CN115612973A - Laser high-temperature flash formation method of oxide film on steel material surface - Google Patents

Abstract

The application discloses a laser high-temperature flash forming method of an oxide film on the surface of a steel material, which comprises the following steps: coating the Fe to be formed by the activating solution ₃ O ₄ Oxidizing the surface of the ferrous material to form a layer containing Fe on the surface of the ferrous material ²⁺ 、Fe ³⁺ An activated membrane of ions; heating by a laser beam for heating requires the generation of the Fe ₃ O ₄ The surface of the iron and steel material of the oxide film reaches 1450-1500 ℃, and the Fe is generated in a flash speed ₃ O ₄ And oxidizing the film, and spraying oxygen to the surface of the ferrous material while irradiating the surface of the ferrous material with a laser beam for heating.

Description

Laser high-temperature flash formation method of oxide film on steel material surface

technical field

The invention relates to the technical field of preparation of an oxide film on the surface of iron and steel materials, in particular to a laser high-temperature flash formation method for the oxide film on the surface of iron and steel materials.

Background technique

Most industrial parts are made of steel materials, such as rolls, which are important parts of the hot rolling mill. The steel strip is rolled under vertical pressure by a pair of rolling rolls, and its direct material consumption is about 5 to 15 of the production cost of rolling steel. %.

In the production process of hot-rolled steel strip, the working conditions of the rolls are very harsh, and they are in contact with the rolled material at a temperature as high as 900-1200 °C. In addition to the strong high-temperature friction and wear of the rolled material, the roll surface is also subjected to high-temperature oxidation. An oxide film is formed on the surface of the roll, and the peeling off of the oxide film aggravates the failure of the roll. In addition, the roll will be repeatedly heated by the rolled material and cooled by the cooling water during work, and it will be subjected to high-frequency shock and heat. The fatigue thermal stress caused by rapid cooling and rapid heat will induce micro-cracks, and fatigue micro-cracks will The continuous expansion will eventually cause the surface of the roll to crack or even peel off, prompting the roll to fail. Therefore, in addition to high wear resistance and toughness, hot rolls should also have excellent oxidation resistance and thermal fatigue resistance.

High-speed steel has the characteristics of high toughness and high hardness in terms of physical properties, especially high-temperature hardness, high wear resistance, good red hardness, good roughness, etc., and has good oxide film formation ability. The amount can reach 2 to 4 times that of high-chromium ferromaterials, so high-speed steel rolls have been widely used in the front-end stands (F1-4) of finish rolling, and new high-speed steel rolls have been gradually developed to provide roughing and finish rolling stands. Promotion and application of the rear rack.

However, the price of high-speed steel is relatively high. In practical applications, in order to reduce costs, composite high-speed steel rolls are often used. The composite high-speed steel roll is formed by a high-speed steel roll sleeve covered with a core roll, and the core roll can be a ductile iron roll, etc. In the process of hot finish rolling steel plates, 6-8 stands need to be rolled sequentially, among which the first four stands have high rolling temperature, about 900-1200°C, large reduction and large rolling force, and generally adopt high-speed steel rolls.

In the process of hot-rolling steel plates, due to the contact between the surface of the roll and the red-hot high-temperature billet, a layer of oxide scale will be formed on the surface of the roll. This layer of oxide scale has both positive and negative effects.

Its beneficial effects are: firstly, it can reduce the friction force and reduce the wear of the roll; secondly, it can prevent the red-hot steel billet from sticking to the surface of the roll; The temperature of the substrate can be reduced to reduce thermal shock and suppress thermal fatigue cracks on the surface of the roll.

The disadvantage of roll surface scale is that due to the scale layer formed in the prior art, it is mainly loose ferrous oxide (FeO). Therefore, in the subsequent rolling process, the scale layer is easily peeled off. The peeled iron oxide scale is pressed into the surface of the slab, and is further elongated into a chain shape as the rolling progresses, which damages the surface quality of the slab, and the rolled steel plate can only be downgraded or scrapped for use.

According to statistics, the scrap reduction rate of hot-rolled high-strength steel sheets due to peeling of iron oxide scale is about 20%. Taking a production line with an annual output of 6 million tons as an example, 1.2 million tons of steel products are scrapped or downgraded for use a year. If it is lowered by one level, the sales price will differ by 500 yuan/ton. Therefore, only one hot rolling production line with 6 million tons will lose 30 million yuan a year. Since the loose ferrous oxide scale peels off with the rolling process, the rolls are severely worn. When rolling high-quality steel plates, in order to improve the quality of the plate surface, the rolls are often rolled less than 3 times on average, and they have to be re-ground after being off the machine. The loss of the roll is extremely large. And frequent grinding roll, can cause frequent downtime to change roll, cause downtime loss, and, can cause the rolling slab quality instability.

There are three kinds of iron oxides, one is ferrous oxide (FeO), and FeO is a metal-deficient p-type semiconductor with about 5% to 16% of cation defects, so there is a higher concentration of cation vacancies in the FeO layer. The mobility of cations and electrons in the FeO layer is high, so the growth rate of the FeO layer is very fast. However, FeO is black, has a loose structure and is easy to fall off.

The second is iron oxide (Fe2O3). Fe2O3 is an n-type semiconductor with insufficient oxygen. The oxygen content is relatively high, and there are many oxygen ion defects inside, forming anion vacancies, which is conducive to the diffusion of oxygen from the outside to the inside. Fe ₂ O ₃ has Two crystal structures, metastable γ-Fe ₂ O ₃ cubic crystal at low temperature, α-Fe ₂ O ₃ with oblique hexahedral structure above 400°C, and Fe ₂ O ₃ is red. The main component of reddish-brown rust is iron oxide with n crystal water (Fe ₂ O ₃ ·nH2O).

The third ferric oxide (Fe ₃ O ₄ ), Fe3O4 is a p-type semiconductor, its stoichiometry is higher than that of FeO, so it is not conducive to the diffusion of Fe ²⁺ , Fe ₃ O ₄ is composed of one Fe ²⁺ and two Fe ^{2 +} , Fe ³⁺ , it belongs to spinel structure, Fe ²⁺ and Fe ²⁺ , Fe ³⁺ are located in the interstitial position of tetrahedron and octahedron respectively. Fe ₃ O ₄ is black, dense in texture and high in hardness. It can be used as abrasive and polishing agent, and can also play a protective role. Therefore, in industry, a layer of Fe ₃ is often formed on the surface of steel parts through blackening or bluish treatment. O ₄ film, play a role in anti-corrosion. Therefore, if a layer of Fe ₃ O ₄ film closely combined with the matrix can be formed on the surface of the roll, the high temperature wear resistance of the roll will be greatly improved, the life of the roll will be prolonged, and the surface quality of the rolled strip will be improved.

As shown in Figure 1, according to the iron-oxygen reaction phase diagram, there are two situations in which Fe ₃ O ₄ can be stably generated. One situation is that Fe ₃ O ₄ is generated at low temperature, when it is lower than 570°C and the oxygen content is less than 57at%. , iron and oxygen can produce ferroferric oxide, further according to the relationship between Gibbs free energy and temperature in the oxidation reaction, Fe ₃ O ₄ is the most stable among the oxidation products of pure iron below 567°C, and the thermodynamic tendency of formation is the largest; another situation Fe ₃ O ₄ is formed at high temperature, that is, at 1450-1582°C, and when the oxygen content is greater than 58at%, iron and oxygen can form iron tetraoxide. In other cases, a mixture of ferrous oxide, trioxide and ferric oxide is generally generated.

For example, the prior art CN114622154A discloses a laser forming prefabrication oxide film equipment and process on the surface of a hot roll, which prepares the oxide film at 800°C to 900°C. However, according to the phase diagram of ferrite-oxygen reaction, at this temperature, a large amount of fuustenite will be produced, and no matter how long the temperature is kept, a high proportion of Fe ₃ O ₄ cannot be obtained.

In fact, in the prior art, most methods are used to form Fe3O4 oxide film at a temperature lower than 570°C, and there are generally two ways.

One is high-temperature water vapor treatment. The specific method is to place the steel piece in high-temperature water vapor at 540-570°C, so that a layer of blue ferric oxide (Fe ₃ O ₄ ) film is formed on the surface, with a thickness of 4 ~6 μm. This kind of oxide film has a fine structure and can be firmly attached to the surface of the metal. The principle is that water vapor contacts with hot iron to decompose and release active oxygen atoms, and then the active oxygen atoms react with metallic iron to form Fe ₃ O ₄ cores , and precipitate on the surface of the workpiece after growing up. The high-temperature steam treatment needs to heat the workpiece to about 550°C. The high-temperature steam treatment takes about 1 hour, plus the process time for the roll to be heated from room temperature to 550°C and slowly cooled to room temperature after the bluing treatment. For small workpieces, the entire The process takes about 3 hours, and this method itself has the problems of high energy consumption and long time. If this method is used to carry out bluing treatment on the surface of the high-speed steel roll, the high-speed steel roll has a length of 5.5 meters, a diameter of up to 1 meter, and a weight of up to 30 tons. If the high-temperature steam method is used for processing, there are many practical difficulties. For example, first, it is difficult to find such a huge heating furnace, and the heating cost is too high. Second, it takes more than 10 hours to heat a 30-ton roll to 550°C. Fire softening reduces the hardness of the roll, which leads to the scrapping of the roll. Fourth, during the air cooling process, the high-speed steel roll is brittle, and the surface of the roll may crack. Therefore, it is not feasible to treat high-speed steel rolls with high-temperature blueing method.

The second method of forming Fe ₃ O ₄ oxide film is alkali boiling oxidation method. The specific method is to put steel parts into a mixed solution of NaOH and NaNO ₂ at a certain concentration at about 140 ° C, and form Fe ₃ O ₄ oxidation through chemical reaction. The film, the thickness and density of the film are related to the concentration of NaOH and NaNO ₂ during oxidation, the temperature and the treatment time. If the temperature is too low, the nucleation rate and growth rate of Fe ₃ O ₄ will be low, and the oxide film will be difficult to form. , the oxide film is easily dissolved, so the treatment temperature must be strictly controlled between 130 and 150 °C. There is serious pollution in this method itself, and after the volatilization of strong alkali solution, the working environment is bad. For high-speed steel with high alloy content, the cooking time in lye is much higher than that of ordinary carbon steel, which takes about 80 minutes. If the Fe ₃ O ₄ oxide film is formed on the surface of the high-speed steel roll by the alkali boiling oxidation method, there are the following problems. First, the treatment time is long, and it takes 80 minutes for alkali boiling alone. High-temperature lye pool, otherwise the temperature of the lye in the entire soda boiling pool will be reduced. It needs to be heated for at least 3 hours to heat the 5.5-meter-long, 1-m-diameter, and 30-ton roll to about 140°C. It takes at least 6 hours to process a roll; second, there is serious pollution, the lye volatilizes and pollutes the working environment, and the residual lye on the surface of the roll needs special treatment; third, the processing cost is high and a large volume of high-temperature alkali is required Fourth, it is difficult to guarantee the quality of the oxide skin. The thickness and uniformity of the oxide film are greatly affected by the concentration and temperature of the lye. For such a huge lye pool, the concentration and temperature of the lye fluctuate greatly, and it is difficult to ensure that different rolls The consistency of the quality of the oxide film formed on the surface, even for the same roll, will result in uneven and inconsistent quality of the oxide film due to differences in concentration, temperature, and lye flow velocity.

The reason why high temperature (1450-1582° C.) is not used in the prior art to form the Fe ₃ O ₄ oxide film is, firstly, the prior art is that the entire workpiece is heated, the energy consumption is too high, and the entire workpiece is heated to such a high temperature, The workpiece will soften, crack due to uneven internal and external temperatures during the cooling process, and the material will also undergo a phase change, and the processing time is long, requiring a large site, complex equipment, and a high-concentration oxygen atmosphere (oxygen content greater than 58at%). , It is difficult to implement in terms of performance, cost and efficiency.

Second, it can be seen from the ferrite reaction phase diagram shown in Figure 1 that the area formed by the Fe ₃ O ₄ oxide film under high temperature conditions is very narrow, and the conditions are strictly controlled. Below 1450°C, the Fe ₃ O ₄ oxide film cannot be formed. film, and once it is higher than 1500 ° C, it will cause the melting of steel materials, so it is necessary to accurately control the processing temperature. On the other hand, if only air or oxygen is provided, since the oxygen provided in the air and oxygen is oxygen molecules, not active oxygen atoms, it cannot quickly react with steel to form an oxide film. .

Contents of the invention

An advantage of the present invention is to provide a laser high-temperature flash formation method of an oxide film on the surface of a steel material. This method proposes a method for flashing an oxide film of Fe ₃ O ₄ at a high temperature (1450-1500°C) for the first time. It solves the problem that the traditional formation of Fe ₃ O ₄ oxide film can only be carried out slowly at low temperature.

An advantage of the present invention is to provide a laser high-temperature flash formation method of an oxide film on the surface of a steel material, wherein the Fe ₃ O can be generated in situ on the surface of a steel material through the laser high-temperature flash formation method of an oxide film on the surface of a steel material. ₄ The oxide film is closely combined with the iron and steel material matrix, which solves the problems of easy formation of FeO and low binding force in traditional oxidation methods.

An advantage of the present invention is to provide a laser high-temperature flash formation method of an oxide film on the surface of a steel material, wherein stable _Fe3O can be formed on the surface of the steel material through the laser high-temperature flash formation method of the oxide film on the surface of the steel material ₄ Oxide film, and the operating conditions are simple and the production cost is low, which solves the problems of long oxidation time, high temperature and high energy consumption of traditional oxidation methods.

Another advantage of the present invention is to provide a laser high-temperature flash formation method of an oxide film on the surface of a steel material, by coating an activation solution on the surface of a steel material to form an activation film, wherein the activation film can play a light-absorbing role on the one hand , improve the laser light absorption rate, in addition, active Fe ^{2 +} and Fe ³⁺ ions can be formed in the active film in advance or at the same time when the laser is at a high temperature. At the same time, the active film can release active oxygen atoms when it is thermally decomposed at high temperature. Active Fe ²⁺ , Fe ³⁺ ions and active oxygen atoms can quickly combine to form Fe ₃ O ₄ oxide film in a flash, thus solving the problems of high laser reflectivity and low light absorption on the steel surface, and also solving the traditional steel oxidation reaction The problem of long time makes millisecond flash oxidation possible.

Another advantage of the present invention is to provide a laser high-temperature flash formation method of an oxide film on the surface of a steel material, wherein the laser high-temperature flash formation method of an oxide film on the surface of a steel material can be used in a very short period of time (such as 0.01- 10 milliseconds) to form a Fe ₃ O ₄ oxide film.

Another advantage of the present invention is to provide a laser high-temperature flash formation method of an oxide film on the surface of a steel material. The high-energy laser beam used for heating quickly scans the surface of the steel material, and only the micron-scale depth of the laser spot on the surface of the steel material The local high temperature is formed under the environment, which solves the problems of the traditional method that requires overall heating, complex equipment, large site, high energy consumption and low efficiency.

In order to achieve at least one of the above advantages, the present invention provides a laser high-temperature flash formation method of an oxide film on the surface of a steel material. The laser high-temperature flash formation method of an oxide film on the surface of a steel material includes:

Coating activation solution on the surface of iron and steel material that needs to form Fe ₃ O ₄ oxide film, to form a layer of activation film on the surface of iron and steel material; and

The surface of the iron and steel material that needs to form the Fe ₃ O ₄ oxide film is scanned by the laser beam used for heating, so that the laser scanning spot on the surface of the iron and steel material is heated to 1450-1500 ° C to generate the Fe ₃ O in a flash ₄ oxide film.

According to an embodiment of the present invention, the activation film contains Fe ²⁺ and Fe ³⁺ ions.

According to an embodiment of the present invention, pretreating the surface of the iron and steel material includes:

Grinding the surface of ferrous materials to remove the surface fatigue layer; and/or

Cleaning the emulsion or oil on the surface of the steel material with alkali, and removing the emulsion or oil on the surface of the steel material by washing with water; and/or

Wipe the surface of the steel material with alcohol.

According to an embodiment of the present invention, the activation solution is an activation solution containing oxyacid ions.

According to an embodiment of the present invention, the activation solution containing oxyacid ions is an activation solution containing phosphate ions and/or sulfate ions and/or nitrate ions and/or hypochlorite ions.

According to an embodiment of the present invention, the laser high-temperature flash formation method of the oxide film on the surface of the steel material includes the steps:

Before or simultaneously with laser beam scanning, a light absorbing agent is coated on the surface of the active film.

According to an embodiment of the present invention, the light absorbing agent is a carbon-based light absorbing agent.

According to an embodiment of the present invention, the steel material is a roll.

According to an embodiment of the present invention, while the surface of the iron and steel material is irradiated with a laser beam for heating, oxygen is injected to the laser spot on the surface of the iron and steel material.

According to an embodiment of the present invention, the flow rate of the oxygen is 0.1-15 L/min.

According to an embodiment of the present invention, the time for forming the oxide film is 0.01-10 milliseconds.

According to an embodiment of the present invention, the color of the activation film is dark.

According to an embodiment of the present invention, the activation solution is an activation solution of oxygen-free acid ions, wherein the laser high-temperature flash formation method of the oxide film on the surface of the steel material comprises:

And while irradiating the surface of the iron and steel material with the laser beam for heating, oxygen is injected to the laser spot on the surface of the iron and steel material.

According to an embodiment of the present invention, the activation solution is an activation solution containing halogen ions.

Description of drawings

Figure 1 shows the ferrite reaction phase diagram.

Fig. 2 shows a flow chart of the laser high-temperature flash formation method of the oxide film on the surface of the iron and steel material in one embodiment.

detailed description

The following description serves to disclose the present invention to enable those skilled in the art to carry out the present invention. The preferred embodiments described below are only examples, and those skilled in the art can devise other obvious variations. The basic principles of the present invention defined in the following description can be applied to other embodiments, variations, improvements, equivalents and other technical solutions without departing from the spirit and scope of the present invention.

Those skilled in the art should understand that in the disclosure of the present invention, the terms "vertical", "transverse", "upper", "lower", "front", "rear", "left", "right", " The orientation or positional relationship indicated by "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, which are only for the convenience of describing the present invention and simplified description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, so the above terms should not be construed as limiting the present invention.

It can be understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element The quantity can be multiple, and the term "a" cannot be understood as a limitation on the quantity.

Referring to FIG. 2 , a method for forming an oxide film on the surface of a steel material by laser high temperature flash flash according to a preferred embodiment of the present invention will be described in detail below. The laser high-temperature flash formation method of the oxide film on the surface of the iron and steel material comprises the steps:

S1001, apply activation solution on the surface of iron and steel materials that need to form Fe ₃ O ₄ oxide film, such as coating on the surface of rolls, to form a layer of activated iron and steel materials containing Fe ²⁺ and Fe ³⁺ ions on the surface of iron and steel materials membrane.

In one embodiment, the activation solution is implemented as an activation solution containing oxyacid ions.

As an example, the activation solution is implemented as sulfuric acid or/and sulfate, and the surface of the steel material such as roll is coated with sulfuric acid or/and sulfate to carry out pre-activation treatment on the surface of the roll, so that the iron element and sulfate radical on the surface of the steel material The ions react, and depending on the concentration of sulfate ions and the reaction temperature, a layer of FeSO ₄ or Fe ₂ (SO ₄ ) ₃ activated film is formed. Compared with Fe atoms, Fe ²⁺ and Fe ³⁺ ions are more active , and further increase the activity of the oxidation reaction, so that a layer of Fe ₃ O ₄ oxide film can be flashed on the steel material at high temperature.

In addition, SO ₄ ^2— decomposes at high temperature to produce active [O] elements, which are more likely to promote the formation of Fe ₃ O ₄ oxide film than oxygen.

By forming an activated film containing Fe ²⁺ and Fe ³⁺ ions on the surface of iron and steel materials, due to the high activity of Fe ²⁺ and Fe ³⁺ ions, it can form Fe ₃ O ₄ oxide film in a high-temperature environment in a flash .

For example, in one example, an activated film containing Fe ²⁺ and Fe ³⁺ ions is formed on the surface of the iron and steel material by coating sulfuric acid or/and sulfate. Sulfuric acid or sulfate reacts with iron and steel materials such as iron on the surface of the roll to form FeSO ₄ , Fe ₂ (SO ₄ ) ₃ film, and the color of FeSO ₄ , Fe ₂ (SO ₄ ) ₃ film is yellow, yellow-brown, brown or brown-black. Color, the specific color is determined by the duration of action, the longer the time, the darker the color.

If there is no such dark activation film, the surface color of the roll after grinding is bright silver, which has a high reflectivity to the laser. On the one hand, it will lead to low laser efficiency. The difference in surface reflectance, that is, the light absorbance at different positions of the same spot is different. Different light absorbance will lead to different temperatures, and different temperatures will lead to uneven oxide films, which will cause uneven oxide films of Fe ₃ O ₄ subsequently formed. . Therefore, the activation treatment by the activation solution on the surface of the roll has three effects at the same time. On the one hand, it is to form active Fe ²⁺ , Fe ³⁺ ions and active [O] elements to promote the rapid formation of Fe ₃ O ₄ oxide film. The dark ferric nitrate film can greatly increase the absorbance, and the third aspect is to ensure the uniformity and consistency of the quality of the generated Fe ₃ O ₄ .

More importantly, since the activated film can decompose at high temperature and release active [O] elements, in this way, no additional oxygen can be introduced, and thus it can be used on iron and steel materials at high temperatures (1450-1500°C). The Fe ₃ O ₄ oxide film is rapidly formed on the surface.

Preferably, in the step S1001, when sulfuric acid or/and sulfate is used as the activation solution, the concentration of sulfate ion [SO ₄ ²⁻ ] in the activation solution is 0.5˜15 mol/L.

In yet another embodiment, the activation solution containing oxoacid ions is implemented as an activation solution containing nitrate ions (NO ₃ ⁻ ), so as to form nitric acid with active Fe ²⁺ and Fe ³⁺ ions on the surface of the iron and steel material. Ferrous, ferric nitrate activated membrane. It can be understood that when the activated film containing nitrate ions (NO ₃ ^- ) is formed at a high temperature under subsequent laser beam irradiation, it can also provide active [O] element, thereby promoting the rapid formation of Fe ₃ O ₄ oxide film. In addition, after the activation solution containing nitrate ions (NO ₃ ^- ) is used, the surface of the iron and steel material will gradually change from silvery white to dark, such as yellow, brown, and brownish black, which can improve the laser light absorption rate, Significantly reduces the effect of laser reflection.

In another embodiment, the activation solution containing oxoacid ions is implemented as an activation solution containing hypochlorite ions (ClO ^- ), so as to form active Fe ²⁺ and Fe ³⁺ ions on the surface of the iron and steel material. Ferrous hypochlorite, ferric chloride activation film. It can be understood that the activated film containing hypochlorite ions (ClO ^- ) can provide active [O] elements through decomposition when the subsequent laser beam is formed at a high temperature, thereby promoting the rapid formation of the Fe ₃ O ₄ oxide film. In addition, after the activated film of chlorine hypochlorite (ClO ^- ) is formed, the surface of the iron and steel material will gradually change from silvery white to dark, such as green, yellow-green, and yellow, which can improve the laser light absorption rate and reduce laser reflection. Effect.

In yet another embodiment, the activation solution containing oxoacid ions is implemented as an iron-based phosphating solution containing phosphate ions.

Preferably, the main components of the iron-based phosphating solution are phosphoric acid (H ₃ PO ₄ ), sodium dihydrogen phosphate (NaH ₂ PO ₄ ), the oxidizing agent is NaNO ₃ , and Fe ²⁺ and Fe ³⁺ are formed from the steel material It is formed by the reaction of surface iron atoms and phosphating solution.

It is worth mentioning that, in this embodiment, the iron-based phosphating solution is an iron-based phosphating solution with a phosphate concentration of 10-30 g/L and a pH value of 2.0-3.0.

Depending on the composition of the phosphating solution, phosphating treatments include zinc-based, manganese-based, zinc- ^calcium -based and iron-based ^phosphating . May be provided by dissolution on steel surfaces. Compared with zinc-based, manganese-based, zinc-calcium-based, iron-based phosphating has the characteristics of thin phosphating film thickness (less than 1 μm), high porosity, and low density (film weight 0.2-1g/m ² ). The color of the membrane is mostly blue-purple, and it can be iridescent or gray depending on the reaction time, thickness of the membrane, and composition of the phosphating solution. Therefore, the dark iron-based phosphating film can be used as a laser light absorbing agent, and its thickness is thin and its porosity is high, allowing oxygen to penetrate the phosphating film and contact the iron element of the steel substrate. Therefore, the present invention selects the iron-based phosphating solution to activate the surface of the steel workpiece.

During the phosphating process, the surface of the steel substrate reacts with phosphoric acid or hypophosphite in the phosphating solution, and the atoms in the outer layer of the iron and steel workpiece react with the anions in the solution as the medium, and the soluble phosphate on the surface is continuously transferred to the insoluble phosphoric acid. Salt conversion, and finally a phosphate conversion film is deposited on the surface of the steel workpiece. The main components of iron-based phosphating film are FePO ₄ , Fe ₃ (PO ₄ ) ₂ and Fe(OH) ₃ .

The range of phosphate radical (PO ₄ ^3- ) concentration in the phosphating solution in this ^example is different from that of ordinary phosphating solution _. The concentration of phosphate in the solution is generally greater than 30g/L. In the present invention, if the phosphate (PO ₄ ^3- ) concentration is less than 10g/L, the film is too thin and the color is too light, which is not conducive to improving the absorbance. When the phosphate (PO ₄ ^3- ) concentration is greater than 30g/L , the thickness of the film is too large, and the compactness is improved, which is not conducive to the subsequent oxygen infiltration. For ordinary phosphating solutions, the purpose is to obtain a phosphating film with low porosity, high corrosion resistance, and large thickness. Phosphating film, so the phosphating process parameters of the two have different selection ranges.

The phosphating film in this embodiment is characterized by blue-purple, iridescent or gray color, thin thickness and low corrosion resistance, so as to increase the laser light absorption rate.

The pH value of the phosphating solution in this embodiment is also different from the traditional phosphating solution. The pH value of the phosphating solution in the present invention is 2.0-3.0, while the pH value of the traditional phosphating solution is generally 3.0-4.5. If the pH value is low, the amount of hydrogen evolution will be large, and the film layer will be loose and porous. However, if the pH value is lower than 2.0, the local corrosion will be too fast, resulting in uneven phosphating film. If the pH value exceeds 3.0, the film density will increase, and the film thickness will increase. It is not conducive to the oxygen penetration of the subsequent oxygen injection process. In traditional phosphating treatment, in order to form a phosphating film with good density, large thickness and corrosion resistance, the pH value of the phosphating solution is relatively high. In another embodiment, the activation solution can also be implemented as an activation solution free of oxyacid ions.

Preferably, the activation solution without oxyacid ions can be implemented as an activation solution containing halogen ions.

For example, the anoxic acid ion activation solution is implemented as an activation solution containing chloride ions (Cl ^- ), so as to form active Fe ²⁺ , Fe ³⁺ ion ferrous chloride, ferric chloride on the surface of the iron and steel material. Activated membrane. The active Fe ²⁺ and Fe ³⁺ ions contained in the activated film are beneficial to the rapid formation of Fe ₃ O ₄ oxide film. However, compared with the activation solution containing oxoacid ions, the activation film containing chloride ions (Cl ^- ) cannot provide active [O] elements when the high temperature is formed under subsequent laser beam irradiation, so when the laser irradiates the surface of steel materials, Oxygen must be injected into the laser spot on the surface of the material at the same time.

In one embodiment, the activation solution free of oxyacid ions may be implemented as an activation solution containing chloride ions (Cl ⁻ ). After the activation solution containing chloride ions (Cl ^- ) is used, the surface of the iron and steel material gradually changes from silvery white to dark, such as yellow, brown, and brown-black, which can improve the laser light absorption rate and greatly reduce laser reflection role.

In yet another embodiment, the activation solution containing oxygen-free acid ions is implemented as an activation solution containing bromide ions (Br ^- ), so as to form active Fe ²⁺ and Fe ³⁺ ions on the surface of the iron and steel material. Iron, ferric bromide activation film. The active Fe ²⁺ and Fe ³⁺ ions contained in the activated film are beneficial to the rapid formation of Fe ₃ O ₄ oxide film. However, compared with the activation solution containing oxoacid ions, the activation film containing chloride ions (Cl ^- ) cannot provide active [O] elements when the high temperature is formed under subsequent laser beam irradiation, so when the laser irradiates the surface of steel materials, Oxygen must be injected into the laser spot on the surface of the material at the same time. In addition, after the activation solution containing chloride ions (Cl ^- ) is used, the surface of the iron and steel material gradually changes from silvery white to dark, such as brownish yellow, reddish brown, and brown, which can improve the laser light absorption rate and greatly Amplitude reduces the effect of laser reflection.

Those skilled in the art can understand that the surface of the activation film containing Fe ²⁺ and Fe ³⁺ ions formed by the above-mentioned activation solution is dark, which is less than that of the iron and steel material without the activation film formed. The color of the surface is deeper and more uniform, so that the reflection of the subsequent laser can be effectively prevented, and the consistency of light absorption can be maintained, so that the surface of the steel material can be uniformly heated to a high temperature by the laser, thereby ensuring the subsequent formation of all Describe the uniformity of Fe ₃ O ₄ oxide film thickness.

The laser high-temperature flash formation method of the oxide film on the surface of the iron and steel material comprises the steps:

S1002, heating the surface of the iron and steel material on which the Fe ₃ O ₄ oxide film needs to be formed to 1450-1500° C. with a laser beam used for heating, and forming the Fe ₃ O ₄ oxide film in a flash.

Specifically, in the step S1002, the laser beam derived by the laser head is irradiated on the surface of the steel material, such as the surface of a roll.

The roll rotates at a high speed at a speed ω, and the speed ω is between 50rpm and 500rpm. At the same time, the laser head and the oxygen injection tube make a linear feed motion along the roll axis at a speed v, and the feed speed v of the roll is 50-500mm /min, the spot area of the laser beam is 0.05-2mm2, the overlapping rate is 30-80%, and the laser power is 2000W-6000W.

While the laser scans the surface of the workpiece, if the activation film is produced by coating the surface of the steel material with an oxygen-free acid, it is necessary to spray oxygen to the laser spot on the workpiece surface through an oxygen injection tube; if the activation film is coated with an oxygen-containing acid Oxygen is generated on the surface of the steel material, and oxygen can be injected to the spot of laser irradiation on the surface of the workpiece through the oxygen injection tube, or no oxygen can be injected. The oxygen flow rate is 0.1-15L/min. Under the irradiation of high-energy laser beam, the temperature of the laser spot on the surface of the roll rises to 1450-1500°C instantaneously, and _Fe3O4 oxide film is formed _on the surface of the roll instantaneously and in situ. .

Preferably, the laser high-temperature flash formation method of the oxide film on the surface of the iron and steel material comprises the steps of:

S1003. Pretreat the surface of the steel material. Those skilled in the art should understand that the step S1003 includes:

S100331, Grinding the surface of iron and steel materials to remove the surface fatigue layer.

More preferably, said step S1003 includes:

S10032, cleaning the emulsion or oil stain on the surface of the iron and steel material with alkali, and removing the emulsion or oil stain on the surface of the iron and steel material by washing with water.

Preferably, after the step S10032, the pretreatment of the surface of the steel material further includes:

S10033, Wipe the surface of the steel material with alcohol.

It is particularly worth mentioning that if the surface of the iron and steel material remains emulsion or oil, the uniformity of the activation film in the subsequent pre-activation process cannot be guaranteed.

In addition, in the step S1002, the surface of the iron and steel material is irradiated by a high-energy laser beam. Therefore, enough heat can be provided instantaneously to raise the temperature of the roll surface to the required temperature. In order to quickly raise the temperature of the roll surface to 1450-1500 °C, the present invention adopts high power and small spot to obtain high energy density, and the high power refers to a laser with a power of 2000W-10000W. If the laser power is less than 2000W, the energy is insufficient and the spot is too small, which will reduce the efficiency of oxide film formation. If the laser power is greater than 10000W, the energy is too large, which may cause overburning, and the steel material needs to move at a high speed. It is difficult to match the corresponding motion mechanism, so the appropriate laser power is 2000W-10000W.

The shape of the spot formed by the laser beam may be a circular, square or rectangular small spot, wherein the small spot refers to a spot with an area of 0.05-10 mm ² . If the laser spot area is less than 0.05mm ² , the production efficiency will be seriously reduced. If the spot area is larger than 10 mm ² , the energy density will be insufficient, and the surface temperature of the iron and steel material will hardly reach 1450-1500° C., so the spot area is preferably 0.05-10 mm ² . The spot overlap rate is 30% to 80%, and the spot overlap rate is less than 30%. Due to the virtual light effect and insufficient laser energy on the edge of the laser spot, the Fe ₃ O ₄ oxide film cannot be formed. If the overlap rate is greater than 80%, it may The steel material will be melted and the generation efficiency will be reduced.

In one embodiment, the iron and steel material is set as a roll. During the preparation process, the roll speed is ω and the speed range is 50-500rpm. If the laser power is high, the speed can be increased appropriately. If the speed is lower than 50rpm, the production efficiency will increase. Low; if the rotational speed exceeds 500rpm, since the weight of the roll can reach 30 tons, excessive rotational speed will cause potential safety hazards in production, so the rotational speed is preferably 50-500rpm.

Correspondingly, in this embodiment, the linear feed speed v of the laser head along the roll axis ranges from 50 to 500 mm/min. If the feed speed is lower than 50 mm/min, firstly, the production efficiency is low, and secondly, due to the power density If the feed rate is higher than 500mm/min, the power density on the surface of the roll will be too low to form Fe ₃ O ₄ oxide film.

Furthermore, the second condition for forming an oxide film at high temperature is that the oxygen content is greater than 58at%, while the oxygen content in the atmosphere is only 21at%. If the oxygen content is not enough, even if the temperature reaches 1450-1500°C, Fe ₃ O ₄ still cannot be formed , the activated film in the present invention can be coated on the steel material surface by oxyacid or anoxic acid activation solution, if the activated film is produced by coating the steel material surface with oxyacid activation solution, then the activated film will be When laser irradiation is heated, a large number of active oxygen atoms can be provided to meet the conditions required for the formation of the _Fe3O4 oxide film _. Oxygen is sprayed at the laser spot on the surface.

Of course, preferably, the laser high-temperature flash formation method of the oxide film on the surface of the iron and steel material includes the steps:

S1004. While irradiating the surface of the iron and steel material with a laser beam, spray oxygen to the laser spot on the surface of the iron and steel material.

It is worth mentioning that if the activation film is formed by coating the surface of the steel material with an oxo-acid activation solution, this step is optional. If the activation film is formed by coating the surface of the steel material with an oxygen-free acid activation solution, Then this step is necessary.

It is worth mentioning that the injected oxygen is directed towards the spot formed by the laser beam on the surface of the steel material.

The present invention proposes a way to spray oxygen onto the roll surface. For example, oxygen can be sprayed onto the laser spot from an air injection tube to provide sufficient oxygen for the oxidation of the roll surface. The oxygen flow is 0.1-15 L/min, and the oxygen flow is less 0.1L/min, the oxygen supply is insufficient, and the oxygen flow rate is greater than 15L/min, the oxygen is excessive.

Further, it has been found through research that if the surface of the iron and steel material is not coated with activation solution, no activation film is formed, even if oxygen is sprayed _on the surface of the roll, the effect of forming _Fe3O4 oxide film is still unsatisfactory, and the oxide film is thin and uneven. Analyzing the reason, it is found that Fe ²⁺ and Fe ³⁺ ions are needed to quickly form Fe ₃ O ₄ oxide film. In order to form Fe ²⁺ and Fe ³⁺ ions on the roll surface before laser oxidation, we coat the roll surface with the activation solution containing oxyacid ions and/or anoxic acid ions, such as sulfate ion [SO ₄ ^2- ] Activation solution, the iron element on the surface layer of the roll reacts with sulfate ions, and forms the activation film containing Fe ²⁺ and Fe ³⁺ ions on the surface layer of the roll, thereby improving the activity of the oxidation reaction. On the other hand, at the same time, it contains ( The activated film of SO ₄ ^2- ) decomposes at high temperature to produce active [O] elements, and the [O] elements produced by these decompositions have high activity and are more utilized than oxygen to promote the formation of Fe ₃ O ₄ oxide film. The concentration of (SO ₄ ^2- ) is controlled at 0.5-15 mol/L, if it is lower than 0.5 mol/L, the reaction will be too slow, if it is greater than 15 mol/L, if the concentration is too high, it will volatilize and cause environmental pollution, and if the concentration is too high, May passivate the surface, which is not conducive to the formation of iron ions. Laser oxidation treatment can be carried out within 3 to 60 minutes after the coating of the activation solution is completed. If it is less than 3 minutes, the reaction will be incomplete, the degree of activation will be low, and the oxide film will be thin. If it exceeds 60 minutes, over-reaction will occur, resulting in poor thickness and color of the activation film. Uniform, resulting in uneven Fe ₃ O ₄ oxide film. Preferably, the laser high-temperature flash formation method of the oxide film on the surface of the iron and steel material comprises the steps of:

S1005, further coating a light absorbing agent on the surface of the activation film of the iron and steel material to form a light absorbing layer on the surface of the iron and steel material to further increase the light absorption rate.

It is worth mentioning that, in a modified embodiment, instead of coating the activation solution on the surface of the steel material, the light absorbing agent can be directly coated on the surface of the steel material and irradiated with a laser beam. Simultaneously with the surface of the iron and steel material, oxygen is injected to the laser spot on the surface of the iron and steel material. In this way, the Fe ₃ O ₄ oxide film oxide film can also be flash formed on the surface of the iron and steel material at a high temperature of 1450-1500°C.

It can be understood that since the surface of the iron and steel material is coated with the light absorbing agent, when the laser beam is subsequently irradiated on the surface of the iron and steel material, the laser absorption efficiency of the iron and steel material can be improved. , so that the surface of the iron and steel material can be flash-heated to 1450-1500°C. It can be understood that the melting point of high-speed steel is generally between 1500°C and 1600°C, and the steel material will melt beyond this temperature range. Therefore, the temperature of laser oxidation should be controlled below 1500°C. In order to form the Fe ₃ O ₄ oxide film on the surface of the steel material, the temperature must be controlled at 1450-1500° C., and this temperature range is very close to the melting range of the steel material. If the laser is used alone to raise the temperature of the iron and steel material and the light absorption efficiency on the surface of the iron and steel material is low, it is difficult to control the absorption rate of the laser, which may cause the iron and steel material to melt during the heating process. In other words, the coated light absorbing agent can effectively stabilize the temperature of the laser heating and prevent the steel material from melting during the heating process.

The light absorber is preferably a carbon-based light absorber. The carbon-based light absorbing agent can be configured as a carbon-based micropowder dispersion liquid, and the carbon-based micropowder is uniformly dispersed in a solvent. For example, the carbon-based micropowder may be carbon-based powder materials such as graphite flakes, graphene, and carbon nanotubes with characteristic sizes ranging from 10 nm to 100 μm. Described solvent is to add sodium carboxymethylcellulose, polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), dodecylbenzenesulfonic acid in organic or inorganic solvents such as water, ethanol, ethylene glycol or acetone Sodium and other surfactants are formed, and then the carbon-based micropowder can be uniformly dispersed in the solvent by stirring, ultrasonic vibration and other processes.

When the light absorbing agent is implemented as a carbon-based light absorbing agent, the carbon-based light absorbing agent will cover a layer of carbon-based lubricating film _on the surface of the _Fe3O4 oxide film, and this layer of carbon-based lubricating film can reduce the thickness of the steel material. Surface friction, thereby reducing the wear of steel materials.

According to another aspect of the present invention, the present invention also provides a roll with the Fe ₃ O ₄ oxide film on the surface formed by the laser high temperature flash formation method of the oxide film on the surface of the steel material.

Example 1

In a hot finish rolling 1780 production line, the F1 rolling mill roll was originally a high-speed steel roll. On the basis of the high-speed steel roll, a layer of Fe ₃ O ₄ oxide film was prepared. The thickness of the oxide film was 5 μm. After adopting the new Fe ₃ O ₄ oxide film composite roll, the rolling capacity in millimeters reaches 12,360 tons, and the service life is increased by 3 times. The preparation method of Fe ₃ O ₄ oxide film consists of three steps. The first step is to treat the front of the roll. The F1 roll after being off the machine is ground on a grinding machine. The surface roughness after grinding is 0.5 μm, and the oil is removed by alkali washing. Finally, it is washed with water and dried. The surface of the roll after pretreatment is bright silver; the second step is the surface pre-activation. _The activation solution is a _H2SO4 solution with a concentration of 3mol/L. A layer of yellow activation film is formed on the surface to form active Fe ²⁺ and Fe ³⁺ ions, and the surface of the roller after pre-activation treatment is yellowish brown; the third step is laser rapid oxidation, laser power 6kw, circular spot, spot diameter 3mm, lap rate 50%, roll speed 160rpm, laser head axial feed speed 200mm/min, oxygen flow rate 5L/min, the roll is completely laser oxidized, and the whole roll is black Fe ₃ O ₄ oxide film.

Example 2

In a hot finish rolling 1422 production line, the F2 rolling mill roll was originally a high-speed steel roll. On the basis of the high-speed steel roll, a layer of black Fe ₃ O ₄ oxide film was prepared. The thickness of the oxide film was 7 μm. The volume is 8,200 tons. After adopting the new Fe ₃ O ₄ oxide film composite roll, the millimeter rolling volume reaches 46,300 tons, and the service life is increased by more than 5 times. The preparation method of Fe ₃ O ₄ oxide film consists of three steps. The first step is to treat the front of the roll. The F2 roll after being off the machine is ground on a grinding machine. The surface roughness after grinding is 0.3 μm, and the oil is removed by alkali washing. Finally, it is washed with water and dried; the second step is surface pre-activation. The activation solution is a NiSO ₄ solution with a sulfate ion concentration of 6 mol/L, and a yellow-green activation film is formed on the surface of the roll to form active Fe ²⁺ , Fe ³⁺ ions; the third step, laser rapid oxidation, laser power 8kw, circular spot, square spot, side length 2.5mm, overlap rate 30%, roll speed 200rpm, laser head axial feed speed 260mm /min, the oxygen flow rate is 10L/min.

Example 3

In a hot finish rolling 2250 production line, the F4 mill roll was originally a high-speed steel roll. On the basis of the high-speed steel roll, a layer of black Fe ₃ O ₄ oxide film was prepared. The thickness of the oxide film was 8 μm. The volume is 6,500 tons. After adopting the new Fe ₃ O ₄ oxide film composite roll, the rolling volume in millimeters reaches 26,370 tons, and the service life is increased by more than 4 times. The preparation method of Fe ₃ O ₄ oxide film consists of three steps. The first step is to treat the front of the roll. The F4 roll after being off the machine is ground on a grinding machine. The surface roughness after grinding is 0.6 μm, and the oil is removed by alkali washing. Finally, wash with water and dry; the second step is surface pre-activation, the activation solution is a mixed solution of Cu(NO ₃ ) ₂ and Y(NO ₃ ) ₃ with a nitrate ion concentration of 12mol/L, and a brown layer is formed on the surface of the roll active film to form active Fe ²⁺ and Fe ³⁺ ions; the third step is laser rapid oxidation, laser power 10000kw, using a rectangular laser spot with a length of 3mm and a width of 2mm, an overlap rate of 50%, and a roll speed of 300rpm , the axial feed speed of the laser head is 300mm/min, and the oxygen flow rate is 12xL/min.

Example 4

On a hot finish rolling 1780 production line, the F3 rolling mill roll was originally a high-speed steel roll. On the basis of the high-speed steel roll, a layer of black Fe ₃ O ₄ oxide film was prepared. The thickness of the oxide film was 4 μm. The rolling capacity is 9100 tons. After adopting the new Fe ₃ O ₄ oxide film composite roll, the rolling capacity in millimeters reaches 27,650 tons, and the service life is increased by more than 3 times. The preparation method of Fe ₃ O ₄ oxide film consists of three steps. The first step is to treat the front of the roll. The F3 roll after being off the machine is ground on a grinding machine. The surface roughness after grinding is 0.3 μm, and the oil is removed by alkali washing. Finally, it is washed with water and dried; the second step is surface pre-activation. The activation solution is a mixed solution of FeCl ₃ with a chloride ion concentration of 7mol/L, and a layer of brown-black activation film is formed on the surface of the roll to form active Fe ²⁺ , Fe ³⁺ ions; the third step, laser rapid oxidation, laser power 6000kw, using a rectangular laser spot, the spot length is 2mm, the width is 2mm, the overlap rate is 50%, the roll speed is 200rpm, and the axial feed speed of the laser head is 200mm/min , Oxygen flow rate 15L/min.

It should be understood by those skilled in the art that the embodiments of the present invention shown in the foregoing description and drawings are only examples and do not limit the present invention. The advantages of the invention have been fully and effectively realized. The functions and structural principles of the present invention have been shown and described in the embodiments, and the embodiments of the present invention may have any deformation or modification without departing from the principles.

Claims (10)

1. The laser high-temperature flash forming method of the oxide film on the surface of the iron and steel material is characterized in that, the laser high-temperature flash formation method of the oxide film on the surface of the iron and steel material comprises: A light absorbing agent is coated on the surface of the activation film. The surface of the iron and steel material that needs to form the Fe ₃ O ₄ oxide film is scanned by the laser beam used for heating, so that the laser scanning spot on the surface of the iron and steel material is heated to 1450-1500 ° C to generate the Fe ₃ O in a flash ₄ oxide film; While irradiating the surface of the iron and steel material with a laser beam for heating, oxygen is injected to the laser spot on the surface of the iron and steel material. 2. according to the laser high-temperature flash forming method of the oxide film on the surface of the iron and steel material of claim 1, it is characterized in that, the surface of the described iron and steel material is pretreated, comprising: Grinding the surface of ferrous materials to remove the surface fatigue layer; and/or Cleaning the emulsion or oil on the surface of the steel material with alkali, and removing the emulsion or oil on the surface of the steel material by washing with water; and/or Wipe the surface of the steel material with alcohol. 3. The laser high-temperature flash formation method of the oxide film on the surface of the iron and steel material according to claim 1, wherein the light absorbing agent is a carbon-based light absorbing agent. 4. The laser high-temperature flash formation method of the oxide film on the surface of the iron and steel material according to claim 1, characterized in that the flow rate of the oxygen is 0.1-15 L/min. 5. The laser high-temperature flash formation method of an oxide film on the surface of a steel material according to any one of claims 1-3, characterized in that the time for forming the oxide film is 0.01-10 milliseconds. 6. The laser high-temperature flash formation method of an oxide film on the surface of an iron and steel material according to any one of claims 1-3, wherein the shape of the spot formed by the laser beam is selected from circular, square or rectangular small spots. 7 . The laser high-temperature flash formation method of an oxide film on the surface of a steel material according to claim 6 , wherein the small spot refers to a spot area of 0.05-10 mm ² . 8. The laser high-temperature flash formation method of the oxide film on the surface of the iron and steel material according to claim 6, characterized in that the iron and steel material is a roll. 9. The method for forming an oxide film on the surface of a steel material by laser high temperature flash according to claim 6, characterized in that, during the preparation process, the rotational speed of the roll is ω and the rotational speed range is 50-500rpm. 10. The laser high-temperature flash formation method of the oxide film on the surface of the iron and steel material according to claim 6, characterized in that, the range of linear feed speed v of the laser head forming the laser beam along the axial direction of the roll is 50-500mm/min .

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