TH101431A - Mild steel plates for cans and methods for producing them. - Google Patents

Abstract

DC60 (09/07/51) Precipitation-strengthened and refined ductile iron sheets, with a crystalline grain size reduction, containing at least one element of 0.005% to 0.05% niobium, 0.005% to 0.05% titanium, and 0.0005% to 0.005% boron as chemical elements, are produced through continuous annealing. Steel containing at least one element of niobium, titanium, and boron is hot-rolled, cooled at a cooling rate of 40 °C/s or less, and coiled at 550 °C or higher to facilitate the precipitation of cementite after recrystallizing annealing. As a result, ductile iron sheets for cans with a tensile strength of 450 to 550 MPa, a total elongation of 20% or more, and a yield elongation of 5% or less are produced. [Selected Figure] None

Claims (16)

------26/03/2561------(OCR) Page 1 of 2 pages. Claim 1. Ductile iron sheets for cans composed, on a percentage by mass, of 0.03% to 0.13% carbon, 0.03% or less of silicon, 0.3% to 0.6% of manganese, 0.02% or less of phosphorus, 0.1% or less of aluminum, 0.012% or less of nitrogen, at least one element selected from a group containing 0.005% to 0.05% of niobium, 0.005% to 0.05% of titanium, and 0.0005% to 0.005% of boron, and the remainder being iron and iron alloying impurities; a perrite structure with a cementite ratio of 0.5% or more; Perrite structure with an average perrite crystal grain size of 7 pn; heat resistance after lacquer baking treatment is 450 to 550 MPa; total elongation at 20% is higher; The yield elongation is 5%, less than 2. The method for producing ductile iron sheets for cans consists of, hot die steel composed, based on percentage by mass, 0.03% to 0.13% carbon, 0.03% less than silicon, 0.3% to 0.6% manganese, 0.02% less than phosphorus, 0.1% less than phosphorus, 0.012% less than phosphorus, at least one element selected from a group containing 0.005% to 0.05% nitrogen, 0.005% to 0.05% titanium, and 0.0005% to 0.005% boron, and the remainder being iron and other impurities; at the finishing temperature of the Ar transition point, less than; The ductile iron sheet is heated and cooled at an average cooling rate of 40 µg/s, with less vapor than before coiling; the heated ductile iron sheet is coiled to a temperature of 550°C, with more vapor; Page 2 of 2 pages: Wash the coiled ductile iron sheet with acid; cool the acid-washed ductile iron sheet at a cooling reduction rate of 80% or more; continuously annealing the cooled ductile iron sheet at a soaking rate of 67°C to 760°C for a soaking time of 40 seconds or less; and continuously tempering (temper rolling) the annealed ductile iron sheet. 3. The method according to claim 2., and also includes heat treatment at temperatures of 200°C to 500°C after coiling. 4. The method according to claim 2. or 3., also includes transformation operations. Physical properties, excessive (over-aging treatment) at temperatures of 200°C to 500°C after continuous annealing. 1. Ductile iron sheets for cans consist of, on a percentage by mass, 0.03% to 0.13% carbon, 0.03% or less silicon, 0.3% to 0.6% manganese, 0.02% or less phosphorus, 0.1% or less aluminum, 0.012% or less nitrogen, at least one element selected from a group containing 0.005% to 0.05% niobium, 0.005% to 0.05% titanium, and 0.0005% to 0.005% boron, and the remainder being iron and any impurities; a ferrite structure with a cementite ratio of 0.5% or more; a ferrite structure with an average ferrite crystal grain size of 7(formula)m or less; Tensile strength after lacquer baking treatment is 450 to 550 MPa; total elongation is 20% or less; and yield elongation is 5% or less; 2. Ductile iron sheets for cans as per claim 1, where the ferrite structure has a cementite ratio of 0.5% to 10%. 3. Ductile iron sheets for cans as per claim 1, where the average ferrite crystal grain size is 4 to 7 (formula) m. 4. Ductile iron sheets for cans as per claim 1, where the total elongation is 20% to 30%. 5. Ductile iron sheets for cans as per claim 1, where the yield elongation is 1.5% to 5%. 6. Ductile iron sheets for cans as per claim 1, in which at least one element is 0.005% to 0.05% niobium. 7. Ductile iron sheets for cans as per claim 1, which contain at least one element, 0.005% to 0.05% titanium. 8. Ductile iron sheets for cans as per claim 1, in which at least one element is 0.0005% to 0.005% boron. 9. Ductile iron sheets for cans as per claim 1, in which at least one element is 0.005% to 0.05% niobium and 0.005% to 0.05% titanium. 10. Ductile iron sheets for cans as per claim 1, in which at least one element is 0.005% to 0.05% niobium and 0.0005% to 0.005% boron. 11. Method for producing ductile iron sheets for cans, the assembly method consists of the following steps: Hot rolling of steel containing, on the basis of percentage by mass, 0.03% to 0.13% of carbon, 0.03% or less of silicon, 0.3% to 0.6% of manganese, 0.02% or less of phosphorus, 0.1% or less of aluminum, 0.012% or less of nitrogen, at least one element selected from a group containing 0.005% to 0.05% of niobium, 0.005% to 0.05% of titanium, and 0.0005% to 0.005% of boron, and the remainder being iron and any resulting impurities, at a finishing temperature of the transition point Ar3 or higher; then cooling the hot-rolled ductile iron sheets to 550 °C or higher; Acid washing of coiled ductile iron sheets; cold rolling of acid-washed ductile iron sheets at a rolling reduction rate of 80% or more; continuous annealing of cold-rolled ductile iron sheets at a soaking temperature of 670°C to 760°C for a soaking time of 40 seconds or less; and tempering of continuously annealed ductile iron sheets. 12. The method for producing ductile iron sheets for cans under claim 11 also includes a heat treatment step at temperatures of 200°C to 500°C after the coiling step. 13. The method for producing ductile iron sheets for cans under claim 11. also includes an over-aging process at temperatures of 200°C to 500°C following a continuous annealing step. 14. A method for producing ductile iron sheets for cans under claim 11, whereby the cooling step consists of cooling the hot-rolled ductile iron sheet at an average cooling rate of 20 °C/s to 40 °C/s before coiling. 15. Method for the production of ductile iron sheets for cans according to claim 11., where the coiling process consists of coiling hot-rolled ductile iron sheets that are cooled to coiling temperatures of 550 °C to 750 °C. 16. Method for the production of ductile iron sheets for cans according to claim 11., whereby the continuous annealing step consists of continuous annealing of cold-rolled ductile iron sheets at a soaking temperature of 670 °C to 760 °C for a soaking time of 10 to 40 seconds.