Aftertreatment method of austenite casting

Abstract

The invention provides a post-treatment method of an austenite casting. The post-treatment method comprises the following steps: S1, cutting: intermittently cutting redundant metal on the surface of the cold-state austenite casting by adopting a flame cutting gun; and S2, air gouging is conducted, specifically, redundant metal is removed from the cut cold-state austenite casting in a distributed layer-by-layer air gouging mode. According to the method, the austenite casting does not need to be preheated, and the cold-state austenite casting is directly subjected to cutting and air gouging treatment, so that a heat affected zone of cutting or air gouging treatment is reduced, and the probability of cracks and carbide precipitation is reduced. Besides, an intermittent cutting process and a distributed layer-by-layer gouging process are adopted, and a heat affected zone in the gouging process of the cutting machine is reduced, so that the problems of cracks and carbide precipitation caused by too high temperature in the gouging process are prevented.

Description

Technical Field

[0001] The invention belongs to the technical field of casting, and more specifically, relates to a post-processing method for an austenite casting. Background Art

[0002] With the rapid development of industry, the issue of high efficiency and energy saving has attracted more and more attention. As far as metal casting production is concerned, the net final mold casting method has always been a goal that people have been pursuing. But for traditional sand casting, at present, the pursuit of net final mold is just a beautiful wish. Because as far as metal is concerned, liquid-solid transition, thermal expansion and contraction are inevitable, so in order to cast dense and defect-free castings, it is necessary to set up a certain pouring system and shrinkage system on the casting prototype, such as runners, risers, subsidies, chillers, etc. These pouring systems need to be removed. Usually cold processing or hot processing methods are used. For example, turning, milling, planing, sawing, etc., and the main hot processing methods are flame cutting, carbon arc gouging, laser, plasma cutting, etc. Flame cutting and carbon arc gouging are the most efficient and convenient methods for removing excess metal in the production and manufacturing process of steel castings.

[0003] However, because the flame cutting and carbon arc gouging process will generate high temperature of molten metal, the molten metal is blown away by air flow, so as to achieve the purpose of separating the metal. In this process, in addition to a part of the heat being taken away by the blown away molten metal, the remaining heat is radiated and conducted to the metal body. This heat will have certain side effects on the metal body, such as causing local metal thermal expansion and contraction, resulting in changes in the metal body structure (especially near the cutting gouging layer surface, generally called the heat affected zone), and at the same time, corresponding thermal stress and structural stress will be generated. These side effects will cause the mechanical properties of the casting metal surface hardness and other mechanical properties to deteriorate, the surface layer to crack or the casting to deform.

[0004] For austenitic steel castings, such as compressor volutes, casings and other products, this thermal impact is particularly obvious and serious. Compared with carbon steel, low alloy steel or most other high alloy steel materials, the expansion coefficient of austenitic steel castings is relatively large. Because it contains carbon and is a high alloy steel, various carbides or other compounds must be formed. Especially in the process of cooling from high temperature, if the cooling rate is lower than the critical cooling rate, various carbides or other compounds will precipitate. These carbides or compounds have relatively high hardness and are mainly distributed on the grain boundaries of the austenite structure, which makes the material brittle and the castings very easy to crack. Especially for large and complex austenitic steel castings, many small cracks are often found on the surface of the castings after cutting and air planing. The existence of these crack defects reduces the quality of the castings and the processing and repair will occupy a lot of production resources and costs. At the same time, these precipitates are mainly formed in the form of CrxCy, which causes the austenitic casting matrix to be poor in Cr, the corrosion resistance is reduced, and pitting pits are easily formed. Summary of the invention

[0005] Based on this, it is necessary to provide a post-processing method for austenitic castings to address the problem that austenitic castings are prone to cracks and carbide precipitation during post-processing in the prior art, which can avoid cracks or carbide precipitation in austenitic castings during post-processing.

[0006] A post-processing method for an austenitic casting comprises the following steps:

[0007] S1, cutting: use a flame cutting gun to intermittently cut the excess metal on the surface of the cold austenite casting;

[0008] S2, gouging: The excess metal is removed from the cold austenitic casting after cutting by using a dispersed layer-by-layer gouging method.

[0009] Furthermore, the intermittent cutting operation in step S1 includes the following steps:

[0010] S11, use the extended cutting gun to cut the excess metal on the surface of the austenite casting for 1 to 2 minutes, and then stop cutting;

[0011] S12, cooling the cut portion of the austenite casting and the casting surface around the cut portion;

[0012] S13, looping the steps S11 to S12 until the excess metal on the surface of the austenitic casting is cut off.

[0013] Furthermore, before the step S11, the method further includes a step S10, in which, before cutting, the ratio of fuel gas to oxygen in the flame gun is adjusted so that the flame reaches a neutral high temperature state.

[0014] Furthermore, in step S12, the temperature of the cut portion of the austenite casting and the surface of the casting around the cut portion is cooled to 50°C to 100°C.

[0015] Furthermore, in the step S12, the austenitic casting is cooled by using an air duct or cooling water.

[0016] Furthermore, in step S2, the decentralized layer-by-layer air gouging method includes the following steps:

[0017] S21, using the carbon rod on the gouging gun to melt the excess metal layer by layer, and using the compressed air on the gouging gun to blow away the molten metal. When the temperature of the gouging area and the surrounding casting surface exceeds 200-300℃, stop gouging;

[0018] S22, spraying water to cool the gouging area and its surroundings, and when the surface temperature of the casting in the gouging area and its surroundings is lower than 50-100°C, returning to step S22;

[0019] S23, looping steps S21 to S22, when the gouging assembly is close to the required size, replacing the carbon rod with a smaller diameter to perform thin-layer brush gouging.

[0020] Furthermore, in the step S21, the diameter of the carbon rod is 19 mm, and the gouging current is 1800-2200 A. Furthermore, in the step S23, the diameter of the carbon rod is 16 mm, and the gouging current is 1000-1200 A.

[0021] Furthermore, in the step S21, the angle between the carbon rod and the surface of the casting to be gouged is 20° to 40°. During gouging, a section is formed at the front end of the carbon rod, and the section angle is 40° to 60°.

[0022] Furthermore, in the step S21, the depth of each layer of metal layer removed by air gouging is 5 to 10 mm; and in the step S23, the depth of each layer of metal layer removed by air gouging is 2 to 5 mm.

[0023] The present invention provides a post-processing method for austenitic castings, which does not require preheating of the austenitic castings, and directly cuts and gouges the cold austenitic castings, thereby reducing the heat-affected zone of cutting or gouging, and reducing the probability of cracks and carbide precipitation. In addition, the present invention adopts an intermittent cutting process, that is, first cutting with a cutting gun for 1 to 2 minutes, cooling, and then cutting again, thereby preventing continuous diffusion of heat, reducing the heat-affected zone, and further reducing the probability of cracks or carbide precipitation during the cutting process; in the gouging process, the present invention adopts a decentralized layer-by-layer gouging method, that is, when the gouging zone temperature is too high, cooling is performed to further prevent the problem of cracks and carbide precipitation caused by the high temperature during the gouging process. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A scanned image of the heat-affected zone after cutting according to the present invention;

[0025] Figure 2 This is a scanned image of the heat-affected zone after gouging of the present invention. DETAILED DESCRIPTION

[0026] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly understood.

[0027] It should be noted that when an element is referred to as being "disposed on" another element, it may be directly on the other element or there may be a centered element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a centered element at the same time. The terms "vertical", "horizontal", "left", "right", "top", "bottom", "bottom end", "top end" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation method.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0029] The present invention provides a post-processing method for an austenitic casting, the post-processing method for an austenitic casting comprising the following steps:

[0030] S1, cutting: use a flame cutting gun to intermittently cut the excess metal on the surface of the cold austenite casting;

[0031] S2, gouging: The excess metal is removed from the cold austenitic casting after cutting by using a dispersed layer-by-layer gouging method.

[0032] The present invention provides a post-processing method for austenitic castings, which does not require preheating of the austenitic castings, and directly cuts and gouges the cold austenitic castings, thereby reducing the heat-affected zone of the cutting or gouging treatment, and reducing the probability of cracks and carbide precipitation. In addition, the present invention adopts an intermittent cutting process and a decentralized layer-by-layer gouging process to reduce the heat-affected zone during the gouging process of the cutting machine, thereby preventing the problem of cracks and carbide precipitation caused by excessively high temperatures during the gouging process.

[0033] The post-processing method of an austenitic casting is described below in conjunction with specific embodiments to further understand the inventive concept of the post-processing method of an austenitic casting.

[0034] In one embodiment, a post-processing method for an austenitic casting comprises the following steps:

[0035] S1, cutting: using a flame gun to intermittently cut the excess metal on the surface of the cold austenite casting. The cold austenite casting is not preheated locally or as a whole before cutting, thereby reducing the thermal impact caused by preheating. During the cutting process, the flame airflow is used as much as possible to blow away the molten metal from the surface of the casting, thereby preventing the molten metal from remaining on the surface of the casting.

[0036] Specifically, step S1 includes the following steps:

[0037] S10, before cutting, adjusting the ratio of fuel gas to oxygen in the flame gun so that the flame reaches a neutral high temperature state;

[0038] S11, use a flame cutting gun to cut the excess technology on the surface of the austenite casting for 1 to 2 minutes, and then stop cutting;

[0039] S12, cooling the cut portion of the austenite casting and the casting surface around the cut portion;

[0040] S13, looping the steps S11 to S12 until the excess metal on the surface of the austenitic casting is cut off.

[0041] S2, gouging: The cold austenitic casting after cutting is subjected to a dispersed layer-by-layer gouging method to remove excess metal. The cold austenitic casting is not preheated locally or as a whole before gouging, thereby reducing the thermal impact of preheating. The gouging gun includes a carbon rod that can melt metal after being energized and an air cavity that can blow out compressed air; the carbon rod is installed at the end of the gouging gun, and the carbon rod is detachably connected to facilitate the replacement of carbon rods of different specifications. It should be noted that gouging is mainly used to remove excess metal remaining after cutting.

[0042] Specifically, step S2 includes the following steps:

[0043] S21, using the carbon rod on the gouging gun to melt the excess metal layer by layer, and using the compressed air on the gouging gun to blow away the molten metal. When the temperature of the gouging area and the surrounding casting surface exceeds 200-300℃, stop gouging;

[0044] S22, spraying water to cool the gouging area and its surroundings, and when the surface temperature of the casting in the gouging area and its surroundings is lower than 50-100°C, returning to step S21;

[0045] S23, looping steps 21 to S2, when the gouging assembly is close to the required size, replacing the carbon rod with a smaller diameter to perform thin-layer brush gouging.

[0046] In another embodiment, in step S12, the temperature of the cut portion of the austenite casting and the surface of the casting around the cut portion is cooled to 50°C to 100°C, specifically, by using a duct or cooling water for cooling. That is, the temperature of the cut portion of the casting and its surroundings is cooled, thereby preventing continuous diffusion of heat, reducing the impact of the heat-affected zone, and avoiding cracks on the casting surface or precipitation of carbides.

[0047] In another embodiment, in step S21, the diameter of the carbon rod used is 18 mm, and the gouging current is 1800-2200 A. The angle between the carbon rod and the surface of the casting to be gouged is 20°-40°. During gouging, a section is formed at the front end of the carbon rod, and the angle of the section is 40°-60°. According to the area and depth of the area to be gouged, dispersed gouging is selected layer by layer, and the depth of the metal layer removed by each gouging layer is controlled to be 5-10 mm.

[0048] In another embodiment, in step S23, the diameter of the replaced carbon rod is 16 mm, and the current of the gouging is 1000-1200 A. The thin-layer brush gouging method is adopted, and the depth of each layer of gouging to remove the metal layer is 2-5 mm, and the gouged surface is as flat as possible, and the angle of the carbon rod and the temperature control and cooling method of the gouging area are the same as those in steps S21-S22.

[0049] In the present invention, after the excess metal on the surface of the austenitic casting is treated according to the above method, Figure 1-2 As shown, according to experimental detection, the depth of the heat affected layer of cutting or gouging is basically less than or equal to 0.5mm. The metallographic structure of the heat affected layer is still mainly austenite, and the precipitation of various carbides or other compounds is relatively small. And through experimental observation, no cracks are generated on the surface.

[0050] It should be noted that the above steps S1 and S2 can be used in combination or separately according to the area and thickness of the excess metal to be removed from the casting. For example, the surface of the cut gouging layer is polished by a single crystal corundum grinding wheel or other tools. After polishing, the structure of the surface of the final casting is basically close to the original casting matrix structure, which maintains the consistency of the surface characteristics of the casting and improves the corrosion resistance of the casting.

[0051] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A post-processing method for austenitic castings, characterized in that: The post-processing method of the austenitic casting comprises the following steps: S1, cutting: use a flame cutting gun to intermittently cut the excess metal on the surface of the cold austenite casting; S2, gouging: The excess metal is removed from the cold austenitic casting after cutting by using a dispersed layer-by-layer gouging method.

2. The post-processing method of an austenitic casting according to claim 1, characterized in that: The intermittent cutting operation in step S1 includes the following steps: S11, use a flame cutting gun to cut the excess metal on the surface of the austenite casting for 1 to 2 minutes, and then stop cutting; S12, cooling the cut portion of the austenite casting and the casting surface around the cut portion; S13, looping the steps S11 to S12 until the excess metal on the surface of the austenitic casting is cut off.

3. The post-processing method of an austenitic casting according to claim 2, characterized in that: Before the step S11, the method further includes step S10, which is to adjust the ratio of fuel gas to oxygen in the flame gun before cutting, so that the flame reaches a neutral high temperature state.

4. The post-processing method of an austenitic casting according to claim 2, characterized in that: In the step S12, the temperature of the cut portion of the austenite casting and the surface of the casting around the cut portion is cooled to 50°C to 100°C.

5. The post-processing method of an austenitic casting according to claim 4, characterized in that: In the step S12, the austenite casting is cooled by using an air duct or cooling water.

6. The post-processing method of an austenitic casting according to claim 1, characterized in that: In step S2, the decentralized layer-by-layer air gouging method includes the following steps: S21, using the carbon rod on the gouging gun to melt the excess metal layer by layer, and using the compressed air on the gouging gun to blow away the molten metal. When the temperature of the gouging area and the surrounding casting surface exceeds 200-300℃, stop gouging; S22, spraying water to cool the gouging area and its surroundings, and when the surface temperature of the casting in the gouging area and its surroundings is lower than 50-100°C, returning to step S22; S23, looping steps S21 to S22, when the gouging assembly is close to the required size, replacing the carbon rod with a smaller diameter to perform thin-layer brush gouging.

7. The post-processing method of an austenitic casting according to claim 6, characterized in that: In the step S21, the diameter of the carbon rod is 19 mm, and the gouging current is 1800-2200A.

8. The post-processing method of an austenitic casting according to claim 6, characterized in that: In step S23, the diameter of the carbon rod is 16 mm, and the gouging current is 1000-1200 A.

9. The post-processing method of an austenitic casting according to claim 7, characterized in that: In the step S21, the angle between the carbon rod and the surface of the casting to be gouged is 20° to 40°. During gouging, a section is formed at the front end of the carbon rod, and the section angle is 40° to 60°.

10. The post-processing method of an austenitic casting according to claim 6, characterized in that: In the step S21, the depth of each layer of metal layer removed by air gouging is 5 to 10 mm; in the step S23, the depth of each layer of metal layer removed by air gouging is 2 to 5 mm.

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