JPH0333773B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing an iron-manganese-silicon-based shape memory alloy that has high strength, high toughness, excellent shape memory effect, and corrosion resistance. be. (Prior art) Japanese Patent Application No. 187403 (1982)
The Fe-Mn-Si shape memory alloy shown in No. 60-40561 (Japanese Unexamined Patent Publication No. 61-201761) etc. is produced by producing an ingot by normal vacuum melting or atmospheric melting, and then producing a plate by hot rolling. It also shows excellent shape memory properties. However, when this alloy is cold pressed, ε-martensite with a dense hexagonal structure is generated and cracks occur. Therefore, in order to manufacture wires, thin plates, etc., it is necessary to process in a warm region where the ε phase does not occur. However, using this method, it is extremely difficult to manufacture plates, wires, etc. with a thickness of 0.5 mm or less. Increasing the amount of Si added improves the shape memory effect, but adding more than 8% deteriorates workability and makes molding difficult. (Problems to be solved by the invention) The present invention solves the above problems and
The purpose is to manufacture Fe-Mn-Si shape memory alloy thin plates, wires, etc. with a thickness of mm or less. (Means for solving the problem) When producing iron-based shape memory alloys, the alloy is melted and made into an ingot or continuously cast slab, and then hot rolled and subsequently warm rolled. The limits of rolling process impose limits on the thickness of thin sheets.
Therefore, by directly solidifying the molten alloy and forming it into a thin plate, it is possible to easily produce plates and wires with a thickness of 0.5 mm or less, which are difficult to produce by rolling. Also,
According to this method, it is possible to contain various elements in excess of their solid solubility limits, and it is also possible to increase the amount of Si, which has been limited in the amount added due to restrictions due to hot working. In addition, certain alloy systems (e.g. Fe-Mn-Si) require annealing after rolling to improve properties when manufactured by hot working or warm working, but thin sheets are produced by directly solidifying the molten alloy. Once formed, there is no need for annealing because the process does not include plastic working. The present invention was made based on this knowledge, and the weight percent of Mn is 20 to 40% and Si is 3.5 to 12%.
iron-based alloy containing as an essential component or
An iron-based shape memory alloy thin plate or wire is produced by melting an iron-based alloy containing 10% or less Cr in a vacuum or inert gas atmosphere and directly solidifying the molten alloy. It is.
The present invention will be explained below. In order to manufacture thin plates and wires according to the present invention, first, a Fe-Mn-Si alloy prepared with a predetermined composition and amount is heated using high frequency or the like in an inert gas atmosphere such as argon gas or in a vacuum. Melt it to form a molten alloy. Next, this molten alloy is flowed into any well-known rapid solidification apparatus such as a single roll system or a twin roll system placed in an inert gas atmosphere or vacuum in the same manner as above, and is rapidly solidified.
Manufacture Fe-Mn-Si shape memory alloy thin sheets and wires with a thickness of 0.5 mm or less. Here, each element in the present invention and the reason for limiting the amount thereof will be explained. When Mn is less than 20%, the shape memory effect in which the ε phase is generated and the α' phase is also introduced due to stress induction is reduced. Moreover, when it exceeds 40%, γ is stabilized and γ
→ γ slip deformation occurs preferentially over ε transformation. Si is an element that promotes γ→ε transformation, and its sufficient effect can be obtained by adding 3.5% or more.
Further, when the molten alloy is directly rapidly solidified as in the present invention, the processing method and formability of the alloy are not impaired up to about 12%. Cr facilitates γ → ε transformation, improves shape memory properties, and also helps improve corrosion resistance, but 10%
If it is added in excess of this amount, it will form a low melting point intermetallic compound with Si, making it impossible to melt the alloy. In addition to the main elements Mn, Si, and Cr mentioned above,
One or more of Ni, Co, Mo, C, Al, and Cu, which will be described later, can be added as necessary to improve the characteristics of the iron-based shape memory alloy. Ni contributes to improving toughness without deteriorating shape memory properties, but when added in excess of 10%, hot processing becomes worse. Although Co improves the shape memory effect and hot workability, it is expensive and the effect is not significant even when added in large amounts, so the upper limit was set at 10%. Mo improves the shape memory effect and also improves heat resistance, but if it exceeds 2%, hot workability deteriorates and shape memory properties also deteriorate. C improves the shape memory effect, but if it exceeds 1%, the toughness deteriorates significantly. Al acts as a deoxidizing agent and improves the shape memory effect, but there is no change in the effect even if it is added in an amount exceeding 1%. Cu improves corrosion resistance without deteriorating the shape memory effect, but an upper limit of 1% is sufficient for its addition. (Example) Table 1 shows argon gas atmosphere (Nos. 1 to 9, 11)
Or, the composition, thickness, surface properties and Shows the shape recovery rate (SME) when subjected to 90° bending. Here, if the surface quality is not a problem at all, it is marked as ◯, when scratches or the like are observed, it is marked as △, and when cracks occur, it is marked as ×. Note that the shape recovery rate (SME) is the recovery angle divided by the bending angle (90°).
In addition, as a comparative example, a case was shown in which a cast slab was manufactured and further subjected to hot rolling and warm rolling.
In this case, it was impossible to manufacture thin plates with a thickness of 0.2 mm or less. (Effects of the Invention) As explained above, according to the present invention, a thin iron-based shape memory alloy can be easily manufactured, so that the range of uses of the shape memory alloy can be expanded. 【table】

Claims (1)

[Claims] 1. An iron-based alloy containing 20 to 40% Mn and 3.5 to 12% Si by weight is melted in a vacuum or an inert gas atmosphere, and the molten alloy is directly solidified to form a thin plate or wire. 1. A method for producing iron-based shape memory alloy thin sheets and wires, characterized by forming iron-based shape memory alloy thin sheets and wires. 2. A method for manufacturing an iron-based shape memory alloy thin plate/wire according to claim 1, wherein the product has a thickness of 0.5 mm or less. 3 Mn20-40%, Si3.5-12% by weight percentage
and an iron-based shape memory alloy thin sheet characterized by melting an iron-based alloy containing 10% or less Cr in a vacuum or an inert gas atmosphere, and directly solidifying the molten alloy to form a thin plate or wire.・Wire manufacturing method. 4. The method for producing iron-based shape memory alloy thin sheets and wires according to claim 3, wherein the product has a thickness of 0.5 mm or less.