KR102222258B1 - Carbon steel material before heat treatment and carbon steel material after heat treatment having excellent scale removability and method for preparing the same, method for removing scale, and film forming agent easy to remove scale - Google Patents

Abstract

It provides a new technology that can easily remove scale generated by heating steel materials.
In the pre-heat treatment steel material having a film on the surface of the carbon steel, the carbon steel contains 0.06 mass% or more of carbon based on the total mass of the carbon steel, and the film is at least one metal selected from Fe, Ni, and Co. It contains element (X) and at least one metal element (Y) selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo, and W, and the total amount of the metal element (Y) attached is 1 to It is a steel material before heat treatment, characterized in that (X)/(Y), which is 100 mg/m2 and a mass ratio of the metal element (X) and the metal element (Y), is in the range of 0.01 to 0.5.

Description

Carbon steel material before heat treatment with excellent scale removal, carbon steel material after heat treatment and their manufacturing method, and formulation for descaling and easy-to-descale film formation {CARBON STEEL MATERIAL BEFORE HEAT TREATMENT AND CARBON STEEL MATERIAL AFTER HEAT TREATMENT HAVING EXCELLENT SCALE REMOVABILITY AND METHOD FOR PREPARING THE SAME, METHOD FOR REMOVING SCALE, AND FILM FORMING AGENT EASY TO REMOVE SCALE}

The present invention is a technology related to easy removal of scale generated when heat treatment of carbon steel.

Metal materials are subjected to heat treatment by heating and cooling in order to improve mechanical strength. The conditions of the heat treatment are different depending on the intended mechanical strength, material, shape, and restrictions on equipment, but in the case of the steel material, the steel material is heated to a high temperature of approximately 700°C or higher. Therefore, in a steel material heated to a high temperature in the atmosphere, scale is generated due to surface oxidation while being heated. If such scales remain on the surface of a steel material, there is a problem that quality deteriorates, such as poor appearance, influence on dimensional accuracy and surface roughness. Therefore, conventionally, after heat treatment of a steel material, scale removal such as pickling or shot blasting has been performed.

In addition, as disclosed in Patent Document 1, by controlling the amount of Si and Cr of the steel material, and further, the surface roughness within a certain range, a technique capable of suppressing the generation of the amount of scale during heating in the atmosphere has also been proposed. have.

On the one hand, as disclosed in Patent Document 2, by applying a high-temperature decarburization prevention coating containing a composition containing silicon carbide to the steel material, it is possible to prevent oxidation and decarburization, and further improve the coating film removal property after heat treatment. A technique is also proposed.

Japanese Patent Publication No. 2005-133180 Japanese Patent Application Laid-Open No. Hei 2-205622

An object of the present invention is to provide a novel technology capable of easily removing scale generated by heating steel materials.

As a result of intensive examination, the inventors of the present invention have found that the above problems can be solved by the following method, and the present invention has been completed.

[1] In the steel before heat treatment having a film on the surface of the carbon steel,

The carbon steel contains 0.06 mass% or more of carbon based on the total mass of the carbon steel,

The coating contains at least one metal element (X) selected from Fe, Ni and Co and at least one metal element (Y) selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo, and W. And also

The total amount of adhesion of the metal element (Y) is 1 to 100 mg/m2, and the mass ratio of the metal element (X) and the metal element (Y), which is (X)/(Y), is in the range of 0.01 to 0.5. Steel before heat treatment.

[2] In the method of manufacturing a steel material before heat treatment,

The steel material before the heat treatment has a film on the surface of the carbon steel,

The carbon steel contains 0.06 mass% or more of carbon based on the total mass of the carbon steel,

The coating contains at least one metal element (X) selected from Fe, Ni and Co and at least one metal element (Y) selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo, and W. And also

The total amount of adhesion of the metal element (Y) is 1 to 100 mg/m 2, and (X)/(Y), which is a mass ratio of the metal element (X) and the metal element (Y), is in the range of 0.01 to 0.5,

The above manufacturing method,

Ti, Zr, Hf, Nb, V, Cr, Mn, Mo, and a formulation containing at least one metal element (Y) selected from W and an etching component in contact with the carbon steel to form the film Method for producing a steel material before heat treatment, characterized in that.

[3] In the method of manufacturing a steel material after heat treatment,

On the surface of carbon steel containing 0.06% by mass or more carbon, at least one metal element (X) selected from Fe, Ni and Co and Ti, Zr, Hf, Nb, V, Cr, Mn, Mo and W selected from A film containing at least one metal element (Y), wherein the total amount of the metal element (Y) adhered is 1 to 100 mg/m 2, and the mass ratio of the metal element (X) and the metal element (Y) is (X) /(Y) forming a film in the range of 0.01 to 0.5 to obtain a steel material before heat treatment, and

A method of manufacturing a steel material after heat treatment, characterized in that it comprises a step of heat-treating the steel material before the heat treatment at 700°C or higher.

[4] In the method of removing scale,

On the surface of carbon steel, at least one metal element (X) selected from Fe, Ni and Co and at least one metal element (Y) selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo and W A step of forming a film containing, to obtain a steel material before heat treatment, and

Heating the steel material before the heat treatment at 700° C. or higher to obtain a steel material after the heat treatment,

Scale removal method comprising the step of removing the scale adhered to the steel material after the heat treatment.

[5] The method for removing scale of [4], wherein the carbon steel contains 0.06 mass% or more of carbon based on the total mass of the carbon steel.

[6] The total amount of adhesion of the metal element (Y) is 1 to 100 mg/m2, and the mass ratio of the metal element (X) and the metal element (Y), (X)/(Y) is in the range of 0.01 to 0.5 , The scale removal method of [4] or [5].

[7] When the steel material is heated to 700°C or higher before heat treatment to obtain a steel material after heat treatment, prior to the heating, it is a formulation used to form a scale-free film on the carbon steel constituting the steel material before the heat treatment,

At least one metal element (Y) selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo and W, and

A formulation for forming an easily scaled-off film, comprising an etching component.

[8] The easily descaled coating is at least one metal element (X) selected from Fe, Ni and Co and at least one metal selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo and W The formulation for forming an easily scale-off film according to the above [7], containing the element (Y).

[9] The formulation for forming an easily descaled film according to [7] or [8], wherein the carbon steel contains 0.06 mass% or more of carbon based on the total mass of the carbon steel.

[10] The total amount of adhesion of the metal element (Y) is 1 to 100 mg/m2, and the mass ratio of the metal element (X) and the metal element (Y), (X)/(Y) is in the range of 0.01 to 0.5 , The formulation for forming an easily scale-off film of [8] or [9].

According to the present invention, it is possible to provide a novel technology capable of easily removing scale generated by heating a steel material (for example, by air blowing or running water). Therefore, compared to the conventional scale removal such as pickling or shot blasting, the simplification and shortening of the treatment process can be drastically achieved.

Hereinafter, a method of manufacturing a steel material before heat treatment, a method of manufacturing a steel material before heat treatment (as well as a formulation used in the manufacturing method), and a method of manufacturing a steel material after heat treatment by heating the steel material before heat treatment (as well as a method of removing scale) are in sequence. Explain as it is.

≪1. Steel before heat treatment≫

In the pre-heat treatment steel material according to the present invention, in the pre-heat treatment steel material having a film on the surface of the carbon steel, the carbon steel contains 0.06 mass% or more of carbon based on the total mass of the carbon steel, and the film is Fe, Ni And at least one metal element (X) selected from Co and at least one metal element (Y) selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo and W, and the metal element The total amount of adhesion of (Y) is 1 to 100 mg/m 2, and (X)/(Y), which is a mass ratio of the metal element (X) and the metal element (Y), is in the range of 0.01 to 0.5. Hereinafter, each component will be described in detail.

<1-1. Carbon steel>

The carbon steel constituting the steel material before heat treatment according to the present invention contains 0.06 mass% or more of carbon based on the total mass of the carbon steel. Preferably it is 0.06 mass% or more and 3.1 mass% or less, More preferably, it is 0.1 mass% or more and 0.77 mass% or less, More preferably, it is 0.15 mass% or more and 0.45 mass% or less. When the carbon content in the carbon steel is within this range, by attaching a specific amount of a film to be described later, the scale adhered to the steel material after heat treatment can be removed very easily. In addition, carbon steel may contain elements other than Fe and C, such as Ni, Co, Mo, V, Ti, Nb, Mn, Cr, B, and the like.

<1-2. Film>

{1-2-1. ingredient}

The film constituting the steel material before heat treatment according to the present invention is selected from one or more metal elements (X) selected from Fe, Ni and Co, and Ti, Zr, Hf, Nb, V, Cr, Mn, Mo and W It contains at least one metal element (Y) to become. Here, as the metal element (X), Fe and Ni are suitable, and Fe is more suitable from the viewpoint of being able to very easily peel off by air blowing or the like and to form a more excellent easily descaled coating. In addition, as the metal element (Y), Ti, Zr, Nb, Cr, Mo are suitable in that it can be very easily peeled off by air blowing or the like and can form a more excellent descaling easily film. Ti is more suitable. In addition, with respect to both of the metal element (X) and the metal element (Y), only one type of them may be contained or a plurality of types may be contained. In addition, in the film, these metal elements are estimated to be present in a mixture of metals, hydroxides, hydrated oxides, and oxides.

{1-2-2. Ingredient ratio}

Here, (X)/(Y), which is the mass ratio of the metal element (X) and the metal element (Y), is in the range of 0.01 to 0.5, suitably in the range of 0.05 to 0.3, and in the range of 0.1 to 0.2 More suitable. If it is within the said range, coagulation cracking of a film can be effectively prevented.

{1-2-3. Adhesion amount}

The adhesion amount of the film constituting the steel material of the present invention to carbon steel before the heat treatment is an amount such that the total amount of the metal element (Y) adhered is 1 to 100 mg/m 2, and the total amount of the metal element (Y) is 2 to It is preferable that the amount is 40 mg/m 2, and it is more preferable that the total amount of the metal element (Y) adheres is 5 to 20 mg/m 2. Since the metal element (Y) is introduced into the scale produced by the heat treatment, the scale adhered to the steel material after the heat treatment can be removed very easily. For this reason, it is preferable that the film constituting the steel material before the heat treatment according to the present invention does not have film cracks and film omissions. When the total amount of adhesion of the metal element (Y) exceeds 100 mg/m 2, film cracking is liable to occur. At the location of the film crack, since the metallic element (Y) is difficult to be introduced into the scale produced by the heat treatment, the scale cannot be easily removed. In addition, if the total amount of the metal element (Y) deposited is less than 1 mg/m 2, the surface of the carbon steel cannot be covered with a film, so that film omission is liable to occur. In the missing portion of the film, the metal element (Y) is not introduced into the scale generated by the heat treatment, and thus the scale is not easily removable. When the carbon content in the carbon steel is within the above range, by attaching the film to the above range, the scale adhered to the steel material after heat treatment can be removed very easily. The adhesion amount of the metal element (Y) can be measured from the surface of a carbon steel material by a fluorescence X-ray analyzer (XRF). The adhesion amount of the metal element (X) can be measured for each depth of the film by an X-ray photoelectron spectroscopy device (XPS), but in the present invention, the oxygen extinction position in the depth profile of the XPS is used as the boundary between the carbon steel material and the film. , The average of the measured values of the metal element (X) detected in the upper layer was determined as the amount of adhesion of the metal element (X).

≪2. Manufacturing method of steel before heat treatment≫

In the method for manufacturing a steel material before heat treatment according to the present invention, a formulation containing at least one metal element (Y) selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo, and W and an etching component is used as the carbon steel. And a step of forming the film by contacting with. Hereinafter, a formulation used for manufacturing a steel material before heat treatment (a formulation for easily forming a descaled film) is first described, and then each step is described.

<2-1. Formulations for easily descaling film formation>

{2-1-1. ingredient}

(2-1-1-1.metal element)

The formulation for forming an easily scaled-off film according to the present invention contains at least one metal element (Y) selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo and W. Here, as the metal element, Ti, Zr, Nb, Cr, and Mo are suitable, and Zr and Ti are more suitable. The suitable reason is as described above. In this case, the concentration of the metal element (Y) in the formulation for easily descaling film formation is preferably 0.5 to 10 mmol/l. In addition, although these metal elements may be supplied from a substrate or not normally dissolved, basically, they exist in a state dissolved in a liquid medium to be described later. Moreover, only 1 type may be sufficient as a metal element, and may contain multiple types. Moreover, although the said metal element is essential, it may contain another metal element. Specifically, it may contain at least one metal element (X) selected from Fe, Ni, and Co, and the concentration of the metal element (X) in the formulation for easily descaling film formation is preferably 0.1 to It is 5mmol/l.

(2-1-1-2. Etching component)

The formulation for forming an easily scaled-off film according to the present invention contains an etching component. Here, the etching component is not particularly limited as long as it is an additive component capable of etching carbon steel, and examples thereof include inorganic acids such as _{HNO 3} , HF, H ₂ SO _{4, and HCl. Among these, HNO 3} , HF and H ₂ SO ₄ are suitable, and HF alone or a _{combination of HF and HNO 3} is more preferable from the viewpoint of stabilizing the film forming treatment agent. In addition, the presence form of the etching component in the formulation for easily descaling film formation can be determined in relation to a suitable pH range (2.5 to 4.5) or the kind or amount of other components present. For example, when the acid is used as an additive component, the dissociated form of the acid is assumed. Moreover, only 1 type may be sufficient as an etching component, and may contain multiple types.

(2-1-1-3. Other ingredients)

The formulation for forming an easily scaled-off film according to the present invention may contain other components as necessary. For example, when an alkali is added to control the pH to a suitable range, strong alkalis such as LiOH, NaOH, and KOH, and _{weak alkalis such as NH 3} {ammonium hydroxide (NH ₃ -H ₂ O)} can be used. When adding an acid, a weak acid such as acetic acid can be used. The alkali _{is preferably NH 3} {ammonium hydroxide (NH ₃ -H ₂ O)}, and the acid is preferably a weak acid.

(2-1-1-4. Liquid medium)

The liquid medium in the formulation for easily descaling film formation according to the present invention is suitably a liquid medium mainly composed of water (for example, deionized water or pure water). Here, "mainly" means 51% by mass or more of water based on the total mass of the liquid medium (suitably 60% by mass or more, more preferably 70% by mass or more, more preferably 80% by mass or more, Especially preferably, it means 90 mass% or more). Further, the liquid medium may contain a liquid medium other than water (for example, a water-miscible liquid medium such as alcohol such as ethanol). In addition, the present formulation may be in a dry form or a concentrated form. In this case, it is used after dissolving or diluting with water on site.

{2-1-2. Liquid}

(2-1-2-1.pH)

The pH of the formulation for forming an easily scaled-off film according to the present invention is preferably 2.5 to 4.5, more preferably 3 to 4. In addition, this pH is a value measured at a treatment temperature (typically 40° C.) in JIS-Z8802:2011 with respect to the formulation for easily descaling film formation.

{2-1-3. Manufacturing method}

The manufacturing method of the formulation for easily descaling film formation according to the present invention includes a source of at least one metal element (Y) selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo, and W, and an etching component. And the step of mixing and adding the source of the liquid to the liquid medium. Hereinafter, the supply source will be described in detail.

(2-1-3-1. Source)

As a source of the metal element (Y), for example, a salt, a complex compound or a metal hydrated oxide containing at least one metal element (Y) selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo and W Can be mentioned. Specifically, in the case of Ti, for example, titanium diammonium oxydioxalate, titanium dipotassium oxydioxalate, titanium (II) oxide, titanium (III) oxide, titanium (IV) oxide, titanium oxysulfate secondary titanium, basic titanium phosphate , Titanium bromide (IV), metatitanic acid, zinc metatitanate (II), aluminum titanate (III), potassium metatitanate, metatitanium tricobalt (II), zirconium titanate, strontium metatitanate, metatitanium Triiron (III), copper metatitanate (II), sodium titanate, neodymium ititanate (III), barium metatitanate, bismuth metatitanate (III), magnesium metatitanate, magnesium titanate, metatitanic acid Manganese (II), lanthanum ititanium (III), lithium metatitanate, ammonium hexafluorotitanium (IV) acid, potassium hexafluorotitanium (IV) acid, titanium (IV) iodide, titanium (III) sulfate, Titanium (IV) sulfate, titanium chloride, titanium nitrate, titanyl sulfate, titanium (III) fluoride, titanium (IV) fluoride, hexafluorotitanic acid, titanium lactate, peroxotitanic acid, titanium laurate, titanium acetylacetonate , Titanium salts such as titanium (IV) hydroxide, or titanium salts; In the case of Zr, for example, tetrakis (acetylacetonato) zirconium (IV), zirconium chloride (IV), zirconium chloride (IV), zirconium silicate, zirconium acetate (IV), zirconium oxide (IV), nitric oxide Zirconium(IV), metazirconate cesium, metazirconate lithium, metazirconate zinc(II), metazirconate aluminum(III), metazirconate calcium, metazirconate cobalt(II), metazirconate strontium, meta Copper (II) zirconate, sodium metazirconate, nickel (II) metazirconate, barium metazirconate, bismuth metazirconate (III), magnesium metazirconate, zirconium oxycarbonate, hexafluorozirconium (IV) acid Ammonium, potassium hexafluorozirconium (IV) acid, zirconium iodide, zirconium phosphate dihydrogen oxide (IV), basic zirconium carbonate, ammonium zirconium carbonate, ammonium zirconyl carbonate, zirconium nitrate, zirconyl nitrate, zirconium sulfate (IV), Zirconium salts such as zirconyl sulfate, hexafluorozirconic acid, zirconium oxyphosphate, zirconium pyrophosphate, zirconyl dihydrogen phosphate, zirconium oxychloride, zirconium fluoride, zirconyl acetate, zirconium oxide, zirconium hydroxide, and the like; In the case of Hf, tetrakis (acetylacetonato) hafnium (IV), hafnium chloride (IV), hafnium oxide (IV), hafnium iodide (IV), hafnium sulfate (IV), hafnium nitrate (IV), hafnium oxyoxalate ( IV), hafnium salts such as fluorohafnic acid, fluorohafnate, and hafnium fluoride, or hafnium salts; In the case of Nb, niobium (II) oxide, niobium oxide (V), oh (hydrogen oxalate) niobium, niobium hydroxide (V), niobium oxyacetylacetonate, metaniobic acid, metaniobate calcium, strontium metaniobate, meta Niobium salts such as barium niobate, magnesium metaniobate, lithium metaniobate, ammonium metaniobate, sodium metaniobate, niobium pentachloride, or niobate salts; In the case of V, vanadium oxydichloride, vanadium oxytrichloride, vanadium trichloride, vanadium oxide, iron savanadate (III), vanadium bromide (III), vanadium oxyoxalate, vanadium iodide (II), vanadium pentoxide, metavanadium acid, pyrovanadium Sodium acid, sodium vanadate, ammonium metavanadate, sodium metavanadate, potassium metavanadate, vanadium oxytrichloride, vanadium trioxide, vanadium dioxide, vanadium oxysulfate, vanadium oxyacetylacetate, vanadium acetylacetate, invanadium molybdate, etc. A vanadium salt or the like or a vanadium salt of; chrome; In the case of Cr, chromium formate (III), chromium fluoride (III), chromium nitrate (III), chromium sulfate (III), chromium oxalate (III), chromium acetate (III), chromium oxide (III), chromium hydroxide ( III), chromium salts such as chromium (III) oxide, chromium (III) bromide, and chromium (III) iodide; In the case of Mn, bis (acetylacetonato) diaquamanganese (II), trimanganese tetraoxide, manganese (II) oxide, manganese (III) oxide, manganese (IV) oxide, manganese bromide (II), manganese oxalate (II), Permanganic acid (VII), potassium permanganate (VII), sodium permanganate (VII), manganese dihydrogen phosphate (II), manganese nitrate (II), manganese sulfate (II), manganese sulfate (III), manganese sulfate (IV), fluoride Manganese (II), manganese fluoride (III), manganese (II) carbonate, manganese (II) acetate, manganese (III) acetate, manganese (II) ammonium sulfate, manganese (II) iodide, manganese (II) hydroxide, etc. Hepatitis or the like or manganate; In the case of Mo, molybdenum chloride (V), molybdenum (IV) oxide, molybdenum (VI) oxide, zinc molybdate (II), potassium molybdate, calcium molybdate, cobalt molybdate (II), cesium molybdate, molybdate Nickel (II), barium molybdate, bismuth molybdate (III) molybdate, magnesium molybdate, lithium molybdate, lithium paramolybdate, strontium molybdate, phosphomolybdate, ammonium phosphomolybdate, sodium phosphomolybdate, molybdate, Molybdenum salts such as ammonium molybdate, ammonium paramolybdate, sodium molybdate, or a molybdate salt; For W, tungsten chloride (VI), iron tungsten oxide (III), tungsten chloride (VI), tungsten oxydichloride, tungsten dioxide, tungsten trioxide, metatungstic acid, ammonium metatungstate, sodium metatungstate, paratungstic acid , Ammonium paratungstate, sodium paratungstate, zinc(II) tungstate, potassium tungstate, calcium tungstate, cobalt(II) tungstate, strontium tungstate, tungstic acid, copper(II) tungstate, nickel tungstate , Tungsten salts such as barium tungstate, magnesium tungstate, manganese (II) tungstate, lithium tungstate, cesium phosphate tungstate, ammonium phosphate tungstate and sodium phosphate tungstate, or tungstate salts.

<2-2. Each step in the manufacturing method of steel before heat treatment>

The manufacturing method of the steel material before heat treatment suitably includes (Step 1) a step of pretreating a carbon steel, and (Step 2) a step of forming a film by contacting the steel material before the heat treatment with an agent for forming a film easily descaled. Hereinafter, each process will be described in detail.

{2-2-1. Pre-treatment process}

Prior to forming a film on the carbon steel constituting the steel material before heat treatment, a pretreatment known in the art (for example, preliminary cleaning of the surface of the carbon steel by degreasing or the like) may be performed.

{2-2-2. Film formation process}

As a film formation process, (First method) a method of forming the film by heating the surface of the carbon steel containing the metal element in a gas containing oxygen (for example, oxygen gas, air, etc.), (2 Method) The surface of the carbon steel is brought into contact with an agent for easily descaling film formation, and the surface of the carbon steel is cleaned by the action of an etching component included in the preparation for easily descaling film, and the above is performed by a chemical reaction or an electrical reaction. The method of forming a film is mentioned. Among these, the coating is preferably uniform on the surface of the carbon steel material, so the second method is suitable from this viewpoint. Hereinafter, these two methods will be described in detail.

First, heating in the first method is not particularly limited as long as it is a temperature at which the surface of the carbon steel containing the metal element can be oxidized, but is preferably performed at 200 to 300°C. For example, when a steel material (SCM material) having a composition of Fe-C-Cr-Mo is heated in an oxygen-containing gas atmosphere for at least 30 minutes, at 200 to 300°C, an oxide film of Fe and Cr+Mo is formed on the surface. Is formed. This oxide film is also subjected to a heat treatment of 700° C. or higher to form a film that is easily descaled.

Next, the second method is a method of contacting the surface of the carbon steel with the agent for forming a easily descaled film containing the metal element, followed by drying, to form a predetermined easily descaled film on the surface of the carbon steel material. In addition, as a contact method in the second method, for example, an immersion method, a spray method, a roll coating method, an air spray method, an airless spray method, an electrolysis method (for example, a cathodic electrolysis method), or a combination of these methods The method can be adopted. In addition, as a method of removing the excess descaling easily film-forming agent adhering to the surface of the carbon steel material after contacting the film-forming agent, an air knife, a squeeze roll, spray washing, immersion washing, or a combination of these methods One method can be adopted, and it is also possible to form a scale-free film on the surface of a carbon steel material efficiently in a short time by combining these and a drying process. In addition, the temperature (liquid temperature) of the film-forming preparation when the carbon steel is brought into contact with the film-forming preparation is not particularly limited, but is preferably 20°C or higher and 50°C or lower, and more preferably 35°C or higher and 45°C or lower. Do.

≪3. Method of manufacturing steel after heat treatment by heating steel before heat treatment≫

Next, a method of manufacturing a steel material after heat treatment by heating the steel material before heat treatment according to the present invention will be described. In addition, this method can be understood as a method of removing scale generated when a steel material is heated before heat treatment to manufacture a steel material after heat treatment.

<3-1. Heat treatment process>

The method of manufacturing a steel material after heat treatment according to the present invention includes a step of heat-treating the steel material at 700° C. or higher before the heat treatment on which the film is formed. Here, the heat treatment temperature is preferably 700°C or more and 1350°C or less, more preferably 850°C or more and 1250°C or less, and even more preferably 900°C or more and 1000°C or less. This is because within this range, it is possible to realize that the easily descaled coating is introduced into the oxide scale while preventing the steel material from being dissolved. In addition, the heating temperature and holding time are different depending on the component, shape, thickness, and desired mechanical strength of the steel, but as an example, in order to perform the quenching treatment, the steel is in the austenite temperature range of 800 to 1000. It is heated to a temperature of °C and maintained for 1 to 120 minutes.

Here, the heating method to be adapted of the present invention is not particularly limited, and a combination of energization heating treatment and high-frequency quenching using high-frequency induction heating may be employed as a heating atmosphere. In addition, laser quenching using laser light introduced as metal surface quenching is also possible.

In addition, the heat treatment that is an object of adaptation of the present invention is adapted for heat treatment that does not require vacuum or an inert gas. Specifically, it is a heat treatment in an oxidizing atmosphere containing 1% by volume or more of oxygen, for example. In addition, the present invention is also adapted to a hot pressing method such as a preliminary press quenching method in which a heated member is pressed in a mold and then molded by rapid cooling in a mold.

Further, the cooling method and speed also vary depending on the component, shape and thickness of the steel, and the desired mechanical strength, but examples thereof include furnace cooling, air cooling, water cooling, and spraying of a coolant. For example, in the quenching treatment in which martensite is obtained after heat treatment, a cooling rate equal to or higher than the critical cooling rate of the steel may be ensured. According to another aspect of the present invention, instead of the rapid cooling quenching, hot press molding may be performed using a molding die.

<3-2. Scale removal process>

The scale removal method according to the present invention includes mechanical methods such as sand blast, shot blast, wet blast, laser peening, honing and grinder, and chemical treatment methods such as phosphoric acid washing, sulfuric acid washing, hydrochloric acid washing, nitric acid washing, etc. You may combine them. In this regard, even in methods such as air blowing and running water washing in which compressed air or compressed water is used at a discharge pressure of 0.1 MPa or more without using a projection material or an abrasive, the scale can be removed.

<Example>

≪Steel material≫

Carbon steel in which the mass% of carbon was 0.03%, 0.06%, 0.1%, 0.15%, 0.3%, 0.45%, 0.77%, 3.1%, and 4% based on the total mass of the carbon steel was used.

≪Preparation of a film-forming formulation≫

As shown in Table 1, after adding various raw materials to water so that the blending amount of Table 1 may be obtained, the mixture was sufficiently stirred to obtain a film-forming formulation according to the treatment solutions 1 to 102. At that time, it adjusted using acetic acid or ammonia so that it might become the pH shown in Table 1.

≪Manufacture of steel before heat treatment≫

As shown in Table 2, various steel materials were immersed for 30 to 300 seconds in the treatment liquids (formulations for film formation) 1 to 102 controlled at 40°C. In addition, the contact time (immersion time) of the various steel materials and the film-forming agent by immersion was adjusted so that the adhesion amount shown in Table 2 might be obtained. Thereafter, the various steel materials brought into contact with the film-forming agent were sufficiently washed with water so that no film-forming agent remained on the surface of the steel material, drained and dried to obtain steel materials 1 to 132 before heat treatment.

≪Manufacture of steel after heat treatment≫

Under the conditions shown in Table 2, the steel materials 1 to 132 before heat treatment were heated to obtain a steel material after the heat treatment.

≪Evaluation items and evaluation methods≫

<Appearance evaluation (evaluation of easy removal of scale by air blow)>

(Assessment Methods)

Using an air blower, after heat treatment at a discharge pressure of 5.5 KPa for 30 seconds, air blowing was performed on the steel material. After the heat treatment, the scale removal area ratio on the surface of the steel material was measured, and based on the following judgment criteria, the easy removal property of scale-off was evaluated based on the following evaluation criteria. If it is an evaluation other than x, it is practical performance.

(Evaluation standard)

◎: 99% or more of the scale removal area ratio

○+: The scale removal area ratio is 95% or more and less than 99%, and the background is white

○-: The scale removal area ratio is 95% or more and less than 99%, and the background is not white (black or gray)

△: Scale removal area ratio 90% or more and less than 95%

×: less than 90% of the scale removal area ratio

<Evaluation of ease of use of formulation for easily descaling film formation>

(Assessment Methods)

After the preparation of the formulation for easily descaling film formation shown in Table 1, the appearance of the liquid after 6 hours was visually observed as the presence or absence of precipitation. In addition, the amount of change (%) of the total adhesion amount of the metal element (Y) immediately after and 24 hours after the preparation of the preparation for easily descaling film formation shown in Table 1 was determined as the film formation conditions (temperature 40° C., immersion time 300 seconds). ), was calculated from the following equation (A) using the steel before heat treatment. Ease of use of the formulation for easily descaling film formation was evaluated based on the following evaluation criteria. If it is an evaluation other than x, it is practical performance.

(Equation A)

Change amount (%) of the total amount of adhesion of the metal element (Y) = (the total amount of adhesion of the metal element (Y) immediately after the adjustment of the film-forming formulation (mg/m2)-24 hours after the adjustment of the film-forming formulation Total amount of metal element (Y) adhesion (mg/m2)}/Total amount of metal element (Y) adhesion immediately after adjustment of the film-forming agent (mg/m2)×100

(Evaluation standard)

(Double-circle): There is no precipitation, and less than 5% of the change in the total amount of adhesion of the metal element (Y)

(Circle): No precipitation and 5% or more of change in the total amount of adhesion of the metal element (Y)

?: There is precipitation, and less than 10% of the change in the total amount of metal element (Y) attached

×: There is precipitation, and the amount of change in the total amount of adhesion of the metal element (Y) is 10% or more (because the property of the liquid in 24 hours after the preparation of the film-forming agent is bad, it is impossible to prepare the steel material before heat treatment, so it is not possible to evaluate it. Including cases that were not possible)

<Stability evaluation when a processing load is applied to the formulation for easily descaling film formation>

After adjusting the preparation for easily descaling film formation shown in Table 1, a steel material having a carbon content of 0.3% per 1000 ml of the film-forming preparation was added to the film-forming preparation with a surface area of 180 cm2 equivalent to the front and back. After being immersed and stored in a thermostat (2 hours at 60°C), evaluation was made based on the following evaluation criteria. If it is an evaluation other than x, it is practical performance.

◎: There is no change in the liquid appearance of the easily descaling film forming agent, and the change in pH of the film forming agent is less than 1.0

○: There is no change in the liquid appearance of the easily descaled film forming agent, and the change in pH of the film forming agent is 1.0 or more and less than 2.0

Δ+: There is no change in the liquid appearance of the easily descaling film forming agent, and the change in pH of the film forming agent is 2.0 or more.

△-: There is a change in the liquid appearance of the film-forming agent that is easily descaled (there are suspensions and precipitates), and the pH change of the film-forming agent is less than 2.0

X: There is a change in the liquid appearance of the easily descaled film-forming agent (there are suspensions and deposits), and the pH change of the film-forming agent is 2.0 or more.

Claims (10)

In steel before heat treatment having a film on the surface of carbon steel,
The carbon steel contains 0.06 mass% or more of carbon based on the total mass of the carbon steel,
The coating contains at least one metal element (X) selected from Fe, Ni and Co and at least one metal element (Y) selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo, and W. And also
The total amount of adhesion of the metal element (Y) is 1 to 100 mg/m 2,
A steel material before heat treatment, characterized in that (X)/(Y), which is a mass ratio of the metal element (X) and the metal element (Y), is in the range of 0.01 to 0.5. In the manufacturing method of steel before heat treatment,
The steel material before the heat treatment has a film on the surface of the carbon steel,
The carbon steel contains 0.06 mass% or more of carbon based on the total mass of the carbon steel,
The coating contains at least one metal element (X) selected from Fe, Ni and Co and at least one metal element (Y) selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo, and W. And also
The total amount of adhesion of the metal element (Y) is 1 to 100 mg/m 2, and (X)/(Y), which is a mass ratio of the metal element (X) and the metal element (Y), is in the range of 0.01 to 0.5,
The above manufacturing method,
Ti, Zr, Hf, Nb, V, Cr, Mn, Mo, and a formulation containing at least one metal element (Y) selected from W and an etching component in contact with the carbon steel to form the film Method for producing a steel material before heat treatment, characterized in that. In the method of manufacturing a steel material after heat treatment,
On the surface of carbon steel containing 0.06% by mass or more carbon, at least one metal element (X) selected from Fe, Ni and Co and Ti, Zr, Hf, Nb, V, Cr, Mn, Mo and W selected from A film containing at least one metal element (Y), wherein the total amount of the metal element (Y) adhered is 1 to 100 mg/m 2, and the mass ratio of the metal element (X) and the metal element (Y) is (X) /(Y) forming a film in the range of 0.01 to 0.5 to obtain a steel material before heat treatment, and
A method of manufacturing a steel material after heat treatment, comprising the step of heat-treating the steel material before the heat treatment at 700°C or higher. In the method of removing scale,
On the surface of carbon steel, at least one metal element (X) selected from Fe, Ni and Co and at least one metal element (Y) selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo and W A step of forming a film containing, to obtain a steel material before heat treatment, and
Heating the steel material before the heat treatment at 700° C. or higher to obtain a steel material after the heat treatment,
Including the step of removing the scale adhered on the steel material after the heat treatment,
The carbon steel contains 0.06 mass% or more of carbon based on the total mass of the carbon steel,
The total amount of adhesion of the metal element (Y) is 1 to 100 mg/m2, and the mass ratio of the metal element (X) and the metal element (Y), which is (X)/(Y), is in the range of 0.01 to 0.5. How to remove the scale. It is a formulation used to form a scale-free film on the carbon steel constituting the steel material before the heat treatment, prior to the heating, when the steel material before heat treatment is heated to 700°C or higher to obtain a steel material after heat treatment,
At least one metal element (Y) selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo and W, and
Has an etching component,
The easily scaled-off coating is at least one metal element (X) selected from Fe, Ni and Co and at least one metal element selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo and W (Y ),
The carbon steel contains 0.06 mass% or more of carbon based on the total mass of the carbon steel,
The total amount of adhesion of the metal element (Y) is 1 to 100 mg/m2, and the mass ratio of the metal element (X) and the metal element (Y), which is (X)/(Y), is in the range of 0.01 to 0.5. Formulation for forming a film that is easy to remove scale. delete delete delete delete delete