A method for evaluating the uniformity of a shaft furnace carburizing quenching system

Abstract

The application relates to the field of a test method for the uniformity of a carburizing and quenching system, in particular to a method for evaluating the uniformity of a shaft furnace carburizing and quenching system, and discloses a method for evaluating the uniformity of a shaft furnace carburizing and quenching system, which comprises the following steps: selecting different steel materials according to different functional parts of the shaft furnace carburizing and quenching system; arranging detection points in the functional parts, a plurality of detection points are arranged in each layer, and the positions of the detection points in each layer are different; placing the steel materials on the detection points; processing the steel materials through the functional parts, and detecting the steel materials after the processing is completed; comparing the average value obtained by counting the detected values with a standard value, if the average value meets the standard value, the uniformity of the functional part is better, otherwise, the uniformity is poorer. The method solves the problem that the effective hardening layer depth uniformity of the entire production system of the shaft furnace carburizing and quenching system cannot be evaluated when a workpiece passes through the shaft furnace carburizing and quenching system, and achieves the effect of performing uniformity detection on the entire production system of the shaft furnace carburizing and quenching system.

Description

Technical Field

[0001] This application relates to the field of testing methods for the uniformity of carburizing and quenching systems, and particularly to a method for evaluating the uniformity of a pit furnace carburizing and quenching system. Background Technology

[0002] Pit-type carburizing furnaces are new energy-saving, cyclic-operation heat treatment electric furnaces, mainly used for gas carburizing of low-carbon alloy steel parts. They are typically vertical cylindrical in shape. These furnaces have a large furnace capacity, suitable for simultaneously processing large and multiple batches of metal workpieces, such as gears, bearings, and automotive parts. They are primarily used for deep hardening, carburizing, and carbonitriding processes to improve the surface properties of metal workpieces.

[0003] Due to the large volume of the pit-type carburizing furnace, the furnace temperature and carbon potential atmosphere are uneven at different locations within the effective heating zone during carburizing, resulting in significant deviations in the carburized layer depth of workpieces at different loading positions. Furthermore, because the quenching oil tank is also large, the varying flow rates of the quenching oil at different locations during quenching lead to different cooling rates for the workpieces, resulting in significant deviations in quenching uniformity.

[0004] Therefore, we need a test method to evaluate the uniformity of a pit furnace carburizing and quenching system, and to solve the problem that the uniformity of the effective hardened layer depth of the entire production system cannot be evaluated when the workpiece is carburized and quenched through a pit furnace. Summary of the Invention

[0005] The purpose of this application is to provide a test method for evaluating the uniformity of a pit furnace carburizing and quenching system, and to solve the problem that the uniformity of the effective hardened layer depth of the entire production system cannot be evaluated when the workpiece is carburized and quenched through a pit furnace.

[0006] To achieve the above objectives, the embodiments of this application adopt the following technical solution: a method for evaluating the uniformity of a pit furnace carburizing and quenching system, comprising the following steps: selecting different steels according to different functional parts of the pit furnace carburizing and quenching system, wherein the steels can best reflect the uniformity of the functional part; the functional part has three layers, upper, middle and lower, and detection points are set in the functional part, with multiple detection points set in each layer, distributed in the inner and outer rings of each layer, and the positions of the detection points in each layer are different; obtaining the same number of steels as the detection points, placing the steels on the detection points, wherein the steels are steels that have undergone smelting, forging, and normalizing and tempering in the same furnace, and whose chemical composition is controlled to be the same; processing the steels through the functional parts, and testing all the steels after processing; statistically analyzing the detected values, obtaining their average value and comparing it with the standard value, wherein if the average value meets the standard value, the uniformity of the functional part is good, otherwise it is poor.

[0007] In the above technical solution, this embodiment sets multiple detection points in each layer, with each detection point located at a different position. The steel is processed by a functional unit, and all steel is inspected after processing. The detected values ​​are statistically analyzed, and their average value is compared with a standard value. If the average value meets the standard value, the uniformity of the functional unit is good; otherwise, it is poor. This allows for testing of the uniformity of carburized layer depth at different locations within the effective heating zone of the pit furnace, the uniformity of cooling rate at different locations in the quenching oil bath, and the uniformity of the effective hardened layer depth of the entire production system after carburizing in the pit furnace and quenching in the quenching oil bath. This solves the problem that the uniformity of the effective hardened layer depth of the entire production system cannot be assessed through the pit furnace carburizing and quenching system, achieving the effect of uniformity testing of the entire pit furnace carburizing and quenching system production system.

[0008] Furthermore, according to an embodiment of this application, the functional unit includes the effective heating zone of the pit furnace.

[0009] Furthermore, according to an embodiment of this application, the effective heating zone is achieved by slow carburizing and cooling within a pit-type carburizing furnace where the furnace temperature uniformity meets the requirements of GB / T9452.

[0010] Furthermore, according to an embodiment of this application, after carburizing and slow cooling, all steel materials are processed by a milling machine according to different decarburization depths.

[0011] Furthermore, according to an embodiment of this application, after the steel is processed, a carbon-sulfur analyzer is used to detect the carbon content of the steel near the center and the average value is taken as the final result.

[0012] Furthermore, according to an embodiment of this application, the steel is carburized steel controlled within the upper limit.

[0013] Furthermore, according to an embodiment of this application, the detection points are twelve.

[0014] Furthermore, according to an embodiment of this application, each layer has four detection points.

[0015] Furthermore, according to an embodiment of this application, the detection points include three located on the outer ring and one located on the inner ring.

[0016] Compared with existing technologies, this application has the following advantages: This application employs a method for evaluating the uniformity of a pit furnace carburizing and quenching system. Multiple detection points are set in each layer, with each detection point located at a different position. Steel is processed through functional sections, and all steel is tested after processing. The measured values ​​are statistically analyzed, and their average value is compared with a standard value. If the average value meets the standard value, the uniformity of the functional section is good; otherwise, it is poor. This allows for testing the uniformity of carburized layer depth at different locations within the effective heating zone of the pit furnace, the uniformity of cooling rate at different locations in the quenching oil bath, and the uniformity of the effective hardened layer depth of the entire production system after carburizing in the pit furnace and quenching in the quenching oil bath. This solves the problem that the uniformity of the effective hardened layer depth of the entire production system cannot be evaluated through a pit furnace carburizing and quenching system, achieving the effect of uniformity testing for the entire pit furnace carburizing and quenching system. Attached Figure Description

[0017] The present application will be further described below with reference to the accompanying drawings and embodiments.

[0018] Figure 1 This is the steel drawing for Example 2.

[0019] Figure 2 These are the detection point locations for Examples 2 and 4.

[0020] Figure 3 This is the steel drawing for Example 3.

[0021] Figure 4 This is the location of the detection point in Example 3.

[0022] Figure 5 This is the steel drawing for Example 4. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the present invention clear and complete, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only some, not all, embodiments of the present invention, and are merely illustrative of the embodiments of the present invention. They are not intended to limit the embodiments of the present invention. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] In the description of this invention, it should be noted that the terms "center," "middle," "upper," "lower," "left," "right," "inner," "outer," "top," "bottom," "side," "vertical," and "horizontal," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "a," "first," "second," "third," "fourth," "fifth," and "sixth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0025] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0026] For purposes of simplicity and illustration, the principles of the embodiments are described primarily by way of example. In the following description, numerous specific details are set forth to provide a thorough understanding of the embodiments. However, it will be apparent to those skilled in the art that these embodiments may not be limited to these specific details in practice. In some instances, well-known methods and structures have not been described in detail to avoid unnecessarily obscuring these embodiments. Furthermore, all embodiments can be used in combination with each other.

[0027] Example 1:

[0028] like Figure 1-5 As shown, this application discloses a method for evaluating the uniformity of a pit furnace carburizing and quenching system, comprising the following steps: selecting different steels according to different functional sections of the pit furnace carburizing and quenching system, the steels being able to best reflect the uniformity of the functional section; the functional section has three layers, upper, middle and lower, and detection points are set in the functional section, with multiple detection points set in each layer, distributed in the inner and outer rings of each layer, and the positions of the detection points in each layer are different; obtaining the same number of steels as the detection points, placing the steels on the detection points, the steels being steels that have undergone smelting, forging, and normalizing and tempering in the same furnace, and whose chemical composition is controlled to be the same; processing the steels through the functional section, and testing all the steels after processing; statistically analyzing the test values, obtaining their average value and comparing it with the standard value, if the average value meets the standard value, the uniformity of the functional section is good, otherwise it is poor.

[0029] This application employs a method that sets multiple detection points at different locations on each layer. Steel is processed through functional sections, and all steel is inspected after processing. The measured values ​​are statistically analyzed, and their average values ​​are compared with standard values. If the average value meets the standard value, the uniformity of the functional section is good; otherwise, it is poor. This allows for testing the uniformity of carburized layer depth at different locations within the effective heating zone of the pit furnace, the uniformity of cooling rate at different locations in the quenching oil bath, and the uniformity of the effective hardened layer depth of the entire production system after carburizing in the pit furnace and quenching in the quenching oil bath. This solves the problem that the uniformity of the effective hardened layer depth of the entire production system cannot be assessed when using a pit furnace carburizing and quenching system, achieving the effect of uniformity testing for the entire pit furnace carburizing and quenching system production system.

[0030] Example 2:

[0031] This embodiment is used to evaluate the uniformity of the carburized layer depth of workpieces at different locations within the effective heating zone of a pit furnace.

[0032] First, select 12 carburizing steels that have undergone the same furnace smelting, forging, and tempering processes, with their chemical composition controlled within the upper-middle range. These carburizing steels are low-carbon alloy steels. Figure 1 As shown in the diagram, 12 carburized steel bars are arranged as follows: Figure 2 The 12 positions shown are used for placement. Carburizing and slow cooling are carried out in a pit-type carburizing furnace where the uniformity of furnace temperature in the effective heating zone meets the requirements of GB / T 9452 (the number of the Chinese national standard, which provides guidance for the materials manufacturing and heat treatment industry in China to ensure that the heat treatment process of metallic materials is properly controlled and monitored to meet specific performance and quality standards).

[0033]

[0034] After slow cooling during carburizing, the 12 round bar samples were milled to the target carburization depth in the table above. Then, the carbon content of the three points closest to the center was detected by a carbon-sulfur analyzer and the average value was taken as the final result.

[0035] Formula 1:

[0036] Where n represents the number of samples, Xn represents the sample data, and X represents the average value of the sample data.

[0037] The sample standard deviation δ1 of carbon content at 0.1 mm and 0.3 mm of the 12 round bar samples was calculated using Formula 1 or the STDEV function.

[0038] The carburized layer depth CD of each round bar sample with a carbon content of 0.35% was calculated using interpolation. The average value and sample standard deviation δ2 of the 12 CDs were calculated using Formula 1 or the STDEV function.

[0039] When the carbon content at 0.1 and 0.3 mm is 0.6%-0.9%, δ1 is less than 0.03, the maximum deviation of the 12 CDs is less than ±10% of their average value, and δ2 is less than 5% of the average value of the 12 CDs, the carburizing uniformity is good.

[0040] Example 3:

[0041] This embodiment is used to test the uniformity of cooling rate at different locations in a quenching oil bath.

[0042] The steel selected consisted of 18 medium-carbon steels that underwent simultaneous smelting, forging, and tempering in the same furnace, with their chemical composition controlled within the upper limit. The steel dimensions were as follows: Figure 3 The stepped axis shown, then press Figure 4 The steel is placed in the 18 positions shown.

[0043] The shaft is heated in a pit furnace with good temperature uniformity, and then quenched in a pit-type oil bath. The required flow rate in the oil bath is 0.3-0.6 m / s at 18 locations across three layers under typical loading conditions. After quenching, each stepped shaft is cut into four sections of different diameters. The core hardness of each section is tested using a Rockwell hardness tester, and the average value is taken from three test points.

[0044] When the maximum deviation of the core hardness for each diameter is less than 4 HRC, the quenching uniformity of the oil bath is good.

[0045] Example 4:

[0046] This embodiment is used to test the uniformity of the effective hardened layer depth of the entire production system after the workpiece is carburized in a pit furnace and quenched in a quenching oil tank.

[0047] Twelve carburizing steels were selected, all of which underwent simultaneous smelting, forging, and tempering in the same furnace, with their chemical composition controlled to the upper-middle limit. The carburizing steel was... Figure 5 The round bar pattern shown is used to shape 12 carburized steel bars. Figure 2 Place it in the position shown.

[0048] The effective hardened layer depth (CHD) at 550HV1 (reference hardness value) of each round bar sample was tested according to the standard of GB / T9450-2005 "Determination and verification of hardened layer depth of carburized and quenched steel parts".

[0049] The sample standard deviation δ3 of the CHD of the 12 round bar samples was calculated using Formula 1 or the STDEV function.

[0050] The carburizing and quenching system has good uniformity when the maximum deviation of the 12 CHDs is less than ±10% of their average value and δ3 is less than 5% of the average value of the 12 CHDs.

[0051] Although the illustrative specific embodiments of this application have been described above to enable those skilled in the art to understand this application, this application is not limited to the scope of the specific embodiments. For those skilled in the art, all applications utilizing the concept of this application are protected as long as various variations are within the spirit and scope of this application as defined and determined by the appended claims.

Claims

1. A method for evaluating the uniformity of a pit furnace carburizing and quenching system, comprising the following steps: Select different steels according to different functional parts of the pit furnace carburizing and quenching system, and the steels can most reflect the uniformity of the functional parts; The functional part has upper, middle and lower layers. Detection points are set within the functional part, and multiple detection points are set on each layer. The detection points are distributed on the inner and outer circles of each layer, and the positions of the detection points on each layer are different; Obtain the same number of the steels as the detection points, place the steels on the detection points, and the steels are steels that have been smelted in the same furnace, forged in the same furnace, normalized and tempered in the same furnace, and the material chemical composition is controlled to be the same; Process the steels through the functional part, and detect all the steels after the processing is completed; Statistically analyze the detected values, obtain their average value and compare it with the standard value. If the average value meets the standard value, the uniformity of the functional part is good, otherwise it is poor; Select 18 medium carbon steels that have been smelted in the same furnace, forged in the same furnace, normalized and tempered in the same furnace, and the material chemical composition is controlled in the upper and middle limits. The steels are stepped shafts, and then place the steels at 18 positions; heat them in a pit furnace with good temperature uniformity, and then quench them in a pit oil tank. Among them, the requirement for the oil tank flow rate is that in the case of typical loading, it is necessary to detect the flow rates at 18 positions in the upper, middle and lower layers. All positions' flow rates meeting 0.3 - 0.6 m / s are qualified. After quenching, cut each stepped shaft into 4 segments according to different diameters, and use a Rockwell hardness tester to detect the core hardness of each round bar sample. Take the average value by testing three points; when the maximum deviation of the core hardness of each diameter is less than 4 HRC, the quenching uniformity of the oil tank is good.

2. The method for evaluating the uniformity of a pit furnace carburizing and quenching system according to claim 1, characterized in that, The functional part includes the effective heating zone of the pit furnace.

3. The method for evaluating the uniformity of a pit furnace carburizing and quenching system according to claim 2, characterized in that, The effective heating zone is subjected to carburizing and slow cooling in a pit carburizing furnace where the furnace temperature uniformity meets the requirements of GB / T 9452.

4. The method for evaluating the uniformity of a pit furnace carburizing and quenching system according to claim 3, characterized in that, After the carburizing and slow cooling, process all the steels with a milling machine according to different decarburization depths.

5. The method for evaluating the uniformity of a pit furnace carburizing and quenching system according to claim 1, characterized in that, The steels are carburizing steels controlled in the upper and middle limits.

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