TW200305650A - A high tensile strength steel excellent in high temperature and a method for producing the same - Google Patents

Abstract

The present invention relates to a method for producing a high tensile strength steel for a building structure (in the form of a steel sheet, a steel pipe, a section steel or a wire rod) to which low alloy carbon is added, the high tensile strength steel being excellent in high temperature strength during a relatively short span of about one hour in the temperature range from 600 DEG C to 800 DEG C and being used for a general structure in the field of building construction, civil engineering, an offshore structure, shipbuilding, a reservoir tank or the like. The present invention, more specifically, is a high tensile strength steel excellent in high temperature strength, characterized by: containing, in mass, not less than 0.005% to less than 0.08% C, not more than 0.5% Si, 0.1 to 1.6% Mn, not more than 0.02% P, not more than 0.01% S, 0.1 to 1.5% Mo, 0.03 to 0.3% Nb, not more than 0.025% Ti, 0.0005 to 0.003% B, not more than 0.06% Al, and not more than 0.006% N, with the balance consisting of Fe and unavoidable impurities; and satisfying the expression P ≥ -0.0029 x T+ 2.80 when the temperature of the steel T(DEG C) is within the range from 600 DEG C to 800 DEG C, wherein P is a stress drop ratio (a yield stress at a high temperature/a yield stress at the ordinary temperature) that is obtained by converting a yield stress at a high temperature into a dimensionless number by using a yield stress at the ordinary temperature.

Description

200305650 发明 Description of the invention (Invention description should be anti-ming: brief description of the technical field, prior technology, content, embodiments and drawings of the invention) [Invention_Technical Field] Technical Field The present invention relates to a method used in Construction, civil engineering, marine structures 5, shipbuilding, storage barrels and other general structures are above 600 ° C, 800. 〇The manufacturing method of high-tensile steel (steel plate, steel pipe, angle steel, wire) for building structures with excellent low-alloy carbon added within a range of less than 1 hour and a short period of time of about 1 hour. 10 Background technology

For example, in the fields of construction and civil engineering, steels standardized by JIS and the like are widely used as various steels for construction. In addition, the general steel used for building construction is reduced in strength from 35 ° (rc). Therefore, the allowable temperature is 550 ° c. 15 In other words, in order to ensure the construction of buildings, offices, residences, three-dimensional parking lots, etc. using the foregoing steel, Safety at the time of fire must be adequately covered by fire. In the construction-related laws, the temperature of the steel during the fire must not exceed 350 ° C. This is because the resistance of the aforementioned steel is about 35 (rc). The required strength is reduced to about 20 2/3 at room temperature. When building materials are constructed using steel, the fire-resistant coating is used before the temperature of the steel does not reach 350 C during fire. Therefore, compared with the cost of steel, the cost of fire-resistant coating works The construction cost has increased significantly. In order to solve the aforementioned problems, there have been inventions such as Japanese Patent Laid-Open Publication 200305650, Patent Description 2-77523, or Japanese Patent Publication No. 10-68044. Used at 600 ° C or higher It is generally called refractory steel. For example, the invention described in Japanese Patent Laid-Open Publication No. 2-77523 is disclosed at 600 ° C. Refractory steel with a high temperature strength of 2/3 (approximately 70%) of the room temperature drop strength. In other examples of inventions related to 600 ° C refractory steel, the drop strength at 600 ° C is also generally 2 of the room temperature drop strength. / 3 or more.

However, at present, there is no common criterion for setting the high temperature strength (ratio to the room temperature drop strength) of 700 ° C and 800 ° C refractory steel. For example, in Japanese Patent Laid-Open Publication 2-77523, a large amount of Mo and Nb 10 added steel can ensure that the endurance at 600 ° C is more than 70% of the endurance at room temperature, but there is no description of 700 ° C, 800 ° C endurance.

In addition, when the endurance at 600 ° C is about 70% of the endurance at room temperature, the amount of fire-resistant coating can be reduced. However, considering the problem of temperature rise during a fire, buildings that can be omitted are limited to open spaces such as three-dimensional parking lots or porches. 15, there are obvious restrictions on use when there is no refractory coating. In Japanese Patent Laid-Open Publication No. 10-68044, it is disclosed that the microstructure is made of toughened iron in steel added with a considerable amount of Mo and Nb, thereby ensuring that the endurance at 700 ° C is more than 56% of the endurance at room temperature. However, there is no description of the endurance of 800 ° (.) That is, as in these examples, steels that can ensure high-temperature strength of about 600 ° C have been used in the market, and already have a certain strength at 700 ° C. The invention of steel materials, however, is not easy to stably manufacture conventional steels that can ensure the strength of the South temperature at 700 ° C, 800 ° C. In addition, 7 200305650 disclosed in Japanese Patent Publication Gazette 2002-105585 玖, invention description 850 ° C refractory steel is recently disclosed by the present inventors and others. This steel is able to ensure effective precipitates at high temperatures by adding a large amount of alloying elements such as Al and Ti to obtain fire resistance at 850 ° C. However, it is not suitable as a steel for refining and construction. 5 As mentioned above, when using steel to build a building, ordinary steel cannot be used without or with a small amount of cover due to its low high-temperature strength, and must be expensive. Its refractory coating. As a refractory steel, its refractory temperature can only be guaranteed up to 600 ~ 700 ° C. It has not yet been used at 700 ° c and 001 without refractory coating 10 and can be developed to omit refractory The steel material for the coating step. [Summary of the invention] The present invention provides a high-tension steel 15 that can be used in construction civil engineering and other applications with excellent high-temperature strength and weldability within a temperature range of 600t: ~ 80 (rc). The production method of the steel is industrially and stably supplied. The gist of the present invention is as follows. (1) A high-tensile steel excellent in high temperature strength, expressed in mass%, containing C. 0.005% or more and less than 〇08%, Si: 〇5 % Or less, broken: 〇 · 1 ~ 1.6%, P: 0 · 02% or less, s: 〇〇1% or less, M〇: 〇 ^ 5% 20, Nb: 0.03 ~ 0.3%, Ti: 〇25% or less, B: 〇〇〇〇〇〇5 ～ 〇〇〇〇3% ^: 0.06% or less, N: 〇〇〇_ or less, and the remainder of the impure impure inclusions. (2 ) The high-tensile steel with excellent high-temperature strength as described in item ，, in which the steel is free from the stress at normal temperature and the stress at high temperature Secondary stress drop 200305650 玖, description of the invention Low rate (high temperature drop stress / normal temperature drop stress): p in the range of steel temperature T (° c) of 600 ° C or more and 800 ° C or less, meet pg-0 · 〇〇29χΤ + 2.80. (3) High-tensile steel with excellent high-temperature strength as described in item (1), in which the aforementioned steel 5 is a toughened iron sheet at normal temperature when heated at a high temperature equivalent to that in a fire. group

Weaving, or a mixture of ferrous iron and toughened iron, and when heated at a high temperature comparable to that in a fire, the temperature (Aq) of the inverted state of Vostian iron exceeds 800 ° C, and from normal temperature to Reduced stress Dimensionless stress reduction rate at high temperature (high temperature reduced stress / normal temperature reduced stress): P in the steel 10 temperature T (° c) is 600 ° c or more, 80 (TC or less, Those who satisfy pg-0 · 0029χT + 2 · 80. (4) High-tensile steel with excellent high-temperature strength as described in item (1), in which the aforementioned steels are used in high-temperature areas above 600 ° C and below 800 ° C from normal temperature. Dimensional Stress Reduction Dimensionless Stress Reduction Rate at High Temperature

15 stress / normal temperature drop stress): p has a strength that satisfies p--〇.〇29χΤ + 2.80 in the range of steel temperature T (° C) of 600 ° C or higher and 800 ° C or lower, and When the fire is heated at a relatively high temperature, the toughened iron single structure at normal temperature, or the mixed structure of fertilized iron and toughened iron, is inverted to the temperature of Vostian iron (Ac0 exceeds 800 ° C, and, The thermodynamically stable precipitated carbonitride phase is maintained at a Mohr fraction of 5x 1 (T4 or higher, and is solid-dissolved in fertilizer iron in the aforementioned toughened iron single 20 structure, or a mixed structure of fertilizer iron and toughened iron. The total amount of Mo, Nb, and Ti in the structure is one with a Mohr concentration of lx 10_3 or more. (5) High-tensile steel with excellent high-temperature strength as described in item (1), in which the aforementioned steel 9 200305650 发明, description of the invention

In the high-temperature area above 600 ° C and below 800 ° C, the dimensionless stress reduction rate from high-temperature drop stress at normal temperature (high-temperature drop stress / normal temperature drop stress): p at the steel temperature T (° C) is in the range of 600 ° C to 800 ° C. It has a strength of 5 ° that satisfies ρ2-〇.〇29χΤ + 2 · 80, and has a normal temperature when heated at a high temperature equivalent to that in a fire. The toughened iron single structure, or the mixed structure of fertilized iron and toughened iron, is transformed into a structure whose temperature (Aq) of Vostian iron exceeds 800 ° C, and the average equivalent circle of the old Vostian iron particles is round. The diameter is 120 / zm or less, and the thermodynamically stable precipitated phase of carbon and nitrogen 10 is maintained at a Mohr fraction of 5x 10_4 or more in the aforementioned single structure of toughened iron, or a mixed structure of fat iron and toughened iron, and The total amount of Mo, Nb, and Ti dissolved in the iron structure of the fertilized grain is excellent in high temperature strength at a Mohr concentration of lx 1 (T3 or more (6), such as any one of (1) to (5)). High-tensile steel, where the aforementioned steels are weld fracture cracks defined by PCM = C + Si / 30 + Mn / 20 + Cu / 20 + Ni / 60 15 + Cr / 20 + Mo / 15 + V / 10 + 5B Sexual composition:

PCM is 0.20% or less. (7) The high-tensile steel excellent in high-temperature strength according to any one of items (1) to (6), wherein the aforementioned steel system is more expressed in mass% and contains Ni: 0.05 to 1.0%,

CikO.05 ~ 1.0%, Cr: 0.05 ~ 1.0%, ν ·· 0.01 ~ 0.1%, one or two kinds of 20 or more. (8) The high-tensile steel excellent in high-temperature strength according to any one of items (1) to (7), wherein the aforementioned steel system is more expressed in terms of mass%, and includes NL0.05 to 1.0%, C "0.05 to 1.0 %, Cr: 0.05 to 1.0%, V: 0.01 to 0.1% of one or more types, and include Ca: 0.0005 to 0.004%, REM: 0.0005 to 0.004% 10 200305650 玖, Description of the invention, Mg: One or more of 0.0001 to 0.006%. (9) A high-tensile steel with excellent high-temperature strength as described in item (ii) or (ii), wherein the above-mentioned steel is above 600 ° C and 800. 〇 In the high-temperature area below, the undulating stress at two temperatures is reduced by 5 times from the undulating stress of Changhu (same as the dishing stress / normal temperature falling stress). In the range of 600 C or more and 800 C or less, it has a strength that satisfies p--000033χT + 2.80, and has a toughened iron single structure at room temperature when heated at a high temperature equivalent to that in a fire, or a fertilizer. The mixed structure of grain iron and toughened iron is transformed into a structure whose temperature (Aci) of Vostian iron exceeds 80. 0, and the average equivalent circle diameter of the old Vostian iron particles is 120 / zm or less. And maintain the thermodynamically stable precipitation phase of carbonitride in the above-mentioned toughened iron single structure, or mixed structure of fertilized iron and toughened iron, with a Mohr fraction of 5χ 10-4 or more, and solid solution in fertilizer The total amount of Mo, Nb, and Ti in the granular iron structure is one with a Mohr concentration of 1 X ΗΓ3 or more. 15 (10) A method for manufacturing a high-tensile steel with excellent high-temperature strength will have the following properties (1) ~ (9) The slab or steel sheet composed of the steel component of any one of the items is reheated in a temperature range of 1100 ~ 1250 C Then, hot rolling was performed at a temperature of 85 ° C or higher so that the cumulative reduction amount below 1100 ° c was 30% or more. After the hot rolling was completed, the temperature range was 800 ° C or higher at a cooling rate of 0.3KS1. Cooling in the temperature range of 20 to 650 c or less, the microstructure of the steel forms a toughened iron structure, or a mixed structure of ferrous iron and toughened iron. (11) A high-tensile steel with excellent high temperature strength, based on quality Shows that it contains C: 0.005% or more and less than 08%, Si: 0.5% or less, Mn: 0 · 1 to 1.6%, P ·· 〇 · 〇2%, S: 0.01% or less, Μ0: 0 · 1 ~ 1.5 200305650 发明, Description of invention%, Nb: 0.03 ~ 0.3%, Ti: 0.025% or less, B: 0.005 ~ 0.003%, Al: 0.06% or less 'N: 0.006% or less' and the remaining part And unavoidable impurities constitute 'and' have a mixed structure of 5 pieces of ferrous grain iron with a ratio of 20 to 95% of ferrous grain iron and strontium iron when heated at a high temperature comparable to that in a fire. Vostian Iron has a structure whose temperature (Ac 1) exceeds 800 ° C and has a low drop ratio. (12) A high-tensile steel with excellent strength as described in (11) above, wherein It is expressed in mass% and further includes one or more of Ni: 0.05 to 1.0%, Cu: 0.05 to 1.0%, (: 1 *: 0.05 to 1.0%, ¥: 0.01 to 0.1%). 1〇 (13) The high-tensile steel with excellent south temperature strength as described in (11) or (12), wherein the aforementioned steel system is expressed by mass%, and further contains Ni: 0.05 to 1.0%,

Cu: 0.05 to 1.0%, Cr: 0.05 to 1.0%, ν ·· 0 · 01 to 0.1%, one or two or more types, and Ca: 0.005 to 0.004%, REM: 0.0005 ~ 0.004%, Mg: 0.0001 ~ 0.006%, one or more of them. 15 (14) A method for manufacturing high-tensile steel with excellent high-temperature strength, comprising casting a slab or steel sheet having a steel composition according to any one of items (11) to (13) at a temperature of 1100 to 1250 C After reheating in the area, hot rolling at a temperature of 850 ° C or higher makes the cumulative reduction of 1100 ° C or lower to 30% or more, and after the hot rolling is completed, the cooling rate is 0.3KS · 1 or higher to 800 ° C or higher. The temperature range is 20 ° C to 650 ° C, which makes the microstructure of steel into a toughened iron structure, or a mixed structure of ferrous iron and toughened iron, and it has a high temperature when fired. , The mixed tissue of fertile grain iron and toughened iron with a toughened iron fraction of 20 to 95% at room temperature is a tissue that has been transformed into a Vostian iron with a temperature (Aq) exceeding 800 ° C, and has a low yield. Than. 12 200305650 发明, Description of the invention I: Embodiment 3 The best form for carrying out the invention The inventors have found that steels with excellent high-temperature strength at 600 ° C and 700 ° C 'have steels with excellent high-temperature strength at 600 ° C. Used in construction and many other fields, however, there is a strong demand in the market for higher temperature resistant steels. At the same time, steels with excellent high temperature strength are also extremely demanded. In terms of refractory design, it is only necessary to maintain high strength for the duration of the fire. For example, the conventional refractory steel does not need to consider the strength for a long time, as long as it can maintain the high temperature drop strength for a short time. For example, if the disk can be maintained at a temperature of 10 80 ° C for a short time of about 30 minutes, it can be fully utilized as 800 ° C refractory steel. In conventional refractory steel, the performance is set so that The high temperature drop strength is 2/3 of normal temperature. However, when the actual design range of the reinforced structure is about 0.2 ~ 0.4 times the lower limit of the normal temperature drop strength, the drop stress at normal temperature will be dimensionless. Stress reduction rate (high temperature drop stress / normal temperature drop stress): p must satisfy ρ ^ · 〇 · 〇〇29χΤ + 2.48 in the range of steel temperature T (° C) above 600 ° C and below 800 ° C When you want to increase the strength at south temperature, you can add Mo and Nb to the high temperature to promote the precipitation of stable carbonitrides and make the microstructure tough and ironized. To increase the strength at room temperature to emphasize the characteristics of high tension steel However, as the fraction of hardened and toughened iron increases, the strength at room temperature increases. Therefore, when the upper limit of the reduction ratio (YR) is required, the required room temperature strength and characteristics are matched. Toughening microstructure formation Single structure or a suitable change 13 200305650 发明 Description of the invention The mixed structure of ferrous iron with toughened iron and toughened iron. In order to make a suitable microstructure to achieve the required normal temperature strength range, low-c Can play a role. The low-c system can improve the thermodynamic stability of the toughened iron or the mixed structure of the fertile grain iron and the toughened iron at high temperature, so that the inverter 5 state becomes the inverter state temperature of the Vostian iron (Ac 丨) Rise. However, in this case, the 'microstructure and material are easily affected by the press-drying conditions and subsequent cooling conditions, and it is not easy to manufacture stably. Therefore, when the present inventors committed to controlling the microstructure to increase the high temperature strength, It was found that adding an appropriate amount of B will contribute to the stabilization of production, and the present invention was invented. 10. The general welding structural steel must have the same weldability as the conventional one. Therefore, the temperature is high at 700 ° C ~ 800 ° C. In order to solve this problem, the present inventors made an effort to review and found that the high-temperature strength at 15 700 ° C ~ 800 ° C can be compounded by adding Mo, Nb, V,

Ti and other alloying elements strengthen the precipitation, and increase the displacement density by the toughening and ironization of the microstructure, and delay the displacement recovery by the solid solution of Mo, Nb, and V. It is found that Ti also has some effects. In order to ensure both the strength at 700 ° C ~ 800 ° C and the 20 strength at normal temperature, and the strength ratio p between normal temperature and high temperature, it is found that the focus is to make the microstructure a mixed structure of ferrous iron and toughened iron. Or toughen the iron single structure, and the amount of alloying elements added is the most appropriate range, in order to obtain the thermal stability of the mother phase structure at high temperature and the appropriate integrated precipitation strengthening effect and displacement recovery delay effect. And, in order to ensure a low drop ratio, it is necessary to make the microstructure into an appropriate fertilizer particle. 14 200305650 玖 Description of the invention A mixed structure of iron and toughened iron. The falling strength of steel generally decreases rapidly from around 450 ° C and this & heat activation capacity decreases due to the increase in over-temperature, and the effective sliding resistance becomes ineffective at low temperatures relative to shifting sliding motion. · 5 'Generally used to strengthen in the temperature range of less than about 700 ° C,

Cr slaves or Mo carbides, etc., have a sliding motion of 6 ㈨ for displacement. c Effective resistance can be exhibited up to a high temperature, but it will solidify again at a high temperature of 80 ° C. Therefore, the strengthening effect can not be maintained. g The inventor has a variety of The compound 10 precipitates were investigated. As a result, it was found that the compound precipitates in which Mo is combined with Nb, Ti, and V have high stability in South temperature, and also have a high strengthening effect in 700 ~ 800 (rc). That is, The appropriate amount of M0, Nb, Ti, v is added and the heating temperature during rolling is increased to make these elements fully solid solution, and by introducing a suitable rolling structure with a shift density of south, to ensure that the precipitates can be precipitated. The precipitation site 15 is used to increase the temperature during reheating, for example, during temperature rise due to a fire.

Nb, Ti, and V combined composite precipitates are finely precipitated. · Such composite precipitates are also maintained at 700 ~ 80 ° C, and the strengthening effect is reduced, but the strengthening effect is reduced. However, when they are dispersed very finely and densely, they last for about 30 minutes. It can fully obtain the aforementioned target value of falling strength of 20 at 700 ~ 800 ° C. In addition, the Mo, Nb, v, and Ti systems that have been dissolved in the BCC phase are helpful to delay the recovery of displacement and have the falling strength The effect of the rapid temperature increase began to decrease. The inventors have reviewed the effects of these high-temperature strengthening factors on the reduced stress in 70 ° C ~ 800 ° C, and obtained the following 15 200305650 发明, description of the invention. That is, at 700 ~ 800 ° C, the temperature of the steel is T (° C), and the high temperature and normal temperature drop stress ratio p (high temperature drop stress / normal temperature drop stress) is satisfied.

0 · 0029χT + 2.48, that is, in order to make the stress drop ratios at 700 ° C and 800 ° C 45% and 16%, respectively, the composite carbonitrides of Mo, Nb, V, and 5 Ti at this temperature must be Above Mohr fraction 5x 1CT4, and the total amount of Mo, Nb, V, and Ti dissolved in BCC phase is above Mohr concentration 莫 χ 10_3. The composition of the important composite carbonitride precipitates that appear at high temperature strength can be easily identified by analysis such as electron microscopy or EDX. In addition, there are 10 thermodynamically stable equilibrium phases and the amount of solid alloy elements in the BCC phase, which can be easily calculated from the amount of alloying elements by using commercially available thermodynamic calculation database software. However, even if the precipitate itself is stable and the substrate is deformed due to temperature rise, the integration loss between the precipitate and the substrate will become non-integrated. Therefore, the strengthening effect of the precipitate decreases rapidly. That is, in order to achieve the strengthening effect that can be achieved by the stable composite precipitates at high temperature, the material must be able to make the base material structure unchanged at the design temperature of 800 ° C. Therefore, specifically, it is necessary to adjust the alloying elements such as reduction and addition of Mn of the Vosstian iron body so that the Aq transformation temperature of the steel is 20 800 ° C or more. In addition, the precipitation and solid solution elements are utilized to enhance high-temperature strengthening. Therefore, the amount of alloying elements added in conventional high-temperature steels such as Cr, Mn, and Mo can be reduced as much as possible, so that the solubility does not decrease. Alloy design is feasible. 16 200305650 Description of invention In addition, due to the increased strength of steel with a single structure of changeable knife iron, it is not necessary to meet the requirements of the low reduction ratio required in construction steel. Therefore, when a low reduction ratio is required in the steel of the present invention, the microstructure is a mixed structure of ferrous iron and toughened iron, and the fraction of the toughened iron ranges from 20% to 95%. This is because when the fraction of ferrous iron in the microstructure is too large, it is not easy to ensure the strength at room temperature and high temperature by adding the alloy 70 element. Hereinafter, the reasons for limitation of each component in the present invention will be described. And,% means mass%. c is an element that can have the most significant effect on the properties of steel, and is an element necessary to form a composite precipitate (carbide) combined with Mo, Nb, Ti, and V. Therefore, at least 0.005% . When the amount of C is less than the foregoing, the strength is insufficient. However, if the addition exceeds 0.88%, the ACi metamorphic temperature decreases, so 800 is not easily obtained. The strength below 〇 and the toughness also decrease, so the limit 疋 is 0.005% or more and 〇 or less. Furthermore, it is desired to maintain the mixed parent structure of fat iron and toughened iron thermodynamically and stably under the same temperature heating at the time of fire, and maintain the integration with the composite carbonitride precipitates of Mo, Nb, V, and Ti. 'To ensure the strengthening effect, it is better to be less than 0.04%.

Sl is an element that is used for deoxidation and is contained in steel, and because of its replacement type solid solution strengthening effect, it helps to improve the strength of the base metal at room temperature, but not 2 ^ 〇λ ^ especially has an improvement of more than 60 (rc The effect of high temperature strength is lower. In addition, the welding limit and HAZ toughness will deteriorate when added too much, so the upper limit is limited to 0.5%. The deoxidation of steel can be achieved only with Ή and A1, and the hardness is hardened by HAZ. From the point of view, the fewer systems, the better, and it is not necessary to add.

Mn is an indispensable element for ensuring strength and toughness. However, 17 200305650 发明, the invention explains that the replacement type of solid solution strengthening element Mη system helps to improve the strength at room temperature, but it is not particularly for the temperature exceeding 600 ° C. The high temperature strength has too much improvement effect. Therefore, in the steel containing a larger amount of Mo as in the present invention, it is considered to be limited to 1.6% or less from the viewpoint of improving the solubility, that is, reducing the PCM.

5 If the upper limit of Mη is low, it is also conducive to the center segregation of continuous casting embryos. Furthermore, in order to make the Ac! Metamorphic temperature be 800 ° C or higher, it is necessary to reduce the addition, and the upper limit should be 0.9%. In addition, there is no particular limitation on the lower limit. However, in terms of adjusting the strength and toughness of the base material, it is better to add 0.1% or more. 10 In order to obtain an appropriate toughened iron structure fraction, it is necessary to make the The cooling rate from 800 ° C to 650 ° C is 0.3Ks-1 or more. That is, thinner steel plates with a thickness of less than about 25mm must be manufactured by air cooling or accelerated cooling (water cooling), and thicker steel plates with a thickness of more than about 25mm must be manufactured by accelerated cooling (water cooling).

15 P is impure in the steel of the present invention, and HAZ can be reduced when P is reduced.

The grain boundary is destroyed, so the less the line, the better. When the content is too large, the low temperature toughness of the base material and the welded part will be deteriorated, so the upper limit is 0.02%. S and P are impure substances in the present invention in the same manner as P. From the viewpoint of low-temperature toughening of the base material, the less the system, the better. If the content is too large, the low temperature toughness of the base material and the welded 20 parts will be deteriorated, so the upper limit is 0.01%.

Mo is a basic element constituting a composite precipitate that enhances high-temperature strength, and is an essential element in the steel of the present invention. In order to obtain high-density composite precipitates combining Mo with Nb, Ti, or composite precipitates combining Mo with Nb, Ti, and V to improve high-temperature strength, it is necessary to add more than 0.1%, and add more than 18 200305650 玖, According to the invention, when L5% is used, it is difficult to control the identity of the base material, and it will cause deterioration of the edge of the heat-affected heat-affected zone, thereby losing economic efficiency. Therefore, the amount of Mo added is more than GU, 1.5% The following is preferred, and more preferably Q.2% or more and ^% or less. 5-In the present invention with a larger amount of Mo added, it is an essential element to ensure high temperature strength at 700 C and 800 ° C. First of all, the general effect is an element that raises the recrystallization temperature of Vostian Iron and makes the effect of controlling the rolling during hot rolling extremely effective. In addition, it is also helpful for the re-heating at the beginning of rolling or the normalization or hardening of the Vostian 10 iron for fine graining. Furthermore, it also has the effect of increasing the strength of precipitation hardening, which can be used to improve the high temperature strength by compounding with Mo. When it is less than 0.003%, the hardening of precipitation hardening at 700 ° C to 800 ° C is reduced, and it is better to add more than 0.01%. In addition, if it exceeds 0.2%, the toughness of the base metal may be reduced. Therefore, the upper limit of 15 is 0.3%. Therefore, 0.03 to 0.3% is a limited range.

Ti also contributes to the improvement of high-temperature strength in the same way as Nb. In particular, it should be added when the toughness of the base material and the weld is strictly required. This is because when the amount of Ti is small (for example, less than 0.003%), it is combined with 0 to form a precipitate containing Ti203 as the main component, which becomes a core for the formation of intra-granular metabolized iron and iron, and the welding part is raised to take the knife. 20 sex. In addition, Ti and N combine to form TiN and finely precipitate into the embryo, which can prevent the coarsening of the 7 grains during heating and contribute to the fine graining of the rolled structure. In addition, the fine TiN existing in the steel plate is used for During welding, the structure of the heat-affected zone of the welding is fine-grained. In order to obtain these effects, Ti must be at least 0.005%. However, when too much TiC is formed, the low-temperature toughness or fascination deteriorates. 19 200305650 发明, description of the invention Therefore, it should be 0.02% or less, and the upper limit is 0.025%. B is extremely important in controlling the intensity through the generation ratio of the modified iron. That is, the B series is segregated to the iron grain boundary of Vostian to control the formation of ferrous iron to make it harden by 1 ±. Even when the cooling rate is slower than air cooling, it will help to stably produce toughened iron. In order to obtain this effect, it must be at least 0.005%. However, adding too much may not only improve the hardening effect

Saturation can also be detrimental to the embrittlement or toughness of the iron grain boundary of the old Vostian and form the B precipitate. Therefore, the upper limit is 0.003%. Modification of A1 is generally used for deoxidation and is included in steel. However, to remove 10 milk, only Si or Ti is required. In the steel of the present invention, the lower limit is not limited (including O / o). However, A1 S is more At this time, not only the quietness of the steel deteriorates, but also the toughness of the weld metal deteriorates. Therefore, the upper limit is 0 06%. The N series exists in steel as an unavoidable impurity, and the lower limit is not particularly limited. However, increasing the amount of N will greatly damage HAZ robustness and weldability15. Therefore, in the steel of the present invention, the upper limit is 0.006. %. Next, the reason for adding Ni, Cu, Cr, V, α, φ REM, and Mg and the range of addition will be described. The main purpose of becoming a basic ingredient and further adding these elements is to make properties such as strength and blade properties without sacrificing the excellent characteristics of the steel of the present invention. 20 properties & Therefore, the amount of addition can be freely limited. ,

Ni is used to improve the strength of the base metal and improve the grip properties without deteriorating the solubility and HAZ residual properties. In order to exert these effects, at least 5% must be added. In addition, "when added too much" is not only detrimental to the economy, but is also not good for dazzling, so the upper limit is 1.0%. 20 200305650 发明, description of invention

The Cu system exhibits almost the same effects and phenomena as Ni, and the upper limit is ι0%, which is limited by excessive addition, which deteriorates weldability, and causes Cu cracking during hot rolling to make it difficult to manufacture. The lower limit is 0.05% of the minimum amount to obtain a substantial effect. 5 Cl series also enhances the strength and durability of the base material. However, if the addition amount is too large, the toughness and weldability of the welded part will be deteriorated. Therefore, the limited range is 0.05 to 1.0%. Above, Cu, Ni, and Cr not only contribute to the strength and toughness of the base material, but also contribute to weather resistance. In order to achieve the above purpose, it can be added within the range of 10 without loss of weldability. V has a compound precipitation effect approximately the same as Nb, however, its effect is smaller compared to Nb. In addition, V also affects the hardenability and contributes to the improvement of high-temperature strength. The effect similar to Nb is less than 0.01%. In addition, when too much, the toughness of the base metal is reduced. Therefore, the lower limit of V in the 15 steel of the present invention is 0.01%, and the upper limit is 0.01%.

The combination of Ca and REM with impurities of s has the function of improving, reducing or preventing the induced cracking caused by the diffusible hydrogen in the welded part. However, if it is too much, coarse inclusions will be formed to cause adverse effects. Therefore, 0.0005 ~ 0.004% 0.0005 to 0.004% is an appropriate range. 〇 If the welding heat-affected zone has the effect of preventing and minimizing the growth of Vostian iron particles, the welding zone can be reduced. In order to obtain this effect, it must be 0 · _% or more. In addition, when the amount of addition is increased, the effect is reduced relative to the amount of addition, and the economy is lost. Therefore, the upper limit is 0 • ⑻6%. In addition, the same amount of w is added as Mo, Nb, and V to ensure 21 200305650 玖, description of the invention High temperature strength is also an effective method to improve the characteristics of the steel of the present invention. To achieve this effect, w must be at least 0.01%. However, when it exceeds 0.1%, the effect is saturated. Therefore, the upper limit is 1% in consideration of economic efficiency.

In order to ensure the cracking susceptibility at normal temperature and normal temperature, and can be welded in 5 ways without preheating, the value of PCM is limited to the range of 0.20% or less. PCM is an indicator that shows weldability. The lower the weldability, the better. In the steel of the present invention, excellent weldability can be ensured when the PCM is in the range of 0.20% or less. In addition, the welding crack susceptibility composition PCM is defined by the following formula. PCM = C + Si / 30 + Mn / 20 + Cu / 20 + Ni / 60 4- Cr / 20 + 10 Mo / 15 + V / 10 + 5B.

In addition, at the position of 1/4 thickness in the plate thickness section direction of the final rolling direction of the steel sheet, the particle size of the old Vostian iron in the final abnormal structure is limited to an average equivalent circle diameter of 150 μm or less. This is because in order to make the particle size of the old Vostian iron strongly affect the toughness together with the structure, especially in the steel added with Mo according to the present invention, 15 it is important to control the particle size of the old Vostian iron to be small and medium in order to improve the toughness. Required. The aforementioned reasons for limiting the particle size of the old Vostian iron are limited based on the experimental results of various manufacturing conditions changed by the inventors. When the average equivalent circle diameter is 120 μm or less, the toughness is not lower than that of the Mo of the present invention. steel. In addition, the old Vostian iron pellets are often easy to identify. At this time, 20 is used as the center of the 1 / 4-thickness plate, and is used for an impact test piece with a cutout that is removed in a direction perpendicular to the final rolling direction of the steel sheet. For example, JIS Z 2202 No. 4 test piece (2mmV Notch), etc., the unit of the fracture surface when brittle failure is caused at very low temperature is defined as the effective crystal grain diameter of another Vostian iron particle diameter reading method, and the average equivalent circle diameter is measured, and the same is true in this case 22 200305650 (2) The description of the invention must be less than 150μm. In the method for manufacturing a high-tensile steel with excellent high-temperature strength according to the present invention, the heating temperature during the rolling of the steel sheet or cast slab is preferably high temperature in order to sufficiently solid-solve Mo, Nb, Ti, and V. However, in consideration of ensuring the toughness of the base material 5, the temperature is above 1100 ° C and below 1250 ° C.

Next, in the temperature range of 1100 ° C or less, the hot-rolling is performed to ensure the cumulative sheet reduction of 30% or more, and the rolling is finished at 850 ° C or more. When the pressure in the low temperature range is too large, the ferrous iron will be deformed, the ferrous iron fraction will be too large, and it is not easy to ensure the strength. Furthermore, Nb, Ti, and V will be precipitated in the state of carbide during the rolling, and it is not necessary. Because of the solid solution of Mo, Nb, Ti, and V, the lower limit of the rolling temperature is 850 ° C, and the toughness is insufficient when the rolling ends at a temperature exceeding 1100 ° C, so the upper limit is 1100 V.

After the end of the rolling, the average surface cooling rate of the steel sheet is 0.3Ks ^ or more to cool the surface temperature of the steel sheet from a temperature range of 800t or more to a temperature range of 650 ° C or less. The purpose is to obtain the deformed band that constitutes the precipitation part or the rolled structure containing a large amount of displacement, and freeze it with water to obtain Mo and Nb, Ti, V, which are finely integrated with the embryo at high density when heating. Combined complex precipitates. In addition, the characteristics of the steel of the present invention are not impaired when the steel of the present invention is manufactured and then dehydrogenated and reheated to a temperature below the Aq transformation point. After water cooling, the steel sheet may be subjected to tempering heat treatment within a temperature range of 500 ° C or less for 30 minutes. In addition, the steel of the present invention can sufficiently obtain the effects of the present invention when it is used as a steel pipe such as a steel pipe, a thin steel plate, 23 200305650 发明, or an angle steel. In the example, a converter-continuous casting-thick plate step was used to manufacture steel plates of various steel compositions (thickness: 15 ~ 50mm), and the strength and toughness of the steel plates were investigated at 700 ° C and 800 ° C, without any preheating. Temperature) y crack test under the root crack

Tables 1 and 2 show the steel composition of the comparative steel and the steel of the present invention, Table 3 shows the manufacturing conditions and structure of the steel sheet, and Table 4 shows the results of investigations of various characteristics. 10 In the examples of the steel Nos. 1 to 9 of the present invention, all the microstructures are a mixed structure of ferrous iron and toughened iron, and the average equivalent circle diameter of the old Vostian iron particle diameter is 120 μm or less. In addition, the actual yielding intensity ratio is also an excellent value at 700 ° C and 800 ° C of 64% and 23%, respectively.

In the examples of the steel No. 10 to 18 of the present invention, the microstructure is a toughened iron single structure 15 or a mixed structure of fertilized iron and toughened iron, and the average equivalent circle diameter of the old Vostian iron particle diameter is 120. Below # m, the actual yielding intensity ratio is also an excellent value at 700 ° C and 800 ° C of 61% and 25%, respectively. In comparison steel No. 19, C is excessive, and the inversion state becomes the inversion state of Vostian Iron. The inversion state Aq is below 800 ° C. Therefore, the normal temperature strength can also obtain a high value of 20. However, the normal temperature / high temperature drop-down strength ratio (p ) Is ρ < -0 · 0029χ T + 2.48. In comparative steel No. 20, C is insufficient, and the yield strength of 490MPa class is insufficient, and the amount of composite carbonitride phase generated at a temperature of 600 ° C or higher is less than 5x 1 (T4, room temperature / high temperature yield strength ratio (p)). Also ρ < -0 · 0029χ T + 2.48 24 200305650 玖, invention description 2.48, which is low. Compared with steel No. 21, the amount of Mη exceeds 1.6%, therefore, Aq is less than 800 ° C, and at temperatures above 700 ° C The room temperature / high temperature drop strength ratio (P) is p < -0 · 0029χ T + 2.48. 5 Compared with steel No. 22, the amount of Mη is less than 0.1%, so the solid solution strengthening effect at room temperature is insufficient, and the drop at room temperature The strength and tensile strength are lowered to the lower limit of 490MPa grade.

In the comparative steel No. · 23, P exceeds 0.02%. Therefore, the ductile brittle transition temperature of the base material deteriorates with the reproduced energy value of ΗΑZ at 0 ° C v 10. In comparative steel No. 24, S exceeds 0.01%. Therefore, like the comparative steel No. 23, the ductile brittle transition temperature of the base material is deteriorated together with the absorbed energy value of the reproduced HAZ at 0 ° C.

In Comparative Steel No. 25, based on the insufficient addition of Mo, the carbonitridation 15 phase and the solid solution Mo in the BCC phase are also insufficient. Therefore, the strength at room temperature is good. However, there is about the actual high temperature and room temperature drop strength ratio at 800 ° C. , 15% is low. In comparison steel No. 26, the amount of Mo is excessive, so the unevenness of the base material material is increased, and even if the susceptibility composition of welding fracture is PCM is 0.18%, root cracks are still generated in the y-crack test without preheating. . In addition, the absorbed energy value of the reproduced HAZ is low. In Comparative Steel No.27, the amount of Nb was insufficient, and sufficient precipitation hardening effects could not be obtained at 700 ° C and 800 ° C. Therefore, the drop-intensity ratio (p) at room temperature / high temperature is ρ < -0 · 0029χΤ + 2 · 48. 25 200305650 (ii) Description of the invention In Comparative Example 28, the amount of Nb was excessive, and therefore a high value was obtained at high temperature strength, but the absorbed energy value of the reproduced HAZ was low. In Comparative Steel No. 29, since the τ * grains were coarse, the absorbed energy value of the reproduced HAZ was low. 5 In Comparative Steel No. 30, the amount of Ti is excessive. Therefore, the ductile brittleness transition temperature of the base metal and the reproduced HAZ absorbed energy value deteriorate simultaneously.

In Comparative Steel No. 31, the amount of B added was insufficient, sufficient hardening was not obtained, and the microstructural transformation iron fraction was too small. Therefore, the ratio of drop strength at room temperature was lowered to the lower limit of the specification value of 490 MPa. 10 In Comparative Steel No. 32, the amount of B added is excessive. Therefore, the ductile brittle transition temperature of the base material is near 0 ° C, and the absorbed energy value of the reproduced HAZ is low. In the comparative steel No. · 33, the amount of A1 exceeds 0.06%. Therefore, the ductile brittle transition temperature of the base material is near 0 ° C, and the reproduced ΗΑZ toughness is also low. In Comparative Steel No. 34, the amount of N exceeds 0.006%, and therefore, reproduction

15 HAZ has low toughness. In Comparative Steel No. 35, the PCM value exceeded 0.20%, and root cracking occurred in the y-crack test without preheating. Moreover, the reproduction HAZ absorbed energy is also low. In Comparative Steel No. 36, the reheating temperature is less than 1100 ° C. Therefore, the alloying elements added during reheating cannot be solid-solved in Vosstian iron and cannot be fully precipitated and strengthened. At the same time, the drop strength and tensile strength are reduced at room temperature. Good, however, the drop-intensity ratio (P) at room temperature / high temperature is ρ < -0 · 0029χΤ + 2 · 48. In the comparative steel No. 37, the reheating temperature exceeded 1250 ° C. Therefore, when reheating, the iron particles of Vostian coarsened, and the absorbed energy value of the reproduced HAZ decreased. In Comparative Steel NO.38, the cumulative reduction below 1100 ° C is less than 26 200305650 玖, and the description of the invention is 30%. Therefore, the old Vostian iron particles are coarse and the HAZ toughness is low. Comparative steel No. 39 was rolled at a temperature of less than 850 ° C. Therefore, the precipitation of Nb, Ti, and V was promoted and sufficient precipitation strength could not be obtained. The normal temperature strength meets the specification value of 490 MPa. However, normal temperature The ratio of fall-intensity (p) at / 5 ° C is ρ < -0 · 0029χΤ + 2.48. In comparison steel No. 40, the reheating temperature is as high as 1250 ° C. Therefore, after the rolling, the iron particles in Vostian exceed 120 // m, which is very coarse and the base material is low in stiffness. Compared to steel No. 41, in After rolling, water cooling was used to increase the strength at room temperature by 10 liters. However, when the plate thickness is too large, the cooling rate near the γ / α transformation temperature in the 1/4 thick portion is insufficient, so the iron content of the fertilizer particles is too large. (≫ 80 ° C: Toughened iron fraction < 20%), the solid solution strengthening effect at room temperature is insufficient, and the tensile strength at room temperature decreases to the lower limit of the specification value of 490MPa grade steel for construction

15 Comparative steel No. 42 has a plate thickness of more than 25mm. Therefore, accelerated cooling is applicable to ensure a cooling rate of 0.3Ks_1 or more. However, the water cooling start speed is less than 700 ° C. After the rolling is completed, the cooling starts (690 ° C). The cooling rate is 0.3KS · 1 or less. Before the water cooling starts, the metamorphosis of ferrous iron has already been performed. Therefore, the toughened iron fraction is less than 20%, and the tensile strength at room temperature is reduced to 490 MPa. 27 200305650 Rose, description of the invention 5 aft mm E «ΑΙ wr 〇σ * 卜 Ο S CO o e7 IA CM d CO d IO i; d CO e ^ id < 〇!« 〇S Ξ! 〇l〇in CO C7 o 'ZZ 〇CD d «Ο f» o to 09 〇CM «Τ 〇Ir-: IP tn 〇 · C * 4« Ρ 〇 · CD * n ▼ d " a ο α. οο 6 s 1 d » CO 〇do 09 〇ooc * jj < 〇 «卜》 ol o did CM d« 〇〇 · r- to d or Ol o JJP da〇IO d < n to d £ | d β > d 91 G〇d Μ 〇〇o ς > (! Mv · 0 0 ς > Ui α: 1 mm 0 0 Q η ο in o., J 1 IA o Q to o 9I > <-> «dsod u > V od 〇 d 0 t0 〇d ood u1 »pdoosod C4 oo CM 〇o IO 〇os 〇o u > v— 0 0 Cl« 0 d 〇〇 < M 〇d ϋ e > od 3 α 〇r > d ta to d 2 * — «1 d 〇d ζ S CO s CM CO to 2 bu ss CM 〇in Ο» bu S 〇 > < S ο let od IA S o «» nds O d 〇O d SO 〇 · sod CM sdso 5 po < * as d < 〇0 d Real J d CM 〇d 〇6 s 0 0 0 S d 0Q 〇 tn one oo one o one-to CNl CM «D — Λ ZO ο ο odod O 2 d« 0 sdos el sis I o | ID U > ooosd to in d O! 〇〇: 0 d 0 »s 0 * IO S d 〇〇d bu ds 0 d ο 2 • wm s • osdo C4 2 d 5i O Is oo A C4 O o IA d cO v · 〇 • 0 «0 0 s ίΑ S ο in o ς > S o Q oo 〇〇〇o IO o see P > so ς» at jo ς »in o ς > < 〇s 〇! Σ »C9 so 9 〇ms 0 s 0 ς > s 0 113 IO 〇〇ς» s 0 Q < in 0 q ί Q α φ β ς »C ^ 4 〇ς» tn gq ς »丨 so ς ίso ς» «〇00 o ς > m 5 oa% n O o ςί O o 9» o in gp? So ί »» ea 0 ς > o 0 〇O ςί 丨 Yu 09 o ς »CM m 0 0 C 2« η ο 00 r · P «> C9 ds 6 CO C9 6 od 1 od 01 〇 · CM d IP tr > dodsd U) ey« Μ ID d ο »sdss 〇 · CO C9 〇 d CM o '< sj 〇〇 »Wm d 00 2 m 5 rt 〇Ol o CM v» · d mm d 〇; d V) 0 in d can be pd 〇 α〇! Ο 〇 > O wod CD iood 90 q IA · od 00 pdwod CP md BU od 00 〇 · d rt CO odoo 0 o! 0 〇 >; 〇0 00 sd BU 04 〇 • 1 0I «0 mrn 0 i〇CM r > d-P4 o! m < 〇I 1 CO 〇 > 〇! -1 丨 1 1 CM r—in | < d -1 1-卜 〇o

§Chang 唞 ^ 3 * n / > i / o2 + u > / L0 + 5 /! N + 2/5 Ten 9 / c2 + o =, ou (CJfflu > + ol / > -fIAl / 02 + oz / k.o409 /! z + oc > l / ao-»-oevl / cs + oc /! co + o = " od (I 28 200305650 Rose, description of the invention㈣C 〇〇 ιη ο Γ- · οι ο Is 1 · ΙΟ τ ο CO S dndld Is d Ϊ o 〇CM O ^ r- to d cn o 1 < 〇 | 5 < 〇Q〇CM 〇 · CO d 5 d Is in 〇 · 5 d < D l 〇d < D 2 d to tn o CD < D o 〇 · s C9 d CS ο σ »< 〇ο ο ▼ ο € QM 〇te > O \ n 1 o 〇» 1 o CM ▼ oo — 1 O! CO ·-* 丨 OO! »O o ··« 〇: 隹 doo CM 〇m O CO Φ V · os _ o by o in «oo« Ρ oo Μ 2 «0 oodm mm oog» 1 O o Q o CM oo ςί CO o ί q Q 1 1 S UI X * m Ο | > o to 〇CM od O d! Ooooooo 〇) mo 〇 · Ρα »Ο ο ο ο ο g ο ο odopoo 〇SO 〇α〇Ο d «0 o -o S dr * 〇 · o < M oo IO oo O oo 04 〇dooo CU oo ο ιη ΙΟ ο CM r > d 〇 »▼ osom _ _ E 3 Ο 1 1 1 〇 < 〇 < 0 do T · o« o 〇; rt r »-〇 ZO« Μ rp «ΙΟ CM S C7« CM r >ss; to CM es s < 〇to in 〇 > «9 ID« CD 〇CD som < rt ο Ο g ο ο C? ο ο 2 ο od ososooog 6 < 0 odooosod to od Γ9 〇2 ID S sooods P ogpo to od SOO 10 oo IO 〇d: oo O od αα ο 1 CM 1 ο ο o CO to a〇00 «0 O rt 〇o CO mm CD 〇 > OL · J3 Zn α ο Ο Ο (Ο ο ο αο CO ο ο ο ΟΙ Ο ο CM so BU os 9 < 〇od 5 O dso «CO 〇d f0 d 00 r > qo 2 pd < 〇« Α 〇〇mnod 5 O b to S d 'm S 〇c〇posoo 2 qd IO sd SO d Ο 2 ο «ο ο S ο Μ — V · ο CD Ο oo ifj oo« 0 to p ID o CM 9 · »2 〇ov— ov ·« 〇 «0 oo 〇 | o 2 O € /) CMI «ο Ο 1 ΙΑ CM σ ς > ο S ο φ * α〇Ο ρ oso 9» oo ς > r »· O ςί oo Q CD o 9 〇 > o to so Qso Q o ς» r · 〇ςί > 2 O ς > O o ς? u > o ID o QO so 9 so <? o CO o ς »CM oo Q a〇〇9 m CN | o ς > CL ο ▼ ο ο ν— V Ο φ 〇 > ο τ τCHJ 2 ο o, so <? OQA 〇oo ς »« 〇II) 〇I ς > CM in 〇 · Q so 〇O s O p CM oso ς > CM 〇Q oo ίί s 〇 ς »soo mm Φ o Q« 0 OQ 〇so ςί «o ςί CS oo QCS C0 50 ο < 0 6 ιπ (Ο Οί 5 |! 齐 i〇sdsdsd S d φ d 04 doo in osd Ο» C4 CM d . · 2 id 1 ooo r > r > 〇 · in in o Φ d ιό ο ο ιη wm Ο ΙΟ ο Μ] ο 1 ~ Τ Ο o 〇 · r «w» do CM d CO d order d 00 〇 · ad od O 〇 · CM d SO d «0 d ▼ 〇 < 〇dooo 〇 · C4 mm d u > d 00 od 〇 CM 00 〇 S ο ο ιη ο ο ο ο ο 〇% q Q oo 'CO 〇〇 言 oo CO od «Μ CM Ο Ο eo pd« 3 odl〇od iM 〇d < 〇ooooood C0 〇d • v «oo V od · oo fl〇ooo 00 O o < 〇od σ > ο CM CM CO s in to BU CM c〇so «i I« e > i 5! IO r > IO CO bu «〇0 σ% to o ▼ 〇 | 镞 d 2 anchor 29 200305650 Rose, description of the invention Table 3 Category The invention of this application Steel heating temperature Rolling end temperature 0c> Cumulative reduction amount below 1000 ° C (%) Accelerated cooling start temperature Accelerated cooling stop temperature (¾) Plate thickness (mm) Microstructure toughening iron fraction (%) Aci temperature Ct :) amount of composite carbonitride 1) X to * BC C solid solution amount 10 * old r particle size 3) ίβ m) in y crack test without preheating 4) 1 «Ί $ ο 880 70 — — 2 $ 45 891 1.35 7.06 $ 5 Νβ crack 2 noo 900 60 — pain 15 6Z» 77 0.57 4. € 2 72 No crack 3 " 00 S80 50 aso 450 40 41 «29 0.82 1.91 45 No crack 4 11SO 910 70 Surface 20 40 833 t.03 6.24 5β N · crack 5 noo B70 50 Y — 25 59 81S 0.62 2.00 ββ No cr ek 6 1100 900 40 880 495 SO 41 883 1.00 4.47 43 N · crick 7 1100 970 30 820 S00 30 63 803 1.40 2.33 51 N · cr strike ck 8 1100 950 SO 620 500 32 44 839 ι.οβ 2.84 Race β No craok 9 1150 880 60 Miscellaneous ** 1ft 50 854 1.12 6.20 55 No crack 10 1150 870 70 Division 1 25 8S St5 1.33 7.08 55 No crack 11 1100 1000 30 — ref 30 73 β〇5 2.73 S.90 51 No cr mine 12 1150 Θ60 65 • 20 55 «21 1.03 6.24 5β No crack 13 1100 920 50 850 S80 50 85 S05 1.84 1.92 βζ No crack 14 noo 900 50 850 400 40 75 β12 «.08 4.09 59 No crack 1S 1100 ββο 60 S20 eso 65 100 832 0.73 4.8S 7β No cr turtle ek 16 1100 900 60 860 600 32 81 Β2β 2.27 7.22 78 No crack 17 1150 ββο 60 810 590 2S 88 808 t.20 3.96 7 a No crack 18 1150 960 50 900 620 4S B9 β17 2.46 6.6S 62 No crack 30 200305650 Rose, invention description Table 3 Continuation category Steel heating temperature (¾) Rolling end temperature (° C) Cumulative pressure below 1000 ° C Down (¾) Accelerated Cooling Start Temperature CC) Accelerated Cooling Stop Temperature (^) Plate Thickness (mm) Microstructure Toughening Iron Fraction ⑻ Act. Temperature (¾) Composite Carbon Nitride Content 1) X 10, BC 丨(: Soluble element content in the phase 10 * old r particle size 3) (μm) Whether there is root crack in the y-crack test without preheating 4) 19 1150 950 so _ do 13 100 810 0.69 ea No crack 20 1t50 925 50 two IS Z5 834 Q.45 3.49 52 Νφ cr pain ck 21 Π50 940 50 — • 20 100 774 0.7B β · 39 B7 No crack ZZ " 50 aoo 35 division ** 2S 45 805 0.56 4.i2 48 No crack 23 1100 β7 $ 40 820 550 40 52 942 1.11 2.29 55 No er «ek 24 1100 920 50 Masked 27 64 β10 1.16 7.47 S3 No crack 25 1050 915 50 — * 16 58 g37 0.74 1.41 S2 No cr turtle ck 21 1050 960 60--ts 100 8t2 1.14 9.2fi 62 Crackinc 27 1100 9 $ 0 50 Series 22 52 β23 1.19 6.B7 7 4 No crack 28 1100 920 50 Noodle 25 ββ 812 2.50 6.21 S4 No cr 29ck 29 1150 930 60 880 550 25 70 809 1.19 6.94 13S No creek 'than 30 1150 925 60 880 500 4S 54 βιβ 1.23 s.ei 42 No cr «ck less than 31 ποο 940 60 one * suspicion 18 15 802 1.69 S.B8 94 No creek steel 32 1150 970 60 • — 16 69 82β 1.04 3.46 56 No crack 33 ΠΟΟ β9〇60 etc. continued 1« 55 aoe 1.15 5.79 72 No crack 34 1200 915 55 000 585 50 52 8S8 0.65 € .34 81 No crack as 1100 920 60 8S0 550 35 48 β34 1.3B 6.69 67 Craekinc 36 980 6Β0 50 8S0 550 25 5B 807 1.13 6.84 5β No cr 钃 ck 37 1280 S95 40-* 25 70 Β12 〇.ββ 6.74 124 No crack 3β 1200 9Β0 25 Shout 16 68 80S 0.90 6.73 t45 No crack 39 1100 β30 70 • One 16 62 Β15 0.91 6.74 53 No crack 40 1250 eeo SO 25 25 824 0.79 2.33 162 No crack 41 mo 960 60 850 600 70 15 807 1.24 7.42 se No crack 42 1100 900 60 790 445 40 10 βZ5 0.92 5.09 91 No crack 1) Thermodynamic calculation of phase moire fraction at 700 ° C. 2) Thermodynamic calculation of phase Mohr fraction at 700 C. 3) The thickness of the steel plate in the final rolling direction of the plate is 1/4 thick in the cross-section direction. 5 The average equivalent circle diameter of the old Vosted iron particles. 4) JIS Z 3158: oblique y-shaped weld fracture test. 31 200305650 Cut and description of the invention Table 4 Category The steel of the invention in this application Normal temperature strength vTrs (¾) 700 ^ eoot Reproduced ΗΛZ toughness (J) i Drop strength 1) (MP ·) Tensile strength 2) (MPa) Drop ratio (%) Ambient Strong Shoulder (MP ·) Actual 'YS ratio 3) ⑻ Ambient Strong β CMP *) Actual' YS, Dagger 4). (%) 1 3ββ 499 73 -51 23S 64 es Z3 Z20 2 409 530 77 -40 257 65 94 23 210 3 3S3 489 72 -32 232 ββ 86 24 199 4 348 486 η -35 225 es 81 23 187 5 408 530 77 -37 263 64 93 23 225 β 362 490 73 -40 237 65 85 24 218 7 421 539 78 -35 274 es 97 23 155 Β 3S7 492 73 -41 233 85 24 230 9 375 506 74 -33 246 ¢ 5 B8 24 224 10 S16 S99 74 -51 337 65 135 2 Xin 250 11 521 089 76 -45 374 7Z 137 2S Z05 12 488 Γ ββ -45 325 69 121 2S 227 13 535 723 74 -42 327 61 1Z1 23 238 14 483 729 «6 -40 335 6S 124 26 241 IS 551 660 81 -42 377 68 136 Z5 254 1β 492 703 70 -43 346 70 128 21 271 17 S24 721 73-♦ e 3S6 74 143 27 242 IS 50β 699 72 -52 343 68 128 25 227 Table 4 Continuation category steel room temperature strength vTrs (" C) 700 * t ΟΟΧ Reproduces HAZ toughness ^ 'U) Yield strength 1: (MP · > Tensile strength 2: (MPa) Yield ratio (X) Yield strength (MP ·) Actual' YS ratio 3) W Yield strength (MP) Actual 'YS ratio 4) (%) 19 516 610 85 -30 ιβο 35 65 13 198 20 304 453 67 -41 128 42 44 14 zto 21 621 755 82 -35 111 44 89 14 tea 21 320 485 69 20! 63 84 26 2ZS 23 3β0 509 75 -1 249 6 «89 23 18 24 420 539 78 -S Z7B 6S 101 24 22 25 402 525 77 -34 181 45 β £ 15 115 26 5 $ 4 670 S3 -4S 351 63 123 22 25 27 383 511 7S -30 168 44 52 14 217 2 «4Z4 542 7β -25 281 68 101 24 2 $ more than 19 438 5S2 79 -40 245 56 82 19 22 less than 30 3B S15 75 -2 253 65 90 23 21 steel 31 276 433 64 -21 175 63 66 24 1B8 ZZ 437 551 79 -β 288 66 103 24 IS 33 390 S17 7β -1 255 es 23 35 34 378 S08 75 -25 248 6S 8β 23 21 35 373 504 74 -28 243 6S ββ 24 42 3S 39B 523 76 -41 172 43 54 14 220 37 435 550 79 —40 285 60 100 23 24 38 431 547 79 -32 282 65 99 23 22 39 413 533 77 -39 178 43 5B 14 215 40 530 620 85 -45 350 96 12 2 23 208 41 326 469 70 -27 215 68 69 2t 196 42 291 444 66 -38 193 66 73 25 20 «32 200305650 玖, Description of invention 1) Room temperature drop strength 2 325MPa 2) Room temperature tensile strength 2490MPa 3) at 700 The ratio of the drop strength in ° C to the actual effect of the drop strength at room temperature (p) ^ 45%. 5 4) The ratio of the fall-off intensity at 800 ° C to the actual effect of the fall-off intensity at room temperature (p) ^ 45G / 〇. 5) PT: 1400 ° C, At8 / 5 = 99S, vE〇2 27J.

Industrial availability

In the steel produced by the chemical composition and manufacturing method of the present invention, the microstructure 10 is a mixed structure of fertilized iron, toughened iron, or a single structure of toughened iron. It is a high-tensile steel with a strength of 490 MPa or more at room temperature. High temperature / normal temperature stress ratio in 600 ~ 800 ° c (high temperature drop stress / normal temperature drop stress): p When the steel temperature is T (° C), p satisfies ρ ^ -〇.〇〇29χΤ + 2 · 48 The characteristics, and the characteristics necessary for building refractory steel, are completely different from the previous 15 new steels. 33

Claims (1)

20030565, patent application scope 1. A high-tensile steel with excellent high-temperature strength, expressed in mass%, containing C: 0.005% or more and less than 0.008%, Si: 0.5% or less, Mn: 0.1 ~ 1.6%, ρ: 0.002% or less, s: 0.01% or less, Mo ·· 0 · 1.5%, Nb: 0.03 ~ 0.3%, Ti: 0.025% or less, B: 0.0005 ~ 0.003%, A1: 0.06% or less, N: 0.006% or less, and composed of the remaining Fe and unavoidable impurities. 2. If the high-tensile steel with excellent high-temperature strength in item 丨 of the patent application scope, the steel is a dimensionless stress reduction rate from the stress at normal temperature to the stress at high temperature (high temperature stress / normal temperature stress) : P In a range where the steel temperature T (° C) is 600 ° C or more and 800 ° C or less, those satisfying -0.029χT + 2.80 are satisfied. 3. If the high-tensile steel with excellent high-temperature strength in item 1 of the scope of the patent application, the aforementioned steel is a toughened iron single-structure at normal temperature, or ferrous iron and toughened iron when heated at a high temperature equivalent to that in a fire. The mixed structure is also 'when heated at a high temperature comparable to that in a fire, the temperature (Ac〗) of the inverse state to Vostian iron is more than 800 ° C, and the fall stress at normal temperature will not be the fall stress at high temperature. Reduced stress reduction rate (high temperature drop stress / normal temperature drop stress): p satisfies p- _〇 · 〇〇 in the range of the steel temperature T (° c) is 600 ° C or more and 800 ° C or less. 29χΤ + 2.80 04. If the high-tensile steel with excellent high-temperature strength is the first item in the scope of patent application, where the aforementioned steel is in the high-temperature area above 600 ° C and below 800t, the stress at normal temperature will reduce the stress at high temperature Stress dimensionless stress reduction rate (high temperature drop stress / normal temperature drop stress): p meets the steel temperature T (34 200305650, application patent range C) in the range of 600 ° C to 800 ° C. 0 · 0029χΤ + 2 · 80, and, When heated at a comparable high temperature in a fire, the toughened iron single structure at normal temperature, or the mixed structure of fertilized iron and toughened iron is inversely converted into a Vostian iron with a temperature (Aci) exceeding 8 ° (^ c In addition, the thermodynamically stable precipitated carbonitriding phase is maintained at a Mohr fraction of 5χ 1 (Γ4 or more and solid solution in the aforementioned toughened iron single structure, or a mixed structure of fat iron and toughened iron. The total amount of Mo, Nb, and Ti in the ferrite grain structure is the Mohr concentration ΐχ 10-3 or more. 5. If the high-tensile steel with excellent high-temperature strength is the first item in the scope of patent application, it is described In the high-temperature field above 60CTC and below 800 ° C, the reduction rate of the stress at high temperature from the book / DZL is a dimensionless stress reduction rate (high temperature drop stress / normal temperature drop stress): p in steel The temperature T (c) is in the range of 600 ° C to 800 ° c, has a strength satisfying ρ ^ _ 〇〇〇〇〇〇〇χχ + 2 · 80, and has a normal temperature when heated at a high temperature equivalent to a fire. The toughened iron single tissue, or the mixed structure of fertilized iron and toughened iron, reverses the state of Vostian Iron Organizations with a degree (Aci) exceeding 8000 ° C 'and' the average equivalent circle diameter of the old Vostian iron granules are below 120 / zm 'and is in the aforementioned toughened iron single structure, or fat iron and toughened iron In the mixed structure, the thermodynamically stable carbonitride precipitated phase is maintained at a Mohr fraction of 5 x 1 (T4 or more, and the total amount of Mo, Nb, and Ti dissolved in the ferrous iron structure is at Mohr concentration. lx 10-3 or more. 6 · As for the South Tensile Steel with excellent high temperature strength according to any of the items 1 to 5 of the scope of patent application, wherein the aforementioned steel is pCM = C + Si / 30 + Mn / 20 + Cu / 20+ Ni / 60 + Cr / 20 + Mo / 15 + V / 10 + 5B Definition of welding 35 200305650 Pickup, patent application scope Fractured sensuous composition: PCM is less than 0.20%. 7. South tension steel with excellent high-temperature strength according to any one of claims 1 to 6 of the patent scope, wherein the aforementioned steel system is more expressed in mass%, and contains Nom: 0.05-1.0%. Cu: 0.05 ^ 1.〇%, Cr: 0.05-1.0% ^ ν ·· ο · οι ~ 0.1% of one or two or more. 8. South tension steel with excellent high-temperature strength according to any one of items i to 7 of the patent scope of the application, wherein the aforementioned steel system is more expressed in mass% and contains Ni: 0.05-1.0%. Cu: 0.05 ^ 1.〇%. Cr: 0.05-1.0% ^ V. One or two or more of 0.01 to 0.1%, and includes Ca: 0.0000-5 ~ 〇〇⑽ ^, REM: 0.0005-0.004%, Mg: j or two or more. 9.-A kind of high-tensile steel with excellent high-temperature strength such as in the patent claims No. 7 or 8, wherein the aforementioned steels are in the high-temperature area of 60 ° C or higher and 80 ° C or lower, which will be reduced by the stress at room temperature. Non-dimensionalized stress reduction rate at high temperature (high temperature drop stress / normal temperature drop stress): p In the range of steel temperature T (° C) of 600 ° C or more and 800 ° C or less, it has PK) · 0033χΤ + 2 · 80, and when heated at a high temperature comparable to a fire, it has a toughened iron single structure at room temperature, or a mixed structure of fertile grain iron and changed knife iron into a vostian iron The structure with a temperature (ACl) exceeding 80 (rc), and the average equivalent circle diameter of the old Vostian iron particles is 120 # m or less, and in the aforementioned single structure of toughened iron, or a mixture of fat iron and toughened iron The thermodynamically stable carbonitride precipitated phase is maintained in the structure at a Mohr fraction of 5x10.4 or more, and the total amount of M °, Nb, and Ti dissolved in the ferrous iron structure is at a Mohr concentration of lx 36 200305650 Pick up and apply for patent scope 1 (T3 or more. 10 · — High tension with excellent high temperature strength The manufacturing method is to reheat the slab or steel sheet with the steel composition as in any of the items 1 to 9 of the patent application range in a temperature range of 1100 to 1250 ° c, and then to a temperature of 5 850C or more. The hot milk reduces the cumulative reduction below 11,000 to 30% or more, and cools the temperature range above 800 C to a temperature range below 650 ° C at a cooling rate of 0.3 KS · 1 after the completion of hot rolling. The microstructure of the steel forms a toughened iron structure, or a mixed structure of fertilized iron and boehmite. 10 u · A high-tensile steel with excellent high temperature strength, expressed in terms of mass, containing C: 0.005% or more and less than 0 · 〇8%, Si: 0.5% or less, Mn ·· 0 · 1 to 1.6%, P: 0.02% or less, S: 0.01% or less, Μ0: 0.1 ~ 1 · 5%, Nb: 0.03 ~ 0.3%, Ti: 0.025% or less, Β: 0.005 to 0.003%, Α1: 0. 06% or less, ν: 0.006% or less, 15 and composed of residual Fe and unavoidable impurities Moreover, when heated at a high temperature comparable to that in a fire, the mixed structure of the fertile grain iron and the toughened iron with an iron fraction of 20 ~ 95% at normal temperature is inversed into Voss. Tiantie has a structure with a temperature (Aci) exceeding 800 ° C, and has a low drop-down ratio of 20 I2. High-tensile steel with excellent strength, such as the scope of patent application No. 11, in which the aforementioned steel is expressed in mass%, and it also contains Ni 0 05 to 10%, Cu: 0.05 to 10%, cr: 0.05 to 1.0%, and ν: 0.00 to 1% or two or more. 13. If the high-temperature strength of the high-strength sheet with excellent high-temperature strength according to item u or 12 of the patent application 37 200305650, pick up and apply for patent scope of force steel, where the aforementioned steel is expressed in mass%, and also contains Ni: 0.05 ~ 1.0%, Cu: 0.05 ~ 1.0%, Cr: 0.05 to 10%, V: 0.01 to 0.1%, one or two or more types, and includes Ca: 0.05 to 0.004%, REM: 0.0005 to 0.005, Mg: 〇〇〇〇〇1 ～ 〇〇_ · 5 or 1 or more. 14. A method for manufacturing a high-tensile steel with excellent high-temperature strength, comprising castings or steel sheets having a steel composition as in any one of the U.13 to 13 of the scope of application for a patent, from 1,100 to 1,250. (: After reheating in the temperature range, hot-roll at a temperature of 850 ° C or higher so that the cumulative reduction of 1100 or less is 10 or more. After the hot rolling is completed, the cooling rate is 800 at 0.3KS · 1. The temperature range above ° C is cooled to 65 ° C or lower, which makes the microstructure of steel into a toughened iron structure, or a mixed structure of ferrous iron and strontium iron, and has a high temperature heating in the event of a fire. Under normal temperature, the toughened iron fraction at room temperature is 20 ~ 95%, and the mixed structure of fertilized iron and 15 of cut iron is inversely changed to a temperature of Vostian Iron (ACl) exceeding 8000C2. Those with low voltage reduction ratio. · 38 200305650 Lu, (1), the representative representative of this case is: _ ^ (2), the representative symbols of the representative diagrams are briefly explained z (none) 柒, if there is a chemical formula in this case, please Reveal the chemical formula that best characterizes the invention: