JPH0282505A - Rare earth-iron-boron cast magnet - Google Patents

Abstract

PURPOSE:To lower the temperature of a hot processing by adding at least one of Ti, P, La, Hy, and Zn besides a given amount of Cu to an R-Fe-B cast magnet having a predetermined composition. CONSTITUTION:The title magnet compsises 8-30% of R, 2-10% of B, 0.1-3% of Cu, and 3% or less of at least one of Ti, P, La, and Zn, with a residual part substantially comprising Fe, and is formed into a magnetically anisotropic one by hot processing. Ti, P, La, and Hg or Zn are to lower the temperature of hot processing and to obviously improve coercive force. The former effect is considered to originate for at least Zn from a fact that the melting point of Zn is low, i.e., 419 deg.C. In the cast magnet, Cu plays an important roll for manifestation of coercive force. When Cu, which has an about 1080 deg.C melting point, is added, it is distributed to an integrannular Nd rich phase and to a R2Fe14B main phase to more or less lower the temperature of hot processing for the R-Fe-B cast magnet.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a rare earth (abbreviated as R herein and includes Y)-Fe-B cast magnet, and in particular, to The present invention relates to an R-Fe-B cast magnet that can reduce coercive force and further improve coercive force.

[Prior Art] R-Fe-B permanent magnets have been developed in recent years due to their good magnetic properties, and have a composition of R8 to 30 atomic percent (hereinafter simply referred to as %), 82 to 28 percent, and the balance Fe. A sintered anisotropic magnet is known (Japanese Patent Publication No. 61-34242).

Here, the sintered anisotropic magnet is the aforementioned Japanese Patent Publication No. 61-3424
As described in Publication No. 2, it refers to an alloy obtained through the steps of melting/casting, pulverizing, orientation/forming in a magnetic field, and sintering. Various additive elements have also been studied in order to improve magnetic properties, particularly coercive force (iHc). That is, Ga addition (Japanese Patent Application No. 183881/1983, which the present applicant is currently filing)
(see Japanese Patent Laid-Open No. 62-291901), A1 and Cu addition (see Japanese Patent Laid-Open No. 62-218543), and other elements are known.

In addition to sintered magnets, ultra-quenched magnets (JP-A-59-64739, JP-A-60-1004) are used as R-Fe-B permanent magnets.
(see Publication No. 02) has been known for a long time. It is reported in the above-mentioned Japanese Patent Publication No. 61-34242 that no coercive force appears at all with regard to narrowly defined cast magnets produced by melting, casting, and aging treatment methods.

However, by hot working after casting, a cast magnet in a broad sense was invented, which significantly improved the coercive force and imparted magnetic anisotropy (Japanese Unexamined Patent Publication No. 62-205226, No. 6
3-114105, 63-114106).

Here, in Japanese Patent Application Laid-Open No. 62-205226, it is stated that in cast magnets, "If more than a trace amount of copper is present, R-Fe-B
It has been found that the energy product of alloys based on . Described as J, Cu in cast magnet
The effect of adding was negative.

However, in July 1988, the 3
M/Intermag (Intermag) international conference smell, Pr17%, Fe76.5% in atomic%,
Br=12.5KG with a composition of 85% and Cu1.5%
, 1Hc = 10KOe cast magnet was announced by Akioka et al. This was obtained by hot working an alloy cast to form columnar crystal fine grains at goo-toooo degrees centigrade.

Regarding R-Fe-B cast magnets, as disclosed in JP-A-63-114105 and JP-A-63-114106 as preferred embodiments, after melting and casting the material alloy, approximately 1000 Hot worked at ℃, approx. 1000
A manufacturing method that involves heat treatment at °C is known.

[Problem to be solved by the invention] Conventional R-Fe-B cast magnets required hot working at relatively high temperatures as described above, so the molds were made of expensive materials that can withstand high temperatures (e.g. Inconel). It had to be manufactured in Furthermore, when hot working at a high temperature of around 1000°C, there is a problem in that rare earth elements seep out to the surface, causing a leaching phenomenon that causes them to seize on the mold, resulting in non-uniform composition and deterioration of magnetic properties. , the hot working temperature is t
It was desired that the test be carried out at ooo°C. Therefore, the present invention provides an R-Fe-B cast magnet that has an energy product equivalent to that of conventional products and an improved coercive force, and that can be hot worked at a relatively low temperature of less than 1000°C. [Means for Solving the Problem] The present invention aims to solve the problems by: 88-30%, 82-10%, Cu 0.1
3% or less of at least one of Ti = P, La, Hg, and Zn, and the remainder substantially consists of Fe,
This is an R-Fe-B cast magnet that has been made magnetically anisotropic by hot working.

Rare earth R is Y, La-Ce, Pr, Nd-P
a, Sm, Eu-Gd, Tb-Dy, Ha, Er,
One or a combination of two or more of Tm and Yb-Lu can be used, preferably light rare earths mainly composed of Pr and Nd, such as Pr, Pr-Nd, and Ce-Pr-N.
d, etc., and may contain unavoidable impurities, and may be substituted with a heavy rare earth such as Dy-Tb in order to improve coercive force. Pure boron or ferroboron can be used as B, and up to 3 atomic % of A1 or the like may be contained as an impurity.

In the present invention, Ti, P + La, Hg, or Zn has the effect of lowering the hot working temperature and has the effect of significantly improving coercive force. The former effect is thought to result from the fact that at least Zn has a low melting point of 419°C.

Cu plays an important role in the expression of coercive force in cast magnets.The melting point of Cu is approximately 1080°C, and when Cu is added, it forms a part of the grain boundary Nd-rich phase and R2FeIaB.
It is distributed to the main phase and lowers the temperature of hot working of R-Fe-B based cast magnets to some extent. In the present invention, by adding Zn in addition to Cu, it was possible to lower the hot working temperature. In other words, since the melting point of Zn is 419°C, the added Zn mainly enters the grain boundaries and facilitates plastic flow, thus imparting magnetic anisotropy even at a low hot working temperature of less than 1000°C. Can be done. Also C
When Ti, P, La, and Hg were added in addition to u,
Magnetic anisotropy could be imparted even at a low hot working temperature of less than 1000°C.

It is presumed that, like Zn, these elements also enter the grain boundaries and facilitate plastic flow.

Next, I will explain the reasons for limiting the composition. First, 88 to 30
%, if it is less than 8%, it becomes cubic crystal and R-Fe
- Tetragonal R2Fe14B, which is the main phase of a B-based permanent magnet, is not formed, and if it exceeds 30%, R is non-magnetic and the magnetic properties deteriorate. Regarding 82 to 10%, if it is less than 2%, it will become a rhombohedral R-Fe system and no main phase will be formed, and if it exceeds 10%, B will be non-magnetic and the main phase will become coarse after casting. Therefore, the residual magnetic flux density Br is reduced. Addition of Cu is effective in improving coercive force, but if it is less than 0.1%, the intrinsic coercive force iHc decreases, and if it exceeds 3%, the residual magnetic flux density Br decreases. In order to obtain the effect of lowering the hot working temperature, it is preferable to add at least one of Zn to Ti-P, La, and H in an amount of at least 0.01%, and if it exceeds 3%, the saturation magnetic flux density Bs decreases. do. Therefore, each composition is preferably within the above range.

In the present invention, inclusion of unavoidable impurities such as C--S and O is allowed.

In addition, in the present invention, columnar crystals may be formed using an iron mold, but since hot working is performed as a post-process, it is not necessarily necessary to form columnar crystals, so a ceramic mold may be used or the mold may be subjected to vibration. The ingot may also be crushed to homogenize any casting segregation that may occur in the ingot.

In the case of ingot crushing, hot consolidation is required in advance as a pre-warm step. Furthermore, heat treatment after hot working stabilizes the magnetic properties of the material and may be performed.

Regarding the composition of the alloy material, Fe can be replaced with W by CO within a range of about 50% in order to increase the Curie point. Further, in order to increase the coercive force, A1 can be added within a range of about 15%, and for the same purpose, heavy rare earth elements such as Dy and Tb, Mo-Si, etc. can be added.

[Example] The present invention will be explained below with reference to Examples.

(Example 1) Each alloy sample having the composition shown in Table 1 was melted by high-frequency melting, and cast into an iron mold with a width of 3 cm, a length of 3 c++, and a thickness of 1.5 cm, and then heated at 800°C with a temperature of 0.5 cm. Hot upsetting is carried out under a pressure of 6 ton/cm2 until the thickness is reduced by 50%, then heat treated at approximately 800°C for 24 hours, cutting and cutting.
Table 2 was obtained by measuring the magnetic properties of the ground samples.6 The samples marked with * in the table are comparative samples without additives.

As is clear from the table, it was found that even if the hot working temperature was lower than that of the conventional example, improvements in energy product and iHe almost equivalent to those of the conventional example could be obtained.

In addition, because an iron mold was used, the macrostructure of the cross section of the sample had a columnar crystal structure in the direction of the thermal gradient. ) were prepared in the same manner as in Example 1 of Table 2 (Table 1 (atomic %)) except for the hot working temperature, and the hot working temperature was set at 500 to 1100.
Required processing pressure, magnetic properties when varied within the range of °C,
The state of seizure with the die and punch is shown in Table 3 (in the case of the present invention) and Table 4 (in the case of the comparative example).

From the diagram, in the case of the present invention, even at relatively low temperatures,
Cast magnets with good magnetic properties can be obtained with low processing pressure.
In the table, ◎ indicates that there is no seizure at all, O indicates that there is some but no problem in practical use, and Δ indicates that the sample is polished but exceeds 0.5 m5z.
× means that the die and punch will need to be reworked due to complete seizure.

[Effects of the Invention] The present invention provides an R-Fe-B cast magnet containing Cu in addition to T.
Since it contains at least one of i, P, La, and HIZn, the hot working temperature can be lowered, and therefore there is no need to require expensive high temperature resistance for molds and lubricants. is gone. Furthermore, since the leaching of rare earth elements is suppressed, the risk of sticking to the mold is reduced, and the risk of non-uniform composition is also reduced, so that magnetic anisotropy can be easily imparted.

Claims (1)

[Claims] R8-30%, B2-10%, Cu0.1-3 in atomic %
%, at least one of Ti, P, La, Hg, and Zn at 3% or less, and the remainder substantially Fe, and is made magnetically anisotropic by hot working.