JP2018009202A - Carbon steel before heat treatment having excellent scale removal property, carbon steel after heat treatment, manufacturing method of the same, scale removing method, and agent for easily forming descaling film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel technology enabling a scale produced by heating a steel material to be easily removed.SOLUTION: In a steel material before a heat treatment that has a film on a surface of a carbon steel, the carbon steel includes carbon of 0.06 mass% or more based on a total mass of the steel carbon. The film includes one or more types of metal elements (X) selected from Fe, Ni, and Co, and one or more types of metal elements (Y) selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo, and W. A total attachment amount of the metal element (Y) is 1-100 mg/m, and (X)/(Y), a mass ratio of the metal element (X) and the metal element (Y) is in a range of 0.01-0.5.SELECTED DRAWING: None

Description

  The present invention is a technique relating to easy removal of scale generated when heat treating carbon steel.

  The metal material is subjected to heat treatment by heating / cooling in order to improve mechanical strength. The heat treatment conditions vary depending on the target mechanical strength, material, shape, equipment restrictions, and the like, but in steel quenching, the steel material is heated to a high temperature of approximately 700 ° C. or higher. Therefore, the steel material heated to a high temperature in the atmosphere generates a scale due to surface oxidation while being heated. If such a scale remains on the surface of the steel material, there is a problem in that quality is deteriorated such as an appearance defect and an influence on dimensional accuracy and surface roughness. Therefore, conventionally, scale removal such as pickling or shot blasting is performed after the heat treatment of the steel material.

  In addition, as disclosed in Patent Document 1, by controlling the Si amount and Cr amount of the steel material, and also the surface roughness within a certain range, there is also a technology that can suppress the generation of the scale amount during heating in the atmospheric furnace. Proposed.

  On the other hand, as disclosed in Patent Document 2, by applying a high-temperature decarburization-preventing coating composed of a composition containing silicon carbide to a steel material, it is possible to prevent oxidation and decarburization, and further remove the coating film after heat treatment. Technologies that can improve the performance have also been proposed.

JP-A-2005-133180 Japanese Patent Laid-Open No. 2-205622

  An object of this invention is to provide the novel technique which can remove easily the scale produced | generated by the heating of steel materials.

As a result of intensive studies, the present inventors have found that the above problem can be solved by the following method, and have completed the present invention.
[1] In the steel material before heat treatment having a film on the surface of carbon steel,
The carbon steel contains 0.06% by mass or more of carbon based on the total mass of the carbon steel,
The film is composed of one or more metal elements (X) selected from Fe, Ni and Co and one or more metal elements (Y) selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo and W. ) And the total adhesion amount of the metal element (Y) is 1 to 100 mg / m ² , and is 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.
[2] In the method of manufacturing a steel material before heat treatment,
The pre-heat treatment steel material has a film on the surface of carbon steel,
The carbon steel contains 0.06% by mass or more of carbon based on the total mass of the carbon steel,
The film is composed of one or more metal elements (X) selected from Fe, Ni and Co and one or more metal elements (Y) selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo and W. ) And the total adhesion amount of the metal element (Y) is 1 to 100 mg / m ² , and is 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 manufacturing method is
Forming the film by bringing the carbon steel into contact with an agent containing one or more metal elements (Y) selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo and W and an etching component The manufacturing method of the steel materials before heat processing characterized by including the process to carry out.
[3] In the method for producing a steel material after heat treatment,
At least one metal element (X) selected from Fe, Ni and Co and Ti, Zr, Hf, Nb, V, Cr, Mn, and Mo are formed on the surface of carbon steel containing 0.06% by mass or more of carbon. And one or more metal elements (Y) selected from W, the total amount of the metal elements (Y) deposited is 1 to 100 mg / m ² , and the metal elements (X) Forming a film in which (X) / (Y), which is a mass ratio between the metal element (Y) and 0.01 to 0.5, and obtaining a steel material before heat treatment,
And a step of heat-treating the steel material before heat treatment at 700 ° C. or higher.
[4] In the scale removal method,
One or more metal elements (X) selected from Fe, Ni and Co and one or more metal elements selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo and W on the surface of carbon steel Forming a film containing (Y) and obtaining a steel material before heat treatment;
Heating the steel material before heat treatment at 700 ° C. or higher to obtain a steel material after heat treatment;
Removing the scale adhered on the steel material after the heat treatment.
[5] The scale removing method according to [4], wherein the carbon steel contains 0.06% by mass or more of carbon based on the total mass of the carbon steel.
[6] The total adhesion amount of the metal element (Y) is 1 to 100 mg / m ² , and is the mass ratio of the metal element (X) and the metal element (Y) (X) / (Y) The method for removing a scale according to [4] or [5], wherein is in the range of 0.01 to 0.5.
[7] When the steel material before heat treatment is heated to 700 ° C. or higher to obtain the steel material after heat treatment, prior to the heating, it is used to form an easily descaleable film on the carbon steel constituting the steel material before heat treatment. An agent,
One or more metal elements (Y) selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo and W;
An easily-descaleable film-forming agent characterized by comprising an etching component.
[8] The easily descaleable film 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 1 [7] The easy-to-descale film-forming agent according to [7], which contains at least a seed metal element (Y).
[9] The easy-to-descale film forming agent according to [7] or [8], wherein the carbon steel contains 0.06% by mass or more of carbon based on the total mass of the carbon steel.
[10] The total adhesion amount of the metal element (Y) is 1 to 100 mg / m ² , and is 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, [8] or [9].

  ADVANTAGE OF THE INVENTION According to this invention, the novel technique which can remove easily the scale produced | generated by the heating of steel materials (for example, easy removal with an air blow or flowing water) can be provided. Therefore, the simplification and shortening of the treatment process can be dramatically achieved as compared with the conventional scale removal such as pickling and shot blasting.

  Hereinafter, a steel material before heat treatment, a method for producing the steel material before heat treatment (in addition, an agent used in the production method), and a method for producing the steel material after heat treatment by heating the steel material before heat treatment (also, The removal method) will be described in order.

<< 1. Steel before heat treatment≫
The pre-heat treatment steel material according to the present invention is the pre-heat treatment steel material having a coating on the surface of carbon steel, wherein the carbon steel contains 0.06% by mass or more of carbon based on the total mass of the carbon steel, and the coating Is one or more metal elements (X) selected from Fe, Ni and Co, and one or more metal elements (Y) selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo and W The total amount of the metal element (Y) deposited is 1 to 100 mg / m ² , and the mass ratio of the metal element (X) to the metal element (Y) is (X) / ( 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 which comprises the steel material before heat processing which concerns on this invention contains 0.06 mass% or more carbon on the basis of the total mass of the said carbon steel. Preferably, 0.06% by mass to 3.1% by mass, more preferably 0.1% by mass to 0.77% by mass, and even more preferably 0.15% by mass to 0.45% by mass. % Or less. When the carbon content in the carbon steel is within the above range, a specific amount of a film, which will be described later, is attached, so that the scale attached to the steel material after the heat treatment can be removed very easily. Carbon steel may contain elements other than Fe and C, such as Ni, Co, Mo, V, Ti, Nb, Mn, Cr, and B.

<1-2. Film>
{1-2-1. component}
The film constituting the pre-heat treatment steel material according to the present invention is composed of one or more metal elements (X) selected from Fe, Ni and Co, and Ti, Zr, Hf, Nb, V, Cr, Mn, Mo and W. One or more metal elements (Y) selected. Here, as the metal element (X), Fe and Ni are preferable, and Fe is more preferable in that it can form a superior easily-descaleable film that can be peeled off very easily by air blow or the like. It is. Further, as the metal element (Y), Ti, Zr, Nb, Cr, and Mo are preferable in that it can form an excellent easily-descaleable film that can be peeled off very easily by air blow or the like. Zr and Ti are more preferable. In addition, regarding any of the metal element (X) and the metal element (Y), these may be contained alone or in plural. In the coating, these metal elements are presumed to be present in a mixture of metals, hydroxides, hydrated oxides and oxides.

{1-2-2. Component ratio}
Here, (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, and 0.05 to 0.3. It is preferable that it is the range of this, and it is more preferable that it is the range of 0.1-0.2. Within this range, cohesive cracking of the film can be effectively prevented.

{1-2-3. Amount of adhesion}
The adhesion amount of the coating film constituting the pre-heat treatment steel material according to the present invention to the carbon steel is such that the total adhesion amount of the metal element (Y) is 1 to 100 mg / m ² , and the metal element (Y) The total amount of adhesion is preferably ² to 40 mg / m ^2, and the total amount of the metal element (Y) is more preferably 5 to ²⁰ mg / m ² . Since the metal element (Y) is taken into the scale generated by the heat treatment, the scale attached to the steel material after the heat treatment can be removed very easily. For this reason, the film which comprises the steel material before heat processing which concerns on this invention has a preferable state which does not have a film crack and a film | membrane missing. When the total adhesion amount of the metal element (Y) exceeds 100 mg / m ² , film cracking is likely to occur. Since the metal element (Y) is difficult to be taken into the scale generated by the heat treatment at the portion where the film is cracked, the scale cannot be easily removed. Further, if the total amount of the metal element (Y) attached is less than 1 mg / m ² , the surface of the carbon steel cannot be covered with the film, and the film is likely to come off. In the part where the film is missing, the metal element (Y) is not taken into the scale generated by the heat treatment, and the scale cannot be easily removed. When the carbon content in the carbon steel is within the above range, the scale attached to the steel material after the heat treatment can be removed very easily by adhering the coating within the range. The adhesion amount of the metal element (Y) can be measured from the surface of the carbon steel material by a fluorescent 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 spectrometer (XPS). In the present invention, the position of oxygen disappearance in the XPS depth profile is defined as the carbon steel material and the film. The average of the measured values of the metal element (X) detected in the upper layer was defined as the amount of adhesion of the metal element (X).

≪2. Manufacturing method of steel before heat treatment≫
The method for producing a pre-heat treatment steel material according to the present invention comprises an agent containing at least one metal element (Y) selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo and W and an etching component. Forming the film by contacting the carbon steel. Hereinafter, the agent (easily descalable film-forming agent) used for manufacturing the steel material before heat treatment will be described first, and then each step will be described.

<2-1. Easily descaling film forming agent>
{2-1-1. component}
(2-1-1-1. Metal elements)
The agent for forming an easily descaleable film according to the present invention contains one or more metal elements (Y) selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo and W. Here, Ti, Zr, Nb, Cr, and Mo are preferable as the metal element, and Zr and Ti are more preferable. The preferred reason is as described above. In this case, the concentration of the metal element (Y) in the easily descalable film-forming agent is preferably 0.5 to 10 mmol / l. These metal elements may be supplied from the base material and may not be in a constantly dissolved state, but basically exist in a dissolved state in a liquid medium to be described later. Moreover, the metal element may contain only 1 type or multiple types. In addition, although said metal element is essential, you may contain another metal element. Specifically, it may contain one or more metal elements (X) selected from Fe, Ni and Co, and the concentration of the metal element (X) in the easy-scaling film forming agent is preferably Is 0.1 to 5 mmol / l.

(2-1-1-2. Etching component)
The easily descalable film-forming agent 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 preferable in that the film-forming treatment agent can be stabilized, and HF alone or a combination of HF and HNO ₃ is more preferable. Moreover, the existence form of the etching component in the agent for forming an easily descalable film can be determined by the relationship with the suitable pH range (2.5 to 4.5) and the type and amount of other existing components. . For example, when the acid is used as an additive component, a dissociated form of the acid is assumed. In addition, the etching component may contain only 1 type or multiple types.

(2-1-1-3. Other components)
The easily descalable film-forming agent according to the present invention may contain other components as necessary. For example, when adding an alkali to control the pH within a suitable range, use a strong alkali such as LiOH, NaOH, KOH, or a weak alkali such as NH ₃ {ammonium hydroxide (NH ₃ —H ₂ O)}. When the acid is added, a weak acid such as acetic acid can be used. As the alkali, NH ₃ {ammonium hydroxide (NH ₃ —H ₂ O)} is preferable, and as the acid, a weak acid is preferable.

(2-1-1-4. Liquid medium)
The liquid medium in the agent for forming an easily descalable film according to the present invention is preferably a liquid medium mainly composed of water (for example, deionized water or pure water). Here, “mainly” means 51% by mass or more of water (preferably 60% by mass or more, more preferably 70% by mass or more, and further preferably 80% by mass) based on the total mass of the liquid medium. As mentioned above, it means 90% by mass or more particularly preferably. In addition, you may contain liquid media other than water (for example, water-miscible liquid media, for example, alcohol, such as ethanol), as a liquid medium. The agent may be in a dry form or a concentrated form. In this case, dissolve or dilute with water on site.

{2-1-2. liquid}
(2-1-2-1. PH)
The pH of the easily descalable film-forming agent according to the present invention is preferably 2.5 to 4.5, more preferably 3 to 4. In addition, this pH is the value measured at the processing temperature (typically 40 degreeC) by JIS-Z8802: 2011 about the agent for easily descaleable film formation.

{2-1-3. Production method}
According to the present invention, there is provided a method for producing an easily-descaleable film forming agent comprising a supply source of one or more metal elements (Y) selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo and W. Adding a source of etching components to the liquid medium and mixing. Hereinafter, the said supply source is explained in full detail.

(2-1-3-1. Supply source)
As a supply source of the metal element (Y), for example, a salt, a complex compound or a metal containing one or more metal elements (Y) selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo and W There may be mentioned hydrated oxides. Specifically, in the case of Ti, for example, titanium diammonium oxalate, dipotassium oxybisuccinate, titanium (II) oxide, titanium (III) oxide, titanium (IV) oxide, titanium oxysulfate, base Titanium phosphate, titanium bromide (IV), metatitanic acid, zinc metatitanate (II), aluminum titanate (III), potassium metatitanate, metatitanium tricobalt (II), zirconium titanate, strontium metatitanate, metatitanium tri Iron (III), copper metatitanate (II), sodium titanate, neodymium dititanate (III), barium metatitanate, bismuth metatitanate, magnesium metatitanate, magnesium titanate, manganese metatitanate (II), Lanthanum dititanate (III), lithium metatitanate, hexafluorotitanium (IV) acid Monium, potassium hexafluorotitanium (IV), titanium iodide (IV), titanium sulfate (III), titanium sulfate (IV), titanium chloride, titanium nitrate, titanyl sulfate, titanium fluoride (III), titanium fluoride ( IV), titanium salts such as hexafluorotitanic acid, titanium lactate, peroxotitanic acid, titanium laurate, titanium acetylacetonate, titanium hydroxide (IV), etc. or titanates, etc .; in the case of Zr, for example, tetrakis (acetyl Acetonato) zirconium (IV), zirconium chloride (IV), zirconium chloride (IV), zirconium silicate, zirconium acetate (IV), zirconium oxide (IV), zirconium nitrate (IV), cesium metazirconate, Lithium metazirconate, zinc metazirconate (II), aluminum metazirconate (III), calcium metazirconate, cobalt (II) metazirconate, strontium metazirconate, copper (II) metazirconate, sodium metazirconate, nickel (II) metazirconate, barium metazirconate, meta Bismuth (III) zirconate, magnesium metazirconate, zirconium oxycarbonate, ammonium hexafluorozirconium (IV), potassium hexafluorozirconium (IV), zirconium iodide, zirconium dihydrogen phosphate (IV), basic Zirconium carbonate, ammonium zirconium carbonate, zirconyl ammonium carbonate, zirconium nitrate, zirconyl nitrate, zirconium (IV) sulfate, zirconyl sulfate, hexafluorozirconic acid, zirconium oxyphosphate Zirconium, zirconium pyrophosphate, zirconyl dihydrogen phosphate, zirconium oxychloride, zirconium fluoride, zirconyl acetate, zirconium oxide, zirconium hydroxide and other zirconium salts; 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), fluorohafnium acid, fluorohafnate, hafnium fluoride In the case of Nb, niobium oxide (II), niobium oxide (V), penta (hydrogen oxalate) niobium, niobium hydroxide (V), niobium oxyacetylacetonate, metaniobic acid, Calcium metaniobate, strontium metaniobate, metani Niobium salts such as barium oblate, magnesium metaniobate, lithium metaniobate, ammonium metaniobate, sodium metaniobate, niobium pentachloride, etc. or niobate salts; in the case of V, vanadium oxydichloride, vanadium oxytrichloride, trichloride Vanadium, vanadium oxide, iron (III) tetravanadate, vanadium (III) bromide, vanadium oxysuccinate, vanadium iodide (II), vanadium pentoxide, metavanadate, sodium pyrovanadate, sodium vanadate, ammonium metavanadate, Sodium metavanadate, potassium metavanadate, vanadium oxytrichloride, vanadium trioxide, vanadium dioxide, vanadium oxysulfate, vanadium oxyacetyl acetate, vanadium acetyl acetate, phosphovanadomolybde Vanadium salt such as acid or vanadate, etc .; chromium; in the case of Cr, chromium (III) formate, chromium (III) fluoride, chromium (III) nitrate, chromium (III) sulfate, chromium (III) oxalate, acetic acid Chromium salts such as chromium (III), chromium biphosphate (III), chromium hydroxide (III), chromium oxide (III), chromium bromide (III), chromium iodide (III), etc .; Acetylacetonato) diaquamanganese (II), trimanganese tetroxide, manganese (II) oxide, manganese (III) oxide, manganese oxide (IV), manganese bromide (II), manganese oxalate (II), permanganate (VII), potassium permanganate (VII), sodium permanganate (VII), manganese dihydrogen phosphate (II), manganese nitrate (II), manganese sulfate (II), manganese sulfate (III), manganese sulfate ( IV), manganese fluoride (II), Manganese salts such as manganese (III), manganese carbonate (II), manganese acetate (II), manganese acetate (III), ammonium manganese sulfate (II), manganese iodide (II), manganese hydroxide (II), etc. or manganic acid In the case of Mo, molybdenum chloride (V), molybdenum oxide (IV), molybdenum oxide (VI), zinc molybdate (II), potassium molybdate, calcium molybdate, cobalt molybdate (II), cesium molybdate , Nickel (II) molybdate, barium molybdate, bismuth molybdate (III), magnesium molybdate, lithium molybdate, lithium paramolybdate, strontium molybdate, phosphomolybdic acid, ammonium phosphomolybdate, sodium phosphomolybdate, Molybdic acid, molybdate ammo Molybdenum salts such as um, ammonium paramolybdate, sodium molybdate, etc. or molybdate, etc .; in the case of W, tungsten chloride (VI), iron tungstate oxide (III), tungsten chloride (VI), tungsten oxydichloride, Tungsten dioxide, tungsten trioxide, metatungstic acid, ammonium metatungstate, sodium metatungstate, paratungstic acid, ammonium paratungstate, sodium paratungstate, zinc tungstate (II), potassium tungstate, calcium tungstate, Cobalt (II) tungstate, strontium tungstate, tungstic acid, copper (II) tungstate, nickel tungstate, barium tungstate, magnesium tungstate, Gusuten manganese (II), lithium tungstate, phosphorus tongue cesium stent acid, ammonium phosphotungstic acid, tungsten salt or tungstate such as sodium phosphotungstic acid; and the like.

<2-2. Each step in the manufacturing method of the steel material before heat treatment>
The method for producing the pre-heat treatment steel material preferably includes (Step 1) a step of pretreating carbon steel, (Step 2) a step of bringing an easily-descaleable film forming agent into contact with the pre-heat treatment steel material to form a film, including. Hereinafter, each process is explained in full detail.

{2-2-1. Pretreatment process}
Prior to forming a film on the carbon steel constituting the pre-heat treatment steel material, a pre-treatment well known in the art (for example, pre-cleaning of the surface of the carbon steel by degreasing or the like) may be performed.

{2-2-2. Film formation process}
As the film forming step, (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.) Second method) The surface of the carbon steel is contacted with an agent for forming an easily-descaleable film, and the surface of the carbon steel is cleaned by the action of an etching component contained in the agent for forming an easily-descaleable film. And a method of forming the coating film by a mechanical reaction or an electrical reaction. Among these, it is desirable that the film is uniform on the surface of the carbon steel material, so the second method is preferable from this viewpoint. Hereinafter, these two methods will be described in detail.

  First, the heating in the first method is not particularly limited as long as it is a temperature capable of oxidizing the surface of the carbon steel containing the metal element, 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 at 200 to 300 ° C. for at least 30 minutes in an oxygen-containing gas atmosphere, an oxide film of Fe and Cr + Mo is formed on the surface. The This oxide film also becomes an easily descalable film by heat treatment at 700 ° C. or higher.

  Next, in the second method, the surface of the carbon steel is brought into contact with the agent for forming an easily descaleable film containing the above metal element, and then dried, and the predetermined easily descaleable film is applied to the surface of the carbon steel material. It is the method of forming. In addition, as a contact method in the second method, for example, a dipping method, a spray method, a roll coating method, an air spray method, an airless spray method, an electrolysis method (for example, a cathode electrolysis method), or a method combining these methods is adopted. can do. In addition, as a method of removing the excessive easily descaleable film forming agent adhering to the surface of the carbon steel material after contacting the film forming agent, air knife, squeeze roll, spray water washing, immersion water washing, or A method combining these methods can be adopted, and it is also possible to efficiently form a descaling film on the surface of the carbon steel material in a short time by combining these and a drying step. The temperature (liquid temperature) of the film-forming agent when carbon steel is brought into contact with the film-forming agent is not particularly limited, but is preferably 20 ° C. or higher and 50 ° C. or lower, and is 35 ° C. or higher. 45 ° C. or lower is more preferable.

≪3. Method of manufacturing steel material after heat treatment by heating steel material before heat treatment >>
Next, a method for 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 also be grasped as a method for removing scale generated when a steel material before heat treatment is manufactured by heating the steel material before heat treatment.

<3-1. Heat treatment process>
The manufacturing method of the steel material after heat processing which concerns on this invention includes the process of heat-processing at 700 degreeC or more the steel material before heat processing in which the said film | membrane was formed. Here, the heat treatment temperature is preferably 700 ° C. or higher and 1350 ° C. or lower, more preferably 850 ° C. or higher and 1250 ° C. or lower, and further preferably 900 ° C. or higher and 1000 ° C. or lower. . This is because, within this range, it is possible to realize that the easily descaleable film is taken into the oxide scale while preventing the steel material from melting. The heating temperature and holding time vary depending on the steel composition, shape and thickness, and the intended mechanical strength.For example, in order to perform the quenching process, the steel material is kept in the austenite temperature range. What is necessary is just to heat to a certain 800-1000 degreeC temperature, and hold | maintain the time for 1-120 minutes.

  Here, the heating method to which the present invention is applied is not particularly limited, and a combination of a heating atmosphere furnace, current heating treatment, and induction hardening using induction heating can also be adopted. Laser quenching using laser light introduced as metal surface quenching is also possible.

  The heat treatment to which the present invention is applied is applicable to heat treatment that does not require a vacuum or an inert gas. Specifically, for example, heat treatment in an oxidizing atmosphere containing 1% by volume or more of oxygen. The present invention is also applied to a hot press method such as a pre-press quench method in which a heated member is pressed and molded with a mold and then quenched by quenching with a mold.

  Furthermore, the cooling method and speed also vary depending on the steel composition, shape and thickness, and the intended mechanical strength, and examples include furnace cooling, air cooling, water cooling, coolant spraying, and the like. For example, in the quenching process for obtaining martensite after the 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, hot press molding may be performed using a molding die instead of the rapid quenching.

<3-2. Scale removal process>
The removal method of scale according to the present invention includes mechanical methods such as sand blasting, shot blasting, wet blasting, laser peening, honing and grinder, and chemical treatment methods such as phosphoric acid washing, sulfuric acid washing, hydrochloric acid washing and nitric acid washing. , But you may combine them. Incidentally, the scale can be removed even in a method such as air blowing or running water cleaning in which compressed air or compressed water is discharged at a pressure of 0.1 MPa or more without using a projection material or an abrasive.

≪Steel material≫
The mass% of carbon based on the total mass of carbon steel is 0.03%, 0.06%, 0.1%, 0.15%, 0.3%, 0.45%, 0.77%, 3 .1% and 4% carbon steel were used.

≪Preparation of film forming agent≫
As shown in Table 1-1 to Table 1-3, various raw materials are added to water so as to have the blending amounts shown in Table 1-1 to Table 1-3, and then sufficiently stirred. A forming agent was obtained. In that case, it adjusted using acetic acid or ammonia so that it might become pH shown in Table 1-1-Table 1-3.

≪Manufacture of steel before heat treatment≫
As shown in Tables 2-1 to 2-3, various steel materials were immersed for 30 to 300 seconds in the treatment liquid (film forming agent) 1 to 102 managed at 40 ° C. In addition, the contact time (immersion time) between various steel materials and the film-forming agent by immersion was adjusted so that the adhesion amounts shown in Table 2-1 to Table 2-3 were obtained. Thereafter, the various steel materials brought into contact with the film-forming agent were sufficiently washed with water so as not to leave the film-forming agent on the surface of the steel material, and then drained and dried to obtain pre-heat treatment steel materials 1-132.

≪Manufacture of steel after heat treatment≫
Under the conditions shown in Tables 2-1 to 2-3, the steel materials 1 to 132 before heat treatment were heated to obtain steel materials after heat treatment.

≪Evaluation items and methods≫
<Appearance evaluation (Easy descalability evaluation by air blow)>
(Evaluation method)
Using an air blower, the steel material was air blown for 30 seconds at a discharge pressure of 5.5 KPa for 30 seconds. After heat treatment, the scale removal area ratio of the steel material surface was measured, and the easy descalability was evaluated based on the following evaluation criteria based on the following criteria. If the evaluation is other than x, it is a practical performance.
(Evaluation criteria)
◎: Scale removal area ratio 99% or more ○ +: Scale removal area ratio 95% or more and less than 99% and the base is white ○ −: Scale removal area ratio 95% or more and less than 99% and the base is other than white (black Or gray)
Δ: Scale removal area ratio of 90% or more and less than 95% ×: Scale removal area ratio of less than 90%

<Evaluation of ease-of-use of easily descalable film-forming agent>
(Evaluation method)
After preparing the easily-descaleable film-forming agent shown in Table 1-1 to Table 1-3, the liquid appearance after 6 hours was visually observed as the presence or absence of precipitation. Furthermore, the change amount (%) of the total adhesion amount of the metal element (Y) immediately after the preparation of the agent for forming an easily-descaleable film shown in Table 1-1 to Table 1-3 and 24 hours after the preparation, Using the steel material before heat treatment prepared at (temperature 40 ° C., immersion time 300 seconds), it was calculated from the following formula A. The ease of use of the easily descalable film-forming agent was evaluated based on the following evaluation criteria. If the evaluation is other than x, it is a practical performance.
(Formula A)
Change amount (%) of total adhesion amount of metal element (Y) = {Total adhesion amount of metal element (Y) immediately after adjustment of film forming agent (mg / m ² ) −After 24 hours of adjustment of film forming agent Total amount of metal element (Y) deposited (mg / m ² )} / Total amount of metal element (Y) deposited immediately after adjustment of the film-forming agent (mg / m ² ) × 100
(Evaluation criteria)
◎: No precipitation and change in total amount of adhesion of metal element (Y) less than 5% ○: No precipitation and change in total amount of adhesion of metal element (Y) 5% or more Δ: Precipitation and metal element Less than 10% change in the total amount of (Y) adhesion x: Precipitation and more than 10% change in the total amount of adhesion of the metal element (Y) (The liquid properties are poor 24 hours after the preparation of the film-forming agent) (This includes cases where the steel material before heat treatment could not be created and evaluated.)
<Stability evaluation when processing load is applied to the agent for forming an easily descalable film>
After adjusting the easily-descaleable film-forming agent shown in Table 1-1 to Table 1-3, a steel material having a carbon content of 0.3% per 1000 ml of the film-forming agent is 180 cm as the surface area including the front and back surfaces. ^{A portion} corresponding to ² was immersed in a film-forming agent and stored in a thermostatic bath ( ² hours at 60 ° C.), and then evaluated based on the following evaluation criteria. If the evaluation is other than x, it is a practical performance.

◎: No change in liquid appearance of easy-scalable film-forming agent, and change in pH of film-forming agent is less than 1.0 ○: No change in liquid appearance of easily-descaleable film-forming agent, and film Change in pH of the forming agent is 1.0 or more and less than 2.0 Δ +: No change in the liquid appearance of the easily descalable film forming agent, and change in pH of the film forming agent is 2.0 or more Δ− : There is a change in the liquid appearance of the easily-descaleable film-forming agent (with suspension and precipitate), and the pH change of the film-forming agent is less than 2.0 x: There is a change (with suspension and precipitate), and the pH change of the film-forming agent is 2.0 or more

Claims (10)

In steel materials before heat treatment having a coating on the surface of carbon steel,
The carbon steel contains 0.06% by mass or more of carbon based on the total mass of the carbon steel,
The film is composed of one or more metal elements (X) selected from Fe, Ni and Co and one or more metal elements (Y) selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo and W. And the total adhesion amount of the metal element (Y) is 1 to 100 mg / m ² ,
(X) / (Y), which is a mass ratio of the metal element (X) to the metal element (Y), is in the range of 0.01 to 0.5, and is a steel material before heat treatment. In the method of manufacturing a steel material before heat treatment,
The pre-heat treatment steel material has a film on the surface of carbon steel,
The carbon steel contains 0.06% by mass or more of carbon based on the total mass of the carbon steel,
The film is composed of one or more metal elements (X) selected from Fe, Ni and Co and one or more metal elements (Y) selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo and W. ) And the total adhesion amount of the metal element (Y) is 1 to 100 mg / m ² , and is 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 manufacturing method is
Forming the film by bringing the carbon steel into contact with an agent containing one or more metal elements (Y) selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo and W and an etching component The manufacturing method of the steel materials before heat processing characterized by including the process to carry out. In the method for manufacturing a steel material after heat treatment,
At least one metal element (X) selected from Fe, Ni and Co and Ti, Zr, Hf, Nb, V, Cr, Mn, and Mo are formed on the surface of carbon steel containing 0.06% by mass or more of carbon. And one or more metal elements (Y) selected from W, the total amount of the metal elements (Y) deposited is 1 to 100 mg / m ² , and the metal elements (X) Forming a film in which (X) / (Y), which is a mass ratio between the metal element (Y) and 0.01 to 0.5, and obtaining a steel material before heat treatment,
And a step of heat-treating the steel material before heat treatment at 700 ° C. or higher. In the scale removal method,
One or more metal elements (X) selected from Fe, Ni and Co and one or more metal elements selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo and W on the surface of carbon steel Forming a film containing (Y) and obtaining a steel material before heat treatment;
Heating the steel material before heat treatment at 700 ° C. or higher to obtain a steel material after heat treatment;
Removing the scale adhered on the steel material after the heat treatment.   The scale removal method according to claim 4, wherein the carbon steel contains 0.06% by mass or more of carbon based on the total mass of the carbon steel. The total adhesion amount of the metal element (Y) is 1 to 100 mg / m ² , and the mass ratio of the metal element (X) and the metal element (Y) is (X) / (Y) is 0. The method for removing a scale according to claim 4 or 5, which is in a range of 01 to 0.5. When the steel material before heat treatment is heated to 700 ° C. or higher to obtain a steel material after heat treatment, prior to the heating, an agent used for forming an easily descaleable film on the carbon steel constituting the steel material before heat treatment. There,
One or more metal elements (Y) selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo and W;
An easily-descaleable film-forming agent characterized by comprising an etching component.   The easily descalable film is one or more metal elements (X) selected from Fe, Ni and Co, and one or more metals selected from Ti, Zr, Hf, Nb, V, Cr, Mn, Mo and W. The agent for easily descaleable film formation according to claim 7, comprising a metal element (Y).   The easily-descaleable film-forming agent according to claim 7 or 8, wherein the carbon steel contains 0.06% by mass or more of carbon based on the total mass of the carbon steel. The total adhesion amount of the metal element (Y) is 1 to 100 mg / m ² , and the mass ratio of the metal element (X) and the metal element (Y) is (X) / (Y) is 0. The easily-descaleable film-forming agent according to claim 8 or 9, which is in the range of 01 to 0.5.