Process for cyaniding 1Cr17Ni2 stainless steel

Abstract

The present application relates to the technical field of heat treatment and relates to a process for cyaniding 1Cr17Ni2 stainless steel, comprising the following steps: cleaning and sandblasting 1Cr17Ni2 stainless steel parts and loading the furnace; step two: after the temperature in the furnace is raised to 800±10 DEG C, ammonia gas with a pressure of 0.3±0.05 MPa and a flow rate of 12±1 L / min is introduced, and the air in the furnace is rapidly exhausted; step three: ammonia gas with a pressure of 0.3±0.05 MPa and a flow rate of 12±1 L / min is maintained, and the temperature is raised to 900±10 DEG C, so that the passivation film of the 1Cr17Ni2 stainless steel parts is removed. The cyaniding temperature is high, the depth of the penetration layer can reach 0.2-0.5 mm, and the uniformity of the penetration layer is ≤±0.05 mm, so that the surface hardness of thin-walled parts can be ensured, the brittleness of the thin-walled parts is not caused, and the service life of the thin-walled parts working in a corrosive or humid environment, working at a temperature above 180 DEG C, or working in water or humid air can be effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat treatment, in particular to a process method for cyaniding 1Cr17Ni2 stainless steel. BACKGROUND

[0002] Some fuel regulating products require 1Cr17Ni2 stainless steel to be cyanided to a layer of 0.2-0.5mm, and the surface hardness of the layer is HRC≥55. Because the content of Cr in the stainless steel is high, especially 1Cr17Ni2 is as high as 17%, a dense passivation film is easily formed on the surface of the steel part due to the contact of Cr and Ni with air, which hinders the penetration of C and N atoms. The traditional cyaniding method is difficult to obtain a layer, and the qualified rate is less than 30%.

[0003] Cyaniding has the advantages of fast speed, good hardenability, wear resistance, corrosion resistance, anti-seizure, high fatigue strength, etc. For those working in a relatively harsh environment, such as working in a corrosive or humid environment, or working at a temperature above 180℃, stainless steel parts are required to adapt to such harsh working environment to improve the service life of the parts. If the parts work in water or humid air, they also require good surface wear resistance and low linear expansion coefficient. Therefore, we provide a process method for cyaniding 1Cr17Ni2 stainless steel. SUMMARY

[0004] The purpose of the present application is to provide a process method for cyaniding 1Cr17Ni2 stainless steel to solve the above problems. According to the electrolytic gas phase catalytic penetration theory, hydrogen is generated from the decomposition products of ammonia gas. Hydrogen can react with the passivation film of stainless steel, and can remove oxygen from the passivation film, thereby destroying the surface passivation film. At the same time, the waste gas generated can be directly burned and discharged into the atmosphere, without polluting the environment. This eliminates the various disadvantages of removing the passivation film by traditional chlorination. By introducing a certain proportion of ammonia gas based on the traditional carburizing process, the passivation film on the surface of the stainless steel is effectively broken, and a certain amount of N atoms can be provided, which can achieve the effect of C and N co-permeation. The performance indicators of the valve parts meet the product design requirements, and the first-time inspection qualified rate reaches 94%.

[0005] The present application achieves the above-mentioned purposes through the following technical solutions:

[0006] A process method for cyaniding 1Cr17Ni2 stainless steel, comprising the following steps:

[0007] Step 1: Clean the 1Cr17Ni2 stainless steel parts and blow sand before loading into the furnace;

[0008] Step two: after the temperature in the furnace is raised to 800±10℃, ammonia gas with a pressure of 0.3±0.05MPa and a flow rate of 12±1L / min is introduced to rapidly remove the air in the furnace;

[0009] Step three: ammonia gas with a pressure of 0.3±0.05MPa and a flow rate of 12±1L / min is continuously introduced, and the temperature is raised to 900±10℃, so that the passivation film of the 1Cr17Ni2 stainless steel part is removed;

[0010] Step four: ammonia gas with a pressure of 0.3±0.05MPa and a flow rate of 12±1L / min is continuously introduced, the heating rate is controlled to be ≤6℃ / min to reduce thermal stress and prevent deformation of the thin-walled part, the temperature is raised to 950±10℃, the carbon potential concentration in the furnace is controlled to be 0.85±0.05% during the temperature rising process, the carbon potential concentration in the furnace is controlled to be 1.15±0.05% after the temperature is reached, and then the temperature is maintained for 3±0.5h;

[0011] Step five: the introduction of ammonia gas is stopped, the carbon potential concentration is controlled to be 0.85±0.05%, and the temperature is maintained at 950±10℃ for 20±5min;

[0012] Step six: the 1Cr17Ni2 stainless steel part is pre-cooled to 880±10℃, and the carbon potential concentration in the furnace is controlled to be 0.85±0.05% during the pre-cooling process;

[0013] Step seven: the 1Cr17Ni2 stainless steel part is oil quenched, the quenching oil is stirred, and the oil quenching time is controlled to be ≥10min until the temperature of the 1Cr17Ni2 stainless steel part reaches room temperature;

[0014] Step eight: the 1Cr17Ni2 stainless steel part at room temperature is low-temperature tempered, the tempering temperature is set to be 160±10℃, the temperature is maintained for 2-2.5h, and then air cooling is performed under natural conditions.

[0015] Preferably, the method for controlling the carbon potential concentration is to add kerosene.

[0016] Preferably, the step of cleaning the 1Cr17Ni2 stainless steel part is:

[0017] S1: the Cr17Ni2 stainless steel part is cleaned with ultrasonic waves at an environment of 50℃ for 15±1min;

[0018] S2: the 1Cr17Ni2 stainless steel part is rinsed with cold water for 2±1min;

[0019] S3: the 1Cr17Ni2 stainless steel part is rinsed with hot water at 70℃ for 3±1min;

[0020] S4: the 1Cr17Ni2 stainless steel part is dried at an environment of 80℃

[0021] S5: Clean the 1Cr17Ni2 stainless steel parts with hydrocarbon ultrasonic cleaning for 15±1 min.

[0022] S6: Dry the 1Cr17Ni2 stainless steel parts at 80℃.

[0023] Preferably, 120-mesh alumina powder is used as the blowing medium, and the 1Cr17Ni2 stainless steel parts are blown at a blowing pressure of 0.3±0.05MPa.

[0024] Preferably, the time interval between sand blowing and loading into the furnace is less than 1 hour.

[0025] The beneficial effects are:

[0026] 1. The present invention has a high cyanidation temperature and a diffusion layer depth of 0.2-0.5 mm, and the uniformity of the diffusion layer is ≤ ±0.05 mm. This not only ensures the surface hardness of thin-walled parts (wall thickness not greater than 2 mm), but also prevents the thin-walled parts from becoming brittle. It can effectively improve the service life of the parts when working in corrosive or humid environments, at temperatures above 180°C, or in water or humid air.

[0027] 2. Due to the control of the heating rate in the furnace, the thermal stress of 1Cr17Ni2 stainless steel parts is effectively reduced. Combined with the pre-cooling process, after carburizing within the range of 950±10℃, pre-cooling, and low-temperature tempering and cooling, 1Cr17Ni2 stainless steel parts will hardly crack.

[0028] 3. Due to the high cyanidation temperature, the cyanidation time is effectively reduced. At the same time, the furnace heating rate, pre-cooling process, and low-temperature tempering process are adopted to ensure that the diffusion layer depth of 1Cr17Ni2 stainless steel parts meets the design requirements of the valve for fuel-controlled products.

[0029] The additional technical features and advantages of the present invention will become more apparent from the following description, or may be learned through practice of the invention. Attached Figure Description

[0030] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings:

[0031] Figure 1 This is a cyanidation process curve diagram of the present invention; Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0033] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and 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 this invention.

[0034] A process for cyaniding 1Cr17Ni2 stainless steel includes the following steps:

[0035] Step 1: Clean the 1Cr17Ni2 stainless steel parts, sandblast them, and then load them into the furnace.

[0036] The steps for cleaning 1Cr17Ni2 stainless steel parts, as needed, are as follows:

[0037] S1: Clean the Cr17Ni2 stainless steel parts with ultrasonic waves at 50℃ for 15±1 min.

[0038] S2: Rinse the 1Cr17Ni2 stainless steel parts with cold water for 2±1 min;

[0039] S3: Rinse the 1Cr17Ni2 stainless steel parts with hot water at 70℃ for 3±1 min;

[0040] S4: Dry the 1Cr17Ni2 stainless steel parts at 80℃.

[0041] S5: Clean the 1Cr17Ni2 stainless steel parts with hydrocarbon ultrasonic cleaning for 15±1 min.

[0042] S6: Dry the 1Cr17Ni2 stainless steel parts at 80℃.

[0043] As required, 120-mesh alumina powder was selected as the sandblasting medium, and the 1Cr17Ni2 stainless steel parts were sandblasted at a sandblasting pressure of 0.3±0.05MPa.

[0044] As required, the time interval between sand blowing and loading into the furnace is less than 1 hour.

[0045] It should be noted that the furnace cavity temperature needs to be preheated before loading the 1Cr17Ni2 stainless steel parts into the furnace. Preferably, the furnace cavity temperature is preheated to 800±10℃.

[0046] It should be noted that when loading 1Cr17Ni2 stainless steel parts into the furnace, the 1Cr17Ni2 stainless steel parts should not be touched with bare hands. Preferably, clean white gauze gloves should be worn, and the 1Cr17Ni2 stainless steel parts should be placed in a single layer in the furnace. That is, the operator should wear clean white gauze gloves, place the 1Cr17Ni2 stainless steel parts on the material rack, and then use other equipment to place the material rack into the furnace.

[0047] Step 2: After raising the furnace temperature to 800±10℃, introduce ammonia gas at a pressure of 0.3±0.05MPa and a flow rate of 12±1L / min to quickly purge the air from the furnace.

[0048] Step 3: Maintain the pressure of ammonia gas at 0.3±0.05MPa and the flow rate at 12±1L / min and raise the temperature to 900±10℃ to remove the passivation film from the 1Cr17Ni2 stainless steel parts.

[0049] Step 4: Continue to supply ammonia gas at a pressure of 0.3±0.05MPa and a flow rate of 12±1L / min. Increase the temperature to 950±10℃ at a heating rate of ≤6℃ / min. During the heating process, control the carbon potential concentration at 0.85±0.05%. After heating, control the carbon potential concentration at 1.15±0.05%. Then, hold the temperature for 3±0.5h.

[0050] Preferably, the carbon potential concentration is controlled by dripping kerosene onto the 1Cr17Ni2 stainless steel parts.

[0051] Step 5: Stop the ammonia gas supply, control the carbon potential concentration to 0.85±0.05%, and keep it at 950±10℃ for 20 minutes;

[0052] Step Six: Pre-cool the 1Cr17Ni2 stainless steel parts. The specific operation is as follows: turn off the furnace heating and cool it with the furnace to 880±10℃. During the pre-cooling process, control the carbon potential concentration in the furnace to 0.85±0.05%.

[0053] Step 7: Oil quench the 1Cr17Ni2 stainless steel parts, stir the quenching oil, and control the oil quenching time to ≥10min until the temperature of the 1Cr17Ni2 stainless steel parts reaches room temperature.

[0054] Step 8: Temper the 1Cr17Ni2 stainless steel parts at room temperature at a low temperature of 160±10℃, hold for 2 to 2.5 hours, and then air cool under natural conditions.

[0055] In one instance: the following steps:

[0056] Step 1: Clean the 1Cr17Ni2 stainless steel parts, sandblast them, and then load them into the furnace.

[0057] The steps for cleaning 1Cr17Ni2 stainless steel parts, as needed, are as follows:

[0058] S1: Clean the Cr17Ni2 stainless steel parts with ultrasonic waves at 50°C for 15 minutes.

[0059] S2: Rinse the 1Cr17Ni2 stainless steel parts with cold water for 2 minutes;

[0060] S3: Rinse the 1Cr17Ni2 stainless steel parts with hot water at 70℃ for 3 minutes;

[0061] S4: Dry the 1Cr17Ni2 stainless steel parts at 80℃.

[0062] S5: Clean the 1Cr17Ni2 stainless steel parts with hydrocarbon ultrasonic cleaning for 15 minutes.

[0063] S6: Dry the 1Cr17Ni2 stainless steel parts at 80℃.

[0064] As required, 120-mesh alumina powder was selected as the blowing medium, and the 1Cr17Ni2 stainless steel parts were blown at a blowing pressure of 0.3MPa.

[0065] As needed, the time interval between sand blowing and loading into the furnace is 0.4 hours.

[0066] Step 2: After raising the furnace temperature to 800℃, introduce ammonia gas at a pressure of 0.3MPa and a flow rate of 12L / min to quickly purge the air from the furnace.

[0067] Step 3: Maintain the ammonia gas pressure at 0.3MPa and the flow rate at 12L / min and raise the temperature to 900℃ to remove the passivation film from the 1Cr17Ni2 stainless steel parts.

[0068] Step 4: Continue to supply ammonia gas at a pressure of 0.3 MPa and a flow rate of 12 L / min, and raise the temperature to 950℃ at a rate of 6℃ / min. During the heating process, control the carbon potential concentration at 0.85%, and after heating, control the carbon potential concentration at 1.15%. Then, maintain the temperature for 3 hours.

[0069] Preferably, the carbon potential concentration is controlled by dripping kerosene onto the 1Cr17Ni2 stainless steel parts.

[0070] Step 5: Stop the ammonia gas supply, control the carbon potential concentration to 0.85%, and keep it at 950℃ for 20 minutes;

[0071] Step 6: Pre-cool the 1Cr17Ni2 stainless steel parts. The specific operation is as follows: turn off the furnace heating and cool it to 880℃ with the furnace. During the pre-cooling process, control the carbon potential concentration in the furnace to 0.85%.

[0072] Step 7: Oil quench the 1Cr17Ni2 stainless steel parts, stir the quenching oil, and control the oil quenching time to 11 minutes until the temperature of the 1Cr17Ni2 stainless steel parts reaches room temperature.

[0073] Step 8: Temper the 1Cr17Ni2 stainless steel parts at room temperature at a low temperature of 160℃, hold for 2 hours, and then air cool.

[0074] In another example: the following steps are included:

[0075] Step 1: Clean the 1Cr17Ni2 stainless steel parts, sandblast them, and then load them into the furnace.

[0076] The steps for cleaning 1Cr17Ni2 stainless steel parts, as needed, are as follows:

[0077] S1: Clean the Cr17Ni2 stainless steel parts with ultrasonic waves at 50°C for 14.5 min;

[0078] S2: Rinse the 1Cr17Ni2 stainless steel parts with cold water for 1.6 minutes;

[0079] S3: Rinse the 1Cr17Ni2 stainless steel parts with hot water at 70℃ for 2.6 minutes;

[0080] S4: Dry the 1Cr17Ni2 stainless steel parts at 80℃.

[0081] S5: Clean the 1Cr17Ni2 stainless steel parts with hydrocarbon ultrasonic cleaning for 15 minutes.

[0082] S6: Dry the 1Cr17Ni2 stainless steel parts at 80℃.

[0083] As required, 120-mesh alumina powder was selected as the blowing medium, and the 1Cr17Ni2 stainless steel parts were blown at a blowing pressure of 0.32MPa.

[0084] As needed, the time interval between sand blowing and loading into the furnace is 0.7 hours.

[0085] Step 2: After raising the furnace temperature to 800℃, introduce ammonia gas at a pressure of 0.32MPa and a flow rate of 12.4L / min to quickly purge the air from the furnace.

[0086] Step 3: Maintain the ammonia gas pressure at 0.32 MPa and the flow rate at 12.4 L / min and raise the temperature to 900℃ to remove the passivation film from the 1Cr17Ni2 stainless steel parts.

[0087] Step 4: Continue to supply ammonia gas at a pressure of 0.32 MPa and a flow rate of 12.4 L / min, and raise the temperature to 960℃ at a rate of 5℃ / min. During the heating process, control the carbon potential concentration at 0.85%, and after heating, control the carbon potential concentration at 1.15%. Then, hold the temperature for 2.8 hours.

[0088] Preferably, the carbon potential concentration is controlled by dripping kerosene onto the 1Cr17Ni2 stainless steel parts.

[0089] Step 5: Stop the ammonia gas supply, control the carbon potential concentration to 0.85%, and keep it at 960℃ for 20 minutes;

[0090] Step 6: Pre-cool the 1Cr17Ni2 stainless steel parts. The operation is as follows: turn off the furnace heating and cool it to 875°C. During the pre-cooling process, control the carbon potential concentration in the furnace to 0.85%.

[0091] Step 7: Oil quench the 1Cr17Ni2 stainless steel parts, stir the quenching oil, and control the oil quenching time to 10 minutes until the temperature of the 1Cr17Ni2 stainless steel parts reaches room temperature.

[0092] Step 8: Temper the 1Cr17Ni2 stainless steel parts at room temperature at a low temperature of 165℃, hold for 2.5 hours, and then air cool under natural conditions.

[0093] In other examples, the heating rate in step four can also be 5.5℃ / min, 5.8℃ / min, or heating to 940℃, 945℃, etc. Preferably, in order to reduce the heating time, the heating rate should generally be no less than 4℃ / min.

[0094] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A process for cyaniding 1Cr17Ni2 stainless steel, characterized in that: Includes the following steps: Step 1: Clean the 1Cr17Ni2 stainless steel parts, sandblast them, and then load them into the furnace. Step 2: After raising the furnace temperature to 800±10℃, introduce ammonia gas at a pressure of 0.3±0.05MPa and a flow rate of 12±1L / min to quickly purge the air from the furnace. Step 3: Maintain the pressure of ammonia gas at 0.3±0.05MPa and the flow rate at 12±1L / min and raise the temperature to 900±10℃ to remove the passivation film from the 1Cr17Ni2 stainless steel parts. Step 4: Continue to supply ammonia gas at a pressure of 0.3±0.05MPa and a flow rate of 12±1L / min. Increase the temperature to 950±10℃ at a heating rate of ≤6℃ / min to reduce thermal stress and prevent deformation of thin-walled parts. During the heating process, control the carbon potential concentration in the furnace to 0.85±0.05%. After reaching the target temperature, control the carbon potential concentration in the furnace to 1.15±0.05%. Then, hold the temperature for 3±0.5h. Step 5: Stop the ammonia gas supply, control the carbon potential concentration to 0.85±0.05%, and keep it at 950±10℃ for 20±5 minutes; Step 6: Pre-cool the 1Cr17Ni2 stainless steel parts to 880±10℃, and control the carbon potential concentration in the furnace to 0.85±0.05% during the pre-cooling process; Step 7: Oil quench the 1Cr17Ni2 stainless steel parts, stir the quenching oil, and control the oil quenching time to ≥10min until the temperature of the 1Cr17Ni2 stainless steel parts reaches room temperature. Step 8: Temper the 1Cr17Ni2 stainless steel parts at room temperature at a low temperature of 160±10℃, hold for 2 to 2.5 hours, and then air cool under natural conditions.

2. The process for cyaniding 1Cr17Ni2 stainless steel according to claim 1, characterized in that: The method for controlling the carbon potential concentration is by adding kerosene.

3. The process for cyaniding 1Cr17Ni2 stainless steel according to claim 1, characterized in that: The steps for cleaning 1Cr17Ni2 stainless steel parts are as follows: S1: Clean the Cr17Ni2 stainless steel parts with ultrasonic waves at 50℃ for 15±1 min. S2: Rinse the 1Cr17Ni2 stainless steel parts with cold water for 2±1 min; S3: Rinse the 1Cr17Ni2 stainless steel parts with hot water at 70℃ for 3±1 min; S4: Dry the 1Cr17Ni2 stainless steel parts at 80℃. S5: Clean the 1Cr17Ni2 stainless steel parts with hydrocarbon ultrasonic cleaning for 15±1 min. S6: Dry the 1Cr17Ni2 stainless steel parts at 80℃.

4. The process for cyaniding 1Cr17Ni2 stainless steel according to claim 1, characterized in that: 120-mesh alumina powder was selected as the blowing medium, and the 1Cr17Ni2 stainless steel parts were subjected to sandblasting treatment at a blowing pressure of 0.3±0.05MPa.

5. The process for cyaniding 1Cr17Ni2 stainless steel according to claim 1, characterized in that: The time interval between sand blowing and loading into the furnace is less than 1 hour.

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