Abstract: The present invention provides a high strength thick steel plate for marine structures superior in weldability and low temperature toughness of the HAZ, which is able to be produced at a low cost without use of a complicated method of production, and a method of production of the same, that is, steel for welded structures excellent in low temperature toughness of the weld heat affected zone and a method of production of the same characterized by casting molten steel containing, by mass %, C: 0.03 to 0.12%, Si: 0.05 to 0.30%, Mn: 1.2 to 3.0%, P: 0.015% or less, S: 0.001 to 0.015%, Cu+Ni: 0.10% or less, Al: 0.001 to 0.050%, Ti: 0.005 to 0.030%, Nb: 0.005 to 0.10%, and N: 0.0025 to 0.0060% by the continuous casting method, making the cooling rate from near the solidification point to 800° C. in the secondary cooling at that time 0.06 to 0.6° C./s, hot rolling the obtained slab, and cooling it from a temperature of 800° C. or more.

Abstract: The oxide film thickness of the steel material surface (dH2O+do2) is made to become 15 nm or less where post-treatment after water-cooling is not needed by suitably setting the conditions of the water-cooling start temperature (Ti), water-cooling end temperature (To), steel material thickness (d), concentration of solute oxygen in the cooling water (Do), and cooling rate (CR) in the equation of dH2O+do2=7.98×10?4(Ti?To)dDo+{5.50×10?3(Ti2?To2)?6.51(Ti?To)}/CR.

Abstract: A method for annealing a strip of steel having a variable thickness in its length direction with at least thicker and thinner sections, wherein the strip has been cold rolled to form the thicker and thinner sections, one thicker and one thinner section having a length of at most a few meter. The annealing is performed by continuous annealing.

Abstract: The invention relates to a method of improving the cooling of a blown-gas cooling chamber or of a blown-air cooling section in a line for heat treating steel and/or aluminum, and/or of improving the quality of products for treatment by reducing the vibration generated by the cooling, in which jets of gas or air are projected against each of the faces of the strip traveling through said section or chamber.

Abstract: A steel sheet excellent in mechanical strength, workability and thermal stability and suited for use as a raw material in such fields of manufacturing automobiles, household electric appliances and machine structures and of constructing buildings, and a manufacturing method thereof are provided. The steel sheet is a hot-rolled steel sheet of carbon steel or low-alloy steel, the main phase of which is ferrite, and is characterized in that the average ferrite crystal grain diameter D (?m) at the depth of ¼ of the sheet thickness from the steel sheet surface satisfies the relations respectively defined by the formulas (1) and (2) given below and the increase rate X (?m/min) in average ferrite crystal grain diameter at 700° C. at the depth of ¼ of the sheet thickness from the steel sheet surface and said average crystal diameter D (?m) satisfy the relation defined by the formula (3) given below: 1.2?D?7??formula (1) D?2.7+5000/(5+350·C+40·Mn)2??formula (2) D·X?0.

Abstract: Iron-based alloys and articles in strips, sheets, workpieces and the like are converted into high strength steel with a minimum of cost, time and effort, including producing dual phase materials. This is achievable by extremely rapid micro-treating of low, medium, and high carbon iron-based alloys and articles by rapid heating and rapid cooling at least a portion of the alloy/article. This heating step involves nearly immediately heating the iron-based alloy to a selected temperature above its austenite conversion temperature. Then, the alloy is immediately quenched, also at an extremely fast rate, on at least a portion of the iron-based alloy in a quenching unit adjacent the heating unit. This procedure forms high strength alloy in a desired area, depending upon where the treatment was performed.

Abstract: A method of cooling both surfaces of steel plate, which stably secures precision of cooling control from a start of cooling to an end so as to uniformly cool the top and bottom surfaces of the steel plate and thereby stably secures the steel plate quality and cools the steel plate down to a target temperature with a good precision. The method comprises dividing a steel plate cooling region into at least a spray impact part region and a spray non-impact part region, predicting a heat transfer coefficient for each divided region in advance, computing a predicted temperature history of the steel plate based on this predicted value, and setting and controlling amounts of sprayed coolant on the spray impact part regions by top and bottom surface nozzles.

Abstract: A method for producing a plate of steel which is resistant to abrasion and whose chemical composition includes, by weight: 0.24%?C<0.35%; 0%?Si?2%; 0%?Al?2%; 0.5%?Si+Al?2%; 0%?Mn?2.5% 0%?Ni?5%; 0%?Cr?<5% 0%?Mo?1%; 0%?W?2%; 0.1%?Mo+W/2?1%; 0%?B?0.02%; 0%?Ti?1.1%; 0%?Zr?2.2%; 0.35%<Ti+Zr/2?1.1%; 0%?S?0.15%; N<0.03%, optionally up to 1.5% of copper; optionally at least one element selected from Nb, Ta and V at contents such that Nb/2 +Ta/4+V?0.5%; optionally at least one element selected from among Se, Te, Ca, Bi, Pb at contents which are less than or equal to 0.1%; and the balance being iron and impurities resulting from the production operation. The chemical composition further complying with the following relationships: C*=C?Ti/4?Zr/8+7×N/8?0.095% and 1.05×Mn+0.54×Ni+0.50×Cr+0.3×(Mo+W/2)1/2+K>1.8 with: K=0.5 if B?0.0005% and K=0 if B<0.0005%.

Abstract: The invention relates to ultrahigh strength hot-rolled steel having a chemical composition consisting of, by weight: 0.05%?C?0.1% 0.7%?Mn?1.1% 0.5%?Cr?1.0% 0.05%?Si?0.3% 0.05%?Ti?0.1% Al?0.07% S?0.03% P?0.05% the remainder comprising iron and impurities resulting from the production thereof. Moreover, the inventive steel has a bainitic-martensitic structure which can contain up to 5% ferrite. The invention also relates to a method of producing bands of said steel.

Abstract: A continuous annealing and pickling process of flat cold-rolled products, such as stainless steel strips, to obtain a high surface quality product at high production rates and with a low environmental impact. It comprises the following steps: heating, up to a temperature comprised in the range 650-1050° C., in an atmosphere with an oxygen content comprised in the range from 0.5 to 12%; heating for a time comprised from 10 to 200 sec up to a temperature comprised in the range from 650 to 1200° C. in presence of oxidizing agents and/or inert agents; cooling down to temperatures comprised in the range from 650° C. to ambient tempera in presence of oxidizing agents and/or inert agents; thermochemical or electrolytic descaling and finally possible pickling and/or passivation, by means of the use of pickling baths consisting of mineral acid solutions.

Abstract: A high strength steel sheet with both excellent elongation and stretch-flanging performance is provided. The high strength steel sheet of the present invention comprises, in percent by mass, C: 0.05 to 0.3%, Si: 0.01 to 3.0%, Mn: 0.5 to 3.0%, Al: 0.01 to 0.1%, and Fe and inevitable impurities as the remainder, and has a structure mainly composed of tempered martensite and annealed bainite. The space factor of the tempered martensite is 50 to 95%, the space factor of the annealed bainite is 5 to 30%, and the mean grain size of the tempered martensite is 10 ?m or smaller in terms of the equivalent of a circle diameter. The steel sheet has a tensile strength of 590 MPa or higher.

Abstract: A galvanized steel sheet having (a) a dual phase microstructure with a martensite phase and a ferrite phase and (b) a composition containing by percent weight: carbon in a range from about 0.01% to about 0.18%; manganese in a range from about 0.2% to about 3%; silicon ? about 1.2%; aluminum in a range from about 0.01% to about 0.1%; one or both of chromium and nickel in a range from about 0.1% to about 3.5%; calcium in a range from about 0.0003% to about 0.01%; phosphorus ? about 0.01%; sulfur ? about 0.03%; nitrogen ? about 0.02%; molybdenum ? about 1%; copper ? about 0.8%; one or more of niobium, titanium, and vanadium ? about 1%; and boron ? about 0.006% by weight; and with the balance of the composition being iron and incidental ingredients. In one embodiment, the steel sheet is both galvanized and galvannealed.

Abstract: Steel strips and methods for producing strip are provided. The method for producing steel strips comprises continuously casting low carbon, silicon/manganese killed or aluminum killed molten steel into a strip, the molten steel comprising a concentration of residuals of 2.0 equal to or less than about 2.0 wt % is selected with regard to the microstructure of the finished strip to provide a desired yield strength, where the residuals are selected in desired amounts from the group consisting of copper, nickel, chromium, molybdenum and tin, and cooling the strip to transform the strip from austenite to ferrite in a desired temperature range. Cast steel with improved yield strength properties is produced by such method.

Abstract: A cooling apparatus for a hot rolled steel strip including a top surface cooling means provided above a hot rolled steel strip which is transferred with transfer rollers; and a bottom surface cooling means provided below the hot rolled steel strip, each of the top surface cooling means and the bottom surface cooling means including a protective member having at least one cooling water passage hole; at least one cooling water header opposing the hot rolled steel strip separated by the protective member; and cooling water jetting nozzles protruding from the cooling water header, wherein the tips of the cooling water jetting nozzles are disposed farther from the hot rolled steel strip than the surface, opposing the hot rolled steel strip, of the protective member.

Abstract: A safety armor for protection against gunfire, comprising a shield composed of an alloy steel which has a base carbon content of less than 0.3% by mass of carbon and has been enriched in strength-increasing elements including at least one of carbon and nitrogen by means of a thermochemical treatment in a surface zone extending from at least one outer surface of the shield, with the steel of the surface zone having an increased surface hardness as a result of a thermal treatment including at least one of hardening and tempering carried out after the thermochemical treatment, the steel is enriched to at least 0.5% by mass of carbon in the surface zone and has a minimum hardness of 55 HRC on the outer surface with the presence of carbides in the surface zone, with the shield having a silicon content of not more than 0.4% by mass both in the surface zone and in a lower hardness region adjoining the surface zone which has a carbon content and hardness less than the surface zone.

Abstract: The present invention provides a method for manufacturing an ultra high strength cold-rolled steel sheet, comprising the step of continuously annealing a cold-rolled steel sheet consisting essentially of, in terms of weight percentages, 0.07 to 0.15% C, 0.7 to 2% Si, 1.8 to 3% Mn, 0.02% or less P, 0.01% or less S, 0.01 to 0.1% Sol. Al, 0.005% or less N, 0.0003 to 0.003% B, and the balance being Fe, in which such continuous annealing comprises the steps of: heating the cold-rolled steel sheet at from 800° C. to 870° C. for 10 seconds or more; slowly cooling the heated steel sheet down to from 650° C. to 750° C.; rapidly cooling the slowly cooled steel sheet down to 100° C. or less at a cooling speed of over 500° C./sec; reheating the rapidly cooled steel sheet at from 325° C. to 425° C. for from 5 minutes to 20 minutes; cooling the reheated steel sheet down to room temperature; and coiling the cooled steel sheet.

Abstract: A continuous process for producing a shaped metal member from a feedstock comprising a flat web of metal includes a roll-forming station for shaping the web, a cutting station for cutting the shaped web into individual members, and a processing station for altering a physical characteristic of the metal comprising the members. The processing may include heat treating and/or shaping. The process may also be operable to carry out further operations such as marking, inspection, sorting and the like. Also disclosed is an apparatus for carrying out the process.

Abstract: The invention concerns a method for making an abrasion-resistant steel part consisting of 0.1%?C?0.23%; 0%?Si?2%; 0%?AI?2%; 0.5%?Si+AI?2%; 0%?Mn?2.5%; 0%?Ni?5%; 0%?Cr?5%; 0%?Mo?1%; 0%?W?2%; 0.05%?Mo+W/2?1%; 0%?B?0.02%; 0%?Ti?0.67%; 0%?Zr?1.34%; 0.05%?Ti+Zr/2?0.67%; 0%?S?0.15%; N<0.030, optionally 0% to 1.5% of Cu; optionally Nb, Ta and V such that Nb/2+Ta/4+V?0.5 %; optionally Se, Te, Ca, Bi, Pb contents ?0.1%; the rest being iron and impurities. Additionally: 0.095%?C*=C?Ti/4?Zr/8+7×N/8, Ti+Zr/2?7×N/2?0.05% and 1.05×Mn+0.54×Ni+0.5O×Cr+0.3×(Mo++W1/2)1/2+K>1.8, with K=1 if B?0.0005% and K=0 if B<0.0005%. After austenitization, the method consists in: cooling at a speed >0.5° C./s between AC3 and T=800?270×C*?90×Mn?37×Ni?70×Cr?83×(Mo+W/2) and about T?50° C.; then cooling at a speed 0.1<Vr<150×ep?1.7 between T and 100° C., (ep=thickness of plate in mm); cooling down to room temperature and optionally planishing. The invention also concerns the resulting plate.

Abstract: The invention concerns a method for making an abrasion resistant steel plate having a chemical composition comprising: 0.35%?C?0.8%, 0%?Si?2%; 0%?AI?2%; 0.35%?Si+AI?2%; 0%?Mn?2.5%; 0%?Ni?5%; 0% ?Cr?5%; 0%?Mo?0.050; 0%?W?1%; 0,1%?Mo+W/2?0.5%; 0%?B?0.02%; 0%?Ti?2%; 0%?Zr?4%; 0.05%?Ti+Zr/2?2%; 0%?S?0.15%; N?0,03; optionally 0% to 1.5% of Cu; optionally Nb, Ta or V with Nb/2+Ta/4 +V?0.5%; optionally less than 0.1% of Se, Te, Ca, Bi or Pb; the rest being iron and impurities; the composition satisfying: 0.1 %<C*=C?Ti/4?Zr/8+7×N/8?0.55% and 1.05×Mn+0.54×Ni+0.5O×Cr+0.3×(Mo+W/2)1/2+K>1.8, with K=0.5 if B ?0.0005% and K=0 if B<0.0005% and Ti+Zr/2?7×N/2?0.05%; hardening after austenitization while cooling at a speed >0.5 ° C./s between a temperature >AC3 and ranging between T=800?270×C*?9O×Mn?37×Ni?70×Cr?83×(Mo+W/2) and T?50° C.; then at a core speed Vr<1150×ep?1.7 between T and 100° C., (ep=plate thickness in mm); cooling down to room temperature. The invention also concerns the resulting plate.

Abstract: A nano-crystalline steel sheet and a method of making a nano-crystalline steel sheet are provided. The nano-crystalline steel sheet may be produced by supplying a liquid metallic glass forming alloy to counter-rotating casting rolls. The liquid alloy may form partially solidified layers on each of the casting rolls. The partially solidified layers may then be pressed together by the counter-rotating casting rolls to form a sheet. The twin casting roll method may provide a sufficiently high cooling rate during solidification of the alloy to create a nano-crystalline microstructure.

Abstract: The present invention relates to A high strength steel sheet having a structure which is mainly composed of MD structure (Micro Duplex structure) comprising a ferrite matrix, and as a secondary phase, martensite or martensite and retained austenite, finely dispersed in said matrix, wherein the proportion that the MD structure occupies in the whole structure is 90% or more, wherein the proportion that the secondary phase present in the whole structure occupies in the whole structure is from 10 to 60%, wherein the secondary phase in the MD structure is present in ferrite grains and at grain boundary, in which the proportion of the secondary phase present in the ferrite grains is 50% or more, and wherein the average grain size of the secondary phase in the whole structure is 3 ?m or less. The secondary phase is constituted of martensite, or martensite and retained austenite.

Abstract: Dual phase steel sheet is made using a time/temperature cycle including a soak at about AC1+45° F. to AC1+135° F. and a hold at 850-940F, where the steel has the composition in weight percent, carbon: 0.02-0.20; aluminum: 0.010-0.150; titanium: 0.01 max; silicon: 0.5 max; phosphorous: 0.060 max; sulfur: 0.030 max; manganese: 0.8-2.40; chromium: 0.03-1.50; molybdenum: 0.03-1.50; with the provisos that the amounts of manganese, chromium and molybdenum have the relationship: (Mn+6Cr+10 Mo)=at least 3.5%. The sheet is preferably in the form of a strip suitable for coating in a continuous galvanizing or galvannealing line, and the product is predominantly ferrite and martensite. The strip may be galvanized or galvannealed at a temperature within thirty degrees F. of the temperature of the bath.

Abstract: The present invention relates to a method for cooling a steel plate comprising the steps of: forming a water pool with jets of cooling water being injected to impinge on one another by using one slit-nozzle and a plurality of induced laminar flow nozzles, the slit nozzle being provided in a position on an upper surface side of the steel plate, and the induced laminar flow nozzles being provided in a position on a lower surface side of the steel plate along a transfer direction and a direction perpendicular to the transfer direction; and passing the steel plate into the water pool, wherein when a top portion of the steel plate passes over the induced laminar flow nozzles located at least on the side of highest upstream, a volume of the cooling water to be injected from each of the induced laminar flow nozzles is reduced.

Abstract: A flat rolled, high strength, formable steel product has a yield strength of at least about 100 ksi. The product has sufficient formability such that it can withstand a longitudinal or transverse 180° bend of less than 1.0 times its thickness and is preferably comprised of a high strength, low alloy steel composition containing a vanadium-nitride microalloy. The steel product is preferably produced by cold rolling a first steel product having a yield strength of at least about 70 ksi and a n-value from about 0.1 to about 0.16. Cold rolling of the first steel product reduces its thickness and increases its yield strength to at least 100 ksi.

Abstract: The present invention provides a process for manufacturing a steel strip with low aluminum content, which includes: hot-rolling a steel strip which includes between 0.050 and 0.080% by weight of carbon, between 0.25 and 0.40% by weight of manganese, less than 0.020% by weight of aluminum, and between 0.010 and 0.014% by weight of nitrogen, the remainder being iron and inevitable trace impurities, to form a strip; subjecting the strip to a first cold-rolling, to form a cold-rolled strip; annealing the cold-rolled strip, to form an annealed cold-rolled strip; optionally, subjecting the annealed cold-rolled strip to a secondary cold-rolling; wherein the annealing is a continuous annealing which includes: raising the temperature of the strip to a temperature higher than the temperature of onset of pearlitic transformation Ac1, holding the strip above this temperature for a duration of longer than 10 seconds, and rapidly cooling the strip to a temperature below 350° C. at a cooling rate in excess of 100° C.

Abstract: A high strength steel sheet having (2-1) a base phase structure, the base phase structure being tempered martensite or tempered bainite and accounting for 50% or more in terms of a space factor relative to the whole structure, or the base phase structure comprising tempered martensite or tempered bainite which accounts for 15% or more in terms of a space factor relative to the whole structure and further comprising ferrite, the tempered martensite or the tempered bainite having a hardness which satisfies the relation of Vickers hardness (Hv)?500[C]+30[Si]+3[Mn]+50 where [ ] represents the content (mass %) of each element, and (2-2) a second phase structure comprising retained austenite which accounts for 3 to 30% in terms of a space factor relative to the whole structure and optionally further comprising bainite and/or martensite, the retained austenite having a C concentration (C?R) of 0.8% or more.

Abstract: A method of manufacturing a high strength steel sheet containing, in mass %, C: 0.02 to 0.04%, Si: at most 0.4%, Mn: 0.5-3.0%, P: at most 0.15%, S: at most 0.03%, Al: at most 0.50%, N: at most 0.01%, and Mo: 0.01-1.0%. The method includes performing hot rough rolling either directly or after heating to a temperature of at most 1300° C., commencing hot finish rolling either directly or after reheating or holding, completing finish rolling at a temperature of at least 780° C., performing coiling after cooling to a temperature of 750° C. or below at an average cooling rate of at least 3° C./second, heating to an annealing temperature of at least 700° C. and then cooling to a temperature of 600° C. or below at an average cooling rate of at least 3° C./second, then holding in a temperature range of 450-600° C. for at least 10 seconds, and performing hot dip galvanizing after cooling.

Abstract: A ferritic steel sheet wherein a mean value of X-ray random intensity ratios of a group of {100}<011> to {223}<110> orientations is 3.0 or more and a mean value of X-ray random intensity ratios of three crystal orientations of {554}<225>, {111}<112>, and {111}<110> is 3.5 or less and further at least one of the r values in a rolling direction and a direction at a right angle of that is 0.7 or less.

Abstract: The present invention provides a cooling apparatus having sufficient cooling ability in the cooling process of a continuous annealing facility and capable of minimizing the strip temperature difference in the width direction caused by the high speed blowing of the gas and preventing the strip from fluttering by making the most of the holding rolls, wherein the continuous annealing facility a plurality of nozzles for blowing gas protruding from a surface of a cooling chamber installed in the continuous annealing facility so as to keep the tips of the nozzles 50 to 100 mm distant from the surface of the steel strip and the cooling chamber is disposed so that the maximum width of the steel strip (Wmax:mm) and the distance (H:mm) from the surface of the cooling chamber to the steel strip satisfy the expression (1) below: 6<Wmax/H<13??(1)

Abstract: A method of controlling a continuous steel strip casting process based on customer-specified requirements includes a general purpose computer in which product specifications of steel product ordered by a customer is entered. The computer is configured to automatically map the product specifications to process parameters/set points for controlling the continuous steel strip casting process in a manner to produce the customer ordered product, and in one embodiment produces a process change report detailing such process parameters/set points for operator use in physically implementing such process parameters/set points in the strip casting process. Alternatively, the computer may provide the process parameters/set points directly to the strip casting process for automatic control thereof in producing the customer ordered steel product.

Abstract: A martensitic stainless steel sheet which is hard to be softened by tempering caused by heating during the use of a disk brake, can maintain the predetermined hardness, and has excellent punching workability, bending workability before quenching, and a particularly small shear drop, and in which a predetermined hardness after quenching is constantly achieved, in a low carbon martensitic stainless steel sheet used only after quenching. Specifically, the sheet contains, on the basis of mass percent, 0.030% to 0.100% C; 0.50% or less of Si; 1.00% to 2.50% Mn; more than 10.00% to 15.00% Cr; at least one selected from the group consisting of 0.01% to 0.50% Ti, 0.01% to 0.50% V, 0.01% to 1.00% Nb, and 0.01% to 1.00% Zr; N in an amount defined by the following expression, N: 0.005% to (Ti+V)×14/50+(Nb+Zr)×14/90; and the balance being Fe and incidental impurities.

Abstract: To determine the temperature profile (Tm(t)) of a hot-rolled material (1) in a cooling line (5), a heat conduction equation which takes the following form ? e ? t - div ? [ ? ? ( e , p ) ? · grad ? ? ? T ? ( e , p ) ] = 0 where e is the enthalpy, ? the thermal conductivity, p the degree of phase transformation, ? the density and T the temperature of the rolled material at the rolled-material location and t is the time, is solved in a cooling-line model (4).

Abstract: The invention relates to a method for producing hot strip which features good forming ability and increased strength. This is achieved in that a hot strip (W) which is produced in particular from continuous casting in the shape of reheated slabs or slabs obtained directly from the casting heat, from thin slabs or cast strip, based on a steel comprising (in mass %) C: 0.001-1.05%; Si: ?1.5%; Mn: 0.05-3.5%; Al: ?2.

Abstract: The invention relates to the iron and steel industry. More specifically, the invention describes the manufacture of steel strip intended to be converted into thin packaging, such as for drinks and preserved food.

Abstract: The present invention relates to a method for cooling a steel plate comprising the steps of: forming a water pool with jets of cooling water being injected to impinge on one another by using one slit nozzle and a plurality of induced laminar flow nozzles, the slit nozzle being provided in a position on an upper surface side of the steel plate, and the induced laminar flow nozzles being provided in a position on a lower surface side of the steel plate along a transfer direction and a direction perpendicular to the transfer direction; and passing the steel plate into the water pool, wherein when a top portion of the steel plate passes over the induced laminar flow nozzles located at least on the side of highest upstream, a volume of the cooling water to be injected from each of the induced laminar flow nozzles is reduced.

Abstract: The invention concerns a method for making a multiphase hot-rolled steel strip comprising an ultra-fast cooling operations, which consists in carrying out said ultra-fast cooling operation after controlled slow cooling of the strip on a conventional slow cooling table of the rolling mill. The controlled cooling constitutes a first slow cooling, at the output of the finishing mill, from an end-of-roll temperature to an intermediate temperature of about 750° C. to 500° C.; said first cooling determines the fraction of the first phase (ferrite) in the steel. The ultra-fast cooling (>150° C./s), which solidifies the resulting structure, lowers the temperature of the strip down to a coiling temperature, ranging between about 600° C. and room temperature, at which a second slow cooling is performed which results if the formation of the second phase (bainite or martensite).

Abstract: A method for manufacturing a steel sheet comprising continuously casting a steel containing 0.04 to 0.2 wt. % C, 0.25 to 2 wt. % Si, 0.5 to 2.5 wt. % Mn, and 0.1 wt. % or less Al to form a slab; hot-rolling by rough-rolling the slab to form a sheet bar and finish-rolling the sheet bar with a reduction in thickness at the final stand of less than 30%, the finish-rolling being completed at a temperature from the Ar3 transformation point to the Ar3 transformation point +60° C.; primary-cooling the hot-rolled steel sheet, the primary cooling being started within 1 second after the completion of hot-rolling and conducting the cooling at a cooling speed of higher than 200° C./sec down to a temperature of Ar3 −30° C. to the Ar1 transformation point; slow cooling or air-cooling the primary-cooled steel sheet at a temperature of the Ar3 transformation point to the Ar1 transformation point at 10° C.

Abstract: A steel sheet composition contains appropriate amounts of C, Si, Mn, P, S, Al and N and 0.5 to 3.0% Cu. A composite structure of the steel sheet has a ferrite phase or a ferrite phase and a tempered martensite phase as a primary phase, and a secondary phase containing retained austenite in a volume ratio of not less than 1%. In place of the Cu, at least one of Mo, Cr, and W may be contained in a total amount of not more than 2.0%. This composition is useful in production of a high-ductility hot-rolled steel sheet, a high-ductility cold-rolled steel sheet and a high-ductility hot-dip galvanized steel sheet having excellent press formability and excellent stain age hardenability as represented by a &Dgr;TS of not less than 80 MPa, in which the tensile strength increases remarkably through a heat treatment at a relatively low temperature after press forming.

Abstract: Steel strips and methods for producing steel strips are provided. In an illustrated embodiment, a method includes continuously casting molten low carbon steel into a strip of no more than 5 mm thickness having austenite grains that are coarse grains of 100-300 micron width; and providing desired yield strength in the cast strip by cooling the strip to transform the austenite grains to ferrite in a temperature range between 850° C. and 400° C. at a selected cooling rate of at least 0.01° C./sec to produce a microstructure that provides a strip having a yield strength of at least 200 MPa. The low carbon steel produced desired microstructure.

Abstract: A heat treated steel strap usable in a strapping machine has a tensile strength of at least about 170 KSI, and an elongation of at least about 6.5 percent. The steel strap is fabricated from a coiled steel reduced by cold rolling. The strap has a composition of 0.30 to 0.36 percent carbon, 0.90 to 1.25 percent manganese, and 0.75 to 1.10 percent silicon. The strap is heated to a temperature of about 815° C. to about 900° C. and quenched to a temperature of about 370° C. to about 510° C. The strap has a seal joint break strength of about 4350 pounds when the strap has a width of about one inch and a thickness of 0.030 inches. A method for forming the strap is also disclosed.

Abstract: Dual phase steel sheet is made using a time/temperature cycle including a soak at about AC1+45° F. to AC1+135° F. and a hold at 850-940F, where the steel has the composition in weight percent, carbon: 0.02-0.20; aluminum: 0.010-0.150; titanium: 0.01 max; silicon: 0.5 max; phosphorous: 0.060 max; sulfur: 0.030 max; manganese: 0.8-2.40; chromium: 0.03-1.50; molybdenum: 0.03-1.50; with the provisos that the amounts of manganese, chromium and molybdenum have the relationship: (Mn+6Cr+10 Mo)=at least 3.5%. The sheet is preferably in the form of a strip suitable for coating in a continuous galvanizing or galvannealing line, and the product is predominantly ferrite and martensite. The strip may be galvanized or galvannealed at a temperature within thirty degrees F. of the temperature of the bath.

Abstract: The present invention provides an effective method for mechanically removing iron oxide films formed on the surfaces of a hot rolled steel strip with a high temperature. The method comprises the steps of: maintaining a steel strip coil at a high temperature of 400° C. or more until the phase transformation is completed, after hot rolling; water-cooling the steel strip coil at a speed of at least 50° C./sec to 100° C. or less while uncoiling the coil; correcting the shape of the steel strip using a correction rolling mill; removing oxide films formed on surfaces of the shape-corrected steel strip by injecting water jets to the surface; and drying the steel strip free of oxide films and winding the steel strip. Also, the present invention provides an apparatus for carrying out this method.

Abstract: The invention relates to a higher-strength steel strip or steel sheet comprising a predominantly ferritic-martensitic microstructure with a martensite content of between 4 and 20%, wherein the steel strip or steel sheet, apart from Fe and impurities due to smelting, comprises (in % by weight) 0.05-0.2% C, ≦1.0% Si, 0.8-2.0% Mn, ≦0.1% P, ≦0.015% S, 0.02-0.4% Al, ≦0.005% N, 0.25-1.0% Cr, 0.002-0.01% B. Preferably the martensite content is approximately 5% to 20% of the predominantly martensitic-ferritic microstructure. Such a higher-strength steel strip or steel sheet made from a dual phase steel comprises good mechanical/technological properties even after being subjected to an annealing process which includes an overageing treatment. Furthermore, the invention relates to a method for producing steel strip or steel sheet according to the invention.

Abstract: The invention relates to processes for the production of a buckling-resistant stove-finished structural member from cold rolled and dressed strip (cold strip) non-ageing steel with high bake-hardening potential, more particularly of more than 70 N/mm2. The characterising feature of the invention is that the cold strip is converted by dressing into a yield point stretch-free state (Reh−Rel<2 N/mm2), then stored at a temperature below room temperature and further processed into the form of a structural member, whereafter the strip is finally stove finished.

Abstract: To provide a steel sheet excellent in painting bake hardenability and anti aging property at room temperature: containing, in mass, 0.0001 to 0.20% of C, 2.0% or less of Si, 3.0% or less of Mn, 0.15% or less of P, 0.015% or less of S, and, in addition, 010% or less of Al and 0.001 to 0.10% of N so as to satisfy the expression 0.52Al/N<5 and, further, one or more of 2.5% or less of Cr, 1.0% or less of Mo and 0.1% or less of V so as to satisfy the expression (Cr+3.5MO+39V) ≧0.1, with the balance consisting of Fe and unavoidable impurities; having the value of BH170, evaluated after applying a 2% tensile deformation and then a heat treatment at 170° C. for 20 min., being 45 MPa or more, and any of the value of BH160, evaluated after applying a 2% tensile deformation and then a heat treatment at 160° C. for 10 min., and the value of BH150, evaluated after applying a 2% tensile deformation and then a heat treatment at 150° C. for 10 min.

Abstract: The present invention relates to a high strength steel sheet consisting essentially of 0.04 to 0.1% C, 0.5% or less Si, 0.5 to 2% Mn, 0.05% or less P, 0.005% or less 0, 0.005% or less S, by weight, having 10 &mgr;m or less of average ferritic grain size, and 20 mm/mm2 or less of generation frequency A, which generation frequency A is defined as the total length of a banded secondary phase structure observed per 1 mm2 of steel sheet cross section along the rolling direction thereof. The steel sheet is manufactured by, for example, a method comprising the steps of: hot-rolling a continuously cast slab having the composition described above at temperatures of Ar3 transformation point or above directly or after reheating thereof; and cooling the hot-rolled steel sheet within 2 seconds down to the temperatures of from 600 to 750° C. at cooling speeds of from 100 to 2,000° C./sec, followed by coiling the cooled steel sheet at temperatures of from 450 to 650° C.

Abstract: The method for manufacturing steel sheet comprises the steps of: rough-rolling to form a sheet bar; finish-rolling the sheet bar to form a steel strip; applying primary cooling and secondary cooling to the finish-rolled steel strip; and coiling the secondary-cooled steel strip. The primary cooling is conducted at cooling speeds of 120° C./sec or more down to the temperatures of from 500 to 800° C. The secondary cooling is conducted at cooling speeds of less than 60° C./sec.

Abstract: The present invention aims to produce a cold rolled metal coated multi-phase steel, characterized by a tensile strength of at least 500 MPa, a yield ratio (Re/Rm) lower than 0.65 in skinned conditions, lower than 0.60 in unskinned conditions, and with good metal coating adhesion behavior. In the case of the aluminized steel according to the invention, the steel also has superior resistance to temperature corrosion up to 900° C. and excellent mechanical properties at this high temperature. The hot metal coated steel product having a steel composition with a manganese content lower than 1.5%, chrome content between 0.2 and 0.5%, molybdenum content between 0.1 and 0.25%, and a relation between the chrome and molybdenum content as follows Cr+2 Mo higher than or equal to 0.7%, undergoes a thermal treatment in the hot dip metal coating line defined by a soaking temperature between Ac1 and Ac3, a primary cooling speed higher than 25° C./sec and a secondary cooling speed higher than 4° C./sec.

Abstract: A high tensile strength hot-rolled steel sheet comprises 0.04 to 0.09% C, 0.1% or less Si, 0.5 to 1.5% Mn, 0.02% or less P, 0.01% or less S, 0.1% or less Al, 0.001 to 0.008% N, and 0.01 to 0.15% Ti, by mass %, the content of ingredient there each satisfying the equation (1), and the ferritic grain size &agr; (&mgr;m) satisfying the equation (2): [C]+7×[Si]+0.1×[Mn]+[P]+14×[S]+1.75×[Al] +23×[N]+[Ti]+18×[O]+7×[Cu]+18×[Sn]+7×[Mo]+ 1.7×[Cr]+70×[B]+7×[Ca]+14×[Zr]+14×[V]+7×[Nb] ≦2  (1) 3≦&agr;≦60×[Ti]+8  (2) where, [X] denotes the content (mass %) of element X.

Abstract: The method for manufacturing steel sheet comprises the steps of: forming a sheet bar; forming a steel strip; primary-cooling; air-cooling; secondary-cooling; and coiling. The sheet bar is finish-rolled at finish temperatures of (Ar3 transformation point −20° C.) or more. The primary cooling cools the finish-rolled steel strip at cooling speeds of more than 120° C./sec down to the temperatures ranging from 500 to 800° C.