Nippon Steel Corporation

Nippon Steel Sumitomo Metal Corporation

Yasushi Tsukano

Masayuki Abe

Kengo Takeda

Takashi Aramaki

Shinichi Yamaguchi

Shuji Yamamoto

Mitsuharu Yamagata

Jun Maki

Toshimasa Tomokiyo

Kazuhisa Kusumi

Nobuo Yoshikawa

There is provided a method for estimating a hardness of a cold worked component including: preparing a test piece for hardness measurement having a dent portion of a shape corresponding to a shape of the contact surface of the punch by using a mounting base on which a test piece is mounted and a punch of which a contact surface to be in contact with the test piece is a curved surface, and compressing the test piece mounted on the mounting base using the punch; measuring hardnesses of the test piece for hardness measurement at a plurality of hardness measurement positions in a measurement direction while taking, as the measurement direction, a direction in the dent portion in which a sheet thickness changes; performing numerical analysis to calculate equivalent plastic strains of the test piece for hardness measurement, and acquiring a hardness-equivalent plastic strain curve on the basis of the hardnesses and the equivalent plastic strains at the hardness measurement positions; and specifying a hardness from the calculated value of equivalent plastic strain of an arbitrary part of the cold worked component on the basis of the hardness-equivalent plastic strain curve by performing numerical analysis to calculate a value of equivalent plastic strain of a cold worked component.

Method for estimating hardness of cold worked component and method for acquiring hardness-equivalent plastic strain curve of steel material

A method of manufacturing a tooth-shaped component including a process of draw-forming a workpiece so as to obtain a cylindrical container, which has a bottom surface portion and a side surface portion; a diameter-reducing process of reducing the diameter of a particular part in which a tooth tip portion is to be formed in the side surface portion of the cylindrical container, so as to increase the thickness of a corner portion such that an external shape of the corner portion between the bottom surface portion and the side surface portion satisfies the following conditional expression (&#x394;R+&#x394;H)&#x2264;2t; and a tooth shape-forming process of forming the tooth tip portion in the particular part of the cylindrical container reduced in diameter in the diameter-reducing process, so as to obtain a tooth-shaped component which has the bottom surface portion, the side surface portion, and the tooth tip portion.

Method of manufacturing tooth-shaped component, and tooth-shaped component

A high-carbon steel sheet has a chemical composition represented by, in mass %, C: 0.60% to 0.90%, Mn: 0.30% to 1.50%, and Cr: 0.20% to 1.00%, and others, and has a structure represented by a concentration of Mn contained in cementite: 2% or more and 8% or less, a concentration of Cr contained in cementite: 2% or more and 8% or less, an average grain diameter of ferrite: 10 &#x3bc;m or more and 50 &#x3bc;m or less, an average particle diameter of cementite: 0.3 &#x3bc;m or more and 1.5 &#x3bc;m or less, and a spheroidized ratio of cementite: 85% or more.

High-carbon steel sheet and method of manufacturing the same

A medium carbon steel sheet for cold working that has a hardness of 500 HV to 900 HV when subjected to high-frequency quenching and a quick cooling to a room temperature is carried out. The medium carbon steel sheet includes, by mass %, C: 0.30 to 0.60%, Si: 0.06 to 0.30%, Mn: 0.3 to 2.0%, P: 0.03% or less, S: 0.0075% or less, Al: 0.005 to 0.10%, N: 0.001 to 0.01%, and Cr: 0.001 to 0.10%, the balance composed of Fe and inevitable impurities. An average diameter d of a carbide is 0.6 &#x3bc;m or less, a spheroidizing ratio p of the carbide is equal to or more than 70% and less than 90%, and the average diameter d (&#x3bc;m) of the carbide and the spheroidizing ratio p % of the carbide satisfy the expression d&#x2266;0.04&#xd7;p&#x2212;2.6.

Medium carbon steel sheet for cold working and method for manufacturing the same

The present invention solves the problem of melting of Al in heating before hot-stamping, which had been a problem in the past in applying hot-stamping to Al-plated steel sheet, and provides Al-plated steel sheet for hot-stamping and a method of hot-stamping using that Al-plated steel sheet to solve the problem of delayed fracture due to residual hydrogen, and, furthermore, a method of a rapid heating hot-stamping using that Al-plated steel sheet. The Al-plated steel sheet of the present invention is produced by annealing the Al-plated steel sheet as coiled in a box-anneal furnace for the time and at the temperature indicated in FIG., and alloying of a plated Al and a steel sheet. Further, a method of rapid heating hot-stamping in the present invention is characterized by cutting out a stamping blank of an Al-plated steel sheet, and heating that blank in heating before hot-stamping by an average temperature with a rising rate of 40&#xb0; C./sec or more and a time of exposure to an environment of 700&#xb0; C. or more of 20 seconds or less, and then hot-stamping it.

Aluminum plated steel sheet for rapid heating hot-stamping, production method of the same and rapid heating hot-stamping method by using this steel sheet

This steel plate for cold forging includes a hot-rolled steel plate, wherein the hot-rolled steel plate includes: in terms of percent by mass, C: 0.13% to 0.20%; Si: 0.01% to 0.8%; Mn: 0.1% to 2.5%; P: 0.003% to 0.030%; S: 0.0001% to 0.008%; Al: 0.01% to 0.07%; N: 0.0001% to 0.02%; and O: 0.0001% to 0.0030%, with a remainder being Fe and inevitable impurities, an A value represented by the following formula (1) is in a range of 0.0080 or less, a thickness of the hot-rolled steel plate is in a range of 2 mm to 25 mm, and an area percentage of pearlite bands having lengths of 1 mm or more in a region of 4/10t to 6/10t when a plate thickness is indicated by t in a cross section of a plate thickness that is parallel to a rolling direction of the hot-rolled steel plate is in a range of not more than a K value represented by the following formula (2),value=O%+S%+0.033Al%&#x2003;&#x2003;(1)value=25.5&#xd7;C%+4.5&#xd7;Mn%&#x2212;6&#x2003;&#x2003;(2).

Growing community of inventors

Tokyo, Japan

Yasushi Tsukano