JPH03219050A - Wear-resistant sliding materials and their manufacturing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a wear-resistant sliding material with improved seizure resistance and wear resistance, and to a method for manufacturing the sliding material.

[Prior art]

Bronze, brass-based cast materials, and sintered materials are generally used for high-speed sliding parts such as gear reducers, hydraulic pumps, and motors. In addition, in these parts where the load is small, molten steel or sintered steel is used after being subjected to soft nitriding or sulfur-nitriding treatment. In particular, for high-load engine cylinder liners, cast iron is treated with Tuftride treatment to improve wear resistance.

Furthermore, for bushes used under high load conditions under grease lubrication, hardened materials such as 5UJ2 and SCM440H and carburized materials such as SCM420H are used. Furthermore, the floating seal, which prevents dirt, water, etc. from entering the shaft from the outside, is made of high-carbon, high-chromium cast iron with excellent wear resistance. Copper-based sliding materials have excellent seizure resistance, which is required for sliding properties, but they do not have sufficient wear resistance despite being expensive materials.

Molten steel or sintered steel that has undergone soft nitriding or sulfonitriding treatment is
When subjected to an impact load due to local uneven contact during sliding, the hard nitride and sulfide phases formed on the surface layer are brittle and may peel off, causing premature seizure or abnormal wear. Often. In particular, improving wear resistance is an important issue for cylinder liners that slide back and forth at high speeds.

[Problem to be solved by the invention] On the other hand, working machines such as construction machinery are susceptible to uneven loads;
Since the sliding surfaces of bushings are treated with high hardness because they are used under high loads, the sliding surfaces have poor conformability (process-induced superplasticity) and may be prone to abnormalities due to localized seizures and grease depletion. Problems such as noise are occurring frequently. In addition, floating seals used for oil sealing are made of high-hardness material, so when they are inserted into the shaft to prevent oil leakage, they lack stainability and slide easily. It becomes difficult to assemble the surfaces. Furthermore, due to the demand for increased vehicle speed, expensive additive elements such as molybdenum, tungsten, vanadium, and cobalt are added because they are used under higher PV value (product of sliding speed and sliding pressure) conditions. The problem is that the anti-seizure property is not improved considering the quality of the material. In addition, for example, in a lower suspension wheel having a high-speed rotation part, when the lubricant does not adapt to the rotation speed, heat is generated locally on the sliding surface, causing heat cracks in the contraction direction. Although cast materials are used for these materials, they have the problem of being brittle and prone to local heat generation due to the composition of a large amount of carbides and alloying elements.

The sliding surface pressure of normal sliding materials is 150 kg/crl, but for articulated work machines, the sliding surface pressure is 900 kg/ci
is required, and when the unevenness of torsion during work is taken into account, the surface pressure reaches as much as 1300 kg/c++1.

The present invention has been made in view of the above, and is a wear-resistant sliding material for high surface pressure that can further improve the seizure resistance and wear resistance of sliding steel materials used under oil or grease lubrication, and can be made at low cost. The purpose is to provide materials and methods for their production.

[Means for solving problems]

The present invention is based on the results of various studies to solve the above problems. Even if the surface hardness of cast steel sliding materials is improved, the seizure resistance cannot be improved.

However, the superior seizure resistance of copper-based sliding materials is thought to be due to their good compatibility with the mating material, and a large amount of soft retained austenite phase is present on the sliding surface of molten steel and sintered steel. If the sliding surface is precipitated to give conformability to the sliding surface, the residual austenite phase will transform into the deformation-induced martensitic phase even if there is a large stress applied during sliding, improving wear resistance and seizure resistance. The present invention was completed after discovering that it could be greatly improved.

The wear-resistant sliding material of the present invention has the following features: (1) The content concentration of carbon and nitrogen in the sliding part of the sliding steel material obtained by melting or sintering is 0.8 to 4.0 wt%, and 600' It is quenched by nitriding, carburizing, carburizing and nitriding, or simultaneous carburizing and nitriding at a temperature of C or higher, and the structure after quenching is 30% by volume compared to molten steel or sintered steel at room temperature.
It is to have a retained austenite phase in the range of ~95vo 1%.

(2) As carbide-forming elements, 0.1-25-1% chromium, 0.05-5.0wt% molybdenum, 0.05-5%
．． Contains one or more of 0 wt% vanadium, and one or more of 0.05 to 10 wt% nickel and 0.05 to 10 wt% manganese as hardenability forming elements.
Molten steel or sintered steel consisting of carbon and iron with a balance of 3.5 wt% or less and unavoidable impurities is subjected to nitriding, carburizing, carburizing and nitriding, or simultaneous carbo-nitriding treatment at a temperature of 600°C or higher. The structure after quenching has a retained austenite phase in the range of 30 to 95 VO 1% by volume compared to molten steel or sintered steel at room temperature, and cementite, carbides, and carbonitrides are precipitated. be.

(3) After nitriding or carburizing/nitriding the molten steel for sliding or sintered steel for sliding at a temperature of 600°C or higher, it is rapidly cooled, and the structure after quenching is 30 to 95 vol% residual by volume at room temperature. This is to form an austenite phase.

Next, the configuration of the present invention will be further explained.

In the structure of the present invention, the total concentration of carbon and nitrogen in the sliding part of the sliding steel material is set to 0.8 to 4.0 wt% to precipitate an appropriate retained austenite phase and blend it into the sliding surface. If a large surface pressure stress is applied during sliding, the hardness due to deformation-induced martensitic transformation (so-called superplastic transformation, which gives conformability due to superplasticity) will ensure sufficient hardness. Therefore, the minimum amount of carbon content is 0.8
It is expressed as wt%. On the other hand, if the carbon content is 4.0 wt% or more, the surface of the sliding chamber will be connected only by carbide, the effect of forming a retained austenite phase will be diluted, and the compatibility will be poor, so the carbon content will be 4.0 wt% or more. %.

With the configuration of the present invention, nitriding, carburizing, and
Carburizing and nitriding, or carbo-nitriding and quenching at the same time, is because when heat treatment is normally performed at about 550°C, like nitriding, normal nitrides are formed on the particle surface, which affects the sliding properties of sintered steel. decreases. Nitriding treatment is different from nitriding and is an essential requirement of the present invention, and the reason why the temperature is set at 600°C or higher is that nitrides such as T and 8 layers precipitate on the surface layer (white) during nitriding treatment. layer) is kept at a temperature that is difficult to cool. Nitriding is the process of diffusing and absorbing nitrogen into molten steel or sintered steel.

The nitriding treatment is carried out in an ammonia decomposition gas atmosphere at a temperature of 800 to 90
Preferably, it is carried out in a temperature range of 0°C. Only nitriding treatment is applied to molten steel or sintered steel that contains carbon, and carburizing treatment is used to obtain sintered steel from a mixed powder of alloyed iron powder and graphite powder that does not contain carbon. According to a conventional method, carburizing is performed first and then nitriding is performed, or carburizing and nitriding are performed simultaneously.

Nitriding causes nitrogen to diffuse and be absorbed into the molten steel or sintered steel, facilitating the precipitation of retained austenite phase.

With the configuration of the present invention, the structure after quenching is 30 to 95 in volume ratio.
The reason for the residual austenite phase in the vol% range is that, as understood from the iron-carbon alloy phase diagram, when the quench hardening of steel is carried out at its most extreme level, that is, when it is extremely rapidly cooled, the state of austenite remains exactly the same. However, in carbon steel, the austenite structure cannot be brought to 100% room temperature no matter how rapidly it is cooled. Generally, a very hard martensitic structure different from the austenite structure coexists. It is called retained austenite because it is a high-temperature austenite structure that remains unchanged. When the matrix structure of the sliding surface is formed with many retained austenite phases, it becomes a conformable matrix. The lower limit of retained austenite phase is
The amount at which the breaking-in effect begins to appear is 30 vol %, and the upper limit of 95 vol % was determined from the observation of seizing and abrasion properties of the sliding surface after a sliding test.

The relationship between the amounts of added carbide-forming elements and hardenability-forming elements in the molten steel or sintered steel used in the present invention is as follows. The limits for chromium, molybdenum, vanadium, etc. are determined based on the amounts added in order to precipitate carbides by carburizing, and the maximum values are limited from the viewpoint of cost.

Nickel and manganese are added in necessary amounts to ensure the hardenability of the matrix. Increasing the amount of nickel and manganese increases the amount of retained austenite phase and produces a conformability effect, but since adding more than necessary increases cost, the upper limit is set to an allowable value. The maximum amount of carbon added is determined based on the relationship between the judgment of ease of sintering in sintered steel and the amount of dispersed carbide required for wear resistance.

Since the structure of the present invention contains carbide-forming elements, in addition to a large amount of retained austenite phase, there is also high hardness cementite, M
Carbides and carbonitrides such as 7C3, M6C, M, C, and MC are precipitated in the sliding parts to ensure further improvement in wear resistance.

[For production]

The wear-resistant sliding material according to the present invention precipitates a large amount of residual austenite phase in the matrix of the sliding surface to impart conformability (toughness) to the sliding surface.
If it hits a local area, it instantaneously causes self-conforming action (plastic deformation) and hardens, significantly improving seizure resistance and abrasion resistance.

With conventional products, if lubrication is poor, a certain part of the surface momentarily heats up and expands in volume, creating abnormal stress and causing heat cracks, but in the present invention, the matrix has toughness, so it has excellent heat crack resistance. It is also excellent.

[Effects of the Invention] As explained above, the wear-resistant sliding material of the present invention forms a large amount of retained austenite phase on the sliding surface, which increases conformability and further improves seizure resistance and wear resistance. Become something. Since it can be manufactured at low cost, it can be used for engines, oil welding,
It can be applied to sliding parts used in joints and automobiles.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

Example 1 Alloy steel powder or iron powder (manufactured by Kobe Steel, Atmel 300M
, 4100.4600.4800D
50.27wt%P) was used to create mixed powders with four types of compositions, 0.5wt% of Acra wax (lubricant) was added to the mixed powders, and after mixing, 6t/p was produced using a press.
Pressure molding of Cl11 was performed to obtain a sintered body under the conditions of 1200° C. for 1 hour in a vacuum atmosphere of 10-'' torr or less.Apart from the sintered body, commercially available SUJ 2, SCM44
After preparing 0H steel materials and machining these sintered bodies and steel materials into the shapes of constant velocity friction and wear test pieces and wear test pieces, each test piece was placed in a gas atmosphere (using RX gas, propane gas, and ammonia). Carburizing and nitriding was performed at 850℃ for 4 hours to adjust the CO2 gas and NHI gas concentrations to 0.15 to 0.25% and 10%, respectively. It was quenched and then tempered at 150°C for 3 hours. Then, each retained austenite I was determined.

In addition, for comparison, test specimens were prepared using P31C material and SCM440H material subjected to tuftride treatment, and the above-mentioned carburizing and nitriding was not performed, but the other conditions were the same. Table 1 shows the results of a sliding test performed on the obtained test piece.

Although Table 1 does not show any examples containing vanadium, a sintered alloy powder containing vanadium in the range of 1 to 4 wt% was subjected to carbonitriding treatment, then quenching and tempering treatment, and a sliding test was performed. As a result, it has been confirmed that good results can be obtained for both the limit PV value and specific wear amount.

Example 2 After machining the same sintered body as test piece No. 3 in Table 1 into the shape of a reciprocating wear test piece, the surface carbon potential of the test piece was 700 ℃
After carburizing for 4 hours, carburize at 850°C in an atmosphere of lO% ammonia decomposition gas (residual ammonia concentration 10%).
The nitriding treatment was carried out for 4 hours and then directly quenched in oil at 80°C. The amount of retained austenite in this test piece was 60% and 1%.

In addition, for comparison, a machined test piece of the same sintered body as the above test piece Nα3 was reheated at 900°C for 3 hours in a vacuum atmosphere of 1O-2 torr or less, and then quenched with nitrogen gas. , tempering was performed in nitrogen at 400° C. for 1 hour. Next, as-cast FC30 material and Fe20 material, which are used as engine cylinder liner materials, were heated to 570°C.
A test piece was prepared which was subjected to tuftride treatment for 3 hours. FIG. 1 shows the results of a reciprocating sliding test performed on each of the obtained test pieces.

(Note) Reciprocating sliding test conditions Load: 5 kg, Speed: 20 Hz (Stroke, 5 m
m), lubricating oil: 10Vl-CD, heating temperature = 180℃
1 Compatible material: FCD50 + chrome plating Example 3 The same sintered body and SC as the test pieces Nα4 and Nα6 in Table 1
M440 steel material with bushing size [outer diameter 96mmφ, inner diameter 80mm diameter, height 80mm, grease groove (width 10mm,
After machining to a depth of 2 mm), carburizing and nitriding were carried out under the same conditions as in Example 1, followed by quenching and tempering.

For comparison, SCM415 (GCTQ heat treated) material and 345C (IQT heat treated) material were machined to the above bushing size, carburized at 930°C for 4 hours, quenched from 850°C, and 180°C x 3 A test piece was prepared which was tempered under certain conditions.

Table 2 shows the results of a seizure test conducted on each of the obtained test pieces. Figure 2 shows the seizure tester, and Figure 3 shows the shape of the grease groove on the bushing.

(Note) Seizure test conditions Bottle material: SCM435 rQT.

Grease: Lithium-based G2-L I, F 3 = 25"", N 3- Rocking angle until seizure: 90° Rocking speed: 20° / SeC The seizure property test was carried out using the apparatus shown in Figure 2. went. This device inserts a pin into a fixed bush specimen,
This pin is swung to test the fit and seizability between the two.

Example 4 Alloy steel powder (manufactured by Mitsubishi Steel, Fe-15cr-3M.

lNi, Fe-9Cr-6Mo-4W)
, graphite powder (manufactured by Lonza, KS6), and carbonyl nickel powder (manufactured by Inconel, average particle size Im) were used to create mixed powders with five different compositions, and 0.5iy was added to the mixed powder.
After adding t% of Acra wax (lubricant) and mixing, it was pressure-molded at 6t/cffl, and sintered at 1100 to 1200°C for 2 hours in a vacuum atmosphere of 1O-2torr or less. A test piece in the shape of a floating seal as shown in FIG. 6 was prepared by quenching with nitrogen gas from a temperature range of 960°C to 960°C.

The 5US431 material was also machined into the floating seal shape shown in Figure 6, and then vacuum carburized at 930°C for 7 hours to form a surface layer with a volume ratio of 30 to 35 vol.
A test piece was prepared in which carbide of Cr7C, .

Each of the above test pieces and the SUJ 2 material were subjected to carbo-nitriding, quenching and tempering treatments under the same conditions as in Example 1.

In addition, for comparison, a test piece was prepared without being subjected to carbo-nitriding treatment, but under the same conditions.

Table 3 shows the results of a seizure test performed on each of the obtained test pieces using the apparatus shown in FIG. 5, and the values for the amount of retained austenite and the amount of carbide precipitation. FIG. 5 shows an apparatus used for the seizure test, in which floating seals are joined and mutually rotated under pressure.

(Note) Seizure test conditions Compatible material: Sliding oil type between similar materials: E (i-#30 Linear pressure: 1 to 3 kg/ci Circumferential speed 2 0.9 to 1.5 cm/sec Results in Table 3 It can be seen from the above that the limit PV value in the seizure test can be further improved by increasing the retained austenite phase.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the relationship between wear amount and sliding time in a sliding test, Fig. 2 is a schematic explanatory diagram of the seizure test device, Fig. 3 is an explanatory diagram of the shape of the groove pattern of the bushing, and Fig. 4 is an explanatory diagram of the relationship between wear amount and sliding time in a sliding test. 5US4
31 vacuum carburized metal structure with Cr7C in the metal structure:
+A photograph showing a state in which carbides are precipitated, FIG. 5 is a schematic explanatory diagram of a seizure test device, and FIG. 6 is an explanatory diagram of the shape of a floating seal. Figure 1 (A) (B) Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. The total concentration of carbon and nitrogen in the sliding part of the sliding steel material obtained by melting or sintering is 0.8 to 4.0 wt.
%, and is quenched by nitriding, carburizing, carburizing and nitriding, or simultaneous carburizing and nitriding at a temperature of 600℃ or higher, and the structure of the sliding part after quenching has a volume of molten steel or sintered steel at room temperature. A wear-resistant sliding material characterized by having a retained austenite phase in the range of 30 to 95 vol%. 2. As carbide-forming elements, 0.1-25 wt% chromium, 0.05-5.0 wt% molybdenum, 0.05-5.
Contains one or more of 0 wt% vanadium, and one or more of 0.05 to 10 wt% nickel and 0.05 to 10 wt% manganese as hardenability forming elements.
Molten steel or sintered steel consisting of carbon and iron with a balance of 3.5 wt% or less and unavoidable impurities is subjected to nitriding, carburizing, carburizing and nitriding, or simultaneous carbo-nitriding treatment at a temperature of 600°C or higher. The structure after quenching is 30 to 95V in volume ratio to molten steel or sintered steel at room temperature.
A wear-resistant sliding material characterized by having a retained austenite phase in the ol% range and having cementite, carbide, and carbonitride precipitated therein. 3 Molten steel for sliding or sintered steel for sliding is subjected to nitriding or carbo-nitriding treatment at a temperature of 600°C or higher, and then rapidly cooled, so that the structure after quenching becomes a retained austenite phase with a volume ratio of 30 to 95 vol% at room temperature. A method for manufacturing a wear-resistant sliding material, characterized by forming a .