CN110592334B

CN110592334B - Method for improving local comprehensive mechanical property of high manganese steel frog

Info

Publication number: CN110592334B
Application number: CN201911001150.3A
Authority: CN
Inventors: 孙登月; 张旭; 陈晨; 张福成
Original assignee: Yanshan University
Current assignee: Yanshan University
Priority date: 2019-10-21
Filing date: 2019-10-21
Publication date: 2021-04-06
Anticipated expiration: 2039-10-21
Also published as: CN110592334A

Abstract

A method for improving the local comprehensive mechanical property of a high manganese steel frog is mainly characterized in that when the high manganese steel frog is cast, a core rail and a wing rail are heightened by 30-40mm within the range of the width of the core rail being 20-50mm, and the horizontal length of the heightened part is 560 mm; then heating the high manganese steel frog to 1100-; placing the high manganese steel frog on a die, forging and pressing the heightened area by using a forging hammer, wherein the pressing height is 15-22mm, only the heightened height of the forged part is obtained, mechanically cutting off the residual heightened part, and the cut-off height is 15-18mm, so that the integral working surfaces of the frog are ensured to be positioned on the same horizontal plane; heating the high manganese steel frog to 1150 +/-10 ℃, and immediately carrying out water toughening treatment after heat preservation for 20-40min to obtain a good single-phase austenite structure. The invention can reduce or even eliminate the inclusion defect inside the frog point rail and the wing rail to a certain extent, improve the wear resistance, prolong the service life, has simpler operation and lower cost, and can be popularized in a large range.

Description

Method for improving local comprehensive mechanical property of high manganese steel frog

Technical Field

The invention relates to the technical field of mechanical engineering, in particular to a method for improving local comprehensive mechanical property of a high manganese steel frog.

Background

The railway track mainly comprises steel rails, sleepers, turnouts, connecting parts and the like. The switch is generally composed of a point switch, a frog and a guard rail, and a connecting part. The frog is the most seriously damaged part in the railway structure, and the point rail in the frog is the weak link in the operation of the turnout.

High speed, heavy load, cross-regional jointless tracks are a big trend of railway development, and this puts new and higher requirements on the wear resistance and service life of railway frog. The method for improving the surface wear resistance of the high manganese steel frog has the advantages that the high manganese steel frog on a serving railway line is taken as a research object, the change condition of a microstructure of a subsurface layer of the frog in the serving process is observed, a phenomenon that a small amount of carbon atoms are accumulated in surface austenite of the high manganese steel frog in the serving process is generated, the failure modes mainly include abrasion, crushing deformation and fatigue shedding, and if the method for improving the surface wear resistance of the high manganese steel frog, which is simple in process operation, low in cost, extremely high in forming rate and capable of being popularized in a large range, can be found, the serving time of the high manganese steel frog can be improved undoubtedly.

Patent No. cn201810109618.x proposes a method for performing local thermomechanical treatment on a cast high manganese steel frog, in which the frog is partially heightened and the heightened part is forged, but in the method, the whole heightened part is flattened in the forging process, a rigid zone at the lower part of a hammer head is not considered, and in the forging process, because a rigid zone exists in the metal at the lower part of the hammer head, the rigid zone and the hammer head rigidly translate downwards together, the equivalent strain is almost zero, and the size of the rigid zone is generally in the range of 10-30mm related to the size of the hammer head, therefore, whether the wear resistance of the high manganese steel frog can be effectively improved and the service life of the frog is still to be further discussed. The size of the rigid region is obtained through simulation calculation, the rigid region is cut off under the pressure of the heightening body part, so that the maximum equivalent strain is generated on the rest part, and the purpose of grain refinement is achieved; the invention can reduce or even eliminate the inclusion defects in the frog point rail and the wing rail to a certain extent, improve the wear resistance of the frog, prolong the service life of the high manganese steel frog, have simple operation and relatively low cost, and can be popularized in a large range.

Disclosure of Invention

The invention aims to provide a method for improving the local comprehensive mechanical property of a high manganese steel frog, which is convenient to operate, simple in process and low in cost, and can greatly improve the wear resistance and the service life of the high manganese steel frog.

The technical means adopted by the invention are as follows:

the invention provides a method for improving local comprehensive mechanical property of a high manganese steel frog, which comprises the following steps of heightening vulnerable surfaces of a core rail and a wing rail within the range of 20-50mm of the width of the core rail when casting the high manganese steel frog, wherein the heightening height is h1, and the horizontal lengths of the heightening parts of the core rail and the wing rail are L; placing the cast and heightened high manganese steel frog into a heating furnace, fully heating to 1100-1200 ℃, and then keeping the temperature for 3-6h at constant pressure, so that the frog center rail and the wing rail are fully austenitized to generate an austenite mixed crystal structure; taking the heated high manganese steel frog out of the heating furnace, forging and pressing the heightened area of the high manganese steel frog on a die by using a forging hammer, wherein the heightened height is h1, the forging and pressing height corresponding to the heightened height is h2, only part of the heightened height is forged, mechanically cutting the rest heightened part, the cut part is a rigid area below a hammer head, so that the equivalent strain of the reserved part can reach 35-85%, and the cut height is h3, thereby ensuring that the whole working surface of the high manganese steel frog is at the same horizontal position; and heating the high manganese steel frog subjected to mechanical cutting treatment to 1150 +/-10 ℃, then carrying out heat preservation treatment for 20-40min, so that the interior of the high manganese steel frog is subjected to free diffusion, recrystallization and grain growth, and then immediately carrying out water toughening treatment to obtain a good single-phase austenite structure.

Compared with the prior art, the invention has the following beneficial effects:

1. the process is relatively simple, through carrying on the multi-direction observation to the high manganese steel frog in service, find the wearing and tearing of the 20-50mm department of frog point rail width are the most serious, this part is apt to take place the fatigue failure, and the crackle produces most in this part and is apart from the horizontal plane 10-15 mm, through this method, only forge and press a part and increase the height, guarantee to concentrate the little regional or even rigid area that the equivalent strain is basically zero above the horizontal plane of frog, cut off all the remaining height, guarantee frog point rail and wing rail remaining surface are the large strain area, refine the internal crystalline grain, optimize and increase the mechanical properties of the position, can improve the mechanical properties of the high manganese steel frog, lengthen its service life.

2. After the easily damaged part is heightened, forged and mechanically cut off, the internal crystal grains of the frog are refined, and the fatigue strength is greatly improved. The austenite grain size of the surface layer reaches 1-2 grades, and the mechanical property of each part on the surface of the frog is improved to a certain degree. The service life is obviously prolonged.

3. Metallographic observation and mechanical property test are carried out on the frog subjected to heightening, forging and mechanical cutting, and the finding that the density between the top of the frog and the surface of the frog is remarkably increased, the yield strength of all areas of the surface layer of the frog is improved by more than 20 percent, the frog is very uniform, and no area with sudden failure exists; the tensile strength is averagely improved by 25 to 30 percent; the elongation is improved by more than 20 percent, the toughness is improved by more than 22 percent, and the fatigue life is improved by more than 1.4 times.

Drawings

FIG. 1 is a high-level schematic casting diagram of a high manganese steel frog used in the present invention;

FIG. 2 is a schematic diagram of a high manganese steel frog used in the present invention;

fig. 3 is a sectional view a-a in fig. 2.

In the figure: 1. a point rail; 2. a wing rail.

Detailed Description

Example 1

Firstly, when the high manganese steel frog is cast, the heights of the core rail and the wing rail are integrally increased within the range of 20-50mm of the width of the core rail, the increased height is 40mm, and the horizontal length of the increased area is 560mm, as shown in figure 1. Putting the high manganese steel frog into a forging furnace, fully heating to 1150 ℃, then preserving heat for 6h to enable the frog to be austenitized, enabling the internal temperature of the frog to also reach 1150 ℃, then taking out the frog from the forging furnace, and placing the frog on a lower die, wherein the lower die needs to be preheated to 300 ℃ in advance; moving a lower die and a frog to the position right below a forging hammer, starting forging and pressing the frog, forging and pressing the heightened surface of the frog by the forging hammer at the speed of 10mm/s for 19s, wherein the pressing height of the forging hammer is 22mm, the heightened height of the frog is changed into 18mm, cutting off the heightened part of 18mm by a mechanical cutting means, heating the processed high manganese steel frog to 1140 ℃, carrying out heat preservation for 40 minutes, carrying out free diffusion, recrystallization and grain growth treatment, and then directly carrying out water quenching treatment to obtain a single-phase austenite mixed crystal structure, wherein the surface austenite grain size of the high manganese steel frog is 2-grade. By the method, the equivalent strain of the rest part is more than 35 percent and can reach 85 percent to the maximum extent, the compactness of the surface layers of the frog point rail and the wing rail can be ensured, and the internal plastic defect of the frog basically disappears. Through later detection on the mechanical properties of the high manganese steel frog, the fact that the yield strength of the surface of the frog is improved by 24% through heightening-forging-mechanical cutting treatment on the frog can be obtained; the tensile strength is improved by 27 percent; the elongation is improved by 23 percent, the toughness is improved by 27 percent, and the fatigue life is improved by about 1.7 times under the normal service state.

Example 2

Firstly, when casting a high manganese steel frog, integrally heightening the heights of a center rail and a wing rail within the range of 20-50mm of the width of the center rail, wherein the heightening height is 30mm, and the length of a heightening area is 560 mm; putting the high manganese steel frog into a forging furnace, fully heating to 1200 ℃, preserving heat for 4h to ensure that the frog is austenitized, ensuring that the internal temperature of the frog also reaches 1200 ℃, taking out the frog from the forging furnace, and placing the frog on a lower die, wherein the lower die needs to be preheated to 300 ℃ in advance; moving a lower die and a frog to the position right below a forging hammer, starting forging and pressing the frog, forging and pressing the heightened surface of the frog by the forging hammer at the speed of 10mm/s for 17s, wherein the pressing height of the forging hammer is 15mm, the heightened height of the frog is changed into 15mm, cutting off the heightened part of 15mm by a mechanical cutting means, heating the processed high manganese steel frog to 1150 ℃, preserving the temperature for 30 minutes, carrying out recrystallization and grain growth treatment, and then directly carrying out water quenching treatment to obtain a single-phase austenite mixed crystal structure, wherein the austenite grain size of the surface layer of the high manganese steel frog is 1.5 grade. Through later detection on the mechanical properties of the high manganese steel frog, the yield strength of the surface of the frog is improved by 22% through heightening-forging-mechanical cutting treatment on the frog; the tensile strength is improved by 25 percent; the elongation is improved by 22 percent, the toughness is improved by 25 percent, and the fatigue life is improved by 1.4 times under the normal service state.

Example 3

Firstly, when casting a high manganese steel frog, integrally heightening the heights of a center rail and a wing rail within the range of 20-50mm of the width of the center rail, wherein the heightening height is 35mm, and the horizontal length of a heightening area is 560 mm; putting the high manganese steel frog into a forging furnace, fully heating to 1100 ℃, then preserving heat for 6 hours to ensure that the frog is austenitized, and ensuring that the internal temperature of the frog also reaches 1100 ℃, taking out the frog from the forging furnace, and putting the frog on a lower die which needs to be preheated to 300 ℃ in advance; moving a lower die and a frog to the position right below a forging hammer, starting forging and pressing the frog, forging and pressing the heightened surface of the frog by the forging hammer at the speed of 10mm/s for 18s, wherein the pressing height of the forging hammer is 18mm, the heightened height of the frog is changed into 17mm, cutting off the heightened part of 17mm by a mechanical cutting means, heating the processed high manganese steel frog to 1160 ℃, carrying out heat preservation for 40 minutes, carrying out free diffusion, recrystallization and grain growth treatment, and then directly carrying out water quenching treatment to obtain a single-phase austenite mixed crystal structure, wherein the surface austenite grain size of the high manganese steel frog is grade 1. Through later mechanical property detection of the high manganese steel frog, the fact that the yield strength of the surface of the frog is improved by 28 through heightening-forging-mechanical cutting treatment of the frog can be obtained; the tensile strength is improved by 32 percent; the elongation is improved by 30 percent, the toughness is improved by 36 percent, and the fatigue life is improved by about 2.5 times under the normal service state.

Although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made on the technical solutions described in the foregoing embodiments, or some or all of the technical features of the embodiments can be equivalently replaced, without departing from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for improving the local comprehensive mechanical property of a high manganese steel frog is characterized by comprising the following steps: the method comprises the following steps:

(1) when the high manganese steel frog is cast, the vulnerable surfaces of the core rail and the wing rail are heightened by 30-40mm within the range of the width of the core rail being 20-50mm, and the horizontal lengths of the heightened parts of the core rail and the wing rail are 560 mm;

(2) placing the cast and heightened high manganese steel frog into a heating furnace, fully heating to 1100-1200 ℃, and then keeping the temperature for 3-6h at constant pressure, so that the frog center rail and the wing rail are fully austenitized to generate an austenite mixed crystal structure;

(3) taking the heated high manganese steel frog out of the heating furnace, forging and pressing the heightened area of the high manganese steel frog on a die by using a forging hammer, wherein the heightened height is 30-40mm, the corresponding forging and pressing height is 15-22mm, only one part of the heightened height is forged and pressed, and the rest heightened part is mechanically cut off, the cut-off part is a rigid area below a hammer head, so that the equivalent strain of the reserved part reaches 35-85%, and the cut-off height is 15-18mm, and the integral working surface of the high manganese steel frog is ensured to be at the same horizontal position;

(4) and heating the high manganese steel frog subjected to mechanical cutting treatment to 1150 +/-10 ℃, then carrying out heat preservation treatment for 20-40min, so that the interior of the high manganese steel frog is subjected to free diffusion, recrystallization and grain growth, and then immediately carrying out water toughening treatment to obtain a good single-phase austenite structure.