Abstract:
鋼線の化学組成が、質量%で、C:0.90~1.10%、Si:0.80~1.50%、Mn:0.30~0.70%、P:0.030%以下、S:0.030%以下、Al:0.010~0.070%、N:0.0010~0.010%、Cr:0~0.50%、V:0~0.10%、B:0~0.005%、Ni:0~1.0%、Cu:0~0.50%、ならびに、残部:Feおよび不純物であり、鋼線の表面から0.1D[D:鋼線の線径]の部位(表層部)のビッカース硬さ(Hv S )と表層部より内側の領域のビッカース硬さ(Hv I )との比が[1.10<Hv S /Hv I ≦1.15]を満足し、鋼線の表面から0.01Dまでの領域(最表層領域)における金属組織が、面積%で、パーライト組織:80%未満、ならびに、残部:フェライト組織および/またはベイナイト組織であり、上記最表層領域より内側の領域における金属組織が、面積%で、パーライト組織:95%以上であり、かつ、引張強さが2000~2400MPaである、高強度PC鋼線。この高強度PC鋼線は、製造方法が容易であって、かつ、耐遅れ破壊特性に優れる。
Abstract:
A wire rod having excellent drawability includes, by wt%, 0.8-1.0% C, 0.3-0.7% Mn, 0.2-0.6% Cr and a balance of Fe and inevitable impurities. A method for manufacturing a super-high-strength steel wire includes: a first heat-treatment step of heating a wire rod having the above steel composition, and maintaining the heated wire rod at 1100~1200?; a second heat-treatment step of maintaining the heated wire rod at 900~1000?; a step of subjecting the wire rod of the second heat-treatment step to lead patenting at 540~640?; and a step of drawing the lead-patented wire rod.
Abstract:
Process for manufacturing rolled steel products, for example tension steels suitable for threading or similar, according to which steels having a C content of between 0.50 and 0.80 % by weight, an Si content of between 0.20 and 0.60 % by weight, and a Mn content of between 0.30 and 0.80 % by weight are subjected, by means of cooling after hot rolling provided by the rolling heat on the output side of the finishing stand, to a surface hardening operation in such a way that the material is immediately and completely transformed into martensite in an edge region, whereas the heat content remaining in the central region causes, during subsequent cooling, the tempering of the martensitic edge region which does not go beyond the bainite region. The process is characterized in that after cooling, cold working is effected followed by tempering. The degree of elongation is preferably 0.5 to 1.5 %; tempering is preferably effected at a temperature between 350 DEG C and 380 DEG C and for a hold time of 5 to 60 seconds at maximum temperature. With this process it is possible to manufacture, in a simple and a profitable manner, rolled steel products, for example tension steels, which fully comply with the requirements of the building industry as regards deformability and mechanical characteristics.
Abstract:
The present invention relates to an ultra-high-strength steel bar and to a method for manufacturing same, wherein the steel bar comprises: C: 0.05 to 0.45 wt %, Si: 0.10 to 0.35 wt %, Mn: 0.1 to 0.85 wt %, Cr: 0.6 to 1.20 wt %, Mo: 0.05 to 0.35 wt %, with the remainder being Fe and other impurities. The method for manufacturing the steel bar involves twice performing a process of reheating and rough-milling billets for the steel bar comprising the above-described alloy composition so as to reduce the prior-austenite grain size, and performing intermediate roll-milling and finishing roll-milling to manufacture steel bars and cooling the steel bars with water to a temperature of 400 to 600°C through a Tempcore process such that a fine ferrite structure is formed at a center layer. The method of the present invention involves forming a martensite structure, serving as a hardening layer, at a surface layer, by means of the alloy design, heat treatment, rolling ratio control, Tempcore process, etc., and enables the center layer to have a fine ferrite structure, thereby producing an ultra-high-strength steel bar which has a yield strength of 800MPa or higher, a tensile strength of 900 MPa or higher, and an elongation percentage of 10% or higher, and which satisfies 180° bending test. The steel bar of the present invention can be combined with high-strength concrete to be effectively used as a main bar or a shear-reinforcing bar in a building structure.
Abstract:
A process of rolling and of thermal treating of rolled sections, in particular steel bars, in which the rolled section is passed through a pre-finishing stand PM, through two waterboxes WB1, WB2 and a finishing mill FM at the inlet temperature T in chosen with a value such that the outlet temperature T out of the rolled section does not exceed temperature T out_max = (Ac3-d 0,7 )°C, where "Ac3" is the temperature at which in the steel, during heating, the transformation of ferrite into austenite ends, and "d" is the diameter of the bar to be treated.
Abstract:
The invention relates to a method for improving the surface characteristics of low-alloyed heat treatable steel in particular for the production of high strength steel wire comprising a martensitic structural base in order to withstand very high pressure and tensile stress in steel constructions. Said low-alloyed martensitic convertible steel is subjected to one or more processing steps in a thermal treatment procedure of a targetted, evenly distributed edge decarburization process at a depth of 1-15 % of the steel mass located below the surface. An arrangement of several steel wire rods produced according to the inventive method is also disclosed.
Abstract:
The invention relates to a method for producing rust-resistant constructional steels which can be used for sheets, strips, pipes, bars etc., in a wide range of areas of application. One preferred use for the inventive steels is the production of smooth or ribbed, weldable concrete steels, i.e. rust-resistant reinforcement steels for reinforced concrete construction. The aim of the invention is to produce rust-resistant, weldable constructional steels which can be classified as martensitic or ferritic-martensitic, which can be manufactured without annealing and cold-forming according a simplified method, and which have at least equivalent material characteristics. According to the invention, the desired characteristics of the rust-resistant constructional steels, such as resistance and strength characteristics, weldability and resistance to corrosion are obtained by means of thermomechanical treatment using the rolling heat instead of annealing and subsequent cold-forming. On cooling, the rust-resistant martensitic or ferritic-martensitic constructional steels were found to have obtained the same or better properties directly from the rolling heat as if they had been heat-treated and then cold-formed. The invention therefore provides a method for producing rust-resistant constructional or concrete steel without annealing and cold-forming, and therefore more cheaply.
Abstract:
A wire rod having excellent drawability includes, by wt%, 0.8-1.0% C, 0.3-0.7% Mn, 0.2-0.6% Cr and a balance of Fe and inevitable impurities. A method for manufacturing a super-high-strength steel wire includes: a first heat-treatment step of heating a wire rod having the above steel composition, and maintaining the heated wire rod at 1100~1200℃; a second heat-treatment step of maintaining the heated wire rod at 900~1000℃; a step of subjecting the wire rod of the second heat-treatment step to lead patenting at 540~640℃; and a step of drawing the lead-patented wire rod.