JPH02154865A - Piston ring - Google Patents

Abstract

PURPOSE:To obtain a piston ring with excellent abrasion resistance and scuff resistance by using a steel material with the specific composition for a base material and forming a hardened layer via nitriding on the outer periphery sliding face. CONSTITUTION:A piston ring is made of 0.4-1.0 wt.% C, 3.0-10.0 wt.% Cr, 3.0-10.0 wt.% Mo, 1.0-2.5 wt.% V, 1.0-3.0 wt.% W, 2.0-10.0 wt.% Co and the remainder of Fe and inevitable impurities. Nitriding is applied at least on the outer periphery sliding face of this base material to form a hard film layer. Among the added elements, C is solid-solved in a substrate to increase the hardness and bound with Cr, Mo, V and W to form a hard carbide. Co forms no carbide and does not contribute in improving abrasion resistance, but it is solid-solved in the substrate and improves temper hardness and red heat hardness. As clearly shown in the test results of a test piece A thus manufactured, the piston ring with excellent abrasion resistance and scuff resistance and rarely abrading a mating material is obtained in this method.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a steel piston ring for an internal combustion engine, and more particularly to a steel piston ring having the durability required for a high-load internal combustion engine.

[Problems to be solved by conventional techniques and inventions] In recent years,
As engines become smaller and lighter and have higher performance, such as higher output, the conditions required for piston rings are becoming increasingly severe.In addition to wear resistance, scuff resistance
Improvements have been made from various perspectives, including breakage resistance.

As a countermeasure to the above, hard chrome plating, which has traditionally been widely used for surface treatment of piston rings for internal combustion engines, has poor wear resistance when using high lead fuel or operating in corrosive atmospheres, so alternative As a result, thermal spraying treatment has been applied. However, although the thermal spray coating has excellent wear resistance, there are problems such as peeling or falling off of the coating during operation and abrasion of the mating material.

Stainless steel piston rings are also used that have a base material of 13Cr or 17Cr martensitic stainless steel and have a nitrided surface. Although there is no problem in terms of abrasion resistance and abrasion of mating materials, the scuff resistance is insufficient and there is a problem in that scuff occurs when used in a high-load internal combustion engine.

Accordingly, an object of the present invention is to provide a piston ring for an internal combustion engine that has excellent wear resistance, less aggressiveness to mating materials, and excellent scuff resistance.

[Means to solve the problem]

As a result of extensive studies to achieve the above object, the inventors of the present invention have found that a piston ring whose base material is made of steel with a specific composition and whose surface is nitrided has excellent wear resistance and scuff resistance. The present invention was completed based on the discovery that

That is, the piston ring of the present invention has a diameter of 0.4 to 1.0
3.0 to 10.0 wt.% Cr;
゜0-10.0 wt% Mo and 1.0-2.5 wt%
of V, 1.0 to 3.0% by weight of W, and 2.0 to 10.
The base material is a steel material with a composition consisting of 0% by weight of Co and the remainder substantially Fe and unavoidable impurities, and is characterized by having a hardened layer formed by nitriding on at least the outer sliding surface thereof.

The present invention will be explained in detail below.

The base material of the piston ring of the present invention is a steel material having the following composition.

C: 0.4-1.0% by weight Cr: 3.0-10.0% by weight Mo: 3.0-10.0% by weight V: l, Q ~ 2.5% by weight W: 1.0-3.0% by weight Co: 2.0-1O10% by weight The remainder is essentially Fe and unavoidable impurities.

Among the additive elements of the steel materials mentioned above, C is dissolved in the matrix to increase hardness, and also combines with Cr, Mo, ■ and W to form hard carbides, and has the effect of increasing wear resistance and scuff resistance. have When the C content is 0.4% by weight, the amount of carbide formed is not sufficient to improve wear resistance and scuff resistance, so it is effective in improving wear resistance and scuff resistance. There is no. In addition, the content of C is 1.0% by weight.
If it exceeds, the toughness of the steel material decreases and the strength required for the piston ring cannot be obtained.

Cr combines with C to form a hard carbide, and
The nitriding process forms Cr nitrides, which has the effect of significantly improving the scuffing resistance of steel materials.

When the Cr content is less than 3.0% by weight, the amount of carbides and nitrides produced is insufficient, resulting in insufficient scuffing resistance, and when the Cr content exceeds 10.0% by weight, the scuff resistance becomes insufficient. The amount of carbides increases and the toughness of the steel deteriorates.

Like the above-mentioned Cr, Mo combines with C to form a hard carbide and improves wear resistance. In addition, it is partially dissolved in the matrix and has the effect of increasing the strength of the matrix and improving the tempering softening resistance at temperatures of 500°C or higher.

By improving the temper softening resistance, it is possible to prevent the hardness of the base material from decreasing during nitriding treatment and to improve the heat setting resistance of the piston ring. M
If the content of o is less than 3.0% by weight, the piston ring will have insufficient heat-setting resistance, and if it exceeds 10.0% by weight, the amount of carbides will increase and the toughness of the steel will deteriorate. .

(2), like the above-mentioned Cr and Mo, combines with C to form a highly hard carbide, which has the effect of improving wear resistance and scuff resistance. If the content of V is less than 1.0% by weight,
The above effects cannot be obtained because the amount of carbide produced is insufficient. Further, since the above effect is sufficient if the content is 2.5% by weight, there is no point in exceeding 2.5% by weight.

A part of W combines with C like the above Cr, lJo and V,
Forms highly hard carbides and improves the wear resistance and durability of steel materials. Furthermore, a part of it dissolves in the matrix and has the effect of improving the softening resistance at high temperatures. When the content of W is less than 1.0% by weight, the above effects are insufficient,
If it exceeds 3.0% by weight, the toughness of the steel material will be significantly reduced.

Although Co does not form carbides and does not contribute to improving wear resistance, it is mostly dissolved in the matrix and has the effect of improving tempering hardness and red-hot hardness, so it improves the scuff resistance of steel materials. is significantly improved. If the Co content is less than 2.0% by weight, the above effects will be insufficient, and if it exceeds 10.0% by weight, the durability and cuffing properties will decrease and the base will become brittle.

Next, the nitriding treatment of the above steel material will be described.

In the present invention, at least the outer peripheral sliding surface of a piston ring made of the above-mentioned steel material is subjected to nitriding treatment to form a hardened layer by the nitriding treatment.

The nitriding treatment or soft nitriding treatment in the present invention is preferably carried out at 550 to 600° C. for 5 to 10 hours in a nitrogen atmosphere.

Due to the above nitriding treatment, the surface of the base material has a depth of 50 to 120 mm.
A hardened layer made of nitride is formed to a depth of approximately μm.

By forming the above-mentioned hardened layer, surface hardness and wear resistance can be improved. At the same time, the heat treatment that accompanies this nitriding treatment removes the internal stress of the steel material, preventing the occurrence of cracks and improving fatigue strength, making it less likely to break.

Such a piston ring is of course suitable for use alone as a compression ring or the like, but it can also be used in combination with a rail control ring such as an oil control link that directly contacts the cylinder wall.

[For production]

The reason why the piston ring of the present invention has excellent wear resistance and scuff resistance is not only due to the inherent characteristics of the base material forming the ring itself, but also because the hardness of the surface is further increased by the nitriding treatment. It also has excellent breakage resistance.
This is thought to be due to the fact that the nitriding treatment acts as a heat treatment on the base material, improving fatigue strength, and removing internal stress, thereby preventing the occurrence of cracks that can cause breakage.

〔Example〕

The present invention will be explained in further detail by the following examples.

Example 1 A piston ring base material shown in Table 1 below was prepared, and the resulting base material was heated at 570±5°C for 7 hours in a N2 gas atmosphere.
After time nitriding, the surface of the base material is approximately 0°1mm deep (7)
A hardened layer was formed.

The surface of the obtained hardened layer was polished to a depth of 0.03 mm to obtain a test piece A.

Comparative Example 1 Test piece B was obtained in the same manner as in Example 1, except that the nitriding treatment and polishing treatment were not performed.

Comparative Examples 2 to 5 A piston ring base material having the composition shown in Table 1 below was created,
Test piece C subjected to nitriding treatment and polishing treatment for each,
A test piece E, and a test piece F without the treatment were obtained.

Comparative Example 6 A test piece G was obtained by subjecting the surface of a piston ring made of S45C material to chromium plating.

Test pieces A to G obtained in the above examples and comparative examples were subjected to the following tests.

(1) Scuff resistance test A test was conducted using an ultra-high pressure abrasion tester shown in Fig. 3. In addition, in this testing machine, a disc 6 made of cast iron material Fe12 used as a cylinder material and having a honed sliding surface 5 is removably attached to the stator holder 4, and the disc 6 is removably attached to the stator holder 4 from the back side. Lubricating oil is supplied through the oil supply hole 7. Here, stator holder 4
A hydraulic device (not shown) applies a pressing force (P) toward the right in the figure at a predetermined pressure.

The test specimen holder 9 mounted on the rotor 8 facing the disk 6 has four mounting holes carved at equal intervals on the circumference concentric with the rotation axis, and each has four mounting holes. The specimen IO is attached. The 5 n++n x 10 mm0 end surfaces of the test pieces 10, each of which has been subjected to a predetermined surface treatment, contact the sliding surface 5 of the disk 6 and are rotated at a predetermined speed by a drive device (not shown). The test is conducted while supplying lubricating oil at a constant temperature to the sliding surface from the oil supply hole 7 on the stator side. When the rotor 8 is rotated, torque is generated in the stator holder 4 due to friction between the test piece 10 and the disk 6. The torque is detected by a load cell (not shown) via a spindle (not shown), and changes in torque due to changes in pressing force are read by a dynamic strain meter (not shown). Since the torque increases rapidly when scuffing occurs, the pressing force at that time was taken as the scuffing resistance of the test piece.

The test conditions were as shown below.

Friction speed: 3 m/sec.

Lubricating oil ・Additive-free motor oil #30 oil temperature
・80℃ Oil supply amount '300cc/min Contact surface pressure:
20kg/7 to 10kg/7 to scuff occurrence
Figure 1 shows the results of increasing the pressure in increments of cat and holding each surface pressure for 3 minutes.

(2) Abrasion resistance test A test was conducted using a Kaken-type abrasion tester shown in Figure 4.

In Fig. 4, cast iron material F used as cylinder material
A test piece 14 is in contact with the outer peripheral surface of a cylinder 11 made of e12 under a constant contact load due to a weight 12, and a sulfuric acid aqueous solution with a pH of 2 is dripped onto the contact surface from a dripping nozzle 13. ing. When the cylinder 11 is rotated in the direction of the arrow by a drive device (not shown), the outer peripheral surface of the cylinder 11 and the 5
Due to friction with the tip surface of the test piece 14 having a curved surface of mm×5 mm and IOR, the tip surface of the test piece 14 and the cylinder 11
The outer circumferential surface of is worn out. Therefore, the wear resistance of the test piece was defined as the depth of wear at a constant friction distance.

The test conditions were as shown below.

Friction speed + 0.25tn/sec.

Contact load: 4kg Friction distance: 5.4km The results are shown in Figure 2.

Furthermore, for test pieces A, C, E, and G that did not cause abnormal wear in the wear resistance test, the amount of wear of the mating material in the same test was measured. The results are also shown in Figure 2.

As is clear from FIGS. 1 and 2, the piston ring of the present invention (test piece A) has excellent scuff resistance and wear resistance, and also causes less wear on the mating material.

〔Effect of the invention〕

As detailed above, the piston ring of the present invention uses a steel material with a specific composition as a base material, and a hardened layer is formed on the surface by nitriding treatment, so it has excellent wear resistance and scuff resistance.
It also has the advantage of causing less wear on the mating material (and less chance of breakage).

[Brief explanation of the drawing]

FIG. 1 is a graph showing the scuff resistance of test pieces according to examples and comparative examples of the present invention, and FIG. 2 is a graph showing the abrasion resistance of the same test pieces as in FIG. FIG. 3 is a partial sectional view showing the main parts of the test apparatus for the scuff resistance test, and FIG. 4 is a side view schematically showing the main parts of the test apparatus for the abrasion resistance test. 4... Stator holder 5... Sliding surface 6... Disc 7... Lubricating hole 8... Rotor 9... Test piece holder 10... Test piece 11... Cylinder 12・ ・ ・Weight 13...Dripping nozzle 14...Test piece

Claims (1)

[Claims] 0.4-1.0 wt% C and 3.0-10.0 wt%
of Cr, 3.0 to 10.0% by weight of Mo, and 1.0 to 10.0% by weight of Mo.
2.5% by weight of V, 1.0 to 3.0% by weight of W, 2
．． The base material is a steel material having a composition consisting of 0 to 10.0% by weight of Co and the remainder substantially Fe and unavoidable impurities, and is characterized by having a hardened layer by nitriding at least on the outer sliding surface thereof. Steel piston rings for internal combustion engines.