Hitachi Metals, Ltd.

Koshi Yoshimura

Masanao Kamachi

Atsushi Kikugawa

Tomoori Odaka

Hideyuki Morimoto

Yoshimi Tochishita

Toshinobu Niinae

Nobuhiro Misumi

Mahoro Fujihara

Koji Kamiyama

Takahiro Isozaki

An object of the present invention is to provide a novel method for forming an electrolytic copper plating film having excellent adhesion on the surface of a rare earth metal-based permanent magnet. The method of the present invention as a means for achieving the object is characterized in that after a magnet is immersed in a plating solution, a cathode current density of 0.05 A/dmto 4.0 A/dmfor performing an electrolytic copper plating treatment is applied thereto over 10 seconds to 180 seconds to start the treatment.

Method for forming electrolytic copper plating film on surface of rare earth metal-based permanent magnet

An object of the present invention is to provide a method for producing a surface-modified rare earth metal-based sintered magnet having extremely excellent corrosion resistance even in an environment with fluctuating temperature and humidity and also having excellent magnetic characteristics. The method for producing a surface-modified rare earth metal-based sintered magnet of the present invention as a means for achieving the object is characterized by comprising a step of subjecting a rare earth metal-based sintered magnet to a heat treatment at 200&#xb0; C. to 600&#xb0; C. in an atmosphere having an oxygen partial pressure of 1&#xd7;10Pa to 1&#xd7;10Pa and a water vapor partial pressure ofPa or less with the ratio between the oxygen partial pressure and the water vapor partial pressure (oxygen partial pressure/water vapor partial pressure) being 450 to 20000.

Method for producing surface-modified rare earth metal-based sintered magnet

An object of the present invention is to provide an R&#x2014;Fe&#x2014;B based sintered magnet that exhibits excellent corrosion resistance and maintains excellent adhesion strength to an adherend even under severe conditions, and a method for producing the same. A corrosion-resistant magnet of the present invention as a means for achieving the object is characterized by comprising a chemical conversion film containing at least Zr, V, Al, fluorine, and oxygen as constituent elements and not containing phosphorus over a surface of an R&#x2014;Fe&#x2014;B based sintered magnet with a film made of Al or an alloy thereof therebetween.

Corrosion-resistant magnet and method for producing the same

An object of the present invention is to provide an R&#x2014;Fe&#x2014;B based sintered magnet having on a surface thereof a chemical conversion film with higher corrosion resistance than a conventional chemical conversion film such as a phosphate film, and a method for producing the same. The corrosion-resistant magnet of the present invention as a means for achieving the object is characterized by comprising a chemical conversion film containing at least Zr, Nd, fluorine, and oxygen as constituent elements and not containing phosphorus directly on a surface of an R&#x2014;Fe&#x2014;B based sintered magnet, wherein R is a rare-earth element including at least Nd.

An object of the present invention is to provide a production method for an R&#x2014;Fe&#x2014;B based sintered magnet having a plating film excellent in adhesiveness on the surface thereof, by conducting a series of processes of acid cleaning and smut removal as pretreatments of an R&#x2014;Fe&#x2014;B based sintered magnet, and the subsequent plating treatment effectively without causing trouble. The production method of the present invention includes a series of processes of acid cleaning and smut removal of a magnet as pretreatments, and the subsequent plating treatment is conducted consistently with a state, in which the magnet is placed in a barrel made of synthetic resin. The smut removal is conducted by ultrasonic cleaning of the magnet with rotating the barrel in water in which the dissolved oxygen amount is set to 0.1 ppm to 6 ppm by degassing.

Production method for R&#x2014;Fe&#x2014;B based sintered magnet having plating film on surface thereof

An objective of the present invention is to provide a rare earth metal-based sintered magnet having imparted thereto sufficient corrosion resistance by an oxidative heat treatment, which is resistant even in an environment of fluctuating humidity, while suppressing the deterioration of the magnetic characteristics ascribed to the oxidative heat treatment, and to provide a method for producing the same. As a means of achieving the objective above, the surface-modified rare earth metal-based sintered magnet of the present invention is characterized in that the surface-modified part comprises a surface-modified layer comprising at least three layers formed in this order from the inner side of the magnet, a main layer containing R, Fe, B, and oxygen, an amorphous layer containing at least R, Fe, and oxygen, and an outermost layer containing iron oxide comprising mainly hematite as the constituent, and the method for producing the same is characterized in that it comprises a step of applying a heat treatment to a bulk magnet body in the temperature range of from 200&#xb0; C. to 600&#xb0; C., under an atmosphere with oxygen partial pressure in a range of from 1&#xd7;10Pa to 1&#xd7;10Pa and water vapor partial pressure in a range of from 0.1 Pa to 1000 Pa (exclusive of 1000 Pa).

Method for producing surface-modified rare earth metal-based sintered magnet and surface-modified rare earth metal-based sintered magnet

In an R&#x2014;Fe&#x2014;B based rare-earth sintered magnet according to the present invention, at a depth of 20 &#x3bc;m under the surface of its magnet body, crystal grains of an RFeB type compound have an (RLRH)FeB (where 0.2&#x2266;x&#x2266;0.75) layer with a thickness of 1 nm to 2 &#x3bc;m in their outer periphery. In this case, the light rare-earth element RL is at least one of Nd and Pr, and the heavy rare-earth element RH is at least one element selected from the group consisting of Dy, Ho and Tb.

R-Fe-B type rare earth sintered magnet and process for production of the same

In a method for producing an R&#x2014;Fe&#x2014;B based rare-earth sintered magnet according to the present invention, first, provided is an R&#x2014;Fe&#x2014;B based rare-earth sintered magnet body including, as a main phase, crystal grains of an RFeB type compound that includes a light rare-earth element RL, which is at least one of Nd and Pr, as a major rare-earth element R. Thereafter, the sintered magnet body is heated while a heavy rare-earth element RH, which is at least one element selected from the group consisting of Dy, Ho and Tb, is supplied to the surface of the sintered magnet body, thereby diffusing the heavy rare-earth element RH into the rare-earth sintered magnet body.

R&#x2014;Fe&#x2014;B rare earth sintered magnet and method for producing same

An R&#x2014;Fe&#x2014;B sinlered magnet having on the surface thereof a vapor deposited film of aluminum or an alloy thereof and a method for producing the same. The vapor deposited film of aluminum or an alloy thereof comprises a columnar crystalline structure grown broader from the surface of the R&#x2014;Fe&#x2014;B sintered magnet body outward to the outer surface, which has a part within a region defined in the thickness direction of the film as taken from the surface of the R&#x2014;Fe&#x2014;B sintered magnet to &#x2153; of the film thickness, 5 to 30 intercrystalline gaps of 0.01 &#x3bc;m to 1 &#x3bc;m in width as counted per 10 &#x3bc;m length in the lateral direction of the film. The method comprises controlling the average film formation rate such that it is slower up to a predetermined point and then is speeded up later thereon.

Growing community of inventors

Osaka, Japan

Koshi Yoshimura