Nippon Steel Corporation

Kurita Water Industries Ltd.

Yoichi Tanaka

Manabu Hoshino

Masaaki Fujioka

Masanori Minagawa

Takeo Fukui

Tatsuya Kumagai

Ikunori Yokoi

Contaminants present inside an ultrapure water production system are prevented from being fed into a feed pipe connected to a water use point and, after sterilization cleaning, the system is prevented from being contaminated by contaminants captured on a microparticle removal membrane during sterilization cleaning. Ultrapure water having high quality is thereby fed to a water use point within a short period of time. An ultrapure water production system is provided with a tank, a pump, a heat exchanger, an ultraviolet device, an ion-exchange device, a first microparticle removal membrane device, and a second microparticle removal membrane device. Parts of sterilization water and flush water are fed into the first microparticle removal membrane device and discharged from a feedwater-side potion to a concentrated-water-side portion without permeating through a microparticle removal membrane thereof, and the remaining part of the water is passed through the second microparticle removal membrane device.

Ultrapure water production system, ultrapure water production feed system, and method for cleaning thereof

A high-tensile steel plate of low acoustic anisotropy and high weldability having yield stress of 450 MPa or greater and tensile strength of 570 MPa or greater and a process for producing the steel plate are provided. The steel has an Si content of 0.10% or less, thereby achieving a volume ratio of island martensite of 3% or less, contains Nb&#x2267;0.025% and Ti&#x2267;0.005% so as to satisfy 0.045%&#x2266;[Nb]+2&#xd7;[Ti]&#x2266;0.105%, contains Nb, Ti, C and N in ranges such that the value of A=([Nb]+2&#xd7;[Ti])&#xd7;([C]+[N]&#xd7;12/14) is 0.0022 to 0.0055, and has a steel structure wherein bainite volume ratio is 30% or more and pearlite volume ratio is less than 5%.

High-tensile steel plate of low acoustic anisotropy and high weldability having yield stress of 450 MPa or greater and tensile strength of 570 MPa or greater, and process for producing the same

In a method of manufacturing a high tensile strength thick steel plate, a steel slab contains 0.03-0.055% of C, 3.0-3.5% of Mn, and 0.002-0.10% of Al, the amount of Mo is limited to 0.03% or less, the amount of Si is limited to 0.09% or less, the amount of V is limited to 0.01% or less, the amount of Ti is limited to 0.003% or less, the amount of B is limited to 0.0003% or less, and of which Pcm value representing a weld cracking parameter is fallen within the range of 0.20-0.24% and DI value representing a hardenability index is fallen within the range of 1.00-2.60, is heated to 950-1100&#xb0; C. The steel slab is subjected to a rolling process with a cumulative draft of 70-90% when a temperature is in a range of 850&#xb0; C. or more, and then, the steel slab is subjected to a rolling process at 780&#xb0; C. or higher with a cumulative draft of 10-40% when a temperature is in a range of 780-830&#xb0; C., and subsequently, accelerated cooling at a cooling rate of 8-80&#xb0; C./sec is started from 700&#xb0; C. or higher and is stopped at a temperature between room temperature and 350&#xb0; C.

Method of manufacturing high tensile strength thick steel plate

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Tokyo, Japan

Yoichi Tanaka