44 results about "Yield ratio" patented technology

The invention discloses a high-toughness low-yield-ratio steel plate for a bridge and a preparation method of the high-toughness low-yield-ratio steel plate, and relates to the technical field of low-alloy high-strength structural steel, and the steel plate for the bridge comprises the following chemical components in percentage by weight: 0.05% < = C < = 0.09%, 0.20% < = Si < = 0.30%, 1.50% < = Mn < = 1.70%, 0.50% < = Cr < = 0.60%, 0.35% < = Cu < = 0.50%, 0.4% < = Ni < = 0.6%, 0.2% < = Mo < = 0.3%, 0.03% < = Nb < = 0.05%, 0.01% < = Ti < = 0.02%, 0 < = B < = 30 ppm, and the balance of Fe and inevitable impurities. The production method comprises the steps of billet heating and heat preservation; controlled rolling and controlled cooling; the yield strength of the produced steel plate is larger than or equal to 870 MPa, the tensile strength is larger than or equal to 780 MPa, the yield ratio is smaller than or equal to 0.86, the ductility is larger than or equal to 15%, and the impact energy at the temperature of minus 40 DEG C is larger than or equal to 150 J. On the basis that the alloy cost is remarkably reduced, the performance combination of high strength, high toughness and low yield ratio is obtained at the full thickness through process regulation and control, and the steel plate is suitable for the scene of outdoor bridge steel.

Provided is a steel sheet that may be used for automobile parts and the like, and to a steel sheet having an excellent balance of strength and ductility, an excellent balance of strength and hole expansion ratio, and an excellent yield ratio evaluation index, and a method for manufacturing the same. The steel sheet includes: by wt %, C: 0.1 to 0.25%, Si: 0.01 to 1.5%, Mn: 1.0 to 4.0%, Al: 0.01 to 1.5%, P: 0.15% or less, S: 0.03% or less, N: 0.03% or less, B: 0.0005 to 0.005%, a balance of Fe, and unavoidable impurities; and as microstructures, bainite, tempered martensite, fresh martensite, retained austenite and unavoidable structures.

Provided is an angular steel pipe having a low yield ratio and excellent low-temperature toughness and ductility. This angular steel pipe has a prescribed steel component composition, and the steel structure in the center of the plate thickness of the flat plate section has ferrite as the main phase, the area ratio of a second phase comprising one or more elements selected from pearlite, pseudo-pearlite, and upper bainite is 5-30%, and the average crystal grain size is 10.0-30.0 [mu] m. The number of pearlites and pseudo pearlites having an equivalent circle diameter of 2-20 [mu] m inclusive is 500 / mm2 or more, the yield strength of the flat plate section is 295 MPa or more, the tensile strength of the flat plate section is 400 MPa or more, the yield ratio of the flat plate section is 0.85 or less, the uniform elongation of the flat plate section is 8.0% or more, the elongation at break of the flat plate section is 27.0% or more, and the Charpy absorption energy of the corner section at-10 DEG C is 80 J or more. And the ductile-brittle transition temperature of the corner section is-10 DEG C or less.

The purpose of the present invention is to provide a technology relating to: a steel sheet which still has high collision resistance characteristics after being subjected to cold pressing and being formed into a component; and a method for producing the steel sheet.　Disclosed is a steel sheet which has a specific component composition and a specific steel structure, and has a yield ratio of 0.80 or less, wherein: in a tensile test according to JIS Z2241, the retained austenite that disappears during the period from the start of the tensile test to the processing of imparting 1% strain in terms of nominal strain is 0.8% or more in terms of the area ratio with respect to the entire steel structure; and when the processing of imparting 1% strain and a heat treatment at a temperature of 100°C are performed, the amount of increase in YS obtained by subtracting YS before (the processing and the heat treatment) from YS after (the processing and the heat treatment) is 200 MPa or more, and El after (the processing and the heat treatment) is not less than 0.9 × (El before (the processing and the heat treatment)). YS and El represent the yield stress and total elongation of the steel sheet, respectively.

This invention discloses a heat treatment method for improving the yield strength ratio of steel used in continuous extrusion dies. Specifically, the steel is subjected to the following sequential heat treatments: high-temperature normalizing, low-temperature normalizing, spheroidizing annealing, high-temperature quenching, high-temperature tempering, and low-temperature tempering. The high-temperature normalizing temperature is 1070℃~1100℃; the low-temperature normalizing temperature is 710℃~730℃; the spheroidizing annealing temperature is 840℃~870℃; the high-temperature quenching temperature is 1070℃~1100℃; the high-temperature tempering temperature is 620℃~640℃; and the low-temperature tempering temperature is 530℃~550℃. The yield strength ratio of the die steel after heat treatment using this method is ≥0.91, and the hardness is 48~52 HRC.

The invention relates to a low-yield-ratio 785MPa-grade ultra-high-strength thin plate and a preparation method thereof, belongs to the technical field of ultra-high-strength steel, and solves the problem of high yield ratio of existing ultra-high-strength steel. The invention discloses a low-yield-ratio 785MPa-grade ultra-high-strength thin plate. The low-yield-ratio 785MPa-grade ultra-high-strength thin plate comprises the following chemical components in percentage by mass: 0.08-0.12% of C, 0.10-0.20% of Si, 0.5-1.0% of Mn, 5.5-6.5% of Ni and the balance of Fe. 0.5 to 1.0 percent of Cr, and 0.5 to 1.0 percent of Mo; 0.06% to 0.10% of V; ti: 0.008% to 0.015%; p < = 0.005%; ni * Mn is greater than or equal to 3.0 * 10 <-4 > and less than or equal to 6.5 * 10 <-4 >. The yield ratio of the steel is not higher than 0.90, and the steel has the comprehensive characteristics of high strength, excellent low-temperature toughness and the like.

The invention discloses a novel high-strength steel bar process control method which comprises the following steps: (1) firstly, in order to ensure that the strength and the yield ratio reach the standard, presetting the weight percentage of C, Si, Mn, V, Nb and Ceq in initial components of steelmaking, and presetting the temperature of a heating furnace, the steel throwing temperature, the heating time and the continuous casting cooling speed; (2) test rolling is conducted, and when the yield strength does not reach the standard, adjustment is conducted according to whether the tensile strength has allowance or not till the yield strength is larger than 635 Mpa, and the yield-strength ratio is larger than 1.26; (3) whether Agt reaches the standard or not and the bending brittle failure condition are checked, and then adjustment is conducted according to a small-specification steel bar technology and a large-specification steel bar technology so that it can be guaranteed that the yield strength and the yield strength ratio reach the standard; and (4) on the basis of the adjustment, the small-specification reinforcing steel bar technology and the large-specification reinforcing steel bar technology are solidified respectively. The high-strength steel bar can be prepared, and meanwhile the problems that the yield strength is not up to the standard, the strength-to-yield ratio is not up to the standard, Agt is not up to the standard and bending is prone to brittle failure are solved.

The invention discloses 540 MPa-grade low-silicon hot-rolled high-strength dual-phase steel and a manufacturing method thereof. The 540 MPa-grade low-silicon hot-rolled high-strength dual-phase steel comprises, by weight, 0.04%-0.15% of C, smaller than or equal to 0.03% of Si, 1.0%-2.0% of Mn, 0.02%-0.22% of Al, 0.005%-0.025% of Nb, 0.005%-0.025% of Ti, 0.01%-0.10% of V, smaller than or equal to 0.015% of P, smaller than or equal to 0.02% of S and the balance Fe and inevitable impurities. The elements also need to meet the condition that C + Si / 24 + Mn / 6 is greater than or equal to 0.20% and less than or equal to 0.49%; 0.5 < = (Nb + V + Ti) / C < = 1.5. The requirements that the steel plate has high strength and plasticity, low yield ratio and high formability are met at the same time, the high surface requirement is met, the tensile strength of the obtained dual-phase steel is larger than or equal to 540 MPa, the ductility is larger than or equal to 22%, the yield ratio is smaller than or equal to 0.72, and the hole expansion rate is larger than or equal to 40%.

The invention discloses 690MPa-grade low-yield-ratio bridge steel with excellent fracture resistance and crack arrest performance and a manufacturing method thereof. The 690MPa-grade low-yield-ratio bridge steel comprises the following chemical components in percentage by weight: 0.03-0.13% of C, 0.10-0.30% of Si, 0.50-1.50% of Mn, less than or equal to 0.010% of P, less than or equal to 0.002% of S, 1.20-2.00% of Ni, 0.015-0.060% of Alt, 0.020-0.080% of Nb, 0.30-0.80% of Mo, 0.015-0.050% of Ti, 0.0020-0.0050% of Ca, less than or equal to 0.004% of N and the balance of Fe and other inevitable impurities, and the following requirements are met: 1.8% < = C + Mn + Ni < = 3.5% The steel for the bridge, disclosed by the invention, has the advantages of excellent fracture resistance and crack arrest capability, low yield ratio, high strength and high toughness, the yield ratio is less than or equal to 0.85, and the steel for the bridge has good toughness, tensile property and fracture resistance and crack arrest capability.

The invention discloses low-yield-ratio and high-toughness bridge steel and a preparation method, relates to the technical field of low-alloy and high-strength structural steel, and aims to solve the problems that bridge construction has higher requirements on steel performance when developing towards the directions of light weight, large span, high speed, heavy load and the like, and traditional bridge steel is high in yield ratio and cost due to the fact that a large amount of Cr, Mo and other alloy elements are added. The bridge steel with excellent comprehensive mechanical properties is developed by optimizing the alloy element ratio, combining offline quenching, two-phase region treatment and tempering processes and accurately regulating and controlling structure transformation and the proportion of all phases, the yield strength of the bridge steel is larger than or equal to 780 MPa, the tensile strength is larger than or equal to 870 MPa, the yield ratio is smaller than or equal to 0.85, the ductility is larger than or equal to 16%, the impact energy at the temperature of 40 DEG C below zero is larger than or equal to 120 J, and the steel can be used for manufacturing bridges. The high-strength and low-yield-ratio bridge steel has high strength, low yield ratio and good welding performance, breaks through the bottleneck of the traditional technology, provides key material support for bridge steel and structural industry upgrading, and promotes green and efficient bridge construction development.

The invention discloses a low-yield-ratio, high-toughness and low-cost L485M pipeline steel coil plate and a manufacturing method thereof, and the low-yield-ratio, high-toughness and low-cost L485M pipeline steel coil plate comprises the following chemical components in percentage by weight: 0.045 to 0.070 percent of C, 0.045 to 0.075 percent of Nb, 0.028 to 0.045 percent of V, 0.008 to 0.018 percent of Ti, 0.15 to 0.28 percent of Cr, 0.012 to 0.045 percent of Als, 0.0010 to 0.0025 percent of Mg, 0.0008 to 0.0018 percent of Ca and 0.6 to 1.2 percent of Ca / Mg. A C-Mn-Nb-Mg-Ca design is adopted, the yield strength of a rolled plate is 530-600 MPa, the tensile strength is 630-730 MPa, the elongation is larger than or equal to 28%, the Akv mean value at the temperature of-40 DEG C is larger than or equal to 280 J, the DWTT mean value at the temperature of-20 DEG C is larger than or equal to 90%, the hardness value HV10 is smaller than or equal to 220, and the yield ratio is smaller than or equal to 0.82. The problems that an existing rolling technology is complex, the rolling pass multi-procedure cost is high, the product low-temperature toughness index is loose, and the yield ratio is high are solved.

The present invention relates to a thick-walled high-toughness low-yield-ratio steel for a petroleum casing pipe, a petroleum casing pipe, and a manufacturing method for the petroleum casing pipe. In addition to Fe and inevitable impurities, the steel further comprises the following chemical components in percentage by mass: C: 0.30-0.40%, Si: 0.10-0.25%, Mn: 1.0-1.5%, Ti: 0.01-0.10%, Cr: 0.1-1.0%, Al: 0.015-0.035%, Ni≤0.2%, Nb: 0.010-0.040%, P≤0.015%, S≤0.003%, and N≤0.005%, satisfying the following relational expressions: C+Mn+5Cr-2Si+Ti+Nb≥1.8%, preferably 1.800-6.288%, and C+Mn / 6+Cr / 10+Ni / 15≤0.65%, wherein element symbols in the expressions are substituted with the mass percentage contents of the corresponding elements. The steel of the present invention has a yield strength of 379-552 MPa, a tensile strength of greater than or equal to 655 MPa, a yield ratio of less than or equal to 0.700, and a 0°C transverse Charpy impact energy of more than 50 J. The steel of the present invention can be used for producing a petroleum casing pipe having stable performance and a wall thickness of greater than or equal to 14 mm, wherein the petroleum casing pipe has a yield ratio of less than or equal to 0.750.

The invention discloses an anisotropic 700MPa-grade steel plate with low yield ratio and low longitudinal and transverse strength and a manufacturing method thereof. The anisotropic 700MPa-grade steel plate comprises the following components in percentage by weight: 0.070-0.11% of C, less than or equal to 0.20% of Si, 1.30-1.70% of Mn, less than or equal to 0.013% of P, less than or equal to 0.003% of S, 0.30-0.65% of Cr, 0.10-0.30% of Mo, 0.018-0.040% of Nb, 0.008-0.015% of Ti, 0.030-0.060% of Als, less than or equal to 0.0050% of N, less than or equal to 0.0004% of B, 0.0010-0.0035% of Mg and the balance of Fe and inevitable impurities. The ratio of (% Als) / [(% N)-0.292 (% Ti)] is greater than or equal to 27.5; (% C) * [(6.53 (% Si) + 5.17 (% Als) + 1.55 (% Mn) + 10.67 (% P) + 26.39 (% S)] < = 0.36, Mg treatment is performed, the Mg / S ratio is controlled to be 1.0-3.0, and (% Mg) * (% S) 0.28 < = 1.5 * 10 <-3 >. According to the steel plate, the yield strength is larger than or equal to 605 MPa, the tensile strength is larger than or equal to 700 MPa, the single value of Charpy impact energy KV2 at the temperature of-40 DEG C is larger than or equal to 120 J, the single value of KV2 of a welding heat affected zone HAZ-40 DEG C is larger than or equal to 47 J, the yield ratio is smaller than or equal to 0.85, and the low longitudinal and transverse strength anisotropy, namely the longitudinal / transverse strength difference is smaller than or equal to 30 MPa.

The application discloses a kind of mechanical properties prediction system after hot-rolled steel bar heat treatment, the system includes database communication module, process control module, machine learning algorithm module, physical metallurgy model module.The system real-time monitoring collection field production data, and according to the production data of different steel rolling process, it is not under the condition of heat treatment to predict its mechanical properties after heat treatment according to national standard heat treatment process, including tensile yield strength, tensile tensile strength, tensile elongation after fracture, tensile yield ratio test, surface shrinkage.The application realizes the on-line prediction of the mechanical properties of 42CrMo steel bar after heat treatment by using deep convolutional neural network, and the relevant prediction results can be used to replace the actual heat treatment inspection process to reduce production cost.

A collision-resistant steel plate for butane pressure vessels, comprising the following components (wt%): C: 0.10–0.20%, Si: 0.20–0.45%, Mn: 1.60–1.80%, Al: 0.025–0.045%, P≤0.015%, S≤0.005%, V: 0.065–0.085%, Nb: 0.027–0.045%. The process involves: smelting, casting into a billet, heating the billet, rough rolling, finish rolling, cooling, normalizing, and stress relief. The static yield strength Rel of this invention is 460–500 MPa, and the dynamic yield strength Re is 510–760 MPa; the tensile strength is 610–700 MPa; the yield ratio is ≤0.85; and the static elongation after fracture A is 29–41% and the dynamic elongation after fracture A... d The strength-ductility product is 18995–27798 MPa·% at 28–41%; the drop hammer tear (DWTT) energy is 15–19 kJ; when the impact velocity is 5–50 m / s and the impact displacement is 1.5 m, the energy absorbed by the steel plate is 3.57–3.89 kJ, and the grain size of ferrite does not exceed 0.008 μm.

A collision-resistant pressure vessel steel for storing and transporting carbonyl chloride, comprising the following components (wt%): C: 0.10–0.20%, Si: 0.25–0.50%, Mn: 1.65–1.90%, Al: 0.025–0.045%, P≤0.015%, S≤0.005%, V: 0.070–0.10%, Nb: 0.028–0.052%. The process involves: smelting, casting into a billet, heating the billet, rough rolling, finish rolling, cooling, normalizing, and stress relief. The static yield strength Rel of this invention is 500–570 MPa, and the dynamic yield strength Re is 520–787 MPa; the tensile strength is 650–730 MPa; the yield ratio is ≤0.85; and the static elongation after fracture A is 29–42% and the dynamic elongation after fracture A... d The strength-ductility product is 21054-28434 MPa·%; the drop hammer tear (DWTT) energy is 15.7-20 kJ; when the impact velocity is 5-50 m / s and the impact displacement is 1.5 m, the steel plate absorbs 3.85-4.15 kJ of energy, and the ferrite grain size does not exceed 0.008 μm.

Disclosed are a steel with controlled steel ratio and a manufacturing method therefor. The steel comprises the following components in percentage by mass: C: 0.245-0.365%, Si: 0.10-0.80%, Mn: 0.20-2.00%, P: ≤0.015%, S: ≤0.003%, Cr: 0.20-2.50%, Mo: 0.10-0.90%, Nb: 0-0.08%, Ni: 2.30-4.20%, Cu: 0-0.30%, V: 0.01-0.13%, B: 0-0.0020%, Al: 0.01-0.06%, Ti: 0-0.05%, Ca: ≤0.004%, H: ≤0.0002%, N: ≤0.013%, O: ≤0.0020%, and the balance of Fe and inevitable impurities, wherein the components satisfy (8.57*C+1.12*Ni)≥4.8% and 1.2%≤(1.08*Mn+2.13*Cr)≤5.6%. The steel has excellent low-temperature impact toughness and aging impact toughness at −20° C. and −40° C., a rationally controlled yield ratio, and ultra-high strength, ultra-high toughness, and ultra-high plasticity, which can be used in applications such as offshore platform mooring chains, mechanical structures, and automobiles that require high strength and toughness of the steel.

This invention discloses a seismic-resistant straight steel bar, its preparation method, and its application, relating to the field of steel production technology. It comprises the following elements by weight percentage: C: 0.26–0.28%, Si: 0.55–0.65%, Mn: 1.50–1.60%, S≤0.025%, P≤0.025%, V: 0.120–0.140%, N: 0.019–0.022%, Nb: 0.010–0.020%, with the balance being Fe and unavoidable impurities. By controlling the content of each alloying element in the steel bar within a narrow range, C, Si, and Mn exert solid solution strengthening effects, ensuring the yield strength of the steel bar. By controlling the content of microalloying elements such as V and Nb within the above range, the yield strength of the steel bar is improved, while the maximum value of the yield strength is limited. This results in a strength-to-yield ratio ≥1.25 for the steel bar with the above component content, exhibiting better seismic resistance.

The present invention provides a steel sheet which has a TS of 1,180 MPa or more and has a high yield ratio, excellent ductility, excellent bending fracture resistance, and excellent fatigue characteristics. A steel sheet according to the present invention has: a specific component composition; a specific steel structure at 1 / 4 the sheet thickness; a superficial soft layer which has a Vickers hardness of 84% or less of the Vickers hardness at 1 / 4 the sheet thickness, and a thickness of 20 µm to 100 µm inclusive; a steel structure in the superficial soft layer, in which the area ratio of ferrite is 50.0% to 100.0% inclusive, the number ratio of ferrite grains having an area of 50 µm2 or less among the ferrite grains is 0.60 to 0.95 inclusive, and the number ratio of ferrite grains having a (length in rolling direction) / (length in sheet thickness direction) ratio of more than 1.00 among the ferrite grains is 0.70 or more; and a tensile strength of 1,180 MPa or more.

The invention discloses a low-yield-ratio, high-crack-arrest-toughness and low-cost L555M pipeline steel coil plate and a manufacturing method thereof, and the low-yield-ratio, high-crack-arrest-toughness and low-cost L555M pipeline steel coil plate comprises the following chemical components in percentage by weight: 0.035 to 0.055 percent of C, 0.065 to 0.095 percent of Nb, 0.030 to 0.065 percent of V, 0.012 to 0.023 percent of Ti, 0.20 to 0.30 percent of Cr, 0.15 to 0.28 percent of Cu, 0.0006 to 0.0015 percent of B, 0.0012 to 0.0030 percent of Mg, 0.0010 to 0.0020 percent of Ca and 0.8 to 1.1 percent of Ca / Mg. A C-Mn-Nb-B-Cu design is adopted, the Rt of a rolled plate is 0.5585-690 MPa, the Rm is 645-750 MPa, the A50 is larger than or equal to 28%, the Akv mean value at-40 DEG C is larger than or equal to 320 J, the DWTT mean value at-20 DEG C is larger than or equal to 90%, the hardness value HV10 is smaller than or equal to 230, and the yield ratio is smaller than or equal to 0.83. The problems that the alloy cost is high, the rolling process is complex, the rolling pass multi-procedure cost is high, the low-temperature crack arrest toughness index of a product is loose, and the yield strength is high are solved.

The application discloses a production method of 1180MPa grade quenched and partitioned steel with high strength, high yield ratio and high elongation, which controls the molten steel composition supplied to the casting machine in the smelting and continuous casting process of the steel plate as follows: C: 0.15-0.17%, Si: 1.80-1.90%, Mn: 1.5-1.8%, P≤0.020%, S≤0.005%, Alt: 0.025-0.060%, Ni: 0.008-0.012%, Ti: 0.035-0.045%, and the rest is Fe and inevitable impurities; and the rolling process, cooling process and continuous annealing process parameters are optimized and controlled, so that the 1180MPa grade quenched and partitioned steel with mechanical properties meeting the following requirements can be obtained: tensile strength≥1280MPa, yield ratio≥0.75, elongation A 50 ≥19.

The present invention provides: a steel sheet which has a TS of 1,180 MPa or more and has a high yield ratio, excellent ductility, excellent bending fracture resistance, and excellent fatigue characteristics; a member which uses the steel sheet; and methods for producing the same. A steel sheet according to the present invention has: a specific component composition; a specific steel structure at 1 / 4 the sheet thickness; a superficial soft layer which has a Vickers hardness of 84% or less of the Vickers hardness at 1 / 4 the sheet thickness, and a thickness of 20 µm to 100 µm inclusive; a steel structure in the superficial soft layer, in which the area ratio of ferrite is 50.0% to 100.0% inclusive, the number ratio of ferrite grains having an area of 50 µm2 or less among the ferrite grains is 0.60 to 0.95 inclusive, and the number ratio of ferrite grains having a (length in rolling direction) / (length in sheet thickness direction) ratio of more than 1.00 among the ferrite grains is 0.70 or more; and a tensile strength of 1,180 MPa or more.

Provided is a steel plate having TS of 780 to less than 1180 MPa, and having a high yield ratio, excellent ductility, excellent bending fracture resistance, and excellent fatigue characteristics. The steel plate of the present invention has: a prescribed component composition; a prescribed steel structure at the 1 / 4 plate-thickness position; a surface soft layer having a Vickers hardness of 84% or less of the Vickers hardness at the 1 / 4 plate-thickness position and a thickness of 20 μm-100 μm; a steel structure in which, in the surface soft layer, the area fraction of ferrite is 50.0%-100.0%, the proportion of ferrite grains having an area of 50 μm2 or less in the ferrite grains of the surface soft layer is 0.20-0.95, and of said ferrite grains, the proportion of ferrite grains having a rolling-direction length / plate-thickness direction length exceeding 1.00 is 0.70 or more; and a tensile strength of 780 MPa or more.

A steel wire according to one embodiment of the present application contains, by weight%, 0.1 to 0.5% of carbon (C), 0.01 to 0.6% of silicon (Si), 0.6 to 1.6% of manganese (Mn), 0.01 to 1.4% of chromium (Cr), more than 0% and not more than 0.02% of nitrogen (N); at least one selected from 0.01 to 0.06% of aluminum (Al), 0.005 to 0.03% of niobium (Nb), 0.001 to 0.03% of titanium (Ti), or 0.01 to 0.3% of vanadium (V); and the remainder of iron (Fe) and inevitable impurities. The microstructure of the steel wire contains ferrite and pearlite, and the ferrite has an average grain size of 3 µm or less, a uniform elongation of 3.5% or more, and a yield ratio of 90% or more.

The present invention provides a steel sheet having a TS of 1180 MPa or higher, a high yield ratio, excellent ductility, excellent bending fracture resistance, and fatigue properties. The steel sheet of the present invention has a predetermined component composition, a predetermined steel structure at the 1 / 4 position of the sheet thickness, a Vickers hardness of 84% or less of the Vickers hardness at the 1 / 4 position of the sheet thickness, a soft surface layer with a thickness of 20 μm to 100 μm, and in the soft surface layer, the area ratio of ferrite is 50.0% to 100.0%, and of the ferrite grains, the area is 50 μm 2 The steel structure has a number ratio of ferrite grains that is 0.60 or more and 0.95 or less, and of the ferrite grains, the number ratio of ferrite grains with a rolling direction length / plate thickness direction length of more than 1.00 is 0.70 or more, and a tensile strength of 1180 MPa or more.

A collision-resistant pressure vessel steel for storing and transporting carbon disulfide, comprising the following components (wt%): C: 0.10–0.20%, Si: 0.20–0.40%, Mn: 1.35–1.80%, Al: 0.025–0.045%, P≤0.015%, S≤0.005%, Nb: 0.025–0.045%. The process involves: smelting, casting into a billet, heating the billet, rough rolling, finish rolling, cooling, normalizing, and stress relief. This invention ensures a yield strength R... eL ≥360MPa, tensile strength R m With a yield strength of 540–630 MPa, a yield ratio ≤0.85, and an elongation after fracture (A) of 24–40%, the drop hammer tearing (DWTT) energy is 15.5–21 kJ; the dynamic yield strength (Re) is 490–700 MPa, and the dynamic elongation after fracture (A) is... d At 27-40%; when the collision velocity is 6-50 m / s and the collision displacement is 1.5 m, the energy absorbed by the steel plate after the collision is 2.80-3.40 KJ, and the strength-ductility product is 15960-25040 MPa·.

The application provides an Al-Zn casting alloy, which comprises the following components in percentage by mass: Zn 4.3-5.2%, Mg 1.2-1.8%, Cu 0.50-0.85%, Ti 0.15-0.25%, Zr 0.10-0.25%, V 0.10-0.25%, Si≤0.2%, Fe≤0.2%, Mn≤0.2%, and the balance of Al; the sum of the percentage by mass of the components is 100%. The application reasonably designs the component proportion of the alloy, controls Zn, Mg and Cu and other elements and uniformizes and solid-solutes coupling process treatment through a special casting process, so that the Al-Zn casting alloy with high strength and high yield ratio can be obtained by means of the particle excitation nucleation effect of the coupled second phase, the grains are refined at the same time, and a high proportion of near P texture is formed.

The application provides a production method of a low yield ratio Q550 grade high-strength medium plate, and the chemical composition of the steel is as follows: C=0.06-0.08, Si=0.25-0.35, Mn=1.60-1.80, P≤0.015, S≤0.003, Alt=0.030-0.060, Nb=0.045-0.055, B=0.0010-0.0015, Ceq≤0.40%, Pcm≤0.20, and the rest is Fe and residual elements. The process flow is as follows: converter smelting-LF refining-RH vacuum refining-continuous casting-plate blank heating-rough rolling-fine rolling-rolling accelerated cooling to 300-400 DEG C, and then air cooling to room temperature. A fine and uniform small amount of ferrite+granular bainite+lath bainite multi-phase structure is obtained, the thickness range is 20-40 mm, the yield strength is 550-650 Mpa, the tensile strength is 730-830 Mpa, the yield ratio is ≤0.80, the impact at-20 DEG C is ≥200 J, and the method can be widely applied to the field of high-strength structure steel for mining machines, engineering machines and the like.

Provided is a tempered martensitic steel having a low yield ratio and an excellent uniform elongation, the tempered martensitic steel: comprising, by wt %, 0.2-0.6% of C, 0.01-2.2% of Si, 0.5-3.0% of Mn, 0.015% or less of P, 0.005% or less of S, 0.01-0.1% of Al, 0.01-0.1% of Ti, 0.05-0.5% of Cr, 0.0005-0.005% of B, 0.05-0.5% of Mo, 0.01% or less of N, and the balance of Fe and inevitable impurities; having a yield ratio of 0.4-0.6; having a product (TS*U-El), of a tensile strength and a uniform elongation, of 10,000 MPa % or more; and having a microstructure containing, by an area fraction, 90% or more of tempered martensite, 5% or less of ferrite and the balance of bainite.