JP4261684B2 - Steel material for high friction joint and method for manufacturing the same - Google Patents

Description

【００２９】
鋳片の冷却はモールド下方の二次冷却帯の水量と鋳片の引き抜き速度の選択により制御した。こうして得られた鋳片を加熱し、粗圧延工程を経て図７に示すユニバーサル圧延装置列でＨ形鋼に圧延し、更に再加熱、急冷することにより表面硬度を上昇させた。この時の加熱、圧延、脱炭抑制剤塗布、浸炭処理の条件を表２に示した。
【００３０】
【表２】

【００３１】
このようにして得られたＨ形鋼の機械的性質を表３に示した。
【００３２】
【表３】

【００３３】
このように、本発明による鋼組成と製造方法の両者の条件が全て満足された時に表３に示すような、十分な強度、靱性、表層部硬度を有する高摩擦継ぎ手用鋼材の生産が可能になる。
【００３４】
なお、本発明が対象とする圧延形鋼は、上記実施例のＨ形鋼に限らずＩ形鋼、山形鋼、溝形鋼、不等辺不等厚山形鋼等のフランジを有する形鋼にも適用できることは勿論である。
【００３５】
【発明の効果】
以上述べたように、本発明は、建造物の構造部材、特に、建造物の接合部材として使用される高張力圧延形鋼から成形されるスプリットＴ形鋼、継ぎ手用圧延鋼板などの継ぎ手用部材を低コストで、しかも簡易な製造方法で提供できることが可能になる。
【図面の簡単な説明】
【図１】スプリットＴ継ぎ手を示す図。
【図２】従来の鋼材における板厚方向の硬度分布を示す図。
【図３】鋼材表層部における内部酸化層および脱炭α層生成による合金元素の濃度分布を示す図。
【図４】本発明による合金元素の鋼材表層部への濃化の状態を示す図。
【図５】本発明による合金元素添加による表面硬度上昇を示す図。
【図６】スラブ加熱温度および熱延仕上げ温度によるシャルピー衝撃値の変化を示す図。
【図７】本発明において使用されるユニバーサル圧延装置列を示す図。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a structural member of a building, and more particularly to a member for a joint such as a split T-shaped steel formed from a high-tensile rolled section steel used as a joint member of a building, a rolled steel sheet for a joint, and a method for manufacturing the same. It is.
[0002]
[Prior art]
Steel materials used for building columns are required to have higher tensile strength, higher toughness, lower yield ratio, and higher reliability of welded joints due to the super-high building and stricter safety standards. It has been. In order to satisfy such required characteristics, conventionally, heat treatment such as normalizing treatment has been performed after the end of rolling. However, as a matter of course, the manufacturing cost increases due to the addition of this heat treatment process, so the development of a shape steel and its manufacturing method with a new alloy design that can provide high-performance material characteristics and weld joint characteristics as rolled. The need for
[0003]
Rolled H-section steel is often used as the shape steel material described above, but when H-section steel is manufactured by universal rolling, the rolling conditions (rolling temperature, rolling reduction, etc.) are limited and the shape is reduced. Due to the peculiarities of the above, there are differences in the rolling finishing temperature, rolling reduction, and cooling rate at each part of the web, flange, and fillet. As a result, variations in strength, ductility, and toughness occur between the portions, and for example, a portion that does not satisfy the standard such as a rolled steel material for welded structure (JIS G3106) occurs. Further, since high temperature rolling is directed to obtain dimensional accuracy of the product by rolling shaping, the thick flange portion becomes high temperature rolling, and the steel material cooling after the rolling is also gradually cooled. As a result, the microstructure becomes coarse and the strength and toughness decrease.
[0004]
On the other hand, there is TMCP (Thermo-Mechanical-Control Process) as a microstructure refinement method in the rolling process. However, because rolling conditions are limited in shape steel rolling, rolling at low temperature and large pressure like TMCP in steel materials. Application is difficult. Further, in the field of thick steel plates, techniques disclosed in, for example, Japanese Patent Publication Nos. 62-50548 and 62-54862 have been proposed for producing high-strength and high-toughness steel using the precipitation effect of VN. However, when these methods are applied to the manufacture of joint members targeted by the present invention, high-carbon island-like martensite is generated in the bainite structure to be produced because it contains a high concentration of solute N. However, there is a problem that it is difficult to clear the standard value due to a significant decrease in toughness.
[0005]
Furthermore, for the joining of pillars and beams in flange-shaped steel, for example H-shaped steel, T-shaped cast steel members or thick steel plates with normal strength and toughness are used as the joining parts. A so-called diaphragm joint, which is welded and joined with high-strength bolts, must be constructed in advance, or a method of constructing the steel frame during assembly has to be adopted. In the Great Hanshin Earthquake and the Northridge Earthquake, there is a fact that the destruction of the steel structure originated from this weld defect. Also, due to the lack of reliability of welded joints, a method has been adopted in which columns and beams are mechanically joined to each other by bolt joining via a T-shaped steel joint without welding (FIG. 1). However, in order to realize the above-described joint method, it is necessary to develop a T-shaped steel having a higher coefficient of friction that is surface hardened with higher strength.
[0006]
[Problems to be solved by the invention]
The present invention has been made to solve the above problems, and is a structural member of a building, in particular, a split T-shaped steel formed from a high-tensile rolled steel used as a joining member of a building, and a rolled steel plate for a joint. And the like, and a manufacturing method thereof.
[0007]
[Means for Solving the Problems]
The present invention is a steel material used as a member for a joint such as a split T-shaped steel or a rolled steel sheet for a joint formed from a high-tensile rolled section steel used as a joining member of the above-mentioned building. Suppressing the formation of the internal oxide layer, which is the cause, adding Cu and Ni, which are harder to oxidize than Fe, increasing the surface hardness by concentrating these in the surface layer when heating the slab, and adding Cr Thus, the present invention succeeds in obtaining a steel material for a high-friction joint having a hardened layer in the steel material surface layer portion by suppressing grain boundary oxidation and applying decarburization suppression and carburizing treatment. The summary is as follows.
(1) By weight%
C: 0.10 to 0.30%,
Si: ≦ 0.1%,
Mn: ≦ 1.6%
Al: ≦ 0.10%,
Cu: 0.1 to 1.5%,
Ni: 0.1 to 1.5%,
Cr: 0.1 to 0.5%,
Mo: ≦ 0.7%,
N: 0.001 to 0.010%
Further,
Ti: 0.005 to 0.025%,
Nb: 0.005 to 0.10%,
V: 0.01-0.20%,
B: 0.0003 to 0.0030%
Mg: 0.0001 to 0.010%,
Ca: 0.0005 to 0.0050%,
REM: 0.0005 to 0.010%
Any one of or two or more of the above, the steel for construction consisting of the balance Fe and inevitable impurities, the internal oxide layer and the decarburized layer are within 0.2 mm from the steel surface, 0.2 from the surface layer A steel material for a high friction joint having a Vickers hardness Hv of more than 420 at a hardened part having a depth of 0.5 mm and a Charpy absorbed energy at 0 ° C. of the hardened part and the base material of 27 J or more. .
(2) By weight%
C: 0.20 to 0.40%,
Si: ≦ 0.1%,
Mn: ≦ 1.6%
Al: ≦ 0.10%,
Cu: 0.1 to 1.5%,
Ni: 0.1 to 1.5%,
Cr: 0.1 to 0.5%,
Mo: ≦ 0.7%,
N: 0.001 to 0.010%
Further,
Ti: 0.005 to 0.025%,
Nb: 0.005 to 0.10%,
V: 0.01-0.20%,
B: 0.0003 to 0.0030%
Mg: 0.0001 to 0.010%,
Ca: 0.0005 to 0.0050%,
REM: 0.0005 to 0.010%
Any one of or two or more of the above, the steel for construction consisting of the balance Fe and inevitable impurities, the internal oxide layer and the decarburized layer are within 0.2 mm from the steel surface, 0.2 from the surface layer A steel material for a high friction joint having a Vickers hardness Hv of more than 520 in a hardened portion having a depth of 0.5 mm and a Charpy absorbed energy at 0 ° C. of the hardened portion and the base material of 27 J or more. .
(3) By weight%
C: 0.10 to 0.30%,
Si: ≦ 0.1%,
Mn: ≦ 1.6%
Al: ≦ 0.10%,
Cu: 0.1 to 1.5%,
Ni: 0.1 to 1.5%,
Cr: 0.1 to 0.5%,
Mo: ≦ 0.7%,
N: 0.001 to 0.010%
Further,
Ti: 0.005 to 0.025%,
Nb: 0.005 to 0.10%,
V: 0.01-0.20%,
B: 0.0003 to 0.0030%
Mg: 0.0001 to 0.010%,
Ca: 0.0005 to 0.0050%,
REM: 0.0005 to 0.010%
Any one or two or more of the above , the decarburization inhibitor is applied to the surface of the slab composed of the balance Fe and inevitable impurities, or carburized, and then in a temperature range of 1100 to 1300 ° C. After reheating, hot rolling is started, the hot rolling is finished at 700 to 900 ° C., and the inner oxide layer and decarburized layer are reheated from the surface to a depth of 0.5 mm above the Ac ₃ point temperature and rapidly cooled. It is within 0.2 mm from the surface, Vickers hardness Hv: 420 is exceeded at the cured portion having a depth of 0.2 to 0.5 mm from the surface layer, and the Charpy absorbed energy at 0 ° C. of the cured portion and the base material is The manufacturing method of the steel material for high-friction joints characterized by having 27J or more.
(4) By weight%
C: 0.20 to 0.40%,
Si: ≦ 0.1%,
Mn: ≦ 1.6%
Al: ≦ 0.10%,
Cu: 0.1 to 1.5%,
Ni: 0.1 to 1.5%,
Cr: 0.1 to 0.5%,
Mo: ≦ 0.7%,
N: 0.001 to 0.010%
Further,
Ti: 0.005 to 0.025%,
Nb: 0.005 to 0.10%,
V: 0.01-0.20%,
B: 0.0003 to 0.0030%
Mg: 0.0001 to 0.010%,
Ca: 0.0005 to 0.0050%,
REM: 0.0005 to 0.010%
Any one or two or more of the above , the decarburization inhibitor is applied to the surface of the slab composed of the balance Fe and inevitable impurities, or carburized, and then in a temperature range of 1100 to 1300 ° C. After reheating, hot rolling is started, the hot rolling is finished at 700 to 900 ° C., and the inner oxide layer and decarburized layer are reheated from the surface to a depth of 0.5 mm above the Ac ₃ point temperature and rapidly cooled. It is within 0.2 mm from the surface, the Vickers hardness Hv is more than 520 in the hardened portion having a depth of 0.2 to 0.5 mm from the surface layer, and the Charpy absorbed energy at 0 ° C. of the hardened portion and the base material is The manufacturing method of the steel material for high-friction joints characterized by having 27J or more.
(5) % by weight
C: 0.10 to 0.30%,
Si: ≦ 0.1%,
Mn: ≦ 1.6%
Al: ≦ 0.10%,
Cu: 0.1 to 1.5%,
Ni: 0.1 to 1.5%,
Cr: 0.1 to 0.5%,
Mo: ≦ 0.7%,
N: 0.001 to 0.010%
Further,
Ti: 0.005 to 0.025%,
Nb: 0.005 to 0.10%,
V: 0.01-0.20%,
B: 0.0003 to 0.0030%
Mg: 0.0001 to 0.010%,
Ca: 0.0005 to 0.0050%,
REM: 0.0005 to 0.010%
Any one or two or more of the above , the decarburization inhibitor is applied to the surface of the slab composed of the balance Fe and inevitable impurities, or carburized, and then in a temperature range of 1100 to 1300 ° C. After reheating, the hot rolling is started, the hot rolling is finished at 700 to 900 ° C., and further carburizing treatment is performed. Then, the surface is reheated to a depth of 0.5 mm from the surface to the Ac ₃ point temperature or more and rapidly cooled. The internal oxide layer and the decarburized layer are within 0.2 mm from the steel surface, the Vickers hardness Hv exceeds 420 at a hardened portion having a depth of 0.2 to 0.5 mm from the surface layer, and the hardened portion and the base material. A method for producing a steel material for a high-friction joint, wherein the Charpy absorbed energy at 0 ° C. is 27 J or more.
(6) % by weight
C: 0.20 to 0.40%,
Si: ≦ 0.1%,
Mn: ≦ 1.6%
Al: ≦ 0.10%,
Cu: 0.1 to 1.5%,
Ni: 0.1 to 1.5%,
Cr: 0.1 to 0.5%,
Mo: ≦ 0.7%,
N: 0.001 to 0.010%,
Further,
Ti: 0.005 to 0.025%,
Nb: 0.005 to 0.10%,
V: 0.01-0.20%,
B: 0.0003 to 0.0030%
Mg: 0.0001 to 0.010%,
Ca: 0.0005 to 0.0050%,
REM: 0.0005 to 0.010%
Any one or two or more of the above , the decarburization inhibitor is applied to the surface of the slab composed of the balance Fe and inevitable impurities, or carburized, and then in a temperature range of 1100 to 1300 ° C. After reheating, the hot rolling is started, the hot rolling is finished at 700 to 900 ° C., and further carburizing treatment is performed. Then, the surface is reheated to a depth of 0.5 mm from the surface to the Ac ₃ point temperature or more and rapidly cooled. The internal oxide layer and the decarburized layer are within 0.2 mm from the steel surface, the Vickers hardness Hv exceeds 520 at the hardened portion having a depth of 0.2 to 0.5 mm from the surface layer, and the hardened portion and the base material. A method for producing a steel material for a high-friction joint, wherein the Charpy absorbed energy at 0 ° C. is 27 J or more.
(7) % by weight
C: 0.10 to 0.30%,
Si: ≦ 0.1%,
Mn: ≦ 1.6%
Al: ≦ 0.10%,
Cu: 0.1 to 1.5%,
Ni: 0.1 to 1.5%,
Cr: 0.1 to 0.5%,
Mo: ≦ 0.7%,
N: 0.001 to 0.010%
Further,
Ti: 0.005 to 0.025%,
Nb: 0.005 to 0.10%,
V: 0.01-0.20%,
B: 0.0003 to 0.0030%
Mg: 0.0001 to 0.010%,
Ca: 0.0005 to 0.0050%,
REM: 0.0005 to 0.010%
After reheating the slab containing any one or more of the above, and the balance consisting of the remaining Fe and inevitable impurities to a temperature range of 1100 to 1300 ° C., hot rolling is started, and hot rolling is performed at 700 to 900 ° C. After finishing the carburizing treatment, the inner oxide layer and decarburized layer are within 0.2 mm from the surface of the steel material and reheated to a depth of 0.5 mm from the surface above the Ac ₃ point temperature and rapidly cooled. High friction characterized by having a Vickers hardness Hv of more than 420 at a hardened portion having a depth of 0.2 to 0.5 mm, and having a Charpy absorbed energy at 0 ° C. of the hardened portion and the base material of 27 J or more. A method of manufacturing steel for joints.
(8) % by weight
C: 0.20 to 0.40%,
Si: ≦ 0.1%,
Mn: ≦ 1.6%
Al: ≦ 0.10%,
Cu: 0.1 to 1.5%,
Ni: 0.1 to 1.5%,
Cr: 0.1 to 0.5%,
Mo: ≦ 0.7%,
N: 0.001 to 0.010%,
Further,
Ti: 0.005 to 0.025%,
Nb: 0.005 to 0.10%,
V: 0.01-0.20%,
B: 0.0003 to 0.0030%
Mg: 0.0001 to 0.010%,
Ca: 0.0005 to 0.0050%,
REM: 0.0005 to 0.010%
Any one or two or more of
After reheating the slab composed of the remaining Fe and unavoidable impurities to a temperature range of 1100 to 1300 ° C., hot rolling was started, hot rolling was finished at 700 to 900 ° C., carburizing treatment was performed, and then deep from the surface. reheated to quenched until 0.5mm above Ac ₃ point temperature is within 0.2mm from the internal oxide layer and a decarburized layer surface of the steel material, curing portion of the depth 0.2~0.5mm from the surface layer And a Vickers hardness Hv of more than 520, and a Charpy absorbed energy at 0 ° C. of the hardened portion and the base material is 27 J or more.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
In the split T-shaped steel having high friction characteristics, in order to obtain the surface hardness satisfying the high friction coefficient, the surface is quenched and the surface hardness Hv ≧ 420, and further the surface hardness Hv ≧ 520 is targeted. Even if quenching is performed, the target surface hardness cannot be obtained because the martensite transformation is not completely performed up to 0.5 mm from the surface. The reason for this is that the high temperature heating of the slab is caused by the presence of (MnSi) -O and a Mn thin band due to the formation of Mn oxide in the internal oxide layer approximately 0.5 mm thick from the surface. Grain boundary oxidation layer generated by increase of γ / α transformation point and generation of firelite by addition of Si, and in addition to this, decarburized α phase is generated from the surface to 0.5 mm, and a carbon-deficient layer exists. I found out that it was caused. In addition, as a result of intensive studies on the grain boundary oxidation mechanism of 60 kg class high-tensile H-section steel, the present inventors have found that the formation of an internal oxide layer and the formation of decarburized α-phase are the same as those of high-tensile H-section steel. There is a close relationship with the seam on the inner surface of the flange, and this seam acts as a starting point for corrosion and pitting corrosion and significantly impairs the weather resistance. It has also been clarified that wrinkles are formed in the inner surface strain concentration part and this is caused by the folding. As measures for preventing the occurrence of seam flaws, the present inventors have formed a grain boundary oxide layer on the slab surface by adding a trace element that contributes to the suppression of soot formation and its effect, and suppressed the formation and decarburization of the grain boundary oxide layer. Research was conducted on the suppression of α-phase formation.
[0009]
In order to observe the hardness change in the surface layer portion of 55 kg class high tensile H-shaped steel to which ordinary Cr and Mo are added, the present inventors heated the slab having the above components at 1280 ° C., and then passed 9 passes. Then, a steel material having a plate thickness of 22 mm was manufactured at a hot rolling finishing temperature of 960 ° C., the surface layer portion was shot blasted, induction-hardened at a temperature of 920 ° C., and the hardness was measured from the outermost surface of the steel material toward the center. As a result, as shown in FIG. 2, it was found that the hardness of the target Hv: 420 or higher was approached at a site of about 1 mm from the surface layer, but the hardness did not increase on the surface layer side. Furthermore, this cause was investigated and the concentration distribution of the alloy elements in the internal oxide layer was observed. As a result, as shown in FIG. 3, it was found that a dealloyed layer was formed by internal oxidation of Mn and Si, and in addition to this, a decarburized α phase was generated.
[0010]
In order to improve the above problems, it is conceived to reduce the thickness of the internal oxide layer and to generate a concentrated alloy layer on the internal oxide layer. First, the thickness of the internal oxide layer increases due to grain boundary oxidation, and the surface quenching curability decreases. In order to suppress this, it is effective to reduce Si (to prevent the formation of grain boundary firelite) and to add Cr, which is an element that is more easily oxidized than Mn. In addition, Cu, Ni, and Mo, which are harder to oxidize than iron, are concentrated on the internal oxide layer by high-temperature oxidation, thereby improving surface quenching curability. In addition, since the formation of decarburized α phase is a phenomenon that occurs inevitably during slab high temperature heating, a decarburization inhibitor is applied to the surface of the slab during slab heating, or carburizing treatment is applied to enrich the carbon. It is possible to ensure the hardness in the outermost layer portion of the steel material by performing.
[0011]
That is, in the present invention, when Cu, Ni, which is harder to oxidize than Fe in order to increase the hardness of the steel surface, and further Cr in order to suppress grain boundary oxidation, as shown in FIG. It was found that Cu and Ni were concentrated on the surface during slab heating. FIG. 4 shows a state observed by CMA analysis. If there is such Cu and Ni surface enrichment, it is possible to ensure an improvement in hardenability accompanying an increase in the hardness of the portion from the steel surface layer to 0.5 mm. This state of surface hardness increase is shown in FIG. FIG. 5 shows that the amount of Cu and Ni added depends on the distance from the steel surface layer in three types of 1.0%, 0.5% and 0.3% for both Cu and Ni and in the state of free addition of Cu and Ni. As can be seen from FIG. 5, when the amount of Cu and Ni is appropriately added, it is 0.2 from the steel surface layer portion compared to the case of free addition of Cu and Ni. An increase in hardness can be reliably obtained even at a site of ˜0.5 mm.
[0012]
The mechanism by which Cr addition suppresses the formation of grain boundary oxidation phase is as follows: 1) Oxygen diffuses inward from the surface through the γ grain boundary, but Cr is easier to oxidize than Fe, so it produces Cr oxide. 2) Cr ₂ O ₃ and FeO easily produce FeO · Cr ₂ O ₃ (spinel), and this spinel is thought to require a large amount of cation vacancies. In addition, the Cr and Fe ions diffusing through the cation vacancies and oxygen diffusing inward through the γ grain boundaries are combined to form an oxide, so that oxygen grain boundary diffusion is inhibited. 3) By generating spinel, it is considered that generation of low melting point firelite is suppressed and a grain boundary oxide layer is not formed.
[0013]
Furthermore, in order to suppress the formation of the decarburized α phase as shown in FIG. 2, the carbon enrichment is performed by applying a decarburization inhibitor on the surface of the slab during slab heating or by performing a carburizing treatment. It is possible to secure the hardness in the outermost layer part of the steel material by carrying out the process. As this specific method, magnesia, a mixture of magnesia and alumina is effective as a decarburization inhibitor, and slab is used as a carburizing process. It is preferable to fill the heating furnace with methane, propane, butane, dilution gas or the like as a raw material gas and perform carburizing treatment in a carburizing gas atmosphere. Further, carburizing treatment may be performed after rolling and before reheating.
[0014]
Thus, as a result of searching for the above-mentioned factors for improving the surface layer hardness of the steel material from the viewpoint of the manufacturing process, the present invention adds Cu and Ni, and concentrates Cu and Ni in the steel surface layer portion during slab heating. In addition, it suppresses grain boundary oxidation by adding Cr, and further applies a decarburization inhibitor to the surface of the slab or suppresses carburizing treatment to suppress the formation of a decarburized α phase that occurs during slab heating. As a result of carbon enrichment, a hardness increase of 0.2 to 0.5 mm from the surface layer is ensured such that the hardness is Hv: 420 or more, and depending on the steel material component, Hv: 520 or more.
[0015]
Next, the alloy component range of the steel material for high friction joints according to the present invention and the manufacturing method thereof will be described in detail.
Carbon (C) is added in the range of 0.10 to 0.40% in order to ensure the yield strength, tensile strength and high hardness of the base material of the high-tensile H-shaped steel. In particular, when the steel surface layer hardness is Hv: 420 or more, the C content is preferably in the range of 0.10 to 0.30%. When hardness is further required, Hv: 520 or more is particularly ensured. In this case, the C content is preferably in the range of 0.20 to 0.40%.
[0016]
Silicon (Si) is necessary for securing the strength of the base metal and preliminary deoxidation of the molten steel. However, addition of 0.1% or more forms MnSi.O and promotes an increase in internal oxide layer and grain boundary oxidation. Since the tendency to form 2SiO ₂ FeO is intensified, it is preferably as small as possible, and the upper limit is made 0.1%.
Manganese (Mn) is an element effective in securing the strength of the base metal, but increases the allowable concentration for toughness and cracking of the base material and welds, and also generates MnS, which is the starting point of pitting corrosion and significantly improves the weather resistance. In order to inhibit, the upper limit is made 1.6%.
[0017]
Chromium (Cr) is an important element in the present invention. By forming FeO · Cr ₂ O ₃ spinel, low melting point firelite is not formed and grain boundary oxidation is not formed. From the standpoint of increase, at least 0.1% is necessary, but excessive addition exceeding 0.5% forms Cr.O and forms an internal oxide layer, so the upper limit is 0.5%. And
[0018]
Aluminum (Al) is a strong deoxidizing element, and is added with an upper limit of 0.10% for deoxidation, cleaning of steel, precipitating AlN, fixing solid solution N, and improving toughness. However, when Ca, Mg, REM, etc. are added and these fine oxides are actively used, the addition of a large amount of Al inhibits the formation of fine oxides such as Ca, Mg, REM, etc. Less is preferable.
[0019]
Next, in the present invention, addition of Ni and Cu is essential. Both of these elements are important elements that increase the strength of the base material and form a concentrated layer on the surface of the steel material during heating, both as elements for enhancing the strength. The addition amounts of Ni and Cu are each in the range of 0.1 to 1.5%. Mo is an element effective for the strength of the base metal and the concentration of the surface layer alloy. However, excessive addition precipitates Mo carbides and saturates the effect of improving hardenability as solid solution Mo, so it is necessary to add 0.7% or less. is there.
[0020]
In the present invention, it is effective to include an appropriate amount of any one or more of Ti, Nb, V, and B as a further additive element. Niobium (Nb) and vanadium (V) are added in amounts of Nb: 0.005 to 0.10% and V: 0.01 to 0.20% for the purpose of increasing the hardenability and increasing the strength, respectively. The However, when Nb exceeds 0.10% and V exceeds 0.20%, the precipitation amount of Nb carbonitride or V carbonitride increases, and the effect as solid solution Nb or solid solution V is increased. Therefore, Nb: 0.10%, V: 0.20% are set as upper limits, and the lower limit is set to Nb: 0.005%, V: 0.01 from the viewpoint of ensuring hardenability and strength of the base material. %.
[0021]
Titanium (Ti) precipitates TiN and reduces the solid solution N to suppress the formation of island martensite, and the finely precipitated TiN contributes to the refinement of the γ phase. These effects are exhibited by addition of 0.005% or more, and the action of these Ti refines the structure and improves the strength and toughness. However, excessive addition of 0.025% or more causes TiC to precipitate and deteriorates the toughness of the base metal and the weld heat affected zone due to the precipitation effect, so the upper limit was made 0.025%.
[0022]
Boron (B) is an element important for the hardenability of the steel material, and is added in an amount of 0.0003 to 0.0030%.
Nitrogen (N) forms nitrides and contributes to crystallization of γ grains, but excessive solute N deteriorates toughness, so that the N content is added in an amount of 0.001 to 0.010%.
Mg, Ca, REM is a starting point for pitting corrosion, and for the purpose of preventing the formation of MnS, which lowers the weather resistance, to form a sulfide of Mg, Ca, REM with high temperature stability and to fix S It is added. Mg reduces the Mg content concentration by alloying, suppresses the deoxidation reaction during addition to molten steel, improves safety during addition and improves the yield of Mg, and further generates fine oxides of MgO. Is added in an amount of 0.0001 to 0.010% for the purpose of contributing to improvement of strength and toughness of the steel by finely dispersing. Further, Ca and REM are added in the range of 0.0005 to 0.0050% and 0.0005 to 0.010%, respectively, for the purpose of preventing slab cracking.
[0023]
The reason why the internal oxide layer and the decarburized layer are defined to be within 0.2 mm from the surface of the steel material is that the high hardness portion is at a depth of 0.2 to 0.5 mm from the surface when used as a high friction joint. Because it is necessary. The reason why the hardness at this position is Hv: 420 or higher, or Hv: 520 or higher is to improve the joint performance by forming protrusions on the surface and biting the protrusions into the beam steel material. Therefore, the hardened layer is harder and thicker, but the effect is enhanced. As a result of measuring the necessary high friction coefficient, the surface hardness Hv: 420 or more in the case of parallel protrusions, and the hardness exceeding Hv: 520 or more in the case of concentric protrusions. Because it was necessary.
[0024]
Next, the manufacturing method in this invention is demonstrated.
An important process in the present invention is that it is necessary to perform high-temperature slab heating at a slab heating temperature of 1100 to 1300 ° C. In the above-described high-temperature slab heating, a concentrated layer of Ni, Cu, and Mo on the internal oxide layer is generated in the steel surface layer portion by high-temperature heat oxidation. The reason why Ni, Cu, and Mo are concentrated on the internal oxide layer in the high-temperature heat oxidation is that the formation energy of these metal oxides is higher than that of iron oxide (FeO), so that no oxide can be generated. This is because it is left behind and thickens. As a result of heating at 1250 ° C., a concentrated layer of Ni, Cu, and Mo is formed with a thickness of about 30 μm. This is stretched by rolling and thins in proportion to the stretch ratio. That is, when the thickness becomes 1/10, the thickness is almost 3 μm.
[0025]
Further, since the joint member targeted by the present invention is used as a structural member for construction, the toughness requires a Charpy impact value of 27 J or more.
FIG. 6 shows the relationship between the slab heating temperature / hot-rolling finishing temperature and the Charpy impact value for slabs having four different steel compositions. As can be seen from FIG. 6, toughness, that is, Charpy impact value is improved by lowering the slab heating temperature and hot rolling finishing temperature. This is to achieve the refinement of the structure in the recrystallization / non-recrystallization temperature range of austenite by controlled rolling that controls the rolling temperature and the rolling reduction.
[0026]
Further, in the present invention, in order to suppress the formation of the decarburized α phase and ensure the hardness in the outermost layer portion of the steel material, a decarburization inhibitor is applied to the surface of the slab during slab heating, or carburization is performed. The carbon is enriched by applying the treatment, but magnesia, a mixture of magnesia and alumina is effective as a decarburization inhibitor, and methane, propane, butane, dilution gas, etc. as raw material gas in the slab heating furnace as carburizing treatment And carburizing treatment is preferably performed in a carburizing gas atmosphere. The carburizing treatment may be performed after rolling and before reheating.
[0027]
【Example】
<Example 1>
As a prototype H-shaped steel, steel having the chemical composition values shown in Table 1 is melted in a converter, and after adding an alloy, preliminary deoxidation treatment is performed, and after adjusting the oxygen concentration of the molten steel, Ca, Mg alloy, and REM are added. It was added and cast into a 250 to 300 mm thick slab by continuous casting.
[0028]
[Table 1]

[0029]
The cooling of the slab was controlled by selecting the amount of water in the secondary cooling zone below the mold and the drawing speed of the slab. The slab thus obtained was heated, subjected to a rough rolling process, rolled into an H-section steel by a universal rolling apparatus array shown in FIG. 7, and further reheated and rapidly cooled to increase the surface hardness. The conditions of heating, rolling, decarburization inhibitor application, and carburizing treatment at this time are shown in Table 2.
[0030]
[Table 2]

[0031]
Table 3 shows the mechanical properties of the H-shaped steel thus obtained.
[0032]
[Table 3]

[0033]
Thus, when all the conditions of both the steel composition and the manufacturing method according to the present invention are satisfied, it is possible to produce a steel material for a high friction joint having sufficient strength, toughness, and surface layer hardness as shown in Table 3. Become.
[0034]
Note that the rolled shape steel targeted by the present invention is not limited to the H-shape steel of the above-described embodiment, but is also a shape steel having a flange such as an I-shape steel, an angle steel, a groove shape steel, an unequal side unequal thickness angle steel. Of course, it can be applied.
[0035]
【The invention's effect】
As described above, the present invention relates to a structural member of a building, in particular, a member for a joint such as a split T-shaped steel formed from a high-tensile rolled section steel used as a joint member for a building, a rolled steel sheet for a joint, etc. Can be provided at a low cost and with a simple manufacturing method.
[Brief description of the drawings]
FIG. 1 shows a split T joint.
FIG. 2 is a diagram showing a hardness distribution in a plate thickness direction in a conventional steel material.
FIG. 3 is a view showing a concentration distribution of an alloy element due to generation of an internal oxide layer and a decarburized α layer in a steel surface layer portion.
FIG. 4 is a view showing a state of concentration of an alloy element according to the present invention on a steel surface layer portion.
FIG. 5 is a graph showing an increase in surface hardness due to addition of alloy elements according to the present invention.
FIG. 6 is a graph showing a change in Charpy impact value according to slab heating temperature and hot rolling finishing temperature.
FIG. 7 is a diagram showing a universal rolling device row used in the present invention.

Claims (8)

% By weight
C: 0.10 to 0.30%,
Si: ≦ 0.1%,
Mn: ≦ 1.6%
Al: ≦ 0.10%,
Cu: 0.1 to 1.5%,
Ni: 0.1 to 1.5%,
Cr: 0.1 to 0.5%,
Mo: ≦ 0.7%,
N: 0.001 to 0.010%
Further,
Ti: 0.005 to 0.025%,
Nb: 0.005 to 0.10%,
V: 0.01-0.20%,
B: 0.0003 to 0.0030%
Mg: 0.0001 to 0.010%,
Ca: 0.0005 to 0.0050%,
REM: 0.0005 to 0.010%
Any one of or two or more of the above, the steel for construction consisting of the balance Fe and inevitable impurities, the internal oxide layer and the decarburized layer are within 0.2 mm from the steel surface, 0.2 from the surface layer A steel material for a high friction joint having a Vickers hardness Hv of more than 420 at a hardened part having a depth of 0.5 mm and a Charpy absorbed energy at 0 ° C. of the hardened part and the base material of 27 J or more. . % By weight
C: 0.20 to 0.40%,
Si: ≦ 0.1%,
Mn: ≦ 1.6%
Al: ≦ 0.10%,
Cu: 0.1 to 1.5%,
Ni: 0.1 to 1.5%,
Cr: 0.1 to 0.5%,
Mo: ≦ 0.7%,
N: 0.001 to 0.010%
Further,
Ti: 0.005 to 0.025%,
Nb: 0.005 to 0.10%,
V: 0.01-0.20%,
B: 0.0003 to 0.0030%
Mg: 0.0001 to 0.010%,
Ca: 0.0005 to 0.0050%,
REM: 0.0005 to 0.010%
Any one of or two or more of the above, the steel for construction consisting of the balance Fe and inevitable impurities, the internal oxide layer and the decarburized layer are within 0.2 mm from the steel surface, 0.2 from the surface layer A steel material for a high friction joint having a Vickers hardness Hv of more than 520 in a hardened portion having a depth of 0.5 mm and a Charpy absorbed energy at 0 ° C. of the hardened portion and the base material of 27 J or more. . % By weight
C: 0.10 to 0.30%,
Si: ≦ 0.1%,
Mn: ≦ 1.6%
Al: ≦ 0.10%,
Cu: 0.1 to 1.5%,
Ni: 0.1 to 1.5%,
Cr: 0.1 to 0.5%,
Mo: ≦ 0.7%,
N: 0.001 to 0.010%
Further,
Ti: 0.005 to 0.025%,
Nb: 0.005 to 0.10%,
V: 0.01-0.20%,
B: 0.0003 to 0.0030%
Mg: 0.0001 to 0.010%,
Ca: 0.0005 to 0.0050%,
REM: 0.0005 to 0.010%
Any one or two or more of the above , the decarburization inhibitor is applied to the surface of the slab composed of the balance Fe and inevitable impurities, or carburized, and then in a temperature range of 1100 to 1300 ° C. After reheating, hot rolling is started, the hot rolling is finished at 700 to 900 ° C., and the inner oxide layer and decarburized layer are reheated from the surface to a depth of 0.5 mm above the Ac ₃ point temperature and rapidly cooled. It is within 0.2 mm from the surface, Vickers hardness Hv: 420 is exceeded at the cured portion having a depth of 0.2 to 0.5 mm from the surface layer, and the Charpy absorbed energy at 0 ° C. of the cured portion and the base material is The manufacturing method of the steel material for high-friction joints characterized by having 27J or more. % By weight
C: 0.20 to 0.40%,
Si: ≦ 0.1%,
Mn: ≦ 1.6%
Al: ≦ 0.10%,
Cu: 0.1 to 1.5%,
Ni: 0.1 to 1.5%,
Cr: 0.1 to 0.5%,
Mo: ≦ 0.7%,
N: 0.001 to 0.010%,
Further,
Ti: 0.005 to 0.025%,
Nb: 0.005 to 0.10%,
V: 0.01-0.20%,
B: 0.0003 to 0.0030%
Mg: 0.0001 to 0.010%,
Ca: 0.0005 to 0.0050%,
REM: 0.0005 to 0.010%
Any one or two or more of the above , the decarburization inhibitor is applied to the surface of the slab composed of the balance Fe and inevitable impurities, or carburized, and then in a temperature range of 1100 to 1300 ° C. After reheating, hot rolling is started, the hot rolling is finished at 700 to 900 ° C., and the inner oxide layer and decarburized layer are reheated from the surface to a depth of 0.5 mm above the Ac ₃ point temperature and rapidly cooled. It is within 0.2 mm from the surface, the Vickers hardness Hv is more than 520 in the hardened portion having a depth of 0.2 to 0.5 mm from the surface layer, and the Charpy absorbed energy at 0 ° C. of the hardened portion and the base material is The manufacturing method of the steel material for high-friction joints characterized by having 27J or more. % By weight
C: 0.10 to 0.30%,
Si: ≦ 0.1%,
Mn: ≦ 1.6%
Al: ≦ 0.10%,
Cu: 0.1 to 1.5%,
Ni: 0.1 to 1.5%,
Cr: 0.1 to 0.5%,
Mo: ≦ 0.7%,
N: 0.001 to 0.010%
Further,
Ti: 0.005 to 0.025%,
Nb: 0.005 to 0.10%,
V: 0.01-0.20%,
B: 0.0003 to 0.0030%
Mg: 0.0001 to 0.010%,
Ca: 0.0005 to 0.0050%,
REM: 0.0005 to 0.010%
Any one or two or more of the above , the decarburization inhibitor is applied to the surface of the slab composed of the balance Fe and inevitable impurities, or carburized, and then in a temperature range of 1100 to 1300 ° C. After reheating, the hot rolling is started, the hot rolling is finished at 700 to 900 ° C., and further carburizing treatment is performed. Then, the surface is reheated to a depth of 0.5 mm from the surface to the Ac ₃ point temperature or more and rapidly cooled. The internal oxide layer and the decarburized layer are within 0.2 mm from the steel surface, the Vickers hardness Hv exceeds 420 at a hardened portion having a depth of 0.2 to 0.5 mm from the surface layer, and the hardened portion and the base material. A method for producing a steel material for a high-friction joint, wherein the Charpy absorbed energy at 0 ° C. is 27 J or more. % By weight
C: 0.20 to 0.40%,
Si: ≦ 0.1%,
Mn: ≦ 1.6%
Al: ≦ 0.10%,
Cu: 0.1 to 1.5%,
Ni: 0.1 to 1.5%,
Cr: 0.1 to 0.5%,
Mo: ≦ 0.7%,
N: 0.001 to 0.010%
Further,
Ti: 0.005 to 0.025%,
Nb: 0.005 to 0.10%,
V: 0.01-0.20%,
B: 0.0003 to 0.0030%
Mg: 0.0001 to 0.010%,
Ca: 0.0005 to 0.0050%,
REM: 0.0005 to 0.010%
Any one or two or more of the above , the decarburization inhibitor is applied to the surface of the slab composed of the balance Fe and inevitable impurities, or carburized, and then in a temperature range of 1100 to 1300 ° C. After reheating, the hot rolling is started, the hot rolling is finished at 700 to 900 ° C., and further carburizing treatment is performed. Then, the surface is reheated to a depth of 0.5 mm from the surface to the Ac ₃ point temperature or more and rapidly cooled. The internal oxide layer and the decarburized layer are within 0.2 mm from the steel surface, the Vickers hardness Hv exceeds 520 at the hardened portion having a depth of 0.2 to 0.5 mm from the surface layer, and the hardened portion and the base material. A method for producing a steel material for a high-friction joint, wherein the Charpy absorbed energy at 0 ° C. is 27 J or more. % By weight
C: 0.10 to 0.30%,
Si: ≦ 0.1%,
Mn: ≦ 1.6%
Al: ≦ 0.10%,
Cu: 0.1 to 1.5%,
Ni: 0.1 to 1.5%,
Cr: 0.1 to 0.5%,
Mo: ≦ 0.7%,
N: 0.001 to 0.010%
Further,
Ti: 0.005 to 0.025%,
Nb: 0.005 to 0.10%,
V: 0.01-0.20%,
B: 0.0003 to 0.0030%
Mg: 0.0001 to 0.010%,
Ca: 0.0005 to 0.0050%,
REM: 0.0005 to 0.010%
After reheating the slab containing any one or more of the above, and the balance consisting of the remaining Fe and inevitable impurities to a temperature range of 1100 to 1300 ° C., hot rolling is started, and hot rolling is performed at 700 to 900 ° C. After finishing the carburizing treatment, the inner oxide layer and decarburized layer are within 0.2 mm from the surface of the steel material and reheated to a depth of 0.5 mm from the surface above the Ac ₃ point temperature and rapidly cooled. High friction characterized by having a Vickers hardness Hv of more than 420 at a hardened portion having a depth of 0.2 to 0.5 mm, and having a Charpy absorbed energy at 0 ° C. of the hardened portion and the base material of 27 J or more. A method of manufacturing steel for joints. % By weight
C: 0.20 to 0.40%,
Si: ≦ 0.1%,
Mn: ≦ 1.6%
Al: ≦ 0.10%,
Cu: 0.1 to 1.5%,
Ni: 0.1 to 1.5%,
Cr: 0.1 to 0.5%,
Mo: ≦ 0.7%,
N: 0.001 to 0.010%
Further,
Ti: 0.005 to 0.025%,
Nb: 0.005 to 0.10%,
V: 0.01-0.20%,
B: 0.0003 to 0.0030%
Mg: 0.0001 to 0.010%,
Ca: 0.0005 to 0.0050%,
REM: 0.0005 to 0.010%
Any one or two or more of
After reheating the slab composed of the remaining Fe and unavoidable impurities to a temperature range of 1100 to 1300 ° C., hot rolling was started, hot rolling was finished at 700 to 900 ° C., carburizing treatment was performed, and then deep from the surface. reheated to quenched until 0.5mm above Ac ₃ point temperature is within 0.2mm from the internal oxide layer and a decarburized layer surface of the steel material, curing portion of the depth 0.2~0.5mm from the surface layer And a Vickers hardness Hv of more than 520, and a Charpy absorbed energy at 0 ° C. of the hardened portion and the base material is 27 J or more.

Images