阅读说明：本技术 一种主轴抗蚀的复合氮化方法 (Composite nitriding method for corrosion resistance of main shaft ) 是由 尹卓君 于香华 董岩 *** 于 2020-07-23 设计创作，主要内容包括：本发明公开了一种主轴抗蚀的复合氮化方法,尤其涉及一种34CrNi3Mo主轴抗蚀的复合氮化方法,其步骤为：1、预先热处理调质：880℃保温4小时,出炉风冷；870℃保温4小时,于18-23℃水中淬火,580-590℃回火6-8小时；2、复合氮化方法：350℃(吹空气,预氧化)-480℃(吹氮气,氮化)-570℃(吹氨气,吹二氧化碳,氮化)-520℃(吹空气,后氧化)-200(吹氮)-出炉。本发明的有益效果是：复合氮化法形成的复合层从外至里依次为：氧化膜、白亮层、扩散层和基体,表面的氧化膜具有很好的耐腐蚀功能,白亮层结构致密,具有优良的防腐和耐磨功能。34CrNi3Mo顶驱主轴的不合格率降至0.3%以下,使用寿命延长2-5倍工作小时数,每年可以节省主轴因材料早期失效带来的数百万元经济损失。(The invention discloses a composite nitriding method for corrosion resistance of a main shaft, in particular to a composite nitriding method for corrosion resistance of a 34CrNi3Mo main shaft, which comprises the following steps: 1. pre-heat treatment quenching and tempering: keeping the temperature at 880 ℃ for 4 hours, and discharging and air cooling; heat preservation at 870 ℃ for 4 hours, quenching in water at 18-23 ℃, and tempering at 580-590 ℃ for 6-8 hours; 2. the composite nitriding method comprises the following steps: 350 ℃ (air blowing, pre-oxidation) -480 ℃ (nitrogen blowing, nitridation) -570 ℃ (ammonia blowing, carbon dioxide blowing, nitridation) -520 ℃ (air blowing, post oxidation) -200 (nitrogen blowing) -tapping. The invention has the beneficial effects that: the composite layer formed by the composite nitriding method sequentially comprises the following components from outside to inside: the surface oxide film has a good corrosion resistance function, and the white bright layer has a compact structure and has excellent corrosion resistance and wear resistance. The failure rate of the 34CrNi3Mo top drive main shaft is reduced to below 0.3 percent, the service life is prolonged by 2-5 times of working hours, and millions of yuan of economic loss caused by early failure of materials of the main shaft can be saved every year.)

1. A composite nitriding method for corrosion resistance of a main shaft comprises the following steps:

firstly, heat treatment quenching and tempering in advance: keeping the temperature at 880 ℃ for 4 hours, and discharging and air cooling; heat preservation at 870 ℃ for 4 hours, quenching in water at 18-23 ℃, and tempering at 580-590 ℃ for 6-8 hours;

then carrying out composite nitriding treatment:

(1) keeping the furnace pressure at 10KPa, heating to 350 ℃ within 10 minutes, starting the pre-oxidation function, keeping the furnace pressure at 5KPa, blowing air for 35 minutes, and closing the pre-oxidation function;

(2) keeping the furnace pressure at 10KPa, continuously heating to 480 deg.C within 5 min, keeping the furnace pressure at 15KPa, blowing nitrogen for 4 min, and controlling the nitrogen concentration at 2m³/h；

(3) Maintaining furnace pressure at 15KPa, heating to 570 deg.C within 10 min, and blowing ammonia gas and carbon dioxide while heating, wherein the ammonia gas concentration is 1m³H, carbon dioxide concentration of 20m³H; maintaining the furnace pressure at 570 deg.C for 15KPa, and blowing ammonia gas and carbon dioxide for 270 min, wherein the ammonia gas concentration is 2m³H, carbon dioxide concentration of 10m³/h；

(4) Keeping furnace pressure at 15KPa, cooling while blowing nitrogen gas, cooling to 520 deg.C within 1 min, and blowing nitrogen gasGas concentration is 4m³H; starting the post oxidation function at 520 ℃, keeping the furnace pressure at 15KPa, blowing air for 120 minutes, and closing the post oxidation function;

(5) keeping the furnace pressure at 8KPa, cooling and blowing nitrogen for 30 minutes, wherein the concentration of the blown nitrogen is 4m³Continuously cooling to 200 ℃; and (5) finishing the composite nitriding process and discharging.

Technical Field

The invention relates to a composite nitriding method for corrosion resistance of a main shaft, in particular to a composite nitriding method for corrosion resistance of a 34CrNi3Mo main shaft, belonging to the technical field of metal heat treatment.

Background

The top drive main shaft of the petroleum drilling well, the related important part joint and the blowout preventer have severe working environment, the cracking failure problem of the main shaft and other important parts often occurs, the maintenance, shutdown and related inspection failure analysis after each failure are calculated by millions of yuan, so that a new method for solving the corrosion resistance problem of the main shaft is urgently needed to be developed, the qualification rate and the service life of the main shaft are improved, the maintenance and normal replacement times of the main shaft are reduced, and the economic loss is reduced.

The prior method for treating the surface of a part which needs to resist both wear and corrosion comprises the following steps: electroplating hard chromium, QPQ, ion nitriding and composite nitriding methods, wherein the electroplating of hard chromium is a technology in 40 years, has low cost and can cause serious environmental pollution; QPQ is mainly a technology used in the 60 s, is wear-resistant and corrosion-resistant, has short production period and low cost, and has the biggest problems of pollution (waste water treatment containing trace cyanide, poor working environment, waste salt treatment and the like), and the QPQ technology is not promoted by the nation at present; in the 80 s, people began to use the ion nitriding technology, which has strict operation requirements, otherwise the nitriding quality is affected by uneven overflow and arc discharge. The composite nitriding method is one of composite surface treatment technologies, namely two or more surface treatment technologies are used simultaneously to achieve the purpose of further strengthening the surface performance, and the composite nitriding has the advantages of higher surface hardness, better corrosion resistance and relatively more environmental protection. The method discusses the steps of the composite nitridation process: pre-oxidation-nitridation-post-oxidation.

Disclosure of Invention

The technical scheme adopted by the invention for solving the technical problems is as follows: a composite nitriding method for main shaft corrosion resistance takes 34CrNi3Mo main shaft as an example, and comprises the following steps:

1. pre-heat treatment quenching and tempering:

keeping the temperature at 880 ℃ for 4 hours, and discharging and air cooling; heat preservation at 870 ℃ for 4 hours, quenching in water at 18-23 ℃, and tempering at 580-590 ℃ for 6-8 hours;

2. composite nitriding treatment:

(1) keeping the furnace pressure at 10KPa, heating to 350 ℃ within 10 minutes, starting the pre-oxidation function, keeping the furnace pressure at 5KPa, blowing air for 35 minutes, and closing the pre-oxidation function;

(2) keeping the furnace pressure at 10KPa, continuously heating to 480 deg.C within 5 min, keeping the furnace pressure at 15KPa, blowing nitrogen for 4 min, and controlling the nitrogen concentration at 2m³/h；

(3) Maintaining furnace pressure at 15KPa, heating to 570 deg.C within 10 min, and blowing ammonia gas and carbon dioxide while heating, wherein the ammonia gas concentration is 1m³H, carbon dioxide concentration of 20m³H; maintaining the furnace pressure at 570 deg.C for 15KPa, and blowing ammonia gas and carbon dioxide for 270 min, wherein the ammonia gas concentration is 2m³H, carbon dioxide concentration of 10m³/h；

(4) Keeping furnace pressure at 15KPa, cooling while blowing nitrogen gas, cooling to 520 deg.C within 1 min, and blowing nitrogen gas with concentration of 4m³H; starting the post oxidation function at 520 ℃, keeping the furnace pressure at 15KPa, blowing air for 120 minutes, and closing the post oxidation function;

(5) keeping the furnace pressure at 8KPa, cooling and blowing nitrogen for 30 minutes, wherein the concentration of the blown nitrogen is 4m³Continuously cooling to 200 ℃; and (5) finishing the composite nitriding process and discharging.

The nitriding equipment adopts a vacuum controllable atmosphere nitriding device and is matched with the vacuum controllable atmosphere nitriding device.

The invention has the beneficial effects that: the composite layer formed by the composite nitriding method sequentially comprises the following components from outside to inside: the surface oxide film has a good corrosion resistance function, and the white bright layer has a compact structure and has excellent corrosion resistance and wear resistance functions; in general, the composite layer formed by the conventional nitriding method is, from outside to inside: the loose layer, the white layer, the diffusion layer and the matrix are not controllable in atmosphere due to the existing light nitriding method, CNO in the atmosphere is high, the surface of the permeation layer is seriously loosened, the loose layer has adverse effects on the mechanical properties of the permeation layer, and the corrosion resistance and the wear resistance are reduced.

The reject ratio of the prior 34CrNi3Mo top drive main shaft for petroleum drilling is about 2 percent, the reject ratio of the 34CrNi3Mo top drive main shaft is reduced to be less than 0.3 percent by applying the method of the invention, the service life is prolonged by 2-5 times of working hours, millions of dollars of economic loss of the main shaft caused by early failure of materials can be saved every year, and the maintenance and normal replacement times of the main shaft are reduced at the same time.

Drawings

FIG. 1 shows the organization structure and the effect of the 34CrNi3Mo top drive spindle after composite nitriding.

FIG. 2 is a diagram of a 34CrNi3Mo spindle composite nitriding process.

Detailed Description

The invention is further described with reference to the following figures and detailed description.

A composite nitriding method for main shaft corrosion resistance takes 34CrNi3Mo main shaft as an example, and comprises the following steps:

1. preliminary heat treatment

In order to ensure that the center of a nitrided part has necessary mechanical properties (also called mechanical properties), eliminate internal stress, improve the nitriding effect, have good original structure and reduce dimensional change, different pre-heat treatments are required to be carried out before nitriding the part. The pre-heat treatment process before the composite nitriding of the 34CrNi3Mo main shaft is quenching and tempering.

Pre-heat treatment quenching and tempering: keeping the temperature at 880 ℃ for 4 hours, and discharging and air cooling; heat preservation at 870 ℃ for 4 hours, quenching in water at 18-23 ℃, tempering at 580-590 ℃ for 6-8 hours, wherein the tempering temperature of the quenching and tempering is at least 10 ℃ higher than the nitriding temperature (generally 20-40 ℃ higher). The hardness of the substrate is HV 320-350.

The higher the tempering temperature is, the lower the hardness of the workpiece is, the smaller the dispersion degree of carbide in the matrix structure is, nitrogen atoms are easy to permeate during nitriding, the thicker the nitriding layer is, but the lower the hardness of the nitriding layer is. Therefore, the tempering temperature is comprehensively determined according to the requirements on the matrix performance and the infiltration layer performance. The ideal structure after hardening and tempering is a fine and evenly distributed sorbite structure, the existence of a coarse sorbite structure is not allowed, and the existence of more free ferrite is not allowed.

The main shaft hardening and tempering need to achieve the following performance indexes:

akv was determined from the average of three trials: the average impact toughness value Akv of three samples at-20 ℃ is not less than 80J, and the impact toughness value of a single sample is not less than 75J. The average impact toughness value Akv of three samples is not less than 55J and the impact toughness value of a single sample is not less than 45J when tested at-45 ℃.

2. Composite nitriding treatment:

(1) keeping the furnace pressure at 10KPa, heating to 350 ℃ within 10 minutes, starting the pre-oxidation function, keeping the furnace pressure at 5KPa, blowing air for 35 minutes, and closing the pre-oxidation function;

(2) keeping the furnace pressure at 10KPa, continuously heating to 480 deg.C within 5 min, keeping the furnace pressure at 15KPa, blowing nitrogen for 4 min, and controlling the nitrogen concentration at 2m³/h；

(3) Maintaining furnace pressure at 15KPa, heating to 570 deg.C within 10 min, and blowing ammonia gas and carbon dioxide while heating, wherein the ammonia gas concentration is 1m³H, carbon dioxide concentration of 20m³H; maintaining the furnace pressure at 570 deg.C for 15KPa, and blowing ammonia gas and carbon dioxide for 270 min, wherein the ammonia gas concentration is 2m³H, carbon dioxide concentration of 10m³/h；

(4) Keeping furnace pressure at 15KPa, cooling while blowing nitrogen gas, cooling to 520 deg.C within 1 min, and blowing nitrogen gas with concentration of 4m³H; starting the post oxidation function at 520 ℃, keeping the furnace pressure at 15KPa, blowing air for 120 minutes, and closing the post oxidation function;

(5) keeping the furnace pressure at 8KPa, cooling and blowing nitrogen for 30 minutes, wherein the concentration of the blown nitrogen is 4m³Continuously cooling to 200 ℃; and (5) finishing the composite nitriding process and discharging.

After the treatment by the method, the main shaft of 34CrNi3Mo reaches the following technical indexes:

(1) hardness greater than HV 0.3560

(2) The nitride white bright layer is less than 20um

(3) The depth of the nitride layer is 0.2-0.3mm

(4) Oxide layer of 1-2 um

(5) Brittleness of 2 or less

(6) Porosity is less than or equal to 2 grade

(7) The nitride grade is less than or equal to 2 grade.

3. Test results of 34CrNi3Mo spindle composite nitriding process:

and (4) conclusion: the composite nitriding process method for the 34CrNi3Mo main shaft achieves various technical indexes of technical requirements, the heat treatment process is completely successful, and the process method can be used for the actual production application of improving the corrosion prevention and wear resistance functions of the surface of the 34CrNi3Mo main shaft.