TH53192B - High carbon hot rolled steel plates and methods for producing them. - Google Patents

Abstract

DC60 (31/03/48) High carbon hot rolled ductile iron sheet has, in terms of mass percentage, 0.10 to 0.7% of carbon, 2.0% or less of silicon, 0.20 to 2.0% of manganese, 0.03% or less of phosphorus, 0.03% or less of sulfur, 0.1% or less of aluminum, 0.01% or less of nitrogen, and the remainder is iron and unavoidable impurities, and has a structure of ferrite with an average grain size of 6 microns or less and carbides with an average grain size of 0.10 microns or more and less than 1.2 microns. Volume ratio. The carbide content with a grain size of 2.0 microns or more is 10% or less, and the volume ratio of ferrite without carbides is 5% or less. The manufacturing process of high-carbon hot rolled ductile iron sheets involves hot rolling, initial cooling, confinement, coiling, acid washing, and annealing. The initial cooling step is to cool the hot rolled ductile iron sheet to its termination temperature, which ranges from 450°C to 600°C at a cooling rate higher than 120°C/second. The confinement step is used as a second cooling step to confine the hot rolled ductile iron sheet that was cooled in the first step at temperatures from 450°C to 650°C until the coiling of the high-carbon hot rolled ductile iron sheet is complete. In terms of percentage by mass, it contains 0.10 to 0.7% carbon, 2.0% or less silicon, 0.20 to 2.0% manganese, 0.03% or less phosphorus, 0.03% or less sulfur, 0.1% or less of aluminum, 0.01% or less nitrogen, and the remainder is iron and unavoidable impurities, with a structure of ferrite with an average grain size of 6 μm or less and carbides with an average grain size of 0.10 μm or more and less than 1.2 μm. Volume ratio. The carbide content with a grain size of 2.0 μm or greater is 10% or less, and the volume ratio of ferrite without carbides is 5% or less. The fabrication method for high-carbon hot-rolled ductile iron sheets involves hot rolling, initial cooling, confinement, coiling, acid washing, and annealing. The initial cooling step is to cool the hot-rolled ductile iron sheet to its termination temperature, which ranges from 450°C to 600°C at a cooling rate higher than 120°C/second. The confinement step is used for the second cooling step to confine the hot-rolled ductile iron sheet that was cooled in the first step at temperatures from 450°C to 650°C until coiling.

Claims (14)

1. Hot-rolled high-carbon ductile iron sheets must contain, in terms of mass percentage, 0.10 to 0.7% carbon, 2.0% or less silicon, 0.20 to 2.0% manganese, 0.03% or less phosphorus, 0.03% or less sulfur, 0.1% or less aluminum, 0.01% or less nitrogen, and the remainder being iron and unavoidable impurities; ferrite with an average grain size of 6 μm or less, and carbide with an average grain size of 0.10 μm or more and less than 1.2 μm; carbides with a volume ratio of 10% or less in the grain size portion of 2.0 μm or more; And ferrite without carbides with a volume ratio of 5% or less. 2. The high-carbon hot-rolled ductile iron sheets under claim 1 also contain at least one element selected from the constituent group in terms of percentage by mass, 0.05 to 1.5% chromium and 0.01 to 0.5% molybdenum. 3. The hot-rolled high-carbon ductile iron sheet pursuant to claim 1 shall also contain at least one element selected from the constituent group in terms of percentage by mass, 0.005% or less of boron, 1.0% or less of copper, 1.0% or less of nickel, and 0.5% or less of tungsten. 4. The hot-rolled high-carbon ductile iron sheet pursuant to claim clause 2 must also contain at least one element selected from the group of elements in terms of percentage by mass, 0.005% or less of boron, 1.0% or less of copper, 1.0% or less of nickel, and 0.5% or less of tungsten. 5. Hot-rolled high-carbon ductile iron sheets, as per any of Reputations 1 through 4, also contain at least one element selected from the constituent group, in terms of percentage by mass, 0.5% or less of titanium, 0.5% or less of niobium, 0.5% or less of vanadium, and 0.5% or less of zirconium. 6. Hot rolled high-carbon ductile iron sheets according to claim 1, in which the silicon content is 0.005 to 2.0% by mass. 7. Hot rolled high carbon steel sheets according to claim 6, where the silicon content is 0.02 to 0.5% by mass. 8. Hot-rolled high-carbon ductile iron sheets according to claim 1, where the manganese content is 0.2 to 1.0% by mass. 9. Hot rolled high carbon steel sheets according to claim 2, where the chromium content is 0.05 to 0.3% by mass. 10. Hot rolled high carbon steel sheets according to claim 2, in which the chromium content is 0.8% to 1.5% by mass. 11. High carbon steel coils according to claim 2, in which the molybdenum content is from 0.05 to 0.5% by mass. 12. The method for producing high-carbon hot-rolled ductile iron sheets consists of the following steps: hot rolling of the steel, which must contain, in terms of percentage by mass, 0.10 to 0.7% carbon, 2.0 or less silicon, 0.20 to 2.0% manganese, 0.03% or less phosphorus, 0.03% or less sulfur, 0.1% or less salt, aluminum, 0.01% or less nitrogen, and the remainder being iron and unavoidable impurities, at the finishing temperature (deformation point Ar3 - 10°C) or higher; the application of an initial cooling stage of the hot-rolled ductile iron sheets down to the termination temperature, ranging from 450°C to 600°C at a cooling rate greater than 120°C/second; and the application of a second cooling stage to confine the hot-rolled ductile iron sheets. The process involves initial cooling at temperatures ranging from 450°C to 650°C until coiling; coiling of hot-rolled ductile iron sheets to a coiling temperature of 600°C or less; acid washing of the coiled hot-rolled ductile iron sheets; and annealing of the acid-washed hot-rolled ductile iron sheets to an annealing temperature ranging from 680°C to the deformation point Ac1. 13. The method under claim 12, where the cooling rate in the initial cooling stage is in the range of 120 to 700 °C/second. 14. The method pursuant to claim 12, where the coil temperature is in the range from 200°C to 600°C.