摘要:
Due to increasing demands for steel to be used for construction such as buildings, pressure vessels, pipe lines or the like, various kinds of high tension steels, particularly steels suitable for welding have increasingly been developed.Heretofore, proposed methods of making such high tension steel have relied on so-called cold rolling and/or rolling followed by quenching and tempering, however, these conventional steels have suffered from drawbacks such as a tempering step indispensable after quenching, softening of welded zone and lack of uniformity in the metal structure in the direction of plate thickness.A compositional feature of the new method resides in addition of minor amounts of Ti and B along with Nb as contributing to grain refining or precipitation hardening elements in addition to limited amounts of other ingredients such as C, Si, Mn, S, Al and N.Further addition of at least one of V, Ni, Cu, Cr, Mo, Ca and REM also acts to improve the properties of the steel.The steel prepared to have the aforesaid composition is subjected to controlled heating, subsequent rolling under prescribed rolling reduction ratio, temperature for terminating rolling and to a specified cooling rate.The steel plate thus processed has a structure having fine bainite grains alone or a duplex grain structure consisting of fine bainite and fine ferrite particularly finer toward the surface so as to satisfy both ductility and toughness without tempering operation and displays good weldability and toughness even at a welded zone as well as stable hardness distribution throughout the plate thickness.
摘要:
A micro-alloy plate having not only high tensile strength and high toughness both at room temperature and low temperature but which also displays superior weldability and excellent toughness at a heat affected zone (HAZ) of welding.The steel contains 0.005-0.08 C, not more than 0.6% Si, 1.4-2.4% Mn, 0.01-0.03% Nb, 0.005-0.025% Ti, 0.005-0.08% Al, not more than 0.003% S, 0.0005-0.005% Ca, not more than 0.005% O, not more than 0.005% N, all being represented by weight and the balance being incidental impurities, further the steel must satisfy the following requirements; ##EQU1## The steel thus prepared is heated at a temperature range of 900.degree.-1000.degree. C., hot rolled with a rolling reduction of more than 60% below 900.degree. C. with a rolling finishing temperature within a range from 20.degree. C. above the Ar.sub.3 point down to 10.degree. C. below the Ar.sub.3 point and, immediately after the rolling, the steel stock is cooled down to 300.degree. C. or lower at a cooling rate of 15.degree.-60.degree. C./sec.The steel may further contain small amounts of at least one alloying element selected from the group of Ni, Cu, Cr, Mo, V and B.Due to these composition controls together with controlled heating, rolling and cooling, the product steel stock obtains a very fine grained and uniform microstructure and thereby satisfies the required mechanical properties suitable for use in welded constructions in many fields such as buildings, pressure vessels, the ship building industry and pipe lines.
摘要:
A method for producing a steel sheet having excellent low-temperature toughness, comprising a step of heating to a temperature not higher than 1150.degree. C., a steel slab containing 0.01 - 0.13% C, 0.05 - 0.8% Si, 0.8 - 1.8% Mn, 0.01 - 0.08% total Al, 0.08 - 0.40% Mo and not more than 0.015% S with the balance being iron and unavoidable impurities, and a step of hot rolling the steel slab thus obtained by at least three passes with a minimum reduction percentage not less than 2% by each rolling pass in a temperature range of 900 - 1050.degree. C, a total reduction percentage not less than 50%, and with a finishing temperature not higher than 820.degree. C.
摘要:
A high-corrosion-resistant martensitic stainless steel possessing excellent weldability and SSC resistance, having a tempered martensitic structure, characterized by comprising steel constituents satisfying by weight C: 0.005 to 0.035%, Si: not more than 0.50%, Mn: 0.1 to 1.0%, P: not more than 0.03%, S: not more than 0.005%, Mo: 1.0 to 3.0%, Cu: 1.0 to 4.0%, Ni: 1.5 to 5.0%, Al: not more than 0.06%, N: not more than 0.01%, and Cr satisfying a requirement represented by the formula 13>Cr+1.6Mo.gtoreq.8, C+N.gtoreq.0.03, 40C+34N+Ni+0.3Cu-1.1Cr-1.8 Mo.gtoreq.10, or further comprising at least one element selected from the group consisting of Ti: 0.05 to 0.1%, Zr: 0.01 to 0.2%, Ca: 0.001 to 0.02%, and REM: 0.003 to 0.4%, with the balance consisting essentially of Fe. A process for producing a martensitic stainless steel, comprising the steps of: subjecting a steel plate, produced by hot-rolling a stainless steel slab having the above composition, to austenitization at a temperature of Ac.sub.3 point to 1000.degree. C. to harden the steel plate; subjecting the hardened steel plate to final tempering at a temperature of 550.degree. C. to Ac.sub.1 point; and cold-rolling the steel plate.
摘要:
A method of producing clad steel plate comprises the steps of preparing an assembly slab by superposing a stainless-steel or nickel alloy cladding material onto base metal consisting essentially of, by weight, 0.020 to 0.06% carbon, 0.5% or less silicon, 1.0 to 1.8% manganese, 0.03% or less phosphorus, 0.005% or less sulfur, 0.08 to 0.15% niobium, 0.005 to 0.03% titanium, 0.05% or less aluminum, 0.002 to 0.006% nitrogen, and one or two elements selected from among a group consisting of 0.05 to 1.0% nickel, 0.05 to 1.0% copper, 0.05 to 0.5% chromium, 0.05 to 0.3% molybdenum and 0.001 to 0.005% calcium, with the balance being iron and unavoidable impurities, and welding its periphery; heating the slab to 1100.degree. to 1250.degree. C.; rolling the slab at a reduction ratio of 5 or more and a rolling finish temperature of 900.degree. to 1050.degree. C.; air cooling for 60 to 200 seconds; cooling the slab from a temperature of at least 750.degree. C. to 555.degree. C. or below at a cooling rate of 5.degree. to 40.degree. C./sec, and following this by air cooling.
摘要:
A process for producing high-tension bainitic steel having high-toughness and excellent weldability by subjecting a bainitic steel of a specific composition to a low-temperature heating and subsequently rolling the steel under specific conditions.
摘要:
An ultra-high strength steel having excellent ultra-low temperature toughness, a tensile strength of at least about 930 MPa (135 ksi), and a microstructure comprising predominantly fine-grained lower bainite, fine-grained lath martensite, or mixtures thereof, transformed from substantially unrecrystallized austenite grains and comprising iron and specified weight percentages of the additives: carbon, silicon, manganese, copper, nickel, niobium, vanadium, molybdenum, chromium, titanium, aluminum, calcium, Rare Earth Metals, and magnesium, is prepared by heating a steel slab to a suitable temperature; reducing the slab to form plate in one or more hot rolling passes in a first temperature range in which austenite recrystallizes; further reducing said plate in one or more hot rolling passes in a second temperature range below said first temperature range and above the temperature at which austenite begins to transform to ferrite during cooling; quenching said plate to a suitable Quench Stop Temperature; and stopping said quenching and allowing said plate to air cool to ambient temperature.
摘要:
This invention adds elements such as Cu, B, Cr, Ca, V, etc., to a low carbon-high Mn--Ni--Mo-trace Ti type steel, and allows the steel to have a tempered martensite/bainite mixed structure containing at least 60% of tempered martensite transformed from un-recrystallized austenite having a mean austenite grain size (d.gamma.) of not greater than 10 .mu.m as a micro-structure, or a tempered martensite structure containing at least 90% of martensite transformed from un-recrystallized austenite. The present invention further stipulates a P value to the range of 1.9 to 4.0 and thus provides a ultra-high strength steel having a tensile strength of at least 950 MPa (not lower than 100 of the API standard) and excellent in low temperature toughness, HAZ toughness and field weldability in cold districts.
摘要:
A method is provided for producing an ultra-high strength steel having a tensile strength of at least about 900 MPa (130 ksi), a toughness as measured by Charpy V-notch impact test at −40° C. (−40° F.) of at least about 120 joules (90 ft-lbs), and a microstructure comprising predominantly fine-grained lower bainite, fine-grained lath martensite, or mixtures thereof, transformed from substantially unrecrystallized austenite grains and comprising iron and specified weight percentages of the additives: carbon, silicon, manganese, copper, nickel, niobium, vanadium, molybdenum, chromium, titanium, aluminum, calcium, Rare Earth Metals, and magnesium. A steel slab is heated to a suitable temperature; the slab is reduced to form plate in one or more hot rolling passes in a first temperature range in which austenite recrystallizes; said plate is further reduced in one or more hot rolling passes in a second temperature range below said first temperature range and above the temperature at which austenite begins to transform to ferrite during cooling; said plate is quenched to a suitable Quench Stop Temperature; and said quenching is stopped and said plate is allowed to air cool to ambient temperature.
摘要:
An ultra-high strength boron-containing steel having a tensile strength of at least about 900 MPa (130 ksi), a toughness as measured by Charpy V-notch impact test at −40° C. (−40° F.) of at least about 120 joules (90 ft-lbs), and a microstructure comprising predominantly fine-grained lower bainite, fine-grained lath martensite, or mixtures thereof, transformed from substantially unrecrystallized austenite grains and comprising iron and specified weight percentages of the additives: carbon, silicon, manganese, copper, nickel, niobium, vanadium, molybdenum, chromium, titanium, aluminum, calcium, Rare Earth Metals, and magnesium, is prepared by heating a steel slab to a suitable temperature; reducing the slab to form plate in one or more hot rolling passes in a first temperature range in which austenite recrystallizes; further reducing said plate in one or more hot rolling passes in a second temperature range below said first temperature range and above the temperature at which austenite begins to transform to ferrite during cooling; quenching said plate to a suitable Quench Stop Temperature; and stopping said quenching and allowing said plate to air cool to ambient temperature.