JPH0361349A - Sintered sliding material - Google Patents

Abstract

PURPOSE:To obtain the sintered sliding material having increased wear resistance and seizure resistance required for high speed sliding, etc., in a lubricating environment by subjecting a ferrous sintered body of prescribed relative density ratio contg. each prescribed amt. of one or two kinds of carbide forming elements as well as Si, Mn, Ni and C to carburizing treatment and precipitating carbide. CONSTITUTION:A ferrous sintered body of 0.8 to 1.0 relative density contg., by weight, one or two kinds of carbide forming elements among 0.1 to 0.25% Cr, 0.1 to 5.0% Mo, 0.1 to 5.0% V, etc., and 0.1 to 2.0% Si, 0.1 to 2.0% Nn, <=5.0% Ni and <=1.5% C is treated as follows. Namely, the ferrous sintered body is subjected to carburizing treatment to precipitate the carbide of cementite, M7C3, M2C and MC type. The sintered sliding material obtd. by this method can reduce the cost by the for alternation for a copper series sliding material of hydraulic parts sliding at a high speed, can prevent the generation of abnormality and the damage caused by seizure in bushes used under high face pressure and can improve the durability of machine parts.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention provides a sintered sliding material with improved wear resistance and seizure resistance required for high-speed sliding or high-load sliding under lubrication. Concerning inexpensive manufacturing methods.

(Conventional technology) Conventionally, high-speed sliding parts of hydraulic parts use LBA and P31C.
Brass-based or high-strength brass-based casting and sintering materials are used. Copper-based sliding materials have excellent sliding properties, especially seizure resistance, but they are expensive, and in order to maintain the strength of parts such as hydraulic parts, expensive processes such as casting and bonding are not required. The parts are expensive because of the use of

For areas with a small load, a Fe-Cu-3n-based sintered material or a sintered material subjected to tuftride or sulfur-nitriding treatment may be used. For bushes used under high loads with grease lubrication, hardened materials such as 5UJ2 and S0M440' and carburized products such as SCM420' are used.

[Conventional example]

Figure 4 (C) and (d) are pure iron powder (Shinko 300H) +
0.6 C, 930″cxi’, vacuum carburizing, 850°
Although the surface structure was oil-quenched with C, uneven precipitation of cementite is observed.

(Problems to be Solved by the Invention) However, when using a sintered material, the Fe-Cu-5u system is often insufficient from the viewpoint of strength and cannot be expected to have much seizure resistance. In addition, when sintered materials are subjected to soft nitriding, sulphonitriding, etc., the resulting hard material has a thin thickness of about 3 to 15 μm, and its wear life is short. In order to perform thick film treatment, a significant decrease in strength will occur unless a pretreatment such as steam treatment is performed to precipitate iron oxide in the porous areas. In addition, the processing temperature is 5
Since it is held at a high temperature of 00 to 600°C for a long time, high strength cannot be expected, and the overall cost increases significantly. In addition, bushings used for high loads with grease lubrication have drawbacks such as abnormal noises from the bushing due to lack of lubrication and frequent breakage due to seizure.

The present invention aims to solve such problems.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a C
r, 0.1-0.25 vt%, Mo 0.1-5.
One or two carbide-forming elements such as 0ht%, V0.1 to 5.0wt%, and 0.1 to 2 of Si + Mn.
．． Contains 0wt%, Ni 5.0wt% or less, C0.5w
An iron-based sintered body having a relative density ratio of 0.8 to 1.0 including t% or less is carburized to produce cementite, M7C:
l + MzCI Mc type carbide is precipitated.

Furthermore, the present invention is characterized in that P, B, and Cu can be optionally added to the above material in a range of 5.0 wt%.

(Function) With the above configuration, Ni contains ordinary elements in addition to carbide-forming elements and guarantees microscopic hardenability.

Since it is a sintered body whose main component is Fe containing C2 and a carbide hard phase such as cementite is precipitated therein, the seizure resistance and wear resistance are improved. Also P.

Since B and Cu can be added, it is possible to control the density of the sintered body.

(Example) Embodiments of the present invention will be described in detail based on the drawings.

[Example 1] Figures 1 (a) and (b) show general metallurgical steel powder containing 1% Cr (
Shinko Atmel 4100) +0.3 C as usual 9
This is a carburized surface structure that was vacuum carburized at 30°C x 1H and OQed at 850"C. Cementite is evenly dispersed, and cementite precipitates evenly in a shorter time than normal melted material (equivalent to SCM 430'). This is due to the porous nature of the sintered body.If cementite precipitation occurs deep from the surface of the sintered body, it tends to cause strength deterioration, so in this case, the degree of vacuum during vacuum carburizing 20
Carburizing at a temperature of ~200 torr makes it possible to control the precipitation of cementite within a range of 0.3 mm near the surface layer in a short period of time, but since this is not possible with the normal RX gas carburizing method, vacuum carburizing is recommended for carburizing. Recommended. An iron-based sintered body containing one or more carbide-forming elements such as Cr + Mo + V with a relative density ratio of 0.8 or more is heated at a temperature of 750°C or more and 1100'C or less after a sintering reaction, Carburizing is performed in a carbon potential atmosphere where carbides can precipitate, and cementite and M4C are added to the surface layer of the sintered body.
3.

After sintering, carburizing treatment imparts seizure resistance and wear resistance by precipitating M, C, and Mc type carbide hard phases.
- Although it is possible to perform the treatment as a separate treatment after cooling, from the viewpoint of cost, it is better to change the temperature to the carburizing treatment after the completion of sintering, and to perform the treatment by introducing carburizing gas into the same furnace.

The treatment temperature of 750 to 1100°C is a higher temperature treatment than the soft nitriding and sulfonitriding treatment temperatures, so a deep carbide dispersed layer can be obtained in a short time, and since ammonia and hydrogen sulfide gas are not used, sintering Processing can be done in the same furnace, resulting in lower costs.

Further, by performing a tempering treatment after the quenching treatment (by forced gas cooling or oil cooling) after the carburizing treatment, the strength of the sintered body can be easily improved.

Bushes used for high-load grease lubrication have grooves on their sliding parts to prevent lubrication from running out, but in sintered bodies, the degree of porosity is adjusted so that grease or lubricating oil tends to accumulate in the holes. This prevents the lubricating oil from running out and prevents abnormal noise and damage caused by seizure. Also, when used in areas where wear resistance and corrosion resistance are particularly important, Cr of the sintered body
, Mo.

By increasing the amount of element (2) added, a large amount of M, C, M2C, and Mc type hard carbides are precipitated and used.

We discovered that the precipitation caused by carburizing a sintered body is more porous than that of molten material, so it occurs very uniformly, in a short time, and easily even with a low alloy content, so we utilized this principle. did.

Reason for component setting Cr: When using the vacuum carburizing method, addition of 0.1 wt% is sufficient for precipitation of cementite, maximum of 25 wt%
This is specified for parts where corrosion resistance is important, such as work equipment bushings. If it exceeds this, no great effect can be expected and the cost will increase.

Mo, V: The lower limit of 0.1 wt% was specified as the lower limit amount of precipitation for stable cementite in the vacuum carburizing method, and the upper limit of 5.0 wt% was specified because it would increase the cost.

Si: The upper limit is intended to improve soft tempering resistance, but it was specified because if it exceeds 2.0 wt%, cementite precipitation tends to become unstable.

Additive elements such as Ni, Cr, Mn, Mo, V, etc. tend to concentrate in precipitated cementite and tend to deteriorate the hardenability of the metal matrix. Therefore, by adding Ni discharged from cementite, hardening of the matrix is Improved sex. The upper limit was determined based on the softening caused by retained austenite.

[Example 2] Using general metallurgical copper powder (Shinko Atmel 4100), graphite (Lonza KS6), and Fe-1 alloy (Fukuda Kinzoku 250), Fe-1Cr-0,2Mo-0,6C-0,8P was prepared. After adding 0.5 wt% of Acrawax and mixing for 30 minutes in a V-type mixer, a hydraulic pump cylinder block and a work machine bushing as shown in Figs. 3 and 4 were prepared. The base was shaped and sintered in a 1200°CXIH vacuum.Then it was machined to the dimensions for actual machine testing.
After vacuum carburizing under the conditions of 93 o'cxt' and 100 torr, finishing processing was performed. This part was attached to a hydraulic pump and work equipment and a 500H operation test was conducted. Table 1 shows the maximum wear amount of a part of the piston bore.

Table As a result, the present invention can be applied to the conventional copper-based sliding material (P31C).
, LBA), it was found to have almost the same performance in terms of seizure resistance and wear resistance. It was also found that no abnormalities occurred in the bushings of the work equipment, and there was almost no problem with the amount of wear.

(Effects of the Invention) Since the present invention is configured as described above, it is possible to reduce costs by replacing copper-based sliding materials in hydraulic parts that slide at high speed, and to prevent abnormalities in bushes used under high surface pressure. Occurrence or
It prevents damage caused by seizure and improves the durability of mechanical parts.

[Brief explanation of drawings]

Figures 1 (a) and (b) are photographs in place of drawings showing the metal Ni weave of the embodiment of the present invention, Figure 2 is a longitudinal cross-sectional side view of a hydraulic pump cylinder block having the surface structure shown in Figure 1, and Figure 3. 1 is a longitudinal sectional side view of a working machine bushing having the surface structure shown in FIG. 1, and FIG. 4 is a photograph in place of a drawing showing the conventional vacuum carburized metal structure. ■...Hydraulic pump cylinder block, 2...Work machine bush.

Claims (2)

[Claims] (1) Mainly Fe and Cr. 0.1-0.25wt%
, Mo. 0.1-5.0wt%, V. 0.1~5.0w
One or two carbide-forming elements such as t% and Si
, Mn in an amount of 0.1 to 2.0 wt%, Ni. 5.0wt
% or less, C. Relative density ratio containing 1.5 wt% or less is 0.
A sintered sliding material characterized in that an iron-based sintered body consisting of 8 to 1.0 is carburized to precipitate cementite, M_7C_3, M_2C, and MC type carbides. (2) In claim (1), P, B, Cu is ~5.0w
A sintered sliding material characterized in that it can be added arbitrarily within a range of t%.