CN117123782A - Steam treatment process of iron-based powder metallurgy part - Google Patents

Abstract

A steam treatment process of an iron-based powder metallurgy part comprises the following steps: filling the part to be treated into a steam treatment furnace, and introducing nitrogen atmosphere for protection; heating to low-temperature permeation temperature, preserving heat, introducing steam to perform steam treatment, vacuumizing at regular intervals in the heat preservation process, requiring the vacuum degree to be lower than-10 kPa relative to atmospheric pressure, and introducing steam again to perform steam treatment, wherein the cycle number is more than or equal to 1; heating to the formation temperature of the steam treatment layer, preserving heat, vacuumizing at regular intervals in the heat preservation process, requiring the vacuum degree of relative atmospheric pressure to be lower than-10 kPa, and introducing steam again to perform steam treatment, wherein the cycle number is more than or equal to 1; and (5) introducing nitrogen again after the steam treatment is finished, and taking out after cooling. The invention has simple process and easy operation, greatly improves the preparation efficiency of the steam treatment process on the premise of keeping the cost advantage, and the steam treatment layer on the surface of the treated part is compact and uniform, thereby effectively improving the wear resistance and the air tightness of the part.

Description

A steam treatment process for iron-based powder metallurgy parts

Technical field

The invention belongs to the technical field of surface protection of iron-based powder metallurgy parts, and relates to a steam treatment process for iron-based powder metallurgy parts.

Background technique

The upgrading of industries such as automobile engines, gearboxes and air-conditioning compressors has continuously increased the requirements for wear resistance and air tightness of iron-based powder metallurgy parts. The existing steam treatment process has low preparation efficiency, parts are prone to wear and air leakage is frequent, and it can no longer meet the requirements. In order to meet the needs of existing industries, how to improve the performance of iron-based steam treatment parts under low-cost conditions has become an urgent problem to be solved.

The steam treatment process is a chemical reaction between superheated steam and iron substrate, which is represented by the following formula:

3Fe+4H ₂ O==Fe ₃ O ₄ +4H ₂

Among them, the generation of Fe ₃ O ₄ is a key factor affecting the hardness, wear resistance, and air tightness of iron-based powder metallurgy parts, and the temperature, atmosphere (water vapor, hydrogen ratio), and furnace loading can greatly affect the steam treatment process. process. It can be observed from the chemical equation that the consumption and generation ratio of water vapor and hydrogen is 1:1. When hydrogen accumulates to a certain concentration in the steam treatment furnace, the reaction kinetic process will be slowed down, greatly affecting the preparation efficiency. The existing steam treatment process is to directly and continuously introduce water vapor into the furnace at a specific temperature for oxidation reaction, and directly discharge the gas in the furnace through a bypass. The proportion of water vapor and hydrogen in the furnace is not controllable, and it can be known from the actual production process that This exhaust method cannot effectively discharge hydrogen in the furnace, and the steam treatment reaction rate will gradually decrease over time. In addition, the hydrogen cannot be discharged smoothly from the furnace body, which will also cause defects in the steam treatment layer, resulting in a decrease in film quality.

Therefore, it is necessary to develop a new steam treatment process for iron-based powder metallurgy parts to meet the requirements of high preparation effect, good wear resistance and air tightness.

Contents of the invention

The technical problem to be solved by the present invention is to provide a steam treatment process for iron-based powder metallurgy parts that is simple to operate and highly efficient. The steam treatment layer on the surface of the treated parts is uniform and dense, effectively improving the wear resistance and air tightness of the parts.

The technical solution adopted by the present invention to solve the above technical problems is: a steam treatment process for iron-based powder metallurgy parts, which is characterized by including the following steps:

1) Load the parts to be processed into the steam treatment furnace and introduce nitrogen atmosphere for protection;

2) Raise the temperature to the low temperature penetration temperature and then keep it warm. At the same time, water vapor is introduced for steam treatment. During the heat preservation process, vacuum processing is performed at certain intervals. The relative atmospheric pressure vacuum degree is required to be lower than -10kPa, and water vapor is introduced again for steam treatment. Number of cycles ≥ 1 time;

3) Then the temperature is raised to the formation temperature of the steam treatment layer and then kept warm. During the heat preservation process, vacuuming is performed at certain intervals. The vacuum degree relative to the atmospheric pressure is required to be lower than -10kPa, and water vapor is introduced again for steam treatment. The number of cycles is ≥ 1 ;

4) After the steam treatment is completed, nitrogen gas is introduced again and taken out after cooling.

Furthermore, the low-temperature penetration temperature of step 2) is 480-530°C.

Further, the steam treatment layer forming temperature in step 3) is 530-600°C.

Furthermore, step 2) or step 3) can be implemented separately according to the usage requirements of the parts.

Finally, the interval time between the vacuuming processes in steps 2) and 3) is 10 to 60 minutes.

Compared with the prior art, the advantages of the present invention are:

(1) Compared with the existing steam treatment process, the steam treatment coating produced by the steam treatment process of the present invention has a dense surface, uniform film thickness, exhibits greater compressive stress, and has a lower friction coefficient (oil lubrication) The friction coefficient is about 0.11) and wear rate, which can effectively improve the wear resistance and fatigue resistance of the steam treatment layer and extend the life of such parts;

(2) The steam treatment process of the present invention can discharge the generated hydrogen in a timely manner, prompting the reaction to continue forward. Compared with the traditional steam treatment process, the preparation efficiency is higher, and the quality of the steam treatment layer is improved in all aspects;

(3) The steam treatment process of the present invention is simple to operate, can be upgraded by simply modifying existing equipment, is suitable for mass production, and can form a standardized process with strong execution;

The process of the present invention is simple and easy to operate. While maintaining the cost advantage, the preparation efficiency of the steam treatment process is greatly improved. The steam treatment layer on the surface of the treated parts is dense and uniform, effectively improving the wear resistance and air tightness of the parts.

Description of the drawings

Figure 1 is a flow chart of the steam treatment process provided by the present invention;

Figure 2 is a surface morphology diagram of the steam treatment layer prepared in Example 1 of the present invention;

Figure 3 is a cross-sectional metallographic diagram of the steam treatment layer prepared in Example 1 of the present invention;

Figure 4 is a chart of XRD stress test results of the steam treatment layer prepared in Example 1 of the present invention;

Figure 5 is a friction coefficient curve of the steam treatment layer prepared in Embodiment 1 of the present invention under oil lubrication conditions;

Figure 6 shows the wear scar morphology of the steam treatment layer prepared in Example 1 of the present invention under oil lubrication conditions;

Figure 7 is a cross-sectional metallographic diagram of the steam treatment layer prepared in Example 2 of the present invention.

Figure 8 is a surface morphology diagram of the steam treatment layer prepared in Comparative Example 1 of the present invention;

Figure 9 is a cross-sectional metallographic diagram of the steam treatment layer prepared in Comparative Example 1 of the present invention;

Figure 10 is a chart of XRD stress test results of the steam treatment layer prepared in Comparative Example 1 of the present invention;

Figure 11 is the friction coefficient curve of the steam treatment layer prepared in Comparative Example 1 of the present invention under oil lubrication conditions;

Figure 12 shows the wear scar morphology of the steam-treated layer prepared in Comparative Example 1 of the present invention under oil lubrication conditions;

Figure 13 is a cross-sectional metallographic diagram of the steam treatment layer prepared in Comparative Example 2 of the present invention.

Detailed ways

The present invention will be described in further detail below with reference to the embodiments of the drawings.

The steam treatment process flow of the present invention is shown in Figure 1.

Example 1:

(1) Load the parts to be processed into the furnace and introduce nitrogen atmosphere for protection;

(2) After heating up to 500°C, keep it warm, introduce water vapor for steam treatment, and perform vacuum treatment every 30 minutes during the insulation process. The relative atmospheric pressure vacuum degree is required to be lower than -15kPa, and introduce water vapor again for steam treatment, and cycle 2 times, a total of one and a half hours;

(3) Raise the temperature to 560°C again and then keep it warm. During the heat preservation process, vacuum treatment is performed every 30 minutes. The relative atmospheric pressure vacuum degree is required to be lower than -15kPa, and water vapor is introduced again for steam treatment. The number of cycles is 2 times, a total of one half an hour;

(4) After the steam treatment process is completed, nitrogen gas is introduced again and taken out after cooling.

The surface morphology of the above-mentioned steam treatment layer is shown in Figure 2, and the cross-sectional metallography of the steam treatment layer is shown in Figure 3. The steam treatment layer exhibits a compressive stress of 400 to 700MPa (Figure 4). Under oil lubrication conditions (10N load, The friction coefficient curve (50mm/s speed) is shown in Figure 5, which is about 0.11, and the wear scar morphology is shown in Figure 6.

Example 2:

(1) Load the parts to be processed into the furnace and introduce nitrogen atmosphere for protection;

(2) After heating up to 520°C, keep it warm, introduce water vapor for steam treatment, and perform vacuum treatment every 20 minutes during the insulation process. The relative atmospheric pressure vacuum degree is required to be lower than -10kPa, and introduce water vapor again for steam treatment, and cycle 3 times, a total of one and a half hours;

(3) After the temperature is raised to 590°C again, vacuum treatment is performed every 40 minutes during the heat preservation process. The relative atmospheric pressure vacuum degree is required to be lower than -10kPa, and water vapor is introduced again for steam treatment. The number of cycles is 2, and a total of two treatments are performed. hours and 20 minutes;

(4) After the steam treatment process is completed, nitrogen gas is introduced again and taken out after cooling.

The cross-sectional metallography of the above-mentioned steam treatment layer is shown in Figure 7.

Example 3:

(1) Load the parts to be processed into the furnace and introduce nitrogen atmosphere for protection;

(2) After the temperature reaches 480°C, water vapor is introduced for steam treatment. During the heat preservation process, vacuum treatment is performed every 20 minutes. The relative atmospheric pressure vacuum degree is required to be lower than -10kPa. Water vapor is introduced again for steam treatment. The number of cycles is 2 times, a total of one hour and 40 minutes;

(3) After the temperature is raised to 540°C again, vacuum treatment is performed every 30 minutes during the heat preservation process. The relative atmospheric pressure vacuum degree is required to be lower than -10kPa, and water vapor is introduced again for steam treatment. The number of cycles is 1, and a total of one treatment is performed. Hour;

(4) After the steam treatment process is completed, nitrogen gas is introduced again and taken out after cooling.

Comparative example 1:

(1) Load the parts to be processed into the furnace and introduce nitrogen atmosphere for protection;

(2) Raise the temperature to 500°C, then keep it warm, and introduce water vapor for steam treatment, which lasts for a total of one and a half hours;

(3) Raise the temperature to 560℃ again and keep it warm for a total of one and a half hours;

(4) After the steam treatment process is completed, nitrogen gas is introduced again and taken out after cooling.

The surface morphology of the steam-treated layer mentioned above is shown in Figure 8, and the cross-sectional metallography of the steam-treated layer is shown in Figure 9. The steam-treated layer exhibits a tensile stress of 300 to 500MPa (Figure 10). Under oil lubrication conditions (10N load, The friction coefficient curve (50mm/s speed) is shown in Figure 11, which is approximately 0.125, and the wear scar morphology is shown in Figure 12.

Comparative example 2:

(1) Load the parts to be processed into the furnace and introduce nitrogen atmosphere for protection;

(2) Raise the temperature to 520°C, then keep it warm, and introduce water vapor for steam treatment, which lasts for a total of one and a half hours;

(3) Raise the temperature to 590°C again and keep it warm for a total of three and a half hours;

(4) After the steam treatment process is completed, nitrogen gas is introduced again and taken out after cooling.

The cross-sectional metallography of the above-mentioned steam treatment layer is shown in Figure 13.

It can be seen from the experimental data in Figures 2 to 13:

(1) The steam-treated coating prepared in Example 1 of the present invention has a dense surface, uniform film thickness, large compressive stress, and low friction coefficient (oil lubrication friction coefficient is about 0.11) and wear rate. The steam treatment process of the present invention can discharge the generated hydrogen in time, prompting the reaction to continue forward. Compared with the traditional steam treatment process, the preparation efficiency is higher, and the quality of the steam treatment layer is improved in all aspects;

(2) Comparing the results of Example 1 and Comparative Example 1, it can be found that the preparation efficiency of the traditional steam treatment process is low, there are many pores on the surface, showing large tensile stress and poor wear resistance.

(3) Comparing the results of Example 2 and Comparative Example 2, it can be found that the new steam treatment process can greatly shorten the steam treatment time and improve production efficiency.

In summary, the steam treatment process of the present invention has high preparation efficiency, which is more than 30% higher than the traditional process; the surface layer of the steam-treated parts produced is uniform and the coating is dense, which can effectively improve the air tightness of the parts; in addition, The prepared steam-treated layer exhibits large compressive stress, which can effectively improve the wear resistance and fatigue resistance of the steam-treated layer and extend the life of such parts. Moreover, the steam treatment process of the present invention is simple, equipment upgrade can be achieved through simple modification of existing equipment, and is suitable for mass production.

The above are only preferred embodiments of the present invention. It should be pointed out that those of ordinary skill in the art can also make several improvements and modifications without departing from the technical principles of the present invention. These improvements and modifications It should also be regarded as the protection scope of the present invention.

Claims (5)

1. A steam treatment process for iron-based powder metallurgy parts, which is characterized by including the following steps: 1) Load the parts to be processed into the steam treatment furnace and introduce nitrogen atmosphere for protection; 2) Raise the temperature to the low temperature penetration temperature and then keep it warm. At the same time, water vapor is introduced for steam treatment. During the heat preservation process, vacuum processing is performed at certain intervals. The relative atmospheric pressure vacuum degree is required to be lower than -10kPa, and water vapor is introduced again for steam treatment. Number of cycles ≥ 1 time; 3) Then the temperature is raised to the formation temperature of the steam treatment layer and then kept warm. During the heat preservation process, vacuuming is performed at certain intervals. The vacuum degree relative to the atmospheric pressure is required to be lower than -10kPa, and water vapor is introduced again for steam treatment. The number of cycles is ≥ 1 ; 4) After the steam treatment is completed, nitrogen gas is introduced again and taken out after cooling. 2. The steam treatment process according to claim 1, characterized in that the low-temperature penetration temperature of step 2) is 480-530°C. 3. The steam treatment process according to claim 1, characterized in that the steam treatment layer formation temperature in step 3) is 530-600°C. 4. The steam treatment process according to claim 1, characterized in that: the interval time of the vacuum treatment in step 2) and step 3) is 10 to 60 minutes. 5. The steam treatment process according to claim 1, characterized in that step 2) or step 3) can be implemented separately according to the use requirements of the parts.