BRPI0301529B1 - Internal combustion engine liner and manufacturing process - Google Patents

Abstract

"liner for internal combustion engine and its manufacturing process". Said liner is obtained from a gray cast iron alloy comprising a bainitic matrix of thermally treated and stabilized structure containing carbides rich in niobium, vanadium and less titanium, and in which the austenite is decomposed. the manufacturing process comprises the steps of casting said alloy; subjecting the molten jacket to a heat treatment in the range of about 680 to 700Â ° C to decompose bainite austenite and stabilize the molten alloy structure; and machine the shirt to its final shape.

Description

INNER COMBUSTION ENGINE SHIRT AND MANUFACTURING PROCESS

Field of the Invention The present invention relates to a gray cast iron liner to be mounted on the internal combustion engine cylinder to ensure increased wear resistance measured across the polished area of the liner inner face.

The invention further relates to a process for obtaining said jacket. Prior Art [003] The advancement of technology worldwide has created new material requirements, generally requiring in the automotive sector an increase in mechanical properties and wear resistance in dimensioned parts. increasingly smaller, due to the weight reduction of vehicles imposed by the new environmental and economic regulations. Another factor that should be taken into consideration concerns the engine characteristics directly related to the environment, which must be maintained over time, thus requiring the above properties, a high dimensional stability, which corroborates the good adjustment of the cylinder system. , piston and ring, ensuring efficient emission control.

[004] Peripheral graphite gray iron liners containing the graphite and perlite are known in the art and are obtained by generally centrifugal casting of the alloy followed by the usual and necessary machining and finishing operations.

Despite being widely used, this periodic gray cast iron liner still has deficiencies in tensile strength, wear and deformation during its service life, which negatively make these liners unsuitable for meeting new requirements. requirements that have been studied for the operation of internal combustion engines, particularly the engines of medium and heavy transport vehicles.

Background of the Invention It is a general object of the present invention to provide a gray cast iron liner for internal combustion engines, with respect to known liners having greater dimensional stability, greater wear resistance and even greater strength. to traction.

It is yet another object of the invention to provide a process for producing a shirt having the improved characteristics defined above.

SUMMARY OF THE INVENTION To meet the above-mentioned first object, the present invention provides a gray cast iron jacket which is characterized in that the gray cast iron comprises a heat treated and stabilized bainitic matrix containing rich carbides. in niobium, vanadium and less titanium, and in which austenite is decomposed.

The jacket fabrication process, which is a further object of the invention, comprises the steps of: melting a gray cast iron alloy comprising a bainitic matrix containing myobium rich carbides, vanadium and less titanium; subjecting the molten jacket to a heat treatment in the range of about 680 to 700 ° C to decompose bainite austenite and stabilize the molten alloy structure; and machine the shirt to its final shape.

Description of the Invention The invention will be described by considering an embodiment of the jacket material subjected to an assay described below.

The methodology employed in the present study aims to exacerbate engine stress conditions in order to promote appreciable wear in a medium duration dynamometric test. The test conditions were such that there was a greater risk of engine failure, requiring careful monitoring in addition to a high-level team involved in judging engine behavior throughout the test, with constant monitoring of engine level. deterioration of the lubricating oil as it was far below the recommended level for the engine class tested due to the high working temperatures and specified average pressure.

Table I below summarizes the test conditions in terms of lubrication power generated by the engine throughout the test and the diesel employed.

Table I

The test was conducted by comparing the behavior of a normal production alloy, the known material, with that of the developing material, as can be seen in the scheme shown in Figure 1. The liners were tested on the MWMX-10 engine. of six cylinders.

The main metallurgical, mechanical and chemical characteristics of these materials are summarized in table II below.

Table II - Microstructure in terms of matrix graffiti, hardness and chemical composition of materials NEW MATERIAL

Average Chemical Composition (% by weight) Hardness of the order of 290 HB.

Bainitic microstructure and predominance of type D and E graphites.

Although the above test was performed with the average percentage values given in table II, it should be understood that similar results in terms of greater dimensional stability, greater wear and tensile strength can be obtained with an iron alloy. bainitic gray cast, comprising by weight%: NAME MATERIAL

Specified Chemical Composition (% by weight) Hardness: in the order of 250 HB

Microstructure: Perlitic Matrix and Type A Graphite Predominance

[0016] The mechanical characteristics in terms of tensile strength of the two materials studied are shown in table III.

Table III - Tensile Test Results The results of this table show that there was a 62% increase in tensile strength of the new material compared to the Known Material.

[0018] At the end of the first SOO hours of testing, dimensional tests of the backlash, piston backlash and ovality clearance of the engine parts were performed directly on the engine, the results of these liner measurements with normal production material and the alloy In development are shown in Tables IV and V. This test stop was used to extract two liners, one for the proposed material and one for the conventional alloy to ensure at least one full dimensional in these, should the engine fail. These shirts were replaced by another pair with the proposed conventional material.

[0019] Tables IV and V are as follows: [0020] The results presented in Tables IV and V indicate the gap between the ends a similar wear for rings working against the proposed material and the known material. The result in which the new material performed better relates to dimensional stability, with an ovality about 40% lower than that determined on the liner with the standard material. Tables VI and VII are as follows: Dimensional summary of the tested liners, tables VI and IX. ♦ Stress-Relieving Liner (MWH Cycle) ♦ Stress-Relieving Liner (KWH Cycle) [0021] The following table X shows the apparent and polished area results for moving material and known material linings tested by 150 ,, 500 and 650 hours The two criteria adopt the following methodology: [0022] Actual polished area: Threshold between the area with and without honing as the region in which uncrossed hazards are to be found.

Apparent Polished Area: A region that visually presents itself as polished but which, upon closer observation, indicates the risk of bruising still crossing.

From the result set presented in this report it can be concluded: [0025] The new material presents a greater dimensional stability in relation to the known material.

The proposed alloy has wear resistance measured across the polished area about three times greater than the known material.

[0027] The behavior of piston rings does not differ significantly when working against both liner materials.

The new material had a tensile strength, about 60% higher than the known alloy. Table X is as follows: Table XI was constructed from the results presented in table X and refers to the overall average wear per cylinder for new material and known material excluding values for cylinders that worked 150 hours, given the short duration of this request.

Table XI - Average Polished Area per Cylinder for Tested Shirts, 500h and 650h The data presented in the table above indicate that the new material showed about three times less wear than the known material.

Linear straightness measurements at the top dead center of the first channel rings indicated no localized wear.

The behavior of rings that worked against known material and new material can be inferred by analyzing the values given in table XII.

Table XII- Dimensions of rings after 650 hours (measured in mm) The results presented in Table XII indicate similar wear behavior for rings working against the known material and the new material.

From the result set presented in this report it can be concluded: The new material has a greater dimensional stability in relation to the known material.

The proposed alloy exhibits greater dimensional stability with respect to the known material.

The proposed alloy exhibits wear resistance measured across the polished area about three times greater than the known material.

The behavior of piston rings does not differ significantly when working against both liner materials.

The new material had a tensile strength, about 60% higher than the known alloy.

Claims (5)

1. Internal combustion engine liner, made from an alloy of gray cast iron, characterized in that the gray cast iron comprises a bainitic matrix with a thermally treated and stabilized structure containing carbides rich in niobium, vanadium and less. titanium, and in which the austenite is decomposed; wherein the bainitic matrix comprises in% by weight: C equiv. 3.13-4.00 C 2.60 - 3.25 Si 1.60 - 2.30 Mn 0.80 Max. P 0.10 Max. S 0.12 Max. Ni 1.00 - 1.60 Cr Residual Mo 1.00 - 1.50 Ti 0.07 Max. Cu Residual V 0.10 - 0.40 Nb 0.10 - 0.40 Fe the remainder Liner according to Claim 1, characterized in that the bainitic matrix gray cast iron alloy comprises in% by weight: C equiv. 3.52 P 0.0370 Ni 1.460 C 2.90 S 0.0170 Mo 1.320 Si 1.82 Cu 0.0630 V 0.155 Μη 0.180 Cr 0.0310 Nb 0.170 Ti 0.04 Fe the remainder An internal combustion engine liner manufacturing process, a liner according to any one of claims 1 or 2, characterized in that it comprises the steps of: casting a gray cast iron alloy comprising a bainitic matrix containing rich carbides in niobium, vanadium and less titanium, and specifically containing, in% by weight: C equiv. 3.13 -4.0; C 2.60 - 3.25; Si 1.60 - 2.30; Mn 0.80 Max; P 0.10 Max .; S 0.12 Max .; Ni 1.0 - 1.60; Residual Cr; Mo 1.0 - 1.50; Ti 0.07 Max .; Residual Cu; V 0.10 - 0.40; and Nb 0.10-0.40; subjecting the molten jacket to a heat treatment in the range of about 680 to 700 ° C to decompose bainite austenite and stabilize the molten alloy structure; and machine the shirt to its final shape. Process according to Claim 3, characterized in that the bainitic matrix gray cast iron alloy comprises in% by weight: C equi. 3.13-4.00 C 2.60 - 3.25 Si 1.60 - 2.30 Mn 0.80 Max. P 0.10 Max. S 0.12 Max. Ni 1.00 - 1.60 Cr Residual Mo 1.00 - 1.50 Ti 0.07 Max. Cu Residual V 0.10 - 0.40 Nb 0.10 - 0.40 Fe the remainder Process according to Claim 4, characterized in that the bainitic matrix gray cast iron alloy comprises, in% by weight: C equiv. 3.52 P 0.0370 Ni 1.460 C 2.90 S 0.0170 Mo 0.1.320 Si 1.82 Cu 0.0630 V 0.155 Mn 0.180 Cr 0.0310 Nb 0.170 Ti 0.04 Fe the remainder