RU2721728C1 - Steel element with modified surface, formed by impregnation with nickel and zinc, and method of production thereof - Google Patents

Abstract

FIELD: metallurgy.SUBSTANCE: group of inventions relates to a steel element with a modified surface with anticorrosion properties and to a method for production thereof. Said steel element with modified anticorrosion surface, having Vickers microhardness in range of 240 to 500, comprises, in the direction from the outside to the inside, a deposited alloy layer, a metal diffusion layer and a steel substrate. Deposited layer of the alloy contains zinc and iron alloys, the metal diffusion layer contains pearlite crystals and ferrite crystals, and the steel substrate contains carbon in amount of 0.3–0.65 wt. %. Method of anticorrosion modification of steel element surface includes the following stages. Step S1, where steel substrate is provided. Step S2, where steel substrate is cleaned from oil and fat adhered to its surface. Step S3, on which steel substrate surface is cleaned from rust by blowing with metal powder. Step S4, where steel substrate and impregnating substance is loaded into closed steel container, steel container is heated to temperature in range of 370 to 430 °C and steel container is rotated at rate of 5 to 10 rpm during heating. Step S5, where steel substrate is washed.EFFECT: providing a steel structure with a modified surface, having 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 abrasion resistance of the steel substrate is improved.9 cl, 7 dwg, 2 ex

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 means of 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 surface-modified steel member formed by impregnation with nickel and zinc. The modified surface steel element contains alloy structures with anticorrosive properties formed on a steel substrate. The steel element with a modified surface with anticorrosive properties contains, in the direction from the outside inward, an alloy deposition layer and a metal diffusion layer. In this case, the steel substrate is made of medium carbon steel or medium carbon alloy steel. The alloy deposition layer contains zinc and iron alloys, the metal diffusion layer contains perlite crystals, ferrite crystals and structures obtained by quenching and tempering. The steel substrate contains a carbon element, which in the steel substrate is contained in the range from 0.3 weight. % to 0.65 weight. % A steel element with a modified surface with anticorrosive properties has a Vickers microhardness in the range from 240 to 500.

In addition, the steel element with a modified surface with anticorrosive properties is not subjected to hardening and tempering, the metal diffusion layer has a Vickers microhardness exceeding the Vickers microhardness of the steel substrate.

In addition, the steel element with a modified surface with anticorrosive properties is subjected to the hardening and tempering process and contains structures formed during hardening and tempering after the hardening and tempering process, while the metal diffusion layer has Vickers microhardness not exceeding the Vickers microhardness of the steel substrate.

In addition, when the steel element with the modified surface is not subjected to hardening and tempering, the color of perlite crystals in the metal diffusion layer is lighter than the color of perlite crystals in the steel substrate after 10 seconds to 50 seconds of immersion of the modified surface steel element in the etching solution, containing nitric acid and alcohol in a concentration of from 1% to 5%.

In addition, when a steel element with a modified surface is quenched and tempered, the metal diffusion layer on medium carbon steel or medium carbon alloy steel contains structures formed during quenching and tempering, while maintaining a brilliant white color of the metal diffusion layer after 10 seconds to 50 seconds of immersion of the steel element with a modified surface in the etching solution containing nitric acid and alcohol in a concentration of from 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 medium carbon steel or medium 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 cleaning the oil and fat adhering to the surface of the steel substrate with an alkaline solution;

step S3, providing for cleaning from rust on the surface of the steel substrate obtained in step S1 by blowing with metal powder;

step S4, comprising loading the steel substrate and the impregnating agent into a closed steel container, heating the steel container to a temperature in the range of 370 degrees Celsius to 430 degrees Celsius, and rotating the steel container at a speed in the range of 5 rpm to 10 rpm during heating, while the impregnating substance contains Zn powder in the range of 25 wt. % to 30 weight. %, Ni powder in the range of 2 wt. % to 2.5 weight. %, Al powder in the range of 1 weight. % to 2.5 weight. %, powder of rare earth metals in the range of 0.5 weight. % to 1.5 weight. %, ammonium chloride in the range of 1 weight. % to 4 weight. % and Al ₂ O ₃ powder as the rest in weight percent;

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 shows a metallographic cross-sectional view of a steel substrate of steel No. 45 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. 45 after modifying a surface that has been subjected to a hardening and tempering process.

In FIG. 4 is a metallographic cross-sectional view of a 42CrMoA steel substrate after modifying a surface that has been quenched and tempered.

In FIG. 5 is a metallographic cross-sectional view of a 35CrMo steel substrate after modifying a surface that has been quenched and tempered.

In FIG. 6 is a metallographic cross-sectional view of a 35VB steel substrate after modifying a surface that has been subjected to a hardening and tempering process.

In FIG. 7 is a metallographic cross-sectional view of a 40Cr 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 surface modification method for manufacturing a steel material with anticorrosion properties by impregnation with nickel and zinc. The method includes the following steps.

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

Medium carbon steel contains a carbon element, and the carbon element in medium carbon steel is in the range of 0.3 weight. % to 0.65 weight. % The medium carbon alloy steel is alloy steel containing a carbon element and an alloying element, and the carbon element in the medium carbon alloy steel is contained in a range of from 0.3 weight. % to 0.65 weight. %

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 the 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, which contains Zn powder in the range of 25 wt. % to 30 weight. %, Ni powder in the range of 2 wt. % to 2.5 weight. %, Al powder in the range of 1 weight. % to 2.5 weight. %, powder of rare earth metals in the range of 0.5 weight. % to 1.5 weight. %, ammonium chloride in the range of 1 weight. % to 4 weight. % 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 430 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.

The steel substrate may be preheated, and the preheated steel substrate and the impregnating agent are mixed and loaded into a steel container. The steel substrate may also not be preheated, and 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.

Prior to step S4, the steel substrate may be preheated, if necessary. The steel substrate may be pre-heated to a temperature of from 400 degrees Celsius to 420 degrees Celsius.

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.

The steel substrate may be quenched and tempered prior to pretreatment. The steel substrate may form structures formed during quenching and tempering on the surface after the quenching and tempering process.

A surface-modified steel member with anticorrosion properties may be formed on the steel substrate after the above steps. In FIG. 1 shows a schematic view of a steel material after surface modification. The steel material contains, from the outside to the inside, 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.

Embodiment 1

In FIG. 2 shows a metallographic cross-sectional view of a steel substrate of steel No. 45 after modifying a surface that has not been hardened and tempered. In the present embodiment, the steel substrate is made of medium carbon steel, in particular, steel No. 45. The surface of the steel substrate of steel No. 45 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 are described above, and more detailed information is not given here.

An impregnating substance was provided, which was in the form of a powder and contained 30 weight. % powder Zn, 2 wt. % Ni powder, 2.5 wt. % Al powder, 0.5 wt. % powder of rare earth metals, 4 wt. % ammonium chloride and Al ₂ O ₃ powder 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 400 degrees Celsius to obtain a steel element with a modified surface with anticorrosive properties.

In the present embodiment, steel No. 45 and the impregnating agent were not preheated during mixing. That is, steel No. 45 and the impregnating substance were mixed at ambient temperature and then loaded into a steel container to perform surface modification procedures in the steel container. More specifically, the steel substrate and the impregnating agent were mixed at room temperature.

In the present embodiment, the steel substrate was No. 45 steel on which a modified surface steel member was formed. The surface-modified steel element on steel No. 45 contained, in the direction from the outside inward, an alloy deposition layer and a metal diffusion layer. The innermost layer was a steel substrate.

As shown in FIG. 2, the color of perlite crystals in the metal diffusion layer was lighter than the color of perlite crystals in the steel substrate. The metal diffusion layer had a Vickers microhardness greater than the Vickers microhardness of the steel substrate. The thickness of the metal diffusion layer was 100 microns. The metal diffusion layer contained perlite crystals and ferrite crystals.

Embodiment 2

As shown in FIG. 3-7, in FIG. 3 is a metallographic view of a steel substrate of steel No. 45 after surface modification, which has been subjected to a hardening and tempering process. In FIG. 4 is a metallographic cross-sectional view of a 42CrMoA steel substrate after modifying a surface that has been quenched and tempered. In FIG. 5 is a metallographic cross-sectional view of a 35CrMo steel substrate after modifying a surface that has been quenched and tempered. In FIG. 6 is a metallographic cross-sectional view of a 35VB steel substrate after modifying a surface that has been subjected to a hardening and tempering process. In FIG. 7 is a metallographic view of a 40Cr steel substrate after modifying a surface that has been quenched and tempered.

In the present embodiment, the steel substrates were made of medium carbon steel or medium carbon alloy steel, in particular including steel No. 45, 42CrMoA, steel 35CrMo, steel 35VB and steel 40Cr. As a result, various structures with a modified surface were obtained.

Differences from embodiment 1 were as follows:

(1) In the present embodiment, the impregnating agent was in powder form and contained 25 weight. % powder Zn, 2.5 wt. % Ni powder, 1 weight. % Al powder, 1.5 wt. % powder of rare earth metals, 1 weight. % ammonium chloride and Al ₂ O ₃ powder as the rest in weight percent.

(2) In the present embodiment, each of the steel substrates in the present embodiment was subjected to a hardening and tempering process prior to pretreatment.

Then, as a result of surface modification of the steel substrates, steel elements with a modified surface were obtained. Each of the steel elements with a modified surface with anticorrosive properties had a general Vickers microhardness in the range from 240 to 400. The steel element with a modified surface contained, 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 a steel substrate after the quenching and tempering process. In particular, the structures formed during quenching and tempering were part of the metal diffusion layer. In addition, structures formed during quenching and tempering were represented by at least one of tempering sorbate and tempering troostite.

Each of the surface-modified steel elements was subjected to an etching process by immersion of the surface-modified steel element in an etching solution containing nitric acid and alcohol in a concentration of 1% to 5%. The results show that the shiny white color of the metal diffusion layer persisted after several seconds (usually from 10 seconds to 50 seconds), which indicated that each steel element with a modified surface had good corrosion resistance. The thickness of each metal diffusion layer was in the range from 30 microns to 100 microns. The Vickers microhardness of each metal diffusion layer formed by modifying the surface of a particular steel substrate was slightly less than the Vickers microhardness of the steel substrate. The metal diffusion layer obtained by modifying the surface of the steel substrate contained metallographic structures, which represented at least one of tempering sorbate and tempering troostite.

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 (16)

1. A steel element with a modified anticorrosive surface having Vickers microhardness in the range from 240 to 500, characterized in that: it contains, in the direction from the outside to the inside, a deposited alloy layer, a metal diffusion layer and a steel substrate, while the deposited alloy layer contains zinc and iron alloys, the metal diffusion layer contains perlite crystals and ferrite crystals, and the steel substrate contains carbon, the content of which is from 0.3 to 0.65 weight. % 2. The steel element according to claim 1, characterized in that it is made without hardening and tempering, while the metal diffusion layer has a Vickers microhardness exceeding the Vickers microhardness of the steel substrate. 3. The steel element according to claim 1, characterized in that it is subjected to a hardening and tempering process and contains structures formed during hardening and tempering and after the hardening and tempering process, while the metal diffusion layer has a Vickers microhardness not exceeding the Vickers microhardness steel substrate. 4. The steel element according to claim 2, characterized in that it is made without hardening and tempering, while the color of the pearlite crystals in the metal diffusion layer is lighter than the color of the pearlite crystals in the steel substrate after 10 seconds to 50 seconds of immersion of the steel element with a modified surface in an etching solution containing nitric acid and alcohol in a concentration of from 1% to 5%. 5. The steel element according to claim 3, characterized in that it is hardened and tempered, while the metal diffusion layer contains structures formed during quenching and tempering, while maintaining the brilliant white color of the metal diffusion layer after 10 seconds to 50 seconds of immersion of the steel element with a modified surface in the etching solution containing nitric acid and alcohol in a concentration of from 1% to 5%. 6. The steel element according to any one of paragraphs. 1-5, characterized in that the thickness of the deposition layer of the alloy is in the range from 60 to 110 microns and the thickness of the metal diffusion layer is in the range from 30 to 120 microns. 7. The steel element according to claim 1, characterized in that the steel substrate is made of medium carbon steel or medium carbon alloy steel. 8. 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 steel substrate is cleaned of oil and grease adhering to its surface; step S3, in which the surface of the steel substrate is cleaned from rust by blowing with metal powder; step S4, in which the steel substrate and the impregnating agent are loaded into a closed steel container, the steel container is heated to a temperature in the range of 370 to 430 ° C. and the steel container is rotated at a speed in the range of 5 to 10 rpm during heating, wherein the impregnating substance contains Zn powder in the range from 25 to 30 weight. %, Ni powder in the range from 2 to 2.5 weight. %, Al powder in the range from 1 to 2.5 weight. %, powder of rare earth metals in the range from 0.5 to 1.5 weight. %, ammonium chloride in the range from 1 to 4 weight. % and powder Al ₂ O ₃ - the rest in weight percent; step S5, in which the steel substrate is washed. 9. The method according to p. 8, in which they use a steel substrate made of medium carbon steel or medium carbon alloy steel.

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