel substrate is provided. Step S2, on which the steel substrate is pre-treated. Step S3, where an impregnating substance is provided. Step S4, on which the steel substrate is loaded into the closed steel container, heating the steel container to a temperature in range of 370 to 450 °C and rotation of steel container with speed in range from 5 to 10 rpm during heating with steel substrate surface modification. Step S5, on which steel substrate is washed after modification.

EFFECT: obtaining a steel structure with a modified surface which has good corrosion resistance, which can reduce losses caused by steel corrosion, wherein the main mechanical properties of the steel substrate are not changed, and the abrasive resistance of the steel substrate is improved.

8 cl, 5 dwg

Description

FIELD OF THE INVENTION

The present invention relates to steel elements with a modified surface and, in particular, to a steel element with a modified surface with anticorrosive properties and to a method for its manufacture.

BACKGROUND OF THE INVENTION

Corrosion of steel causes great damage to the world. According to studies, scrap steel due to corrosion accounts for more than 20% of the annual steel production annually, causing damage estimated at approximately $ 7,000 hundred million. The cost of damage far exceeds the total cost of damage caused by natural disasters such as earthquakes, floods and typhoons. Currently, in order to reduce steel corrosion, several technologies are being developed to prevent corrosion. However, protective coatings made by technologies aimed at preventing corrosion do not completely solve the corrosion problem and their hardness is low. Impregnation with nickel and zinc can give the workpiece a higher corrosion resistance, higher wear resistance and high vibration resistance. Thus, there is a need for the manufacture of a steel structure with a modified surface with anticorrosive properties formed by impregnation with nickel and zinc.

SUMMARY OF THE INVENTION

There is a need for a steel structure with a modified surface with anticorrosive properties formed by impregnation with nickel and zinc.

The present invention provides a steel element with a modified surface formed by impregnation with nickel and zinc, while the steel element with a modified surface contains alloy structures with anticorrosive properties formed on a steel substrate, while the steel element with a modified surface contains, from the outside, the inside, an alloy deposition layer and a metal diffusion layer; wherein the steel substrate is made of low carbon steel or low carbon alloy steel, wherein the alloy deposition layer contains zinc and iron alloys, the metal diffusion layer contains perlite crystals, ferrite crystals and structures formed during quenching and tempering.

In addition, the steel substrate is not subjected to hardening and tempering, while the metal diffusion layer has a Vickers microhardness exceeding the Vickers microhardness of the steel substrate, and the Vickers microhardness of the steel substrate is in the range from 150 to 260, and the Vickers microhardness of the metal diffusion layer is in the range from 200 to 400.

In addition, the steel substrate was hardened and tempered, while the metal diffusion layer had a Vickers microhardness not exceeding the Vickers microhardness of the steel substrate, while the Vickers microhardness of each of the steel substrate and the metal diffusion layer was in the range from 240 to 450.

In addition, the color of perlite crystals in each metal diffusion layer is brighter than the color of perlite crystals in a steel substrate after several seconds of immersion of the surface-modified steel element in an etching solution containing nitric acid and alcohol in a concentration of 1% to 5%.

In addition, the metal diffusion layer on mild steel or mild alloyed steel contains at least one of tempering sorbate and tempering troostite while maintaining a brilliant white metallic diffusion layer after several seconds of immersion of the surface-modified steel element in an etching solution containing nitric acid and alcohol in a concentration of 1% to 5%.

In addition, the thickness of the alloy deposition layer is in the range of 60 microns to 110 microns, and the thickness of the metal diffusion layer is in the range of 30 microns to 120 microns.

In addition, the steel substrate of the steel element with a modified surface with anti-corrosion properties is made of low carbon steel or low carbon alloy steel.

The present invention further provides a method for modifying the surface of a steel material, comprising:

step S1, providing for a steel substrate that is made of medium carbon steel or medium carbon alloy steel;

step S2, comprising pretreatment of the steel substrate, the pretreatment comprising cleaning from oil and grease adhering to the surface of the steel substrate, and cleaning from rust on the surface of the steel substrate by blowing with metal powder;

step S3, comprising providing an impregnating agent, wherein the impregnating agent comprises Zn powder in the range of 15 wt.% to 20 wt.%, Ni powder in the range of 3 wt.% to 4 wt.%, Al powder in the range of 2 wt. % to 2.5% by weight, rare earth metal powder in the range from 2% to 3% by weight, ammonium chloride in the range from 1% to 4% by weight and Al ₂ O ₃ powder as the rest in weight percent;

step S4, comprising loading the steel substrate obtained in step S2 and the impregnating agent obtained in step S3 into a closed steel container, heating the steel container to a temperature in the range of 370 degrees Celsius to 450 degrees Celsius and rotating the steel container at a speed in the range from 5 rpm to 10 rpm during heating to modify the surface of the steel substrate;

step S5, including flushing.

BRIEF DESCRIPTION OF GRAPHIC MATERIALS

In FIG. 1 is a schematic view of an embodiment of a steel material with anticorrosion properties.

In FIG. 2 is a metallographic cross-sectional view of a Q235 steel substrate after modifying a surface that has not been hardened and tempered.

In FIG. 3 is a metallographic cross-sectional view of a steel substrate of steel No. 20 after modifying a surface that has not been hardened and tempered.

In FIG. 4 is a metallographic cross-sectional view of a 20MnTiB steel substrate after modifying a surface that has been quenched and tempered.

In FIG. 5 is a metallographic cross-sectional view of a 25CrMoV steel substrate after modifying a surface that has been quenched and tempered.

DETAILED DESCRIPTION

The following is a description of embodiments of the present invention solely through embodiments with reference to the accompanying figures. The embodiments shown and described above are solely examples. The detailed description may be modified within the framework of the principles of the present invention, up to the extent fully established by the broad general meaning of the terms used in the claims. Therefore, it should be borne in mind that the embodiments described above may be changed within the scope of the claims.

The present invention provides a method of surface modification to form a steel material with anti-corrosion properties by impregnation with nickel and zinc. The method includes the following steps.

Step S1 comprises providing a steel substrate made of low carbon steel or low carbon alloy steel.

In one embodiment, the steel substrate is made of one of Q235 steel, No. 20 steel, 20MnTiB steel, and 25CrMoV steel.

In step S2, the steel substrate is pretreated.

In one embodiment, the pretreatment includes cleaning the oil and fat adhering to the surface with an alkaline solution (or ultrasonic waves and heating) and cleaning the surface of rust with a metal powder blast.

Removal of oil and fat with an alkaline solution: The alkaline solution may contain a basic salt, and the basic salt contains caustic soda, sodium carbonate, tribasic sodium phosphate, sodium silicate or sodium borate. The base salt may contain at least two of the above components. In addition, the alkaline solution may further comprise a chelating agent for steel and an organic additive to improve surface cleaning. The chelating agent for steel contains at least one of ethylenediaminetetraacetic acid (EDTA), sodium citrate and triethanolamine. The organic additive contains at least one of ethylene glycol and ethylene glycol monoethyl ether.

Oil and grease cleaning by ultrasonic waves (ultrasonic cleaning) involves the use of ultrasonic waves to mix the washing liquid, thereby exerting great efforts directly or indirectly on the pollutants to disperse, emulsify or separate the pollutants, thereby providing cleaning. Ultrasonic cleaning requires proper flushing fluid.

Cleaning from oil and fat by heating involves heating the steel substrate to a temperature not lower than the flash point of oil and fat, thereby causing the burning and evaporation of oil and fat.

Prior to cleaning, the steel substrate may have contaminants adhering to the surface, including oil and grease, as well as dust. If no contaminants are cleaned, the contaminants will carbonize, leading to carbonization during heating, and carbonization affects the appearance and surface modification results. Removing oil and grease can remove contaminants adhering to the surface, thereby preparing the basis for subsequent surface modification.

Powder blasting may further clean the surface of the steel substrate. Metal powder blowing provides forced removal of rust and oxide layer by a jet of small solid balls under high pressure, thereby contributing to the surface gaining the required roughness and gloss and preparing the basis for subsequent surface modification.

In step S3, an impregnation agent is prepared.

An impregnating substance is prepared based on the type and the required anticorrosive properties of the alloy. The impregnating agent is in the form of a powder that contains Zn powder in the range of 15 wt.% To 20 wt.%, Ni powder in the range of 3 wt.% To 4 wt.%, Al powder in the range of 2 wt.% To 2 , 5 wt.%, Rare earth metal powder in the range from 2 wt.% To 3 wt.%, Ammonium chloride in the range from 1 wt.% To 4 wt.% And Al ₂ O ₃ powder as the rest in weight percent. The specific concentration of each type of powder in the impregnating substance may vary based on the material of the steel substrate or its intended use.

In step S4, the surface of the steel substrate is modified.

The steel substrate obtained in step S2 and the impregnating substance obtained in step S3 are loaded into a closed steel container. The steel container is heated and rotated during heating. Due to heating by the impregnating substance due to thermal conductivity, the steel substrate and the impregnating substance can have the same temperature, and the impregnating substance can penetrate into the steel substrate with surface modification of the steel substrate. In the present invention, the steel container is rotated at a speed in the range of 5 revolutions per minute (rpm) to 10 rpm during heating. The rotation speed of the steel container ensures uniform heating of the impregnating substance and the steel substrate. Thus, the impregnating substance uniformly penetrates the steel substrate, thereby providing a steel material with anticorrosive properties.

The steel substrate is made of medium carbon steel or medium carbon alloy steel.

In one embodiment, the steel container is heated at a temperature in the range of 370 degrees Celsius to 450 degrees Celsius. The heating temperature of the steel container is also important, a higher temperature provides a significantly higher penetration rate of atoms in the impregnating substance. The specific heating temperature and the specific heating time of the steel container may vary based on the material of the steel substrate or its intended use. The time required to modify the surface is in the range from 1 hour to 10 hours.

In this embodiment, the steel substrate and the impregnating agent are mixed at room temperature. The steel substrate and the impregnating substance are at the same temperature during the heating of the steel container.

Step S5 comprising flushing.

After step S4, the steel substrate is subjected to natural cooling. After removing dust on the surface, the steel substrate is then washed with water to remove remaining powder and other impurities.

A surface-modified steel material with anticorrosion properties is formed by modifying the surface of a steel substrate. In FIG. 1 is a schematic view of a steel material. The modified surface steel material comprises, from the outside inward, an alloy deposition layer, a metal diffusion layer, and a steel substrate. The metal diffusion layer forms a transition region between the steel substrate and the alloy deposition layer. If the steel substrate is not quenched and tempered, the Vickers microhardness of the steel substrate is in the range of 150 to 260, and the Vickers microhardness of the metal diffusion layer is in the range of 200 to 400. In another embodiment, if the steel substrate is quenched and tempered , on the surface of the steel substrate, structures formed during quenching and tempering are formed. The Vickers microhardness of each of the steel substrate and the metal diffusion layer is in the range from 260 to 450.

Embodiment 1

With reference to FIG. 2 and 3, in FIG. 2 is a metallographic cross-sectional view of a Q235 steel substrate after modifying a surface that has not been hardened and tempered. In FIG. 3 shows a metallographic cross-sectional view of a steel substrate of steel No. 20 after modifying a surface that has not been hardened and tempered.

In the present embodiment, the steel substrate is made of low carbon steel, in particular, Q235 steel or No. 20 steel. The surface of the steel substrate of Q235 steel or No. 20 steel is modified as follows.

The steel substrate was pretreated, including cleaning oil and fat with an alkaline solution and removing rust by blowing with metal powder. The processes for cleaning oil and fat with an alkaline solution and removing rust by blowing with metal powder have been described above, and no more detailed information is given here.

An impregnating substance was provided which was in the form of a powder and contained 15% by weight of Zn powder, 4% by weight of Ni powder, 2% by weight of Al powder, 3% by weight of rare earth powder, 1% by weight of ammonium chloride and Al powder ₂ O ₃ as the rest in weight percent.

In addition, the surface of the steel substrate was modified. Both the steel substrate after pretreatment and the impregnating substance were at room temperature when loaded into a closed steel container. The steel container was heated and rotated during heating. Due to heating by the impregnating substance due to thermal conductivity, the steel substrate and the impregnating substance could have the same temperature, and the impregnating substance could penetrate the steel substrate with a modification of the surface of the steel substrate. In the present invention, the steel container was rotated at a speed of 5 rpm during heating. The rotation speed of the steel container provided uniform heating of the impregnating substance and the steel substrate, thereby modifying the surface of the steel substrate. The time required to modify the surface was 1 hour, the heating temperature was 420 degrees Celsius to obtain a steel element with a modified surface.

In this embodiment, Q235 steel or No. 20 steel and the impregnating agent were not preheated during stirring. That is, Q235 steel or No. 20 steel and the impregnating agent were mixed at ambient temperature and then loaded into a steel container to carry out surface modification.

In this embodiment, the low carbon steel substrate was Q235 steel or No. 20 steel. In the case of Q235 steel, a structure with a modified surface with anticorrosion properties was formed on the steel substrate. The surface-modified steel element contained two metallographic layers, i.e., an alloy deposition layer and a metal diffusion layer, from the outside to the inside. The innermost layer was a steel substrate.

In the case of steel No. 20, a surface-modified steel element was also formed on the steel substrate, which contained two metallographic layers, that is, an alloy deposition layer and a metal diffusion layer, from the outside to the inside. The innermost layer was a steel substrate.

In this embodiment, the surface of each steel substrate was modified without using a hardening and tempering process. More specifically, the steel substrate and the impregnating agent were mixed at room temperature.

In FIG. 2 and 3 show that the color of perlite crystals in each metal diffusion layer is lighter than the color of perlite crystals in a steel substrate. The Vickers microhardness of each metal diffusion layer exceeded the Vickers microhardness of the steel substrate. The thickness of the metal diffusion layer was in the range from 30 microns to 80 microns.

Embodiment 2

As shown in FIG. 4 and 5, in FIG. 4 is a metallographic view of a steel substrate of 20MnTiB steel after modifying a surface that has been subjected to a hardening and tempering process. In FIG. 5 is a metallographic cross-sectional view of a 25CrMoV steel substrate after modifying a surface that has been quenched and tempered.

In the present embodiment, the steel substrates were made of low carbon alloy steel, in particular including 20MnTiB steel or 25CrMoV steel. The surface of the steel substrate of low carbon alloy steel was modified as follows.

The steel substrate was subjected to a quenching and tempering process to form structures formed during quenching and tempering.

The steel substrate was then pretreated, including cleaning the oil and fat with an alkaline solution and removing rust by blowing with metal powder. The processes for cleaning oil and fat with an alkaline solution and removing rust by blowing with metal powder are described above, and more detailed information is not given here.

An impregnating substance was prepared which was in the form of a powder and contained 20% by weight of Zn powder, 3% by weight of Ni powder, 2.5% by weight of Al powder, 2% by weight of rare earth powder, 4% by weight of ammonium chloride and powder Al ₂ O ₃ as the rest in weight percent.

In addition, the surface of the steel substrate was modified. In more detail, the steel substrate after pretreatment and the impregnating substance were loaded into a closed steel container. The steel container was heated and rotated during heating. Due to heating by the impregnating substance due to thermal conductivity, the steel substrate and the impregnating substance could have the same temperature, and the impregnating substance could penetrate the steel substrate with a modification of the surface of the steel substrate. In the present invention, the steel container was rotated at a speed of 8 rpm during heating. The rotation speed of the steel container ensures uniform heating of the impregnating substance and the steel substrate, thereby modifying the surface of the steel substrate. The time required to modify the surface was 10 hours, the heating temperature was 370 degrees Celsius to obtain a steel element with a modified surface.

In this embodiment, 20MnTiB steel or 25CrMoV steel and the impregnating agent were not preheated during stirring. That is, 20MnTiB steel or 25CrMoV steel and the impregnating agent were mixed at ambient temperature and then loaded into a steel container to modify the surface.

In this embodiment, the low carbon alloy steel substrate contained 20MnTiB steel or 25CrMoV steel.

On the surface of each of 20MnTiB steel and 25CrMoV steel, two layers with a modified surface were formed. The two surface modified layers were, in the direction from the outside inward, an alloy deposition layer and a metal diffusion layer. The innermost layer was a steel substrate.

Structures formed during quenching and tempering were formed on each steel substrate after the quenching and tempering process. In this embodiment, the structures formed during quenching and tempering are contained in a metal diffusion layer. The structures formed during quenching and tempering were sorbate tempering. In this embodiment, 20MnTiB steel or 25CrMoV steel and the impregnating agent were mixed at room temperature.

In FIG. Figures 4 and 5 show that when a metal diffusion layer is exposed on each of 20MnTiB steel and 25CrMoV steel to an etching process by immersing the metal diffusion layer in an etching solution containing nitric acid and alcohol in a concentration of 1% to 5%, the shiny white color of the metal diffusion layer persisted after several seconds, indicating that each steel element with a modified surface has good corrosion resistance. The Vickers microhardness of the metal diffusion layer did not exceed the Vickers hardness of the steel substrate after hardening and tempering. The thickness of the metal diffusion layer was in the range from 80 microns to 120 microns.

Compared with the prior art, the steel structure with a modified surface according to the present invention has good corrosion resistance, which can reduce losses caused by corrosion of the steel. In addition, the basic mechanical properties of the steel substrate do not change, but the abrasion resistance of the steel substrate is improved due to the fact that these processes give high hardness.

The embodiments shown and described above are solely examples. The present disclosure is illustrative only, and the detailed description may be modified within the framework of the principles of the present invention, up to the extent fully established by the broad general meaning of the terms used in the claims. Therefore, it should be borne in mind that the embodiments described above may be changed within the scope of the claims.

Claims (15)

1. A steel element with a modified anti-corrosion surface of the steel substrate, comprising, in the direction from the outside inward, an alloy deposition layer and a metal diffusion layer; wherein the alloy deposition layer contains zinc and iron alloys, the metal diffusion layer contains perlite crystals and ferrite crystals, characterized in that: the thickness of the alloy deposition layer is in the range of 60 microns to 110 microns, and the thickness of the metal diffusion layer is in the range of 30 microns to 120 microns. 2. The steel element according to claim 1, characterized in that the steel substrate is made of low carbon steel or low carbon alloy steel. 3. The steel element according to claim 1, characterized in that the steel substrate is not subjected to hardening and tempering, while the metal diffusion layer has a Vickers microhardness greater than the Vickers microhardness of the steel substrate, and the Vickers microhardness of the steel substrate is in the range from 150 to 260, and the Vickers microhardness of the metal diffusion layer is in the range of 200 to 400. 4. The steel element according to claim 1, characterized in that the steel substrate is subjected to hardening and tempering, while the metal diffusion layer has a Vickers microhardness not exceeding the Vickers microhardness of the steel substrate, while the Vickers microhardness of each of the steel substrate and metal diffusion layer is in the range from 240 to 450. 5. The steel element according to claim 3, characterized in that the color of the perlite crystals in each metal diffusion layer is lighter than the color of the perlite crystals in the steel substrate after a predetermined period of time for the surface-modified steel element to be immersed in the etching solution containing nitric acid and alcohol in a concentration of from 1% to 5%. 6. The steel element according to claim 4, characterized in that the metal diffusion layer contains at least one of tempering sorbate and tempering troostite while maintaining a brilliant white color of the metal diffusion layer after a predetermined time period of immersion of the surface-modified steel element in an etching solution containing nitric acid and alcohol in a concentration of from 1% to 5%. 7. A method of anticorrosive modification of the surface of a steel element, including: step S1, which provides a steel substrate; step S2, in which the pre-treatment of the steel substrate is carried out, the pre-treatment includes cleaning from oil and grease adhering to the surface of the steel substrate, and cleaning from rust on the surface of the steel substrate by blowing with metal powder; step S3, which provides an impregnating substance containing Zn powder in the range from 15 to 20 wt.%, Ni powder in the range from 3 to 4 wt.%, Al powder in the range from 2 to 2.5 wt.%, rare earth powder metals in the range from 2 to 3 wt.%, ammonium chloride in the range from 1 to 4 wt.% and Al ₂ O ₃ powder - the rest in weight percent; step S4, in which the steel substrate processed in step S2 and the impregnating agent obtained in step S3 are loaded into a closed steel container, heating the steel container to a temperature in the range from 370 to 450 ° C. and rotating the steel container at a speed in the range from 5 to 10 rpm during heating to modify the surface of the steel substrate; step S5, in which the steel substrate is washed after modification. 8. The method according to p. 7, which use a steel substrate made of low carbon steel or low carbon alloy steel.

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