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HIGH CARBON STEEL PIPE HAVING EXCELLENT COLD WORKABILITY, MACHINABILITY, AND QUENCHING PROPERTIES, AND METHOD FOR MANUFACTURING SAME
HIGH CARBON STEEL PIPE HAVING EXCELLENT COLD WORKABILITY, MACHINABILITY, AND QUENCHING PROPERTIES, AND METHOD FOR MANUFACTURING SAME
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机译:具有出色的冷加工性,可加工性和淬火特性的高碳钢管材及其制造方法
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摘要
Provided are a high-carbon electric-resistance-welded steel tube that combines superior cold workability, machinability, and hardenability and a method for manufacturing such a high-carbon electric-resistance-welded steel tube. Specifically, a high-carbon steel tube is provided as a raw steel tube. The raw steel tube has a composition containing, by mass, 0.25% to 0.60% carbon, 0.01% to 2.0% silicon, 0.2% to 3.0% manganese, 0.001% to 0.1% aluminum, 0.001% to 0.05% phosphorus, 0.02% or less sulfur, 0.0010% to 0.0100% nitrogen, 0.0003% to 0.0050% boron, and 0.0001% to 0.0050% calcium, the balance being iron and incidental impurities. The raw steel tube is heated to and soaked at an Ac 3 transformation point or higher and is then subjected to stretch-reducing rolling at a finishing temperature of rolling of 900°C to (Ac 1 transformation point) with a cumulative reduction in diameter of 30% to 70% within the temperature range of 900°C or lower. This allows the formation, without spheroidizing annealing, of a microstructure containing a ferrite phase and cementite grains dispersed therein that have an average grain size d of 0.1 to less than 0.5 µm and an average distance L between surfaces of adjacent cementite grains of 0.5 to 10 µm. In particular, the steel tube has significantly improved machinability.
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