TH57258B - High carbon hot rolled steel plates and methods for producing them. - Google Patents

Abstract

DC60 (08/02/60) High-carbon hot-rolled ductile iron sheet, a hot-rolled spherical annealed material, exhibiting both excellent flange formability and excellent thickness uniformity, is produced using a process involving: hot rolling of steel with 0.2 to 0.7% carbon by mass to a finishing temperature (deformation point Ar3 - 20 °C) or higher to prepare hot-rolled sheets; cooling the hot-rolled sheets to 650 °C or lower at a cooling rate from 60 °C/s or more to less than 120 °C/s; coiling the hot-rolled sheets after cooling to a coiling temperature of 600 °C or lower; and annealing the coiled hot-rolled sheets at a temperature... Annealing from 640 °C or higher to the transformation point Ac1 or lower. Revised 08/02/2017. High carbon hot rolled ductile iron sheets, which are hot-rolled ductile iron sheets, exhibiting both excellent flange forming ability and excellent thickness uniformity, are produced by a manufacturing process consisting of: hot rolling of steel with 0.2 to 0.7% carbon by mass to a finishing temperature (deformation series Ar3 - 20 °C) or higher to prepare hot-rolled sheets; cooling of the hot-rolled sheets to 650 °C or lower at a cooling rate from 60 °C/sec or higher to less than 120 °C/sec; coiling of the hot-rolled sheets after cooling to a coiling temperature of 600 °C or lower; and annealing of the coiled hot-rolled sheets at a temperature... Annealing from 640°C or higher to transition point A c1 or lower -------------------- High-carbon hot-rolled ductile iron sheets, which are hot-rolled ductile iron sheets, exhibiting both excellent flange formability and excellent thickness uniformity, are produced by a process consisting of: hot rolling of steel with 0.2 to 0.7% carbon by mass to a finishing temperature of (transition point Ar3 - 20°C) or higher to prepare hot-rolled sheets; cooling of the hot-rolled sheets to 650°C or lower at a cooling rate from 60°C/sec or more to less than 120°C/sec; coiling of the hot-rolled sheets after cooling to a coiling temperature of 600°C or lower; and annealing of the coiled hot-rolled sheets at an annealing temperature of 640°C or higher to transition point Ac1 or lower. Selected Figure: Figure 1

Claims (5)

Revised 08/02/2017 1. Method for producing high carbon hot rolled ductile iron sheets consisting of the following steps: Hot rolling of steel with 0.2 to 0.7% carbon, 2% or less of silicon, 2% or less of manganese, 0.03% or less of phosphorus, 0.03% or less of sulfur, 0.08% or less of salt, aluminum, and 0.01% or less of nitrogen, which may be optional. There must also be at least one of the following elements: 0.005% or less of boron, 3.5% or less of chromium, 3.5% or less of nickel, 0.7% or less of molybdenum, 0.1% or less of copper, 0.1% or less of titanium, 0.1% or less of niobium, and 0.1% or less of the total amount of tungsten, vanadium, and zirconium by mass, with the remainder being iron and unavoidable impurities, at a finishing temperature of (transition point Ar3-20°C) or higher to prepare hot-rolled sheets; cooling the hot-rolled sheets to a temperature of 600°C or lower at a cooling rate ranging from 80°C/sec or more to less than 120°C/sec; and winding the hot-rolled sheets after cooling at a winding temperature of 550°C or lower. And the annealing of hot-rolled coiled sheets at an annealing temperature ranging from 640°C to the transition point Ac1 or lower. 2. High-carbon hot-rolled ductile iron sheets, which are hot-rolled ductile iron coils containing 0.2 to 0.7% carbon, 2% or less silicon, 2% or less manganese, 0.03% or less phosphorus, 0.03% or less sulfur, 0.08% or less of salt, aluminum, and 0.01% or less of nitrogen, which may be selected. There is also at least one element present: 0.005% or less of boron, 3.5% or less of chromium, 3.5% or less of nickel, 0.7% or less of molybdenum, 0.1% or less of copper, 0.1% or less of titanium, 0.1% or less of niobium, and 0.1% or less of the total amount of tungsten, vanadium, and zirconium, by mass, with the remainder being iron and unavoidable impurities; the amount of carbides less than 0.5 (formula) m of particle size is 10% or less by volume of the total amount of carbides; and the difference between the maximum hardness Hv max and the minimum hardness Hv min, (formula) Hv(=Hvmax - Hv min) in the sheet thickness direction is 8 or less. 1. The method for producing high-carbon hot-rolled ductile iron sheets consists of the following steps: hot rolling of steel with 0.2 to 0.7% carbon by mass to a finishing temperature of (transition point Ar3 - 20°C) or higher to prepare hot-rolled sheets; cooling the hot-rolled sheets to a temperature of 650°C or lower at a cooling rate ranging from 60°C/second or more to less than 120°C/second; coiling the hot-rolled sheets after cooling at a coiling temperature of 600°C or lower; and annealing the coiled hot-rolled sheets at an annealing temperature ranging from 640°C or higher to transformation point A or lower. 2. Method for the production of hot-rolled high-carbon ductile iron sheets according to claim 1, whereby the cooling step cools the hot-rolled sheet to a temperature of 600 °C or lower at a cooling rate ranging from 80 °C/s or more to less than 120 °C/s, and the coiling step coils the sheet to a temperature of 550 °C or lower. 3. High-carbon hot-rolled ductile iron sheets, which are annealed spherical hot-rolled materials containing 0.2 to 0.7% carbon, 2% or less silicon, 2% or less manganese, 0.03% or less phosphorus, 0.03% or less sulfur, 0.08% or less aluminum, and 0.01% or less nitrogen, by mass; the amount of carbides with particle size less than 0.5 μm is 15% or less by volume to the total amount of carbides; and the difference between the maximum hardness Hvmax and the minimum hardness Hvmin, delta Hv (=Hvmax - Hvmin), in the sheet thickness direction is 10 or less. 4. High carbon steel hot rolled sheets, according to claim 3, where the amount of carbides with particle size less than 0.5 μm is 10% or less by volume of the total amount of carbides, and the difference between the maximum hardness Hvmax and the minimum hardness Hvmin delta Hv (=Hvmax - Hvmin) in the sheet thickness direction is 8 or less. 5. Hot-rolled high-carbon ductile iron sheets, as per claim 3 or claim 4, also contain at least one of the following elements: approximately 0.005% or less of boron, approximately 3.5% or less of chromium, approximately 3.5% or less of nickel, approximately 0.7% or less of molybdenum, approximately 0.1% or less of copper, approximately 0.1% or less of titanium, approximately 0.1% or less of niobium, and approximately 0.1% or less of a combined approximation of tungstate, vanadium, and zirconium by mass.