阅读说明：本技术 一种使用离子氮化炉进行真空去应力退火的方法 (Method for performing vacuum stress relief annealing by using ion nitriding furnace ) 是由 邓为林 刘军凯 刘金寿 张和 于 2021-06-25 设计创作，主要内容包括：本发明涉及一种使用离子氮化炉进行真空去应力退火的方法,在离子氮化炉中对曲轴进行真空去应力退火,包括如下步骤：将离子氮化气氛换成去应力退火气氛及采用纯氩或高纯氩的气氛,再设置对曲轴的退火参数进行自动退火,退火保温结束后,随炉冷却至120℃以下,即完成曲轴真空去应力退火。本方法可利用现有离子氮化炉对曲轴进行真空去应力退火,无需采购价格高昂的真空回火炉设备,能有效去除曲轴加工内应力,且热处理后工件表面不会被氧化,硬度也不会发生明显变化,便于后续机加工,本方法可大批量稳定处理曲轴。(The invention relates to a method for performing vacuum stress relief annealing by using an ion nitriding furnace, which is used for performing vacuum stress relief annealing on a crankshaft and comprises the following steps: and (3) changing the ion nitriding atmosphere into a stress-relief annealing atmosphere and adopting a pure argon or high-purity argon atmosphere, then setting annealing parameters of the crankshaft for automatic annealing, and cooling the crankshaft to below 120 ℃ along with the furnace after annealing and heat preservation are finished, thus finishing the vacuum stress-relief annealing of the crankshaft. The method can utilize the existing ion nitriding furnace to carry out vacuum stress relief annealing on the crankshaft, does not need to purchase expensive vacuum tempering furnace equipment, can effectively remove the internal stress of crankshaft processing, does not oxidize the surface of a workpiece after heat treatment, does not have obvious change in hardness, is convenient for subsequent machining, and can stably process the crankshaft in large batch.)

1. A method for performing vacuum stress relief annealing by using an ion nitriding furnace is characterized in that the method for performing vacuum stress relief annealing on a crankshaft in the ion nitriding furnace comprises the following steps:

switching an air path switch of an ion nitriding furnace to an annealing atmosphere, opening an annealing atmosphere valve, switching the air path switch to an argon conveying atmosphere, opening an argon valve, flushing a pipeline with argon to remove a residual nitriding atmosphere in the pipeline, and then closing the argon valve;

secondly, cleaning the crankshafts by using an ultrasonic cleaning machine, putting the cleaned and dried crankshafts on a cathode disc in sequence, wherein the distance between the crankshafts is more than or equal to 2cm, plugging small holes and narrow gaps on the crankshafts by using a tool, and then covering a bell jar;

setting annealing process parameters: the voltage is 630V, the duty ratio is 50%, the arc striking is started when the vacuum pumping is carried out until the air pressure is less than or equal to 40Pa, and the temperature rising speed is 1.5 ℃/min during the period from the room temperature to the temperature of less than 350 ℃; the temperature rising speed is 1 ℃/min between 350 ℃ and less than 500 ℃; at this time

If the crankshaft is a 42CrMo steel part: when the temperature rises from 350 ℃ to less than 500 ℃, the voltage is 640V, and the air pressure is 60 Pa; keeping the temperature for 10 hours after the temperature is increased to 550 ℃ at 500-550 ℃, the temperature rising speed is 0.5 ℃/min, the voltage is 620V, the air pressure is 70Pa, and the flow of argon is kept at 0.2-0.3L/min;

if the crankshaft is made of nodular cast iron: the temperature is increased from 350 ℃ to less than 500 ℃, the voltage is 670V, and the air pressure is 75 Pa; the temperature is 500-570 ℃, the heating rate is 0.5 ℃/min, the voltage is 670V, the air pressure is 95Pa, the temperature is kept for 10h after the temperature reaches 570 ℃, and the flow of argon is kept at 0.2-0.4L/min;

fourthly, turning on a power supply, a cooling water switch, an argon valve and a vacuum butterfly valve, starting a control system of the ion nitriding furnace, and automatically performing vacuum stress relief annealing on the ion nitriding furnace according to the set process parameters; after the annealing and heat preservation are finished, the power supply, the argon valve and the vacuum butterfly valve are closed, and the control system of the ion nitriding furnace is automatically closed; cooling to below 120 ℃ along with the furnace, closing a cooling water switch, opening a bell jar and discharging.

2. The method of vacuum stress relief annealing using an ion nitriding furnace as claimed in claim 1, wherein: the purity of the argon is more than or equal to 99.99 percent, and the argon with the purity more than or equal to 99.999 percent is preferred.

Technical Field

The invention relates to a method for performing vacuum stress relief annealing by using an ion nitriding furnace, in particular to a method for performing vacuum stress relief annealing on a crankshaft by using the conventional ion nitriding furnace, and belongs to the technical field of vacuum heat treatment.

Background

For such crankshafts that require ion nitriding, due to the structural particularity, a large amount of internal machining stresses may be present inside the crankshaft after rough machining. If the internal stress of the crankshaft cannot be eliminated before finish machining, the size precision of the crankshaft finished product can be seriously influenced by ion nitriding treatment after finish machining. It is necessary to perform stress relief annealing before finishing to eliminate internal stress.

The traditional method for eliminating internal stress is to directly heat up the mixture in a heating furnace to a certain temperature, preserve the temperature for a period of time, and then cool the mixture along with the furnace. However, this method causes the surface of the crankshaft to be oxidized and is not suitable for ion nitriding the crankshaft. Therefore, it is necessary to use a vacuum tempering apparatus to prevent the surface of the crankshaft from being oxidized.

Although there are many more advanced vacuum tempering furnace apparatuses on the market today. However, these devices are particularly expensive to purchase and have problems in flexibility and maintenance. In order to save the cost of purchasing equipment, realize mass stable production and facilitate subsequent machining, the conventional vacuum stress relief annealing is carried out by utilizing the ion nitriding furnace capable of being vacuumized, but the hardness of the surface of the crankshaft is increased due to the filling of gases such as nitrogen and the like, so that the subsequent machining is difficult, and the temperature of the ion nitriding furnace is difficult due to the fact that the filling of part of gases cannot be ionized. For this reason, it is necessary to develop a method of performing vacuum stress relief annealing using an ion nitriding furnace.

Disclosure of Invention

The invention aims to solve the problems in the prior art, and provides a method for performing vacuum stress relief annealing by using an ion nitriding furnace, which can optimize various heat treatment parameters by using the existing ion nitriding equipment and provides a protective atmosphere which can not cause the surface hardness of a crankshaft to be high and can be ionized to rapidly heat up.

In order to achieve the purpose, the invention adopts the technical scheme that: the method for performing vacuum stress relief annealing on a crankshaft in an ion nitriding furnace comprises the following steps:

switching an air path switch of an ion nitriding furnace to an annealing atmosphere, opening an annealing atmosphere valve, switching the air path switch to an argon conveying atmosphere, opening an argon valve, flushing a pipeline with argon to remove a residual nitriding atmosphere in the pipeline, and then closing the argon valve;

secondly, cleaning the crankshafts by using an ultrasonic cleaning machine, putting the cleaned and dried crankshafts on a cathode disc in sequence, wherein the distance between the crankshafts is more than or equal to 2cm, plugging small holes and narrow gaps on the crankshafts by using a tool, and then covering a bell jar;

setting annealing process parameters: the voltage is 630V, the duty ratio is 50%, the arc striking is started when the vacuum pumping is carried out until the air pressure is less than or equal to 40Pa, and the temperature rising speed is 1.5 ℃/min during the period from the room temperature to the temperature of less than 350 ℃; the temperature rising speed is 1 ℃/min between 350 ℃ and less than 500 ℃; at this time

If the crankshaft is a 42CrMo steel part: when the temperature rises from 350 ℃ to less than 500 ℃, the voltage is 640V, and the air pressure is 60 Pa; keeping the temperature for 10 hours after the temperature is increased to 550 ℃ at 500-550 ℃, the temperature rising speed is 0.5 ℃/min, the voltage is 620V, the air pressure is 70Pa, and the flow of argon is kept at 0.2-0.3L/min;

if the crankshaft is made of nodular cast iron: the temperature is increased from 350 ℃ to less than 500 ℃, the voltage is 670V, and the air pressure is 75 Pa; the temperature is 500-570 ℃, the heating rate is 0.5 ℃/min, the voltage is 670V, the air pressure is 95Pa, the temperature is kept for 10h after the temperature reaches 570 ℃, and the flow of argon is kept at 0.2-0.4L/min;

fourthly, turning on a power supply, a cooling water switch, an argon valve and a vacuum butterfly valve, starting a control system of the ion nitriding furnace, and automatically performing vacuum stress relief annealing on the ion nitriding furnace according to the set process parameters; after the annealing and heat preservation are finished, the power supply, the argon valve and the vacuum butterfly valve are closed, and the control system of the ion nitriding furnace is automatically closed; cooling to below 120 ℃ along with the furnace, closing a cooling water switch, opening a bell jar and discharging.

The purity of the argon is more than or equal to 99.99 percent, and the argon with the purity more than or equal to 99.999 percent is preferred.

Compared with the prior art, the method for performing vacuum stress relief annealing by using the ion nitriding furnace has the advantages that:

the method for performing vacuum stress relief annealing by using the ion nitriding furnace provided by the invention has the advantages that the vacuum stress relief annealing can be performed on the crankshaft by using the ion nitriding furnace only by changing the atmosphere of the ion nitriding furnace into a stress relief annealing atmosphere, adopting pure argon with the purity of more than or equal to 99.99% or high-purity argon with the purity of more than or equal to 99.999%, and setting appropriate annealing parameters.

The method of the invention can utilize the existing ion nitriding equipment, does not need to purchase expensive vacuum tempering furnace equipment, can effectively remove the processing internal stress, does not oxidize the surface of the crankshaft after heat treatment, does not have obvious change in hardness, is convenient for subsequent machining, and can stably process the crankshaft in large batch.

Drawings

FIG. 1 is a schematic view of the overall structure of an ion nitriding furnace used in the present invention.

In the figure: 1-bell jar; 2-cathode disk; 3, water outlet; 4, an air inlet pipe; and 5, a water inlet.

Detailed Description

The method of vacuum stress relief annealing using an ion nitriding furnace according to the present invention will be further described with reference to the accompanying drawings and specific examples, but the practice of the present invention is not limited thereto.

Example 1: the invention provides a method for carrying out vacuum stress relief annealing by using an ion nitriding furnace, the structure of the used ion nitriding furnace is shown in figure 1, a bell jar 1 of the ion nitriding furnace is provided with an air inlet pipe 4 and a water inlet 5, the top of the furnace is provided with a water outlet 3, and a cathode disc 2 is arranged in the furnace; the vacuum stress relief annealing method specifically takes an XX type steel part crankshaft and 42CrMo as a material as an example, and comprises the following steps:

the method comprises the steps of switching an air path switch of an ion nitriding furnace to an annealing atmosphere, opening an annealing atmosphere valve, switching the air path switch to a high-purity argon atmosphere, and opening a high-purity argon valve, wherein the purity of the high-purity argon is 99.999%, argon enters a pipeline through an air inlet pipe 4 and is flushed, so that a nitriding atmosphere remained in the pipeline is removed, and the high-purity argon valve is closed after flushing;

secondly, cleaning the crankshafts by using an ultrasonic cleaning machine, putting the cleaned and dried crankshafts on a cathode disc 2 in sequence, wherein the distance between the crankshafts is more than or equal to 2cm, plugging small holes and narrow gaps on the crankshafts by using a tool, and then covering a bell jar 1;

setting annealing process parameters:

the voltage is 630V, the duty ratio is 50%, arc striking is started when the vacuum pumping is carried out until the air pressure is less than or equal to 40Pa, and the temperature rising speed is 1.5 ℃/min during the temperature rising from the room temperature to less than 350 ℃; the temperature rising speed is 1 ℃/min between 350 ℃ and less than 500 ℃;

the crankshaft of the embodiment is a 42CrMo steel piece: when the temperature rises from 350 ℃ to less than 500 ℃, the voltage is 640V, and the air pressure is 60 Pa; at 500-550 ℃, the temperature rise speed is 0.5 ℃/min, the voltage is 620V, the air pressure is 70Pa, the temperature is kept for 10h after the temperature reaches 550 ℃, and the argon flow is kept at 0.2L/min;

fourthly, turning on a power supply, a cooling water switch, an argon valve and a vacuum butterfly valve, starting a control system of the ion nitriding furnace, and automatically performing vacuum stress relief annealing on the ion nitriding furnace according to the set process parameters; after the vacuum stress relief annealing and heat preservation are finished, the power supply, the argon valve and the vacuum butterfly valve are closed, and the control system of the ion nitriding furnace is automatically closed; cooling to below 120 ℃ along with the furnace, closing a cooling water switch, opening a bell jar and discharging.

TABLE 1 hardness comparison before and after annealing of steel part crankshaft

The surface of the crankshaft after being taken out of the furnace has no oxidation phenomenon, and the Vickers hardness detection shows that the surface hardness has no obvious change with the hardness before annealing.

Example 2: the invention provides a method for performing vacuum stress relief annealing by using an ion nitriding furnace, which basically has the same steps as example 1 except that: the purity of the argon is more than or equal to 99.99 percent, and the flow of the argon is kept at 0.3L/min; the effect of the vacuum stress relief annealing was substantially the same as in example 1.

Example 3: the invention provides a method for performing vacuum stress relief annealing by using an ion nitriding furnace, which specifically takes an XX type cast iron crankshaft and nodular cast iron as an example, the steps of the vacuum stress relief annealing are basically the same as those of the embodiment 1, the purity of high-purity argon is 99.999 percent, the difference is only the step three, and the set annealing process parameters are different:

when the voltage is 630V and the duty ratio is 50 percent, vacuumizing is carried out until the air pressure is less than or equal to 40Pa, arc striking is started, and the temperature rises from room temperature to 350 ℃, and the temperature rising speed is 1.5 ℃/min; 350-500 ℃, the heating rate is 1 ℃/min, the voltage is 670V, and the air pressure is 75 Pa; 500-570 ℃, the heating speed is 0.5 ℃/min, the voltage is 670V, the air pressure is 95Pa, the temperature is kept for 10h after the temperature reaches 570 ℃, the argon flow is kept at 0.2L/min, after the heat preservation is finished, the power supply, the argon valve and the vacuum butterfly valve are closed, and the ion nitriding furnace control system is automatically closed; cooling to below 120 ℃ along with the furnace, closing a cooling water switch, and opening the bell jar 1 to discharge.

The surface of the crankshaft after being taken out of the furnace has no oxidation phenomenon, and the Vickers hardness detection shows that the surface hardness has no obvious change with the hardness before annealing.

TABLE 2 comparison of hardness before and after annealing of cast crankshaft

Example 4: the invention provides a method for performing vacuum stress relief annealing by using an ion nitriding furnace, which basically has the same steps as example 3 except that: the purity of the argon is more than or equal to 99.99 percent, and the flow of the argon is kept at 0.4L/min; the effect of the vacuum stress relief annealing was substantially the same as in example 3.

The method can utilize the existing ion nitriding equipment, does not need to purchase expensive vacuum tempering furnace equipment, can effectively remove the processing internal stress, does not oxidize the surface of the crankshaft after heat treatment, does not have obvious change in hardness, is convenient for subsequent machining, and can stably process the crankshaft in large batch.