JPS60155666A - Manufacture of soft steel cylinder liner for internal combustion engine - 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 The present invention relates to a method of manufacturing cylinder liners for internal combustion engines of the type comprising treating the internal piston use surface of a mild steel cylinder liner to prevent wear of the coupled piston and piston rings.

BACKGROUND OF THE INVENTION In many internal combustion engines, each piston reciprocates within a cylinder, typically formed by a generally cylindrical dry liner press-fitted, retracted, or inserted into the engine block. The inner surface (or "bore") of the cylinder liner is subject to wear and scuffing in contact with the coupling piston. Dry liners can also scratch the mating engine block, so
A well-dried cylinder liner must be able to prevent such wear and at the same time be easily press-fit or slip-fit into, and removable from, the mating engine block.

One material commonly used for such liners is low carbon mild steel, but this does not have sufficient wear resistance. For this reason, various techniques have been used to improve wear resistance.

One such technique is to use materials that are harder and more wear resistant than mild steel.

For example, cast iron or cast steel with a high content of nickel, chromium, and iron can be used, especially if hardened or tempered. However, although these materials have high wear resistance, they have the disadvantage that their ductility is significantly lower than that of mild steel. Additionally, finished cylinder liners obtained from such materials can be brittle and may fracture if the liner is press fit into a cylinder block.

A second technique is to provide a hard surface layer on a cylinder liner made of mild steel or cast iron. Such a layer is a hard chrome plated layer on the lumen of the liner. However, chrome plating is an expensive method and
This increases the cost of the liner and has the disadvantage that such a plating layer does not easily retain oil and is therefore susceptible to galling during use. Also, the chrome plating layer can soften at temperatures above 300° C. and reduce its wear resistance, requiring costly finishing operations. Hard surface treatments are also fairly expensive to apply.

According to the invention, a method for producing a cylinder liner for an internal combustion engine of the type comprising treating at least the internal piston use surface of the mild steel cylinder liner in order to prevent wear of the coupled piston and the piston ring. The cylinder liner formed into the final shape and then molded is placed in an air-excluded chamber and heated with carburizing gas and nitrogen-containing gas in a ratio of 25 nia 5 to 75 = 25 (by volume). 500 mixed gas
The cylinder liner is nitrogen carburized by feeding the cylinder liner at a temperature of ~650°C.
A method of manufacturing a mild steel cylinder liner is provided.

The following examples illustrate some embodiments of the invention.

EXAMPLE 1 A dry cylinder liner is formed from low carbon steel. For example, the material has the following composition: carbon '0.05-0
．． 30 - Silicon 0.10-0.35 Manganese: 0.40-1.4 Sulfur max 0.050 Phosphorus 0.050 Iron: The remaining billet of such material is first punched. or by drawing or extruding through a suitably shaped die, or by pressing or deep drawing to form a generally cylindrical blank.

This blank is then machined into the final shape of the cylinder liner by machining the end flanges and, if necessary, shaping the inner and outer surfaces of the cylinder to the required dimensions.

The shaped cylinder liner is then placed in a chamber from which air is excluded. Next, 500% of carburizing gas such as nitrogen-containing gas such as ammonia and exothermic hydrocarbon gas
It is fed into the channel at a temperature of .degree. C. to 650.degree. The ratio of nitrogen-containing gas to carburizing gas may be between 25:75 (by volume) and 75:25 (by volume), but tests for ammonia and exothermic hydrocarbon gases have shown that
It has been demonstrated that a ratio of 0:50 (volume ratio) or 60:40 (capacity ratio) gives improved results.

Both gases contact the surface of the cylinder liner and the carbon and nitrogen from both gases diffuse from the surface into the mild steel of the liner and into the body of the liner to a thickness of 25-20 μm.
For a particular material, the total penetration depth depends on the time during which the gas is supplied, for example a 1.0 μm thick layer of "nibusilon". '' layer and a total penetration of O,l mm to 0.3 mm.For example, the gas supply time may be 2 to 4 hours.A surface hardness of more than 800 HV can be obtained. , gradually but unevenly decreases to the hardness of the base material, which surface hardness is maintained during subsequent exposure of the liner to working temperatures of up to 550°C.

The cylinder liner is then removed from the chamber and the liner is ready for use without any other finishing steps. The liner has a hard, wear-resistant outer surface and a ductility of 6 parts. Furthermore, the fatigue strength of the liner is also significantly increased by the treatment.

This can be particularly important if the liner is provided with a flange that protrudes significantly outwardly of the liner, since high fatigue strength increases the fatigue strength of the flange. This is because the range of fracture and cracking of the flange at the flange portion is thereby reduced.

Example 2 A dry cylinder liner was formed from mild steel having a carbon content of 0.18% as described above with respect to Example 1. The formed liner was then placed in an air-excluding chamber and subjected to nitrogen carburization as described in Example 1. The temperature was 570°C and the treatment time was 3 hours.

The liner was immediately gas cooled after processing and then removed from the chamber and inspected. The inner bore and outer surface of the liner were found to have a uniform nitrogen carburization layer. Thickness 0.04
mm, the white "Ezosilon" surface layer covers the surface of the complex structure of acicular iron nitride in the ferrite grains.
．． The depth exceeds 2 mm, and the total penetration area is 0.3 mm.
was observed.

In the internal structure, the hardness is 540 HV just below the surface layer.
to 3 80 HV at a depth O, l 5 mrn. The core hardness of the material is 160 to 178 Hv at a diameter of 0.35 mm.

The cylinder liner treated as described above was then used in an exhaust turbine supercharged diesel engine. There was negligible wear on the liner surface after 300 hours of running. Oil consumption is acceptable at 0.5 inch of fuel consumption and power is approximately 1 inch lower than with untreated cylinder liners.
% thick. This should be due to the low friction liner surface which had a glass-like appearance after running.

After 550 hours, oil consumption gradually increased to 0.7% of fuel consumption due to piston ring fit, but was still acceptable. Power increased by 1.3% without increased fueling.

The manufacturing method described above and the cylinder liner produced thereby have a number of advantages. Because the liner is manufactured from ductile mild steel and all machining is performed before nitrogen carburization takes place, the shaping of the cylinder liner can be accomplished easily and quickly. Suitable mild steel and cast iron are inexpensive, reducing the cost of cylinder liners. The nitrogen carburizing process provides cylinder liners with high wear resistance, is effective at high temperatures (up to 550°C), and is effective at virtually no depth to the surface. Ol mm”=0.3 mm
) to provide a surface finish that penetrates up to

Such a liner can be pushed into the engine block without risk of brittle fracture because the central 6 portion remains ductile; the outer surface is resistant to wear due to friction with the engine block.

The inner surface receiving the piston is resistant to wear and galling of the coupled piston and piston ring, since the inner surface is well moistened by a film of oil. In addition, piston rings are also
It is particularly advantageous if nitrogen carburization is carried out as described in No. 112,025. Hard surfaces on piston rings tend to wear the cylinder liner in the absence of a corresponding hard surface on the liner. If the liner is a wet liner, the inner surface will be cavitated.
It has been found that this method sufficiently prevents on-erosion.

It should also be noted that cylinder liners produced as described above offer increased resistance to atmospheric oxidation, thereby reducing packaging and shipping costs.

Claims (1)

[Claims] 1. The method consists of treating the internal piston use surface of a mild steel cylinder liner to prevent wear of the combined piston and piston ring, and then molding the cylinder liner to remove air. Place it in the chamber, 2
The cylinder liner is nitrogen carburized by supplying a mixed gas of carburizing gas and nitrogen-containing gas in a ratio of 5 to 75:25 (by weight) to the chamber at a temperature of 500 to 650°C. manufacturing method. 2. The method according to claim 1, wherein the nitrogen-containing gas is ammonia and the carburizing gas is an exothermic hydrocarbon gas. 3. The method according to claim 1 or 2, wherein the gas ratio is 50:50 to 60:40 (capacity). 4. The method according to any one of claims 1 to 3, wherein the temperature is 550°C. 5. The total penetration depth of the nitrogen carburized layer into the surface of the cylinder liner is 0.1~0.3 mm, and the thickness of the Nibsilon surface layer is 0.05~0.020 mm. A method according to any one of claims 1 to 3, wherein the cylinder liner is treated during the treatment of the cylinder liner. 6. The method according to claim 5, wherein the treatment time is 2 to 4 hours. 7. Prior to nitrogen carburizing, a generally tubular mild steel cylinder blank is formed and machined to form a cylinder liner in its final shape, and the cylinder liner in its final shape is characterized by claims 1-6. The method described in any one of the preceding paragraphs. 8. The method according to claim 7, wherein the tubular cylinder blank is formed by extrusion or pressing or deep drawing.