JPS63241139A - High strength high ductility toughness semi-hard magnetic material - Google Patents

Abstract

PURPOSE:To provide magnetic characteristics, high strength, high ductility and toughness with the titled material by subjecting the alloy contg. specific ratios of C, Si and the balance consisting substantially of Fe to an austempering treatment. CONSTITUTION:The alloy contg., by weight, 0.30-0.80% C, 1.70-3.70% Si and the balance Fe with inevitable impurities is subjected to the austempering treatment. The working such as rolling and forging is preferably executed as well to the alloy at the temp. lower than the A3 transformation point during the austempering treatment or after the austempering treatment. One or more kinds among 0.15-1.10% Mn, 0.20-2.30% Cu, 0.15-1.10% Mo and 0.30-5.50% Ni are furthermore incorporated into the above-mentioned compsn. at need. The semi-hard magnetic material unites the magnetic characteristics, tensile strength and impact toughness and these characteristics can be furthermore changed at need, by the above-mentioned constitution.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a semi-finished material with high strength, excellent ductility and toughness, which is made by austempering an alloy containing as few expensive rare elements as possible. It relates to hard magnetic materials.

[Prior Art] It is difficult to impart high strength and excellent ductility and toughness to a semi-hard magnetic material due to the characteristics of the material.
Conventionally, semi-hard magnetic materials have rarely been made to have high strength and excellent ductility and toughness. Recently, there has been a demand for semi-hard magnetic materials that can be used under high stress conditions, and typical examples include P-6, Picaloy,
Strong steel is used.

[Problems to be solved by the invention] The magnetic properties of conventional P-6 and Picaloy at room temperature are saturation magnetic flux density of 14 to 18 KG, coercive force of 3G to 800
There are 6 kinds of degrees. Tensile strength is 100-150kgf/n5
m2, but it often breaks at extremely low stress of less than 50k (if/ml12).Elongation and reduction of area are both about 1% or less, high notch sensitivity, and lack of ductility and toughness. Therefore, there is a high risk of breakage when used under stress-loaded conditions, making it unreliable.

Furthermore, the typical chemical composition of these alloys is that P-6 is 45C.
o-6N i -4V-Fe, Picaloy is 52Co-
10V-Fe, and both contain large amounts of expensive elements and are expensive.

On the other hand, AIS I 434011゜Al5 is a strong steel that has high strength and commensurate ductility and toughness.
The strength of I H-11 steel and maraging steel at room temperature is 0.
．． The 2% yield strength is about 130 to 240 k (Jf/2), but the magnetic properties are about 20 to 300 e, and the coercive force is insufficient for a semi-hard material. Under conditions where stress is applied. Currently, strong steel is unavoidably used to avoid destruction.

This strong steel also contains large amounts of expensive elements, making it expensive as a whole.

The present invention aims to solve various problems of such conventional semi-hard magnetic materials and to provide a material with magnetic properties, high strength, high ductility, and toughness.

[Means for Solving the Problems] The present invention is aimed at producing an inexpensive semi-hard magnetic material that has high strength, ductility, and toughness without impairing its magnetic properties as a semi-hard magnetic material. As a result of repeated consideration, F.
It has been found that this objective can be achieved by austempering the e-c-si alloy.

That is, in the first invention, C: 0.30 to 0.8 on a weight basis
It is a high-strength, high-ductility, and tough semi-hard magnetic material made by austempering an alloy containing 0% Si, 1.70 to 3.70% Si, and the remainder consisting of unavoidable impurities and Fe. .

In addition, the second invention further includes M n
: 0.15-1.10%, Cu: 0.20-2.3
0%, Mo: 0.15~1.10%, Ni: 0.30~
5.50% of any one type or two or more types are added.

The austempering treatment in the present invention involves rapid cooling from the austenitic temperature range, which is higher than the AI transformation point of the material, to a temperature of 200 to 400°C, which is higher than the Ms point, using a salt bath, mist, or a similar cooling medium. , and is maintained at that temperature for a predetermined distance between the brim.

The main base structures of this alloy are bainite and austenite. Pearlite and ferrite are not necessarily preferred. Therefore, as shown in Figure 1, when cooling from the austenite temperature range, by passing through the pay part without crossing the nose part of the pearlite transformation, the bainite transformation is carried out and the temperature is cooled to room temperature, resulting in bainite and residual austenite. The desired magnetic properties, tensile properties, and impact toughness are imparted by adjusting the respective structure forms.

In order to avoid crossing the nose of pearlite transformation, it is necessary to increase the cooling rate. The cooling rate is affected by the size, especially the thickness, of the workpiece. As the thickness increases, the cooling rate slows down and pearlite transformation occurs across the nose of pearlite transformation.

It is necessary to adjust the chemical composition to move the nose of pearlite transformation to the right so that it does not cross the nose of pearlite transformation even if the cooling rate becomes slower. By adjusting the chemical composition in this way, it is possible to create a coexisting structure of bainite and austenite even if the processed material becomes thick, and if necessary, the cooling medium can be changed from a liquid to a gas with a slower cooling rate. This makes it possible to reduce the amount of deformation during cooling.

Furthermore, since the bainite transformation proceeds in a isothermal manner, the transformation progresses with the time the material is kept in the bainite transformation temperature range, and the progress of the transformation can be stopped by cooling to a temperature lower than the bainite transformation temperature range. The rate of transformation is not rapid in terms of shear as in martensitic transformation, but is gradual.

Since the structure, morphology, etc. of baitiite depend on the transformation temperature and time, it is necessary to adjust the chemical composition so that bainite and austenite with the desired properties can be obtained within an industrially possible time, taking into account cost. .

In this way, bainite transformation occurs from the austenite temperature range without crossing the nose of pearlite transformation, and by cooling to room temperature, bainite and retained austenite are generated, and the magnetic properties necessary for a semi-hard magnetic material are obtained. At the same time, high strength, high ductility, and toughness can be obtained.

Although the range of the chemical composition of the high strength, high ductility, and toughness semi-hard material according to the present invention is limited for the above-mentioned reasons, the reason for limiting the chemical composition range will be specifically explained in detail.

In order for the main base structure to become a coexistence structure of bainite and austenite through austempering treatment, C
:0.30~0.80%, Si:1.70~3.70%
, the balance is basically an alloy consisting of unavoidable impurities and Fe.

Further, the addition of Mn in the second invention is extremely effective for improving hardenability. The Mn content is effective from 0.15%, and as the amount added increases, the hardenability is improved accordingly, but if it exceeds O or aO%, the impact toughness decreases, so it is preferably 1.10% or less.

Addition of CU is effective not only for improving strength but also for improving hardenability. The Cu content is effective from 0.20%, and increasing the amount increases strength and improves hardenability, but from around 2.00% the ductility and toughness decrease, so 2.30% The following are desirable.

Addition of Mo and Ni is extremely effective in improving hardenability. Move the nose part of the pearlite metamorphosis to the right,
Since the start of pearlite transformation is delayed, even thick materials can suppress pearlite transformation and allow bainite transformation.

In particular, the addition of Ni has the effect of suppressing the decrease in ductility and toughness that occurs when the strength is increased.

When comparing the ductility and impact toughness of an alloy with and without Ni added at the same strength level, it was found that the former is superior. The effect becomes noticeable from Mo content of 0.15%. If the amount added is increased, the improvement in hardenability will be greater, but if too much is added, bainite and austenite with the required properties will not be obtained within the industrially possible @processing time, and too much austenite will remain. As the strength decreases, the saturation magnetic flux density also decreases, making it impossible to obtain the required characteristics.
Desirably 0% or less. The effect appears from the Ni content of 0.30%, and the upper limit is preferably 5.50% for the same reason as Mo.

Note that the above-mentioned Mn53i and A1 have an action as a deoxidizing agent. In addition to the above-mentioned effects, Mn forms a compound with sulfur and has the effect of improving processability. It is sufficient that the amount of A1 is 0.2% or less.

Since P and S among the impurities reduce the ductility and toughness of the high-strength material, it is desirable that they be as small as possible. When the content is 0.05% or less, even if the strength level is increased, the decrease in ductility and toughness is small.

[Example] The present invention will be described with reference to examples.

Alloy materials having chemical compositions shown in No. 1 to 13 in Table 1 were melted and cast in an induction melting furnace, and hot forged after homogenization treatment. Test materials were prepared from hot-rolled materials as required.

The test material was heated and maintained at a temperature of 900 to 950°C, where it becomes an austenite phase, and then subjected to austempering treatment at 200 to 450°C for 0.5 to 24 hours.

The test material No. 12 was obtained by rolling the test material No. 11 at air temperature after austempering treatment, and No. 13.
50 in the middle of austempering treatment of No. 11 test material
The rolling process was started at 0°C.

As a semi-hard magnetic material, the coercive force is preferably about 3000 or more. When used under conditions where stress is applied, it is necessary to have the strength to withstand the applied stress, and
Appropriate ductility and toughness are also required.

Table 1 also shows test results regarding magnetic properties, tensile properties, and impact toughness.

As is clear from Table 1, the tensile strength is equal to or higher than that of high-strength steel, and the elongation and reduction of area are 15% or more and 3%, respectively.
It is 0% or more and has high ductility.

2mm V-notch Charpy is 3.5kgfm/cm2
The impact toughness is also high. The coercive force is 300 e or more.

It can be seen that the Ni-added alloy has improved elongation and reduction of area, and improved impact toughness, compared to the Ni-free alloy.

It can be seen that when rolling is applied after austempering or during austempering, the residual magnetic flux density is improved by about 2 KG, and the tensile properties and impact toughness are improved.

The high strength, high ductility, and toughness semi-hard magnetic material of the present invention can be relatively easily modified in magnetic properties, tensile properties, and impact toughness by changing and combining the chemical composition, austempering treatment conditions, and processing conditions as necessary. It is versatile as it can be adjusted.

[Effects of the Invention] The semi-hard magnetic material of the present invention has magnetic properties, tensile properties, and impact toughness, and these properties can be changed as appropriate. However, it is inexpensive because it contains as few expensive rare elements as possible. Since there is no risk of breakage even under conditions of high stress, it can be used in fields that require high reliability.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the austempering process of the present invention.

Claims (4)

[Claims] (1) C: 0.30-0.80%, Si: 1 by weight
．． Contains 70-3.70%, the remainder being unavoidable impurities and Fe
A semi-hard magnetic material with high strength, high ductility, and toughness, which is made by austempering an alloy consisting of: (2) High strength and high ductility according to claim (1), which is processed at a temperature lower than the A_3 transformation point during austempering or after austempering;
Tough semi-hard magnetic material. (3) C: 0.30-0.80%, Si: 1 by weight
．． Contains 70 to 3.70%, and further includes Mn: 0.15 to 1
．． 10%, Cu: 0.20-2.30%, Mo: 0.1
5 to 1.10%, Ni: 0.30 to 5.50%, and the remainder is unavoidable impurities and F.
A semi-hard magnetic material with high strength, high ductility, and toughness, characterized by being made by austempering an alloy consisting of E. (4) High strength and high ductility according to claim (3), which is processed at a temperature lower than the A_3 transformation point during austempering or after austempering;
Magnetic semi-hard magnetic material.