Process for the production of prestressed steels and its named product
OwnerMax W. Tischhauserinventor
Life of this patent
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Abstract
In a process for producing high-strength, corrosion-resistant and brittle fracture-resistant prestressing steels, there is a fine grain and/or solid solution and/or particle or precipitation hardening, linked with a thermodynamic treatment and subsequent strain hardening. As strengthening measures are used both a solid solution, fine grain and particle or precipitation hardening with a substantially additive effect. The thermomechanical treatment is performed by a controlled rolling of microalloyed, fine grain-melted steels, whilst excluding martensite formation.
Claims22
A process for the production of low carbon, high strength, weldable corrosion-resistant, brittle-fracture-resistant prestressing steel comprising the steps of heating a steel composition containing:
- ______________________________________ 0.04 to 0.20 percent by weight carbon 1.20 to 1.70 percent by weight manganese 0.30 to 0.50 percent by weight silicon 0.035 to 0.06 percent by weight niobium 0.035 to 0.05 percent by weight vanadium 0.30 to 0.50 percent by weight molybdenum 0.30 to 2.00 percent by weight copper 0.04 to 0.06 percent by weight aluminum 0.015 to 0.02 percent by weight nitrogen .ltoreq.0.030 percent by weight phosphorus .ltoreq.0.020 percent by weight sulphur ______________________________________
- the balance being iron and incidental impurities to melt the composition, thereafter cooling said melted composition to form a solidified ladle-composition and thermomechanically treating said solidified ladle-composition by reheating at a temperature below about 1150.degree. C. in a pusher-type furnace, and then rolling said reheated steel into billets of about 120 mm in diameter;
- wherein the thermomechanical treatment comprises a stage in which accelerated cooling is effected without rolling to approximately 650.degree. to 550.degree. C. whereby there is a reduction of the .sigma.-.alpha. transformation and a recrystallization delay;
- and
- wherein the thermomechanical treatment comprises another stage in which rolling takes place in a controlled manner with at least one with a high degree of deformation and at a high speed from approximately 650.degree. to 550.degree. C. to a low final rolling temperature just above the Ar.sub.3 limit, followed by a residence time and delayed cooling of approximately 0.25 minutes per mm diameter.
A process for the production of low carbon, high strength, weldable corrosion-resistant, brittle-fracture-resistant prestressing steel comprising the steps of heating a steel composition containing:
- ______________________________________ 0.04 to 0.20 percent by weight carbon 1.20 to 1.70 percent by weight manganese 0.30 to 0.50 percent by weight silicon 0.035 to 0.06 percent by weight niobium 0.035 to 0.05 percent by weight vanadium 0.30 to 0.50 percent by weight molybdenum 0.30 to 2.00 percent by weight copper 0.04 to 0.06 percent by weight aluminum 0.015 to 0.02 percent by weight nitrogen .ltoreq. 0.030 percent by weight phosphorus .ltoreq. 0.020 percent by weight sulphur ______________________________________
- the balance being iron and incidental impurities to melt the composition, thereafter cooling said melted composition to form a solidified ladle-composition and thermomechanically treating said solidified ladle composition by reheating at a temperature below about 1150.degree. C. in a pusher-type furnace, and then rolling said reheated steel into billets of about 120 mm in diameter;
- wherein the thermomechanical treatment begins by reheating the steel quickly up to 850.degree. C. and then slowly to a temperature at about below 1150.degree. C. observing a staying time in order to dissolve completely micro-alloying elements selected from the group consisting of niobium and vanadium used in the composition;
- wherein the thermomechanical treatment, after reheating and dissolving the micro-alloying elements at a temperature below about 1150.degree. C., comprises a first stage wherein a hot-rolling deformation at a low deformation-temperature above 850.degree. C. is 10 to 45 percent in which rolling takes place in a controlled manner with at least one or several passes with a high degree of deformation and a high speed.
Dependencies are inferred from the claim text.