Linear bearing alloy steel and linear bearing using the same

Abstract

To provide a linear bearing alloy steel and a linear bearing using the same that can achieve a high hardness (64 HRC or higher on the Rockwell hardness C scale) by overall quenching at a low temperature (900°C or less) followed by tempering (150 to 200°C) without a carburizing treatment.SOLUTION: A linear bearing alloy steel consisting, in terms of weight%, of 0.90% or more and 1.50% or less of C, 0.70% to 2.50% of Si, 0.10% to 1.00% of Mn, 1.00% to 4.00% of Cr, 0.20% to 1.50% of Mo, 0.40% to 3.00% of W+2Mo, and 0.10% to 0.80% of V, with the balance being Fe and inevitable impurities.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an alloy steel for use in linear bearings and a linear bearing using the same. [Background technology]

[0002] In recent years, there has been an increasing demand for linear bearings, such as linear bushings and ball splines, to be more compact (thinner) and lighter. To meet these various needs, linear bearings are required to have higher static strength. For example, Patent Document 1 discloses a linear bearing used in a special environment (high-temperature atmosphere), and explains that the bearing can maintain its hardness even in a high-temperature atmosphere. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-59957 Summary of the Invention

[0004] However, most linear bearings are made of bearing steel, such as SUJ2 steel, which has a hardness of around 61 to 62 HRC on the Rockwell hardness C scale. Therefore, if an existing linear bearing is made smaller (thinner), sufficient hardness cannot be obtained.

[0005] If we focus only on the hardness of the steel type, special steels containing rare metals such as V and W, and high-speed tool steels have a hardness of 64HRC or more on the Rockwell hardness C scale, so they can be used as materials, but they require quenching at a temperature in the range of 1100 to 1200°C, which could lead to higher manufacturing costs and increased heat treatment costs.

[0006] Furthermore, as disclosed in Patent Document 1, it is possible to improve (maintain) hardness by using heat treatment conditions such as quenching and tempering, or special surface treatments such as carburizing and nitriding that harden only the surface layer, but it is difficult to improve internal hardness, and at the same time, this leads to an increase in manufacturing costs, which has been a problem. [Problem to be solved by the invention]

[0007] Therefore, the present invention aims to provide an alloy steel for linear bearings that can be hardened at a low temperature (900°C or less) without special surface treatment such as carburizing, and can be subjected to a subsequent tempering treatment (150 to 200°C) to obtain high hardness (64 HRC or higher on the Rockwell hardness C scale), and a linear bearing using the alloy steel. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the alloy steel of the present invention is an alloy steel for linear bearings containing, by weight, C: 0.90% or more and 1.50% or less, Si: 0.70 to 2.50%, Mn: 0.10 to 1.00%, Cr: 1.00 to 4.00%, Mo: 0.20 to 1.50%, W+2Mo: 0.40 to 3.00%, V: 0.10 to 0.80%, with the remainder being Fe and unavoidable impurities.

[0009] Alternatively, the alloy steel for linear bearings is composed of, by weight, C: 0.90% or more and 1.50% or less, Si: 0.70 to 2.50%, Mn: 0.10 to 1.00%, Cr: 1.00 to 4.00%, Mo: 0.20 to 1.50%, W+2Mo: 0.40 to 3.00%, Nb: 0.05 to 0.40%, with the remainder being Fe and unavoidable impurities.

[0010] Furthermore, in the invention of a linear motion bearing using the aforementioned alloy steel for linear motion bearings, the surface of the linear motion bearing has a Rockwell hardness C scale of 64 HRC or more. [Effects of the Invention]

[0011] The alloy steel for linear bearings of the present invention can be subjected to a full quenching treatment at a low temperature (900°C or less) without carburizing, followed by a tempering treatment (150 to 200°C), thereby achieving sufficient surface and internal hardness (64 HRC or more on the Rockwell hardness C scale) and an appropriate amount of retained austenite.

[0012] Therefore, since the linear motion bearing made of the alloy steel for linear motion bearings that has been fully hardened is hardened to the inside, it is less susceptible to partial damage compared to a linear motion bearing made of alloy steel for machine structures.

[0013] In addition, the manufacturing cost of the linear bearing alloy steel can be reduced by limiting the content of rare metals such as Cr, Mo, and V in the linear bearing alloy steel to 5 wt % or less. Furthermore, since the linear bearing alloy steel has excellent tempering softening resistance, the decrease in hardness is small even when the temperature rises. DETAILED DESCRIPTION OF THE INVENTION

[0014] As one embodiment of the present invention, the chemical components of an alloy steel for a linear motion bearing and a linear motion bearing using the alloy steel for a linear motion bearing will be described.

[0015] 《C (Carbon)》 The C (carbon) content in the linear bearing alloy steel of the present invention is set to 0.90% to 1.50% by weight. Carbon ensures the hardness of the linear bearing alloy steel after quenching and tempering, and plays a role in ensuring a high fatigue life when used as a material for mechanical parts. If the C content in the linear bearing alloy steel is less than 0.90%, the required surface and internal hardness cannot be obtained, while if it exceeds 1.50%, the amount of retained austenite (γ amount) becomes too large, deteriorating the fatigue life of the mechanical parts.

[0016] Silicon The content of Si (silicon) is set to a range of 0.70% to 2.50% by weight. Silicon plays a role in increasing the temper softening resistance of the linear bearing alloy steel. If the Si content in the linear bearing alloy steel is less than 0.70%, the required temper softening resistance cannot be obtained, and if it exceeds 2.50%, the hot forgeability deteriorates significantly. Preferably, the Si content is 1.50% to 2.50%.

[0017] Manganese (Mn) The Mn (manganese) content is 0.10% or more and 1.00% or less by weight. Manganese improves the hardenability of linear bearing alloy steel, which is effective in improving fatigue life when used as a machine part material. If the Mn content in the linear bearing alloy steel is less than 0.10%, the hardenability of the linear bearing alloy steel deteriorates, and if it exceeds 1.00%, the hot forgeability deteriorates significantly.

[0018] 《Cr (Chromium)》 The Cr (chromium) content is set to 1.00% or more and 4.00% or less by weight. Chromium improves the hardenability of the linear bearing alloy steel and also thermally stabilizes cementite, preventing the cementite from dissolving in the matrix at high temperatures. If the Cr content in the linear bearing alloy steel is less than 1.00%, the hardenability of the linear bearing alloy steel will deteriorate, and if it exceeds 4.00%, coarse carbides will form in the linear bearing alloy steel.

[0019] Mo (Molybdenum) The content of Mo (molybdenum) is 0.20% or more and 1.50% or less by weight. Molybdenum forms carbides in the alloy steel for linear bearings, contributing to ensuring hardness. If the Mo content in the alloy steel for linear bearings is less than 0.20%, the required temper hardness and softening resistance cannot be obtained. On the other hand, if the Mo content exceeds 1.50%, coarse carbides are formed.

[0020] "V (Vanadium)" The content of V (vanadium) is 0.10% or more and 0.80% or less by weight. V has the role of increasing temper softening resistance when added in combination with silicon in the linear bearing alloy steel. Furthermore, if the V content in the linear bearing alloy steel is less than 0.10%, the required temper softening resistance cannot be obtained, and if it exceeds 0.80%, coarse carbides are generated. Note that a similar effect can be achieved by adding Nb (niobium) as a substitute element for V. In this case, the Nb content is preferably in the range of 0.05% or more and 0.40% or less by weight.

[0021] W (Tungsten) W (tungsten) can be included in the range of 0.40% to 3.00% by weight as the W equivalent (W + 2Mo). In this case, tungsten, like molybdenum, forms carbides in the linear bearing alloy steel, contributing to ensuring hardness. If the W equivalent in the linear bearing alloy steel is below 0.40%, the required temper hardness and softening resistance cannot be obtained. On the other hand, if the W equivalent exceeds 3.00%, coarse carbides will form.

[0022] Linear bearings made from the above-mentioned alloy steel for linear bearings have a surface with a Rockwell hardness of 64 HRC or higher on the C scale. Linear bearings can be applied to various types of linear bearings, such as bushings, linear bushings, and ball splines.

Claims

1. An alloy steel for a linear bearing, characterized in that it contains, by weight, C: 0.90% or more and 1.50% or less, Si: 0.70 to 2.50%, Mn: 0.10 to 1.00%, Cr: 1.00 to 4.00%, Mo: 0.20 to 1.50%, W+2Mo: 0.40 to 3.00%, V: 0.10 to 0.80%, with the remainder being Fe and unavoidable impurities.

2. An alloy steel for linear bearings, characterized in that it contains, by weight, C: 0.90% or more and 1.50% or less, Si: 0.70 to 2.50%, Mn: 0.10 to 1.00%, Cr: 1.00 to 4.00%, Mo: 0.20 to 1.50%, W+2Mo: 0.40 to 3.00%, Nb: 0.05 to 0.40%, with the remainder being Fe and unavoidable impurities.

3. 3. A linear motion bearing using the alloy steel for linear motion bearings according to claim 1 or 2, wherein the surface of said linear motion bearing has a Rockwell hardness C scale of 64 HRC or more.