CN111733377B

CN111733377B - Resistance furnace for chromizing and nitriding austenitic stainless steel workpiece and chromizing and nitriding method

Info

Publication number: CN111733377B
Application number: CN202010749676.6A
Authority: CN
Inventors: 何飞; 刘林涛; 李龙博; 吕海兵; 乔江江
Original assignee: Northwest Institute for Non Ferrous Metal Research
Current assignee: Northwest Institute for Non Ferrous Metal Research
Priority date: 2020-07-30
Filing date: 2020-07-30
Publication date: 2021-06-01
Anticipated expiration: 2040-07-30
Also published as: CN111733377A

Abstract

The invention discloses a resistance furnace for chromizing and nitriding an austenitic stainless steel workpiece and a chromizing and nitriding method, wherein the resistance furnace for chromizing and nitriding comprises a furnace body and a vacuum chamber; the method comprises a chromizing method and a nitriding method, wherein the chromizing method comprises the steps of firstly, hoisting a vacuum chamber; step two, arranging the workpiece and the chromium-impregnated powder in the vacuum chamber; step three, sealing the vacuum chamber; step four, mounting a sensor; step five, vacuumizing the vacuum chamber; heating the workpiece; step seven, cooling the workpiece; the nitriding method includes step S1, preparation work; s2, hoisting a workpiece in the vacuum chamber; step S3, closing the vacuum chamber; step S4, replacing the gas in the vacuum chamber; step S5, repeating step S4 for four to eight times; step S6, heating the workpiece; and step S7, cooling the workpiece. The invention can lead the chromizing and nitriding of the workpiece to adopt the same resistance furnace, is convenient to improve the heating speed of the workpiece, ensures the uniform heating of the workpiece and can improve the chromizing and nitriding quality of the workpiece.

Description

Resistance furnace for chromizing and nitriding austenitic stainless steel workpiece and chromizing and nitriding method

Technical Field

The invention belongs to the technical field of resistance furnaces, and particularly relates to a resistance furnace for chromizing and nitriding an austenitic stainless steel workpiece and a chromizing and nitriding method.

Background

Austenitic stainless steel materials have a series of advantages such as good corrosion resistance, cold-working formability, weldability and the like, so that the austenitic stainless steel materials become main materials for supporting structural parts. However, such steels are low in strength, poor in wear resistance, and cannot be strengthened by quenching heat treatment. For this reason, it is necessary to improve the wear-resistant, corrosion-resistant, high-temperature oxidation-resistant chromium carbide layer and the chromium solid solution carburized layer on the surface thereof by the chromizing technique. However, austenitic stainless steel is subjected to chromizing on the surface, and Cr is precipitated along grain boundaries₂₃C₆Phase, resulting in the occurrence of intergranular corrosion. Therefore, solid solution nitriding treatment is needed after chromizing treatment, the surface chromium concentration is uniform, intergranular corrosion behavior after independent chromizing is eliminated, and finally, the chromizing and nitriding composite protective layer is formed on the surface of the stainless steel.

In the chromizing and nitriding composite treatment technology of the stainless steel material, the chromizing is carried out by adopting a scheme of solid powder embedding and chromizing, the chromizing powder generally comprises chromium powder and a permeation assistant, and the chromizing powder can form a chromizing layer of about 100 mu m after being thermally treated for 10-20 hours at 1050-1150 ℃. And nitriding is carried out by adopting a gas solid solution nitriding scheme, nitrogen is generally adopted as an N source, and heat treatment is carried out for 10-20 hours at 1050-1150 ℃, so that a chromizing and nitriding composite layer with the thickness of about 100 micrometers is finally formed.

At present, a resistance furnace special for chromizing and nitriding of large-scale ultra-long austenitic stainless steel materials is not common, similar process tests are only carried out by a very individual unit in China, but no resistance furnace special for chromizing and nitriding is available.

The electric furnace is an electric furnace taking joule heat generated by current passing through a conductor as a heat source, and the traditional electric furnace is difficult to meet the continuous production requirements of chromizing and nitriding. And the temperature control of the resistance furnace has great hysteresis, so that the requirement for more accurate temperature control is difficult to meet.

Disclosure of Invention

The invention aims to solve the technical problem that the defects in the prior art are overcome, and the resistance furnace for chromizing and nitriding of the austenitic stainless steel workpiece is provided.

In order to solve the technical problems, the invention adopts the technical scheme that: the utility model provides an austenitic stainless steel work piece chromizing is resistance furnace for nitrogenize which characterized in that: including upper portion open-ended furnace body and be used for installing the real empty room as the stove courage in the furnace body, be provided with the homogeneous temperature district in the furnace body, all be provided with furnace temperature sensor in the homogeneous temperature district, the furnace body is by outer to interior stove outer covering, heat preservation and the heating member of including in proper order, stretch out to the furnace body top on real empty room's upper end opening and its upper end, real empty room's upper end opening part is provided with sealed thermal-insulated mechanism, stretch out to the one end outside at furnace body top on the real empty room and be provided with water-cooling mechanism, sealed thermal-insulated mechanism is last to be provided with outlet duct, intake pipe, temperature measurement pipe and is used for connecting vacuum measuring device's pressure measurement pipe.

The electric resistance furnace for chromizing and nitriding of the austenitic stainless steel workpiece is characterized in that: the sealing heat insulation mechanism comprises a heat insulation plug arranged in the upper end of the vacuum chamber and a furnace cover used for sealing the upper end opening of the vacuum chamber.

The electric resistance furnace for chromizing and nitriding of the austenitic stainless steel workpiece is characterized in that: and a limiting edge for limiting the heat insulation plug is arranged in the vacuum chamber, and the furnace cover is connected with a flange of the vacuum chamber.

The electric resistance furnace for chromizing and nitriding of the austenitic stainless steel workpiece is characterized in that: the upper end of the temperature measurement pipe is located above the furnace cover, the lower end of the temperature measurement pipe sequentially penetrates through the furnace cover and the heat insulation plug from top to bottom and then extends into the vacuum chamber, the upper ends of the outlet pipe, the inlet pipe and the pressure measurement pipe are located above the furnace cover, and the lower ends of the outlet pipe, the inlet pipe and the pressure measurement pipe are located between the furnace cover and the heat insulation plug after penetrating through the furnace cover.

The electric resistance furnace for chromizing and nitriding of the austenitic stainless steel workpiece is characterized in that: the water cooling mechanism is a cooling water circulating pipe wound on the vacuum chamber and extending out of one end of the furnace body.

The electric resistance furnace for chromizing and nitriding of the austenitic stainless steel workpiece is characterized in that: and a welding flange is further arranged on the outer side of one end of the vacuum chamber extending to the top of the furnace body, the welding flange is positioned on the lower part of the water cooling mechanism, and the vacuum chamber is fixed in the furnace body through the welding flange.

The electric resistance furnace for chromizing and nitriding of the austenitic stainless steel workpiece is characterized in that: chromizing part of admitting air is annular air inlet structure, annular air inlet structure is including hugging closely the annular intake pipe that real empty room bottom was laid, the annular intake pipe communicates each other through first L type air duct and intake pipe, the lower extreme of first L type air duct is connected on one side upper portion of annular intake pipe, the upper end and the intake pipe interconnect of first L type air duct, a plurality of venthole groups have been seted up in the annular intake pipe, the inside wall that real empty room was hugged closely to first L type air duct is laid.

The electric resistance furnace for chromizing and nitriding of the austenitic stainless steel workpiece is characterized in that: the nitriding air inlet part is a uniform annular multilayer air inlet structure, the uniform annular multilayer air inlet structure comprises an annular multilayer air inlet pipeline tightly attached to the bottom of a vacuum chamber, the annular multilayer air inlet pipeline is communicated with an air inlet pipe through a second L-shaped air guide pipe, the lower end of the second L-shaped air guide pipe is connected to the upper portion of one side of the annular multilayer air inlet pipeline, the upper end of the second L-shaped air guide pipe is connected with the air inlet pipe, a plurality of vent hole groups are formed in the annular multilayer air inlet pipeline, and the second L-shaped air guide pipe is tightly attached to the inner side wall of the vacuum chamber and arranged.

Meanwhile, the invention also discloses a method for chromizing and nitriding an austenitic stainless steel workpiece, which is characterized by comprising the chromizing method and the nitriding method, wherein the chromizing method comprises the following steps:

step one, hoisting a vacuum chamber: hoisting a vacuum chamber in the furnace body through a hoisting tool, and placing the chromizing gas inlet component in the vacuum chamber;

step two, the setting of work piece and chromizing powder in the vacuum chamber will treat the chromizing work piece through assembled work rest and place in the vacuum chamber, assembled work rest and treat that the clearance between the chromizing work piece is filled through chromizing powder, assembled work rest divides bottom support body, middle level support body, upper support body and upper cover to hoist to the vacuum chamber in proper order in, and concrete process is as follows:

step 201, hoisting a bottom layer frame body: hoisting a bottom layer frame body to the bottom of the vacuum chamber through a lifting appliance, wherein the bottom of the bottom layer frame body is closely arranged on the upper end surface of the annular air inlet pipe, and chromizing powder with the depth of 100-300 mm is poured into the bottom of the bottom layer frame body;

step 202, hoisting of the workpiece: hoisting a workpiece to be chromized into a bottom layer frame body through a lifting appliance, and simultaneously pouring chromizing powder into the bottom layer frame body;

step 203, hoisting the middle-layer frame body: hoisting the middle layer frame body into a vacuum chamber through a hoisting tool, clamping the middle layer frame body on the upper part of the bottom layer frame body, and pouring chromium infiltration powder into the middle layer frame body;

step 204, hoisting the upper layer frame body: hoisting the upper layer rack body into a vacuum chamber through a lifting appliance, clamping the upper layer rack body on the upper part of the middle layer rack body, and filling the upper layer rack body with chromium infiltration powder;

step 205, hoisting the upper cover: hoisting the upper cover into a vacuum chamber through a hoisting tool, clamping the upper cover on the upper layer frame body, and sealing a gap between the upper layer frame body and the upper cover by adopting glass powder;

step three, sealing the vacuum chamber: the upper end opening of the vacuum chamber is sealed through the sealing and heat insulating mechanism, the upper end of the first L-shaped air guide pipe is connected with the air inlet pipe, the sealing and heat insulating mechanism comprises a heat insulating plug arranged at the upper end opening of the vacuum chamber and a furnace cover used for sealing the upper end opening of the vacuum chamber, a limiting edge for limiting the heat insulating plug is arranged in the vacuum chamber, and the furnace cover is connected with a vacuum chamber flange;

step four, mounting a sensor: a vacuum measuring device is connected to the pressure measuring tube to measure the vacuum degree in the vacuum chamber, a vacuum gauge tube, a pressure sensor and an exhaust valve are connected in parallel to the exhaust pipe, a vacuum gauge is installed on the vacuum gauge tube to display the vacuum degree in the vacuum chamber, the vacuum measuring device and the pressure sensor are both connected with a controller, a temperature measuring sensor in the vacuum chamber is installed in the vacuum chamber through a temperature measuring tube, the temperature measuring sensor in the vacuum chamber is connected with the controller, and the temperature measuring sensor in the vacuum chamber is closely arranged on the upper end face of the upper cover;

step five, vacuumizing the interior of the vacuum chamber: the air outlet pipe is connected with a vacuum pump through a vacuum pipeline, and the vacuum chamber is vacuumized to 10 degrees by the vacuum pump⁰Pa～10¹Pa；

Step six, heating the workpiece, wherein the process is as follows:

step 601, preheating of the workpiece: the temperature of a plurality of uniform temperature areas is uniformly raised and preheated through a heating body, and a hearth temperature measuring sensor in each uniform temperature area is connected with a controller;

step 602, introducing protective gas: when the temperature value measured by a hearth temperature measuring sensor in a uniform temperature zone reaches 200-300 ℃, introducing argon into the vacuum chamber through an air inlet pipe, monitoring the vacuum degree in the vacuum chamber through a vacuum measuring device, monitoring the air pressure in the vacuum chamber through a pressure sensor when the vacuum degree in the vacuum chamber is zero, and stopping introducing the argon into the vacuum chamber when the air pressure in the vacuum chamber reaches the set air pressure for chromizing;

step 603, temperature rise of the workpiece: in the process of introducing argon, the heating body is continuously heated, the temperature of the workpiece to be chromized in the vacuum chamber gradually rises along with the continuous heating of the heating body, the air pressure in the vacuum chamber is monitored by a pressure sensor in the temperature rising process of the workpiece to be chromized, and when the air pressure in the vacuum chamber is greater than the set air pressure of chromizing, the air is automatically exhausted through an exhaust valve to relieve the pressure to the set air pressure of chromizing;

step 604, judging whether the temperature of the workpiece reaches a set temperature: measuring the surface temperature of the upper frame body through a temperature measuring sensor in the vacuum chamber, and stopping heating the vacuum chamber by the heating body when the surface temperature of the upper frame body reaches a set temperature; when the surface temperature of the upper layer frame body does not reach the set temperature, continuing to execute step 503;

step seven, cooling the workpiece: lifting the vacuum chamber provided with the workpiece to be chromized out of the furnace body, naturally cooling to room temperature, completing chromizing of the workpiece to be chromized and forming a chromized workpiece; monitoring the air pressure in the vacuum chamber through a pressure sensor in the process of naturally cooling the chromized workpiece to room temperature, and introducing argon into the vacuum chamber when the air pressure in the vacuum chamber is less than the set air pressure of chromizing until the air pressure in the vacuum chamber is equal to the set air pressure of chromizing;

the nitriding method comprises the following steps:

step S1, preparation: replacing a new vacuum chamber in the furnace body through a lifting appliance, disassembling a sealing heat insulation mechanism on the vacuum chamber after chromizing is finished, and taking out the chromized workpiece from the vacuum chamber after chromizing is finished;

step S2, hoisting the workpiece in the vacuum chamber: the chromized workpiece is placed in a vacuum chamber in a furnace body through an assembled workpiece frame, and the specific process is as follows:

step S201, hoisting the bottom layer frame body, the middle layer frame body and the upper layer frame body: sequentially hoisting a bottom layer frame body, a middle layer frame body and an upper layer frame body into a vacuum chamber through a hoisting tool, wherein a plurality of air passing holes are formed in the bottom of the bottom layer frame body, and the bottom of the bottom layer frame body is closely arranged on the upper end face of an annular multilayer air inlet pipeline;

step S202, hoisting of the workpiece: after the surface of the chromized workpiece is subjected to floating ash removal treatment, hoisting the chromized workpiece into a bottom layer frame body through a hoisting tool;

step S203, hoisting of the upper cover: hoisting the upper cover into the vacuum chamber through a hoisting tool, and clamping the upper cover on the upper layer frame body;

step S3, closing of the vacuum chamber: closing the upper end opening of the vacuum chamber provided with the chromized workpiece by the sealed heat insulation mechanism detached in the step S1, wherein the upper end of the second L-shaped air duct is connected with the air inlet pipe;

step S4, replacement of gas inside the vacuum chamber: the air outlet pipe is connected with a vacuum pump through a vacuum pipeline, and the vacuum chamber is vacuumized to 10 degrees by the vacuum pump⁰Pa～10¹After Pa, introducing nitrogen into the vacuum chamber through an air inlet pipe, monitoring the vacuum degree in the vacuum chamber through a vacuum measuring device, monitoring the air pressure in the vacuum chamber through a pressure sensor when the vacuum degree in the vacuum chamber is zero, and stopping introducing the nitrogen into the vacuum chamber when the air pressure in the vacuum chamber reaches a first set air pressure;

step S5, repeating the step S4 for four to eight times until the nitrogen concentration in the vacuum chamber reaches the set nitrogen concentration;

step S6, heating the workpiece, the process is as follows:

step S601, pressurization in the vacuum chamber: introducing nitrogen into the vacuum chamber through the air inlet pipe, monitoring the air pressure in the vacuum chamber by using the pressure sensor, and stopping introducing the nitrogen into the vacuum chamber when the air pressure in the vacuum chamber reaches a second set air pressure;

step S602, heating of the workpiece: the temperature of the uniform temperature areas is uniformly increased through the heating body, the temperature measuring sensor of the hearth in each uniform temperature area is connected with the controller, the temperature of the chromized workpiece in the vacuum chamber is gradually increased along with the continuous heating of the heating body, the air pressure in the vacuum chamber is monitored through the pressure sensor in the temperature increasing process of the chromized workpiece, and when the air pressure in the vacuum chamber is greater than a second set air pressure, the air is automatically exhausted through the exhaust valve to be released to the second set air pressure;

step S603, determining whether the temperature of the workpiece reaches a set temperature: measuring the surface temperature of the upper part of the bottom layer frame body by a temperature measuring sensor in the vacuum chamber, and stopping heating the vacuum chamber by the heating body when the surface temperature of the bottom layer frame body reaches a set temperature; when the surface temperature of the bottom shelf body does not reach the set temperature, continuing to execute step 602;

step S7, cooling of the workpiece: lifting the vacuum chamber provided with the chromized workpiece out of the furnace body, and naturally cooling to room temperature to finish the nitriding process of the chromized workpiece; and in the process of naturally cooling the chromized workpiece to the room temperature, monitoring the air pressure in the vacuum chamber through a pressure sensor, and introducing nitrogen into the vacuum chamber when the air pressure in the vacuum chamber is less than a second set air pressure until the air pressure in the vacuum chamber is equal to the second set air pressure.

The chromizing and nitriding method is characterized by comprising the following steps: in step 603, when the workpiece to be chromized is heated, dividing the heating process of the workpiece into N heating stages and N heat preservation stages according to the size of the workpiece to be chromized, wherein N is a positive integer and is not less than 1 and not more than 5;

step seven, when the workpiece to be chromized is cooled, dividing the cooling process of the workpiece into N natural cooling stages and N-1 heat preservation stages according to the size of the workpiece to be chromized;

in step S602, when heating the chromized workpiece, dividing the temperature rise process of the workpiece into N heating stages and N heat preservation stages according to the size of the chromized workpiece, wherein N is a positive integer and is not less than 1 and not more than 5;

in step S7, when cooling the chromized workpiece, the cooling process of the workpiece is divided into N natural cooling stages and N-1 heat preservation stages according to the size of the chromized workpiece.

Compared with the prior art, the invention has the following advantages:

1. according to the resistance furnace for chromizing and nitriding the austenitic stainless steel workpiece, the vacuum chamber is arranged in the furnace body and serves as the furnace pipe of the resistance furnace, so that the furnace body and the furnace pipe of the resistance furnace can be completely separated, the vacuum chamber can be directly lifted out of the furnace body after chromizing or nitriding of the workpiece is completed, the next procedure is convenient to perform, the whole operation is simple and convenient, and the working efficiency can be effectively improved.

2. According to the electric resistance furnace for chromizing and nitriding the austenitic stainless steel workpiece, the uniform temperature areas are arranged in the furnace body, the number of the uniform temperature areas can be adaptively adjusted according to the specific size of the furnace body, the heating speed of the workpiece is convenient to improve, the workpiece is uniformly heated, and the chromizing or nitriding quality of the workpiece is further improved.

3. According to the electric resistance furnace for chromizing and nitriding of the austenitic stainless steel workpiece, the water cooling mechanism is arranged on the outer side of one end, extending out to the top of the furnace body, of the vacuum chamber, so that the water cooling mechanism can cool the upper end of the vacuum chamber during chromizing and nitriding processes of the workpiece, and the sealing and heat-insulating mechanism is prevented from being damaged at high temperature.

4. According to the electric resistance furnace for chromizing and nitriding the austenitic stainless steel workpiece, the sealing and heat-insulating mechanism is arranged at the opening at the upper end of the vacuum chamber, so that the workpiece can be conveniently taken and placed, meanwhile, the sealing performance of the vacuum chamber can be ensured, the energy loss in the vacuum chamber is reduced, and the working efficiency is effectively improved.

5. According to the electric resistance furnace for chromizing and nitriding the austenitic stainless steel workpiece, the temperature measuring tube is arranged on the sealing and heat insulating mechanism, when the chromizing or nitriding process of the workpiece is carried out, the temperature sensor is arranged in the vacuum chamber through the temperature measuring tube and used for measuring the temperature of the workpiece, and the hearth temperature measuring sensor is arranged in each temperature equalizing zone, so that a double-closed-loop temperature control mode can be realized, namely the temperature outside the vacuum chamber is correspondingly adjusted according to the temperature in the vacuum chamber, and the workpiece can be ensured to reach the required processing temperature.

6. According to the chromizing method adopted by the invention, the assembled workpiece frame is divided into the bottom layer frame body, the middle layer frame body, the upper layer frame body and the upper cover to be sequentially hoisted into the vacuum chamber, so that chromizing powder can be gradually filled along with the layer number of the assembled workpiece frame, the filling compactness of the chromizing powder can be ensured, the chromizing powder can be fully contacted with the surface of a workpiece, and the chromizing quality of the workpiece is further improved.

7. The nitriding method adopted by the invention can flush and replace the gas in the vacuum chamber by repeatedly vacuumizing the vacuum chamber and introducing nitrogen, so that the nitrogen with enough concentration is contained in the vacuum chamber, the replacement of the gas in the vacuum chamber is realized, and the nitriding quality of the workpiece is ensured.

In conclusion, the vacuum chamber is arranged in the furnace body to serve as the furnace pipe of the resistance furnace, so that the furnace body of the resistance furnace can be completely separated from the furnace pipe, the whole operation is simple and convenient, the working efficiency can be effectively improved, meanwhile, the number of uniform temperature zones arranged in the furnace body can be adaptively adjusted according to the specific size of the furnace body, the heating speed of a workpiece can be conveniently improved, the workpiece is uniformly heated, the chromizing and nitriding of the workpiece can be ensured by adopting the same resistance furnace, the application range is wide, the specific assembly structure of the assembly type workpiece frame can be adaptively adjusted according to the chromizing or nitriding process, and the chromizing and nitriding quality of the workpiece can be effectively improved.

The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.

Drawings

FIG. 1 is a diagram showing a state of use of a resistance furnace in chromizing a workpiece according to the present invention.

FIG. 2 is a view showing a state of use of the resistance furnace in nitriding a workpiece according to the present invention.

FIG. 3 is a schematic structural view of a chromizing air-intake component of the present invention.

Fig. 4 is a top view of fig. 3.

FIG. 5 is a schematic structural view of a nitrided intake component of the present invention.

Fig. 6 is a top view of fig. 5.

FIG. 7 is a schematic block circuit diagram of the control system of the present invention.

FIG. 8 is a block flow diagram of the chromizing method of the present invention.

FIG. 9 is a block diagram of a nitridation method of the present invention.

Description of reference numerals:

1-furnace shell; 2, insulating layer; 3-a heating body;

4-vacuum chamber; 5-a uniform temperature zone; 6-hearth temperature measuring sensor;

7-air outlet pipe; 8, an air inlet pipe; 9-temperature measuring tube;

10-pressure measuring tube; 11-a thermal insulating plug; 12-furnace cover;

13-cooling water circulation pipe; 14-welding a flange; 15-1-bottom layer frame body;

15-2-middle layer frame body; 15-3-upper layer frame body; 15-4-upper cover;

16-1-a workpiece to be chromized; 16-2-a chromized workpiece; 17-vacuum measuring device;

18-a controller; 19-temperature measuring sensor in vacuum chamber;

20-1-annular inlet pipe; 20-2 — a first L-shaped airway; 21-audible and visual alarm;

22-a pressure sensor; 23-1-annular multilayer air inlet pipeline;

23-2-a second L-shaped airway; 23-3-T-shaped stents;

24-exhaust valve.

Detailed Description

The electric resistance furnace for chromizing and nitriding an austenitic stainless steel workpiece shown in FIGS. 1 to 7 comprises a furnace body with an upper opening and a vacuum chamber 4 as a furnace pipe arranged in the furnace body, a uniform temperature zone 5 is arranged in the furnace body, hearth temperature measuring sensors 6 are arranged in the uniform temperature zone 5, the furnace body comprises a furnace shell 1, a heat preservation layer 2 and a heating body 3 from outside to inside in sequence, the upper end of the vacuum chamber 4 is opened, the upper end of the vacuum chamber extends to the top of the furnace body, a sealing and heat-insulating mechanism is arranged at an opening at the upper end of the vacuum chamber 4, a water cooling mechanism is arranged on the outer side of one end of the vacuum chamber 4 extending to the top of the furnace body, the sealed heat insulation mechanism is provided with an air outlet pipe 7, an air inlet pipe 8, a temperature measuring pipe 9 and a pressure measuring pipe 10 used for connecting a vacuum measuring device 17, and the chromizing air inlet component and the nitriding air inlet component are arranged in the vacuum chamber 4.

During the in-service use, through the furnace pipe of installing a real empty room 4 as resistance furnace in the furnace body, can realize separating resistance furnace's furnace body and furnace pipe completely, after work piece chromizing or nitrogenize completion, can directly hang out real empty room 4 from the furnace body, conveniently carry out next process, whole easy operation is convenient, can effectively improve work efficiency.

In the embodiment, one or more temperature equalizing regions 5 can be arranged in the furnace body according to the size of the furnace body, and the temperature equalizing regions 5 are arranged in the furnace body, so that the heating speed of the workpiece is increased, the workpiece is heated uniformly, and the chromizing and nitriding quality of the workpiece is improved.

During the in-service use, through stretching out to the one end outside at furnace body top on vacuum chamber 4 and setting up water cooling body, when carrying out the chromizing or the nitrogenize technology of work piece, water cooling body can cool down vacuum chamber 4's upper end, avoids sealed thermal-insulated mechanism to take place to destroy under high temperature.

In this embodiment, through being provided with sealed thermal-insulated mechanism at the upper end opening part of real empty room 4, can be convenient for getting of work piece and put, can guarantee real empty room 4's leakproofness simultaneously, reduce the energy loss in real empty room 4, and then effectively improve work efficiency.

During the in-service use, through set up temperature measurement buret 9 on the sealed heat-proof mechanism, when carrying out the chromizing or the nitrogenize technology of work piece, can be used for measuring the temperature of work piece through temperature measurement buret 9 installation temperature sensor in vacuum chamber 4, simultaneously every all be provided with a furnace temperature measurement sensor 6 in the even temperature district 5, can realize two closed loop accuse temperature modes, adjust the temperature outside vacuum chamber 4 according to the temperature in the vacuum chamber 4 correspondingly promptly, ensure that the work piece can reach required processing temperature.

In practical use, the sealing and heat-insulating mechanism is provided with the air outlet pipe 7 and the air inlet pipe 8, so that required protective gas and reaction gas can be conveniently filled into the vacuum chamber 4, and meanwhile, the vacuum degree in the vacuum chamber 4 can be flexibly controlled.

In the embodiment, the furnace shell 1 is an airtight steel plate assembly welding piece, and the inner surface and the outer surface of the furnace shell 1 are treated by adopting anti-corrosion and temperature-resistant paint and the like; the heat-insulating layer 2 adopts a refractory brick and refractory fiber composite structure; the heating body 3 is made of iron chromium aluminum.

In practical use, only one chromizing gas inlet component or one nitriding gas inlet component can be arranged in each vacuum chamber 4.

In this embodiment, the sealing and heat insulating mechanism includes a heat insulating plug 11 provided inside the upper end of the vacuum chamber 4, and a furnace cover 12 for closing the upper end opening of the vacuum chamber 4.

In practical use, the heat transfer between the air inside the vacuum chamber 4 and the outside air can be reduced by arranging the heat insulating plug 11 at the opening at the upper end of the vacuum chamber 4, and further the heat loss in the vacuum chamber 4 can be effectively prevented.

In this embodiment, a limiting edge for limiting the thermal insulation plug 11 is arranged in the vacuum chamber 4, and the furnace cover 12 is connected to the vacuum chamber 4 by a flange.

In this embodiment, the limiting edge is disposed inside the vacuum chamber 4, the limiting edge may be a whole annular closed limiting edge, and the limiting edge may also be formed by a plurality of arc-shaped limiting members disposed at the same height at equal intervals along the circumferential direction of the inner wall of the vacuum chamber 4.

In this embodiment, the insulating plug 11 is located inside the vacuum chamber 4, and the furnace cover 12 is located at the upper portion of the vacuum chamber 4; the heat insulation plug 11 is made of graphite and is wound by a stainless steel wire mesh.

In this embodiment, the upper end of the temperature measurement pipe 9 is located above the furnace cover 12, the lower end of the temperature measurement pipe 9 from top to bottom passes through the furnace cover 12 and the heat insulation plug 11 in proper order and then stretches into the vacuum chamber 4, the upper end of the outlet pipe 7, the inlet pipe 8 and the pressure measurement pipe 10 is located above the furnace cover 12, the lower end of the outlet pipe 7, the inlet pipe 8 and the pressure measurement pipe 10 is located between the furnace cover 12 and the heat insulation plug 11 after passing through the furnace cover 12.

In practical use, a temperature measuring port can be provided for the vacuum chamber 4 by arranging a temperature measuring tube 9 communicated with the inside of the vacuum chamber 4 on the furnace cover 12, thereby facilitating the measurement of the temperature of the workpiece in the vacuum chamber 4.

In this embodiment, the heat insulating plug 11 only plays a role of heat insulation, and does not seal the vacuum chamber 4, so that the gas at the two sides of the heat insulating plug 11 can be communicated.

When the furnace is actually used, the furnace cover 12 is connected with a safety valve, and when the pressure in the vacuum chamber 4 exceeds the upper limit of a set value, automatic pressure relief can be realized through the safety valve, so that the safety of the chromizing process of a workpiece is ensured.

In this embodiment, the water cooling mechanism is a cooling water circulating pipe 13 wound on the vacuum chamber 4 and extending to the outside of one end of the furnace body.

When the vacuum heat-insulation furnace is in practical use, the cooling water circulating pipe 13 is wound on the outer side of one end, extending out of the top of the furnace body, of the vacuum chamber 4, when the vacuum chamber 4 is heated, cooling water can be pumped into the cooling water circulating pipe 13 in a circulating mode all the time, heat at the upper end of the vacuum chamber 4 is continuously transmitted to the cooling water circulating pipe 13 through heat transfer, cooling water in the cooling water circulating pipe 13 is discharged after taking away a part of heat, cooling water is continuously pumped into the cooling water circulating pipe 13, and the purpose of cooling the sealed heat-insulation mechanism in the vacuum chamber 4 is achieved.

In this embodiment, a welding flange 14 is further disposed on the outer side of one end of the vacuum chamber 4 extending to the top of the furnace body, the welding flange 14 is located at the lower portion of the water cooling mechanism, and the vacuum chamber 4 is fixed in the furnace body through the welding flange 14.

In practical use, a welding flange 14 is arranged on the outer side of one end, extending out of the top of the furnace body, of the vacuum chamber 4, and the vacuum chamber 4 is seated on the furnace body through the welding flange 14.

In this embodiment, the distance between the bottom of the welding flange 14 and the upper end of the vacuum chamber 4 is 10cm to 40 cm.

As shown in fig. 3 and 4, in this embodiment, the chromizing air inlet component is an annular air inlet structure, the annular air inlet structure includes an annular air inlet pipe 20-1 arranged to be closely attached to the bottom of the vacuum chamber 4, the annular air inlet pipe 20-1 is communicated with an air inlet pipe 8 through a first L-shaped air guide pipe 20-2, the lower end of the first L-shaped air guide pipe 20-2 is connected to the upper portion of one side of the annular air inlet pipe 20-1, the upper end of the first L-shaped air guide pipe 20-2 is connected to the air inlet pipe 8, a plurality of air vent groups are arranged on the annular air inlet pipe 20-1, and the first L-shaped air guide pipe 20-2 is arranged to be closely attached to the.

In practical use, when the workpiece is chromized, the chromizing gas inlet component is arranged in the vacuum chamber 4, so that protective gas required by chromizing is conveniently introduced into the vacuum chamber 4.

As shown in fig. 5 and 6, in this embodiment, the nitriding air inlet component is a uniform annular multilayer air inlet structure, the uniform annular multilayer air inlet structure includes an annular multilayer air inlet pipeline 23-1 closely attached to the bottom of the vacuum chamber 4, the annular multilayer air inlet pipeline 23-1 is communicated with the air inlet pipe 8 through a second L-shaped air guide pipe 23-2, the lower end of the second L-shaped air guide pipe 23-2 is connected to the upper portion of one side of the annular multilayer air inlet pipeline 23-1, the upper end of the second L-shaped air guide pipe 23-2 is connected to the air inlet pipe 8, the annular multilayer air inlet pipeline 23-1 is provided with a plurality of vent groups, and the second L-shaped air guide pipe 23-2 is closely attached to the inner side wall of the vacuum chamber 4.

In this embodiment, the annular multilayer air inlet pipeline 23-1 comprises a plurality of annular pipelines from inside to outside, the plurality of annular pipelines are all communicated with one another, one annular pipeline at the outermost ring is not a complete ring, one end of the annular pipeline at the outermost ring is connected with the annular pipeline at the inner ring, and the other end of the annular pipeline at the outermost ring is connected with the L-shaped air duct 23-2; each annular pipeline is provided with a plurality of vent hole groups, and each vent hole group consists of a plurality of tiny holes which are arranged in order.

In practical use, the second L-shaped air duct 23-2 is close to the inner wall of the vacuum chamber 4, and the placement of the workpiece is not influenced.

In this embodiment, the annular multi-layer air inlet duct 23-1 is mounted at the bottom of the vacuum chamber 4 through a T-shaped support 23-3, and a groove for clamping the annular multi-layer air inlet duct 23-1 and the T-shaped support 23-3 is formed at the bottom of the vacuum chamber 4.

In practical use, the annular multilayer air inlet pipeline 23-1 is arranged, and the annular multilayer air inlet pipeline 23-1 is provided with a plurality of vent hole groups, so that nitrogen can uniformly and quickly enter the vacuum chamber 4 from bottom to top.

A method for chromizing and nitriding an austenitic stainless steel workpiece using a resistance furnace according to the present invention, as shown in fig. 7, 8 and 9, is characterized in that the method comprises a chromizing method and a nitriding method, the chromizing method comprising the steps of:

step one, hoisting a vacuum chamber: hoisting a vacuum chamber 4 in the furnace body through a hoisting tool, and placing the chromizing gas inlet component in the vacuum chamber 4;

in actual use, the vacuum chamber 4 is detachably mounted in the vacuum chamber 4.

Step two, arranging a workpiece and chromizing powder in a vacuum chamber, placing a workpiece 16-1 to be chromized in the vacuum chamber 4 through an assembled workpiece frame, filling a gap between the assembled workpiece frame and the workpiece 16-1 to be chromized through the chromizing powder, and sequentially hoisting the assembled workpiece frame into the vacuum chamber 4 by a bottom frame body 15-1, a middle frame body 15-2, an upper frame body 15-3 and an upper cover 15-4, wherein the specific process is as follows:

in actual use, the number of layers of the frame body forming the assembly type workpiece frame can be flexibly adjusted according to the specific size of the workpiece 16-1 to be chromized, so that the compactness of a gap between the workpiece 16-1 to be chromized and the assembly type workpiece frame is conveniently improved by chromizing powder, and the chromizing quality of the workpiece 16-1 to be chromized can be effectively improved.

In this embodiment, the upper ends of the bottom layer frame body 15-1, the middle layer frame body 15-2 and the upper layer frame body 15-3 are all provided with an inserting ring, and the lower ends of the middle layer frame body 15-2, the upper layer frame body 15-3 and the upper cover 15-4 are all provided with a U-shaped groove for inserting the inserting ring.

Step 201, hoisting a bottom layer frame body: hoisting a bottom layer frame body 15-1 to the bottom of the vacuum chamber 4 through a lifting appliance, wherein the bottom of the bottom layer frame body 15-1 is closely arranged on the upper end surface of an annular air inlet pipe 20-1, and chromizing powder with the depth of 100-300 mm is poured into the bottom of the bottom layer frame body 15-1;

when the chromizing powder pouring device is actually used, the chromizing powder poured into the bottom of the bottom layer frame body 15-1 is tiled and compacted at the bottom of the bottom layer frame body 15-1, the thickness of the chromizing powder is smaller than the depth of the bottom layer frame body 15-1, the chromizing powder with the depth of 100 mm-300 mm is poured into the bottom of the bottom layer frame body 15-1, the chromizing powder with a certain thickness can be arranged on the lower portion of the workpiece 16-1 to be chromized, and the chromizing quality of the workpiece 16-1 to be chromized is guaranteed.

Step 202, hoisting of the workpiece: hoisting a workpiece 16-1 to be chromized into the bottom layer frame body 15-1 through a lifting appliance, and simultaneously pouring chromizing powder into the bottom layer frame body 15-1;

when the chromium-infiltrated workpiece is actually used, after the workpiece 16-1 to be chromized is hoisted to the bottom layer frame body 15-1, the gap between the inner side wall of the bottom layer frame body 15-1 and the workpiece 16-1 to be chromized is completely filled with chromium-infiltrated powder.

Step 203, hoisting the middle-layer frame body: hoisting the middle layer frame body 15-2 into the vacuum chamber 4 through a lifting appliance, clamping the middle layer frame body 15-2 on the upper part of the bottom layer frame body 15-1, and pouring the chromium infiltration powder into the middle layer frame body 15-2;

step 204, hoisting the upper layer frame body: hoisting the upper layer frame body 15-3 into the vacuum chamber 4 through a hoisting tool, clamping the upper layer frame body 15-3 on the upper part of the middle layer frame body 15-2, and pouring chromium infiltration powder into the upper layer frame body 15-3;

in actual use, when the chromizing powder is filled, the chromizing powder is gradually filled along with the layer number of the assembled workpiece frame, so that the filling compactness of the chromizing powder can be ensured, and the chromizing powder can be fully contacted with the surface of the workpiece 16-1 to be chromized.

It should be noted that the upper end surface of the workpiece 16-1 to be chromized is 100 mm-300 mm lower than the upper end of the upper rack 15-3, and the upper end of the workpiece 16-1 to be chromized is ensured to be provided with chromizing powder with the thickness of 100 mm-300 mm.

In this embodiment, when the upper frame 15-3 is filled with chromium infiltration powder, it needs to be compacted and filled.

Step 205, hoisting the upper cover: hoisting an upper cover 15-4 into the vacuum chamber 4 through a hoisting tool, clamping the upper cover 15-4 on an upper layer frame body 15-3, and sealing a gap between the upper layer frame body 15-3 and the upper cover 15-4 by adopting glass powder;

when the vacuum assembled workpiece rack is actually used, the gap between the upper rack body 15-3 and the upper cover 15-4 is sealed by the glass powder, the glass powder is changed into liquid at high temperature, so that gas in the vacuum chamber 4 can be effectively prevented from entering the assembled workpiece rack, and meanwhile, when the gas pressure in the assembled workpiece rack is too high, the gas can be discharged to the assembled workpiece rack through the gap of the glass powder, so that the control of the gas pressure in the assembled workpiece rack is realized.

Step three, sealing the vacuum chamber: the upper end opening of the vacuum chamber 4 is closed through the sealing and heat insulating mechanism, the upper end of the first L-shaped air guide pipe 20-2 is connected with the air inlet pipe 8, the sealing and heat insulating mechanism comprises a heat insulating plug 11 arranged at the upper end opening of the vacuum chamber 4 and a furnace cover 12 used for closing the upper end opening of the vacuum chamber 4, a limiting edge for limiting the heat insulating plug 11 is arranged in the vacuum chamber 4, and the furnace cover 12 is in flange connection with the vacuum chamber 4;

during the in-service use, seal the back through the upper end opening of sealed thermal-insulated mechanism with real empty room 4, the one end of outlet duct 7, intake pipe 8 and pressure measurement buret 10 all is located bell 12 upper end, and its other end all passes bell 12 and stretches into to the vacuum chamber 4 in, the one end of temperature measurement buret 9 all is located bell 12 upper end, and its other end passes bell 12 and thermal-insulated stopper 11 in proper order and stretch into to the vacuum chamber 4 after.

In the embodiment, the temperature measuring tube 9 passes through the heat insulation plug 11, so that the temperature sensor can be conveniently arranged to measure the temperature of the workpiece 16-1 to be chromized.

Step four, mounting a sensor: a vacuum measuring device 17 is connected to the pressure measuring tube 10 to measure the vacuum degree in the vacuum chamber 4, a vacuum gauge, a pressure sensor 22 and an exhaust valve are connected in parallel to the exhaust tube 7, a vacuum gauge is installed on the vacuum gauge to display the vacuum degree in the vacuum chamber 4, the vacuum measuring device 17 and the pressure sensor 22 are both connected with a controller 18, a vacuum chamber inner temperature measuring sensor 19 is installed in the vacuum chamber 4 through a temperature measuring tube 9, the vacuum chamber inner temperature measuring sensor 19 is connected with the controller 18, and the vacuum chamber inner temperature measuring sensor 19 is closely arranged on the upper end face of the upper cover 15-4;

in practical use, the temperature measuring sensor 19 in the vacuum chamber is preferably an N-type nickel-chromium-silicon-nickel-silicon-magnesium thermocouple, and the controller 18 is preferably a programmable digital control instrument of Japanese island electric FP 93.

It should be noted that the air outlet pipe 7 is provided with a valve, the air outlet pipe 7 is connected with a vacuum gauge pipe in parallel, and a vacuum gauge is arranged on the vacuum gauge pipe to measure the vacuum degree in the air pipe 7; when the chromizing of the workpiece is finished and the nitriding of another workpiece needs to be carried out in the resistance furnace, the valve on the air outlet pipe 7 can be closed to ensure that the air pressure in the vacuum chamber 4 is kept stable; the air pressure on the connecting section between the valve on the air pipe 7 and the vacuum pump is discharged through the exhaust valve, so that the pressure is ensured to return to the atmospheric state; thus, the vacuum chamber 4 can be lifted out, the vacuum chamber 4 for nitriding can be replaced, and then the next nitriding process can be performed; the suspended vacuum chamber 4 can be naturally cooled in a room temperature environment, meanwhile, a certain pressure is kept in the vacuum chamber, the oxidation of the workpiece is effectively avoided, the chromized workpiece can be taken out after the natural cooling is finished, and the chromizing and nitriding time is effectively saved.

In this embodiment, the vacuum measuring device 17 is preferably a vacuum gauge model YZ-100.

Step five, vacuumizing the interior of the vacuum chamber: the air outlet pipe 7 is connected with a vacuum pump through a vacuum pipeline, and the vacuum chamber 4 is vacuumized to 10 degrees by the vacuum pump⁰Pa～10¹Pa；

In actual use, when the vacuum chamber 4 is vacuumized, the vacuum degree in the vacuum chamber 4 is monitored through the vacuum measuring device 17, and when the vacuum degree in the vacuum chamber 4 meets the requirement, the vacuum pump is closed, and vacuumizing is stopped.

Step six, heating the workpiece, wherein the process is as follows:

step 601, preheating of the workpiece: the heating and preheating of the uniform temperature zones 5 are carried out at a constant speed through a heating body 3, and a hearth temperature measuring sensor 6 in each uniform temperature zone 5 is connected with a controller 18;

in practical use, the hearth temperature measuring sensor 6 is preferably an S-type double platinum rhodium thermocouple.

In the embodiment, when a workpiece 16-1 to be chromized is heated by a heating body 3, a signal is sent to a controller 18 through a hearth temperature regulator, the controller 18 controls the heating body 3 to carry out electric heating, the hearth temperature regulator is preferably a power regulator with the model number of SR30-0170, and the controller 18 controls the magnitude of voltage and current by controlling the trigger pulse of a controllable silicon on the power regulator and regulating the waveform of three-phase voltage so as to change the magnitude of power loaded on the heating body; the heating body 3 is an electric heating element, and the currently used material is 0Cr27Al7Mo 2.

Step 602, introducing protective gas: when the temperature value measured by a hearth temperature measuring sensor 6 in one uniform temperature zone 5 reaches 200-300 ℃, introducing argon gas into the vacuum chamber 4 through an air inlet pipe 8, monitoring the vacuum degree in the vacuum chamber 4 through a vacuum measuring device 17, monitoring the air pressure in the vacuum chamber 4 through a pressure sensor 22 when the vacuum degree in the vacuum chamber 4 is zero, and stopping introducing the argon gas into the vacuum chamber 4 when the air pressure in the vacuum chamber 4 reaches the set air pressure of chromizing;

when the device is actually used, argon is introduced to prevent 16-1 of a workpiece to be chromized from being oxidized, the set air pressure of chromizing is 50-100 kPa, finally, the air pressure in the vacuum chamber 4 is stabilized at 50-100 kPa, and the reaction in the workpiece rack can reach certain balance.

During the in-service use, be connected with a display on the controller 18, can show the vacuum that vacuum measuring device 17 measured and the atmospheric pressure that pressure sensor 22 measured and obtained, in order to remind the staff in time to open and close the vacuum pump, be connected with an audible-visual annunciator 21 on the controller 18, when atmospheric pressure in the vacuum chamber 4 reached and set for atmospheric pressure, maximum atmospheric pressure limit value, and minimum atmospheric pressure limit value, audible-visual annunciator 21 all can be controlled to the controller 18 and report to the police, and then reminds the staff.

In this embodiment, the heating body 3, the furnace temperature measuring sensor 6, the vacuum measuring device 17, the controller 18, the temperature measuring sensor 19 in the vacuum chamber, the audible and visual alarm 21, and the exhaust valve 24 constitute a control system of the resistance furnace for chromizing and nitriding the austenitic stainless steel workpiece.

Step 603, temperature rise of the workpiece: in the process of introducing argon, the heating body 3 is continuously heated, the temperature of the workpiece 16-1 to be chromized in the vacuum chamber 4 is gradually increased along with the continuous heating of the heating body 3, the air pressure in the vacuum chamber 4 is monitored by the pressure sensor 22 in the temperature rising process of the workpiece 16-1 to be chromized, and when the air pressure in the vacuum chamber 4 is greater than the set air pressure of chromizing, the air is automatically exhausted through the exhaust valve 24 to relieve the pressure to the set air pressure of chromizing;

during the in-service use, with the continuous heating to vacuum chamber 4 of heating body 3, along with the continuous rising of the inside temperature in vacuum chamber 4, the atmospheric pressure in vacuum chamber 4 also increases gradually, consequently need get rid of some argon gas and chromizing reaction gas and go out, guarantees that vacuum chamber 4 is inside always in a relatively stable constant voltage environment.

Step 604, judging whether the temperature of the workpiece reaches a set temperature: measuring the surface temperature of the upper frame body 15-3 by a temperature measuring sensor 19 in the vacuum chamber, and stopping heating the vacuum chamber 4 by the heating body 3 when the surface temperature of the upper frame body 15-3 reaches a set temperature; when the surface temperature of the upper layer frame body 15-3 does not reach the set temperature, continuing to execute step 503;

in practical use, the chromium infiltration powder is completely filled between the workpiece 16-1 to be chromized and the assembled workpiece holder, so that the surface temperature of the workpiece 16-1 to be chromized is inconvenient to measure, and the surface temperature of the workpiece holder can be measured to approximately represent the surface temperature of the workpiece 16-1 to be chromized.

Step seven, cooling the workpiece: lifting the vacuum chamber 4 provided with the workpiece 16-1 to be chromized out of the furnace body, naturally cooling to room temperature, completing chromizing of the workpiece 16-1 to be chromized and forming a chromized workpiece 16-2; in the process of naturally cooling the chromized workpiece 16-2 to the room temperature, monitoring the air pressure in the vacuum chamber 4 through the pressure sensor 22, and introducing argon into the vacuum chamber 4 when the air pressure in the vacuum chamber 4 is smaller than the set air pressure of the chromizing until the air pressure in the vacuum chamber 4 is equal to the set air pressure of the chromizing;

in practical use, a relatively stable constant pressure environment is maintained in the vacuum chamber 4 during the cooling process of the workpiece 16-1 to be chromized from the set temperature to the room temperature.

In this embodiment, in the process of naturally cooling the workpiece 16-1 to be chromized to room temperature, since the temperature in the vacuum chamber 4 is gradually reduced and the air pressure in the vacuum chamber 4 is also gradually reduced, argon needs to be introduced into the vacuum chamber 4 in time to ensure the constant pressure environment of the vacuum chamber 4.

It should be noted that, during the process of naturally cooling the workpiece 16-1 to be chromized to room temperature, argon gas does not need to be introduced into the vacuum chamber 4 all the time, a minimum pressure limit value can be set, and when the pressure in the vacuum chamber 4 is smaller than the set pressure and reaches the minimum pressure limit value, argon gas is introduced into the vacuum chamber 4.

The nitriding method comprises the following steps:

step S1, preparation: replacing a new vacuum chamber 4 in the furnace body through a lifting appliance, disassembling a sealing heat insulation mechanism on the vacuum chamber 4 after chromizing is finished, and taking out the chromized workpiece 16-2 from the vacuum chamber 4 after chromizing is finished;

step S2, hoisting the workpiece in the vacuum chamber: the chromized workpiece 16-2 is placed in the vacuum chamber 4 in the furnace body through the assembled workpiece rack, and the specific process is as follows:

in practical use, the assembled workpiece frame for workpiece nitriding can be consistent with the assembled workpiece frame for workpiece chromizing in structure, and in order to improve the working efficiency, the assembled workpiece frame for workpiece nitriding can be simplified and only comprises an upper cover and a bottom layer frame body, and under the condition, the depth of the bottom layer frame body for workpiece nitriding is certainly larger than the height of the chromized workpiece 16-2.

In this embodiment, the assembled workpiece holder for workpiece nitriding is a new workpiece holder, and the occurrence of chromizing powder participating in chromizing on the assembled workpiece holder for chromizing is avoided.

Step S201, hoisting the bottom layer frame body, the middle layer frame body and the upper layer frame body: sequentially hoisting a bottom layer frame body 15-1, a middle layer frame body 15-2 and an upper layer frame body 15-3 into a vacuum chamber 4 through a hoisting tool, wherein the bottom of the bottom layer frame body 15-1 is provided with a plurality of air passing holes, and the bottom of the bottom layer frame body 15-1 is closely attached to the upper end face of an annular multilayer air inlet pipeline 23-1;

in practical use, when the chromized workpiece 16-2 is nitrided, the inner cavity of the assembly type workpiece frame can be communicated with the inside of the vacuum chamber 4 by arranging the plurality of air passing holes at the bottom of the bottom layer frame body 15-1, so that the air pressure in the assembly type workpiece frame is consistent with the air pressure in the vacuum chamber 4.

It should be noted that the air holes are formed at the bottom of the bottom layer frame body 15-1, so that air enters the assembly type workpiece frame from the bottom of the bottom layer frame body 15-1 and exits from the bottom of the bottom layer frame body 15-1, and thus, the nitrogen can be more fully contacted with the chromized workpiece 16-2.

Step S202, hoisting of the workpiece: after the surface of the chromized workpiece 16-2 is subjected to floating ash removal treatment, hoisting the chromized workpiece 16-2 into the bottom layer frame body 15-1 by a hoisting tool;

step S203, hoisting of the upper cover: hoisting the upper cover 15-4 into the vacuum chamber 4 through a hoisting tool, and clamping the upper cover 15-4 on the upper-layer frame body 15-3;

in practical use, the upper cover 15-4 and the upper layer frame body 15-3 are sealed to realize semi-sealing of the assembly type workpiece frame, namely, gas in the assembly type workpiece frame can only be discharged from the air passing hole at the bottom of the bottom layer frame body 15-1.

In this embodiment, in order to ensure that nitrogen gas is sufficiently in contact with the workpiece when nitriding the workpiece, the upper cover 15-4 and the upper frame 15-3 do not need to be sealed with glass powder, and the upper opening of the upper frame 15-3 is sealed to some extent by the weight of the upper cover 15-4.

Step S3, closing of the vacuum chamber: the upper end opening of the vacuum chamber 4 provided with the chromized workpiece 16-2 is closed by the sealing and heat insulating mechanism detached in the step S1, and the upper end of the second L-shaped air duct 23-2 is connected with the air inlet pipe 8;

in practical use, the vacuum measuring device 17, the vacuum gauge pipe, the pressure sensor 22, the exhaust valve 24 and the temperature measuring sensor 19 in the vacuum chamber are not detached from the sealing and heat insulating mechanism, when the chromized workpiece 16-2 is nitrided, the temperature measuring sensor 19 in the vacuum chamber can also be directly arranged by being clung to one side of the chromized workpiece 16-2, and the upper cover 15-4 is provided with a hole for the cable of the temperature measuring sensor 19 in the vacuum chamber to pass through.

Step S4, replacement of gas inside the vacuum chamber: the air outlet pipe 7 is connected with a vacuum pump through a vacuum pipeline, and the vacuum chamber 4 is vacuumized to 10 degrees by the vacuum pump⁰Pa～10¹After Pa, introducing nitrogen into the vacuum chamber 4 through the air inlet pipe 8, monitoring the vacuum degree in the vacuum chamber 4 through the vacuum measuring device 17, monitoring the air pressure in the vacuum chamber 4 through the pressure sensor 22 when the vacuum degree in the vacuum chamber 4 is zero, and stopping introducing the nitrogen into the vacuum chamber 4 when the air pressure in the vacuum chamber 4 reaches a first set air pressure;

in actual use, when nitriding a workpiece, the first set gas pressure is preferably 1.1 × 10⁵MPa。

in actual use, when nitriding the chromized workpiece 16-2, the reaction gas is nitrogen, and therefore, it is necessary to repeatedly evacuate the vacuum chamber 4 and introduce nitrogen gas, so that the gas in the vacuum chamber 4 can be flushed and replaced to have a sufficient concentration of nitrogen gas in the vacuum chamber 4, indicating that the replacement with nitrogen gas is complete.

In this embodiment, during evacuation, the gas in the vacuum chamber 4 is directly evacuated, and during introducing the nitrogen gas, the nitrogen gas is directly introduced into the assembly type work rest, so that other gases in the assembly type work rest can be exhausted from the bottom of the assembly type work rest.

Step S6, heating the workpiece, the process is as follows:

step S601, pressurization in the vacuum chamber: introducing nitrogen into the vacuum chamber 4 through the air inlet pipe 8, monitoring the air pressure in the vacuum chamber 4 by the pressure sensor 22, and stopping introducing the nitrogen into the vacuum chamber 4 when the air pressure in the vacuum chamber 4 reaches a second set air pressure;

in practical use, when nitriding the workpiece, the second set gas pressure is preferably 1.1 × 10⁵MPa～1.8×10⁵MPa。

Step S602, heating of the workpiece: the temperature of a plurality of uniform temperature areas 5 is uniformly increased through a heating body 3, a hearth temperature measuring sensor 6 in each uniform temperature area 5 is connected with a controller 18, the temperature of a chromized workpiece 16-2 in a vacuum chamber 4 is gradually increased along with the continuous heating of the heating body 3, the air pressure in the vacuum chamber 4 is monitored through a pressure sensor 22 in the temperature increasing process of the chromized workpiece 16-2, and when the air pressure in the vacuum chamber 4 is greater than a second set air pressure, the air is automatically exhausted through an exhaust valve 24 to relieve the pressure to the second set air pressure;

step S603, determining whether the temperature of the workpiece reaches a set temperature: measuring the surface temperature of the upper part of the bottom layer frame body 15-1 by a temperature measuring sensor 19 in the vacuum chamber, and stopping heating the vacuum chamber 4 by the heating body 3 when the surface temperature of the bottom layer frame body 15-1 reaches a set temperature; when the surface temperature of the bottom shelf body 15-1 does not reach the set temperature, continuing to execute step 602;

step S7, cooling of the workpiece: the vacuum chamber 4 provided with the chromized workpiece 16-2 is lifted out of the furnace body and naturally cooled to room temperature, and the nitriding process of the chromized workpiece 16-2 is completed; and in the process of naturally cooling the chromized workpiece 16-2 to the room temperature, monitoring the air pressure in the vacuum chamber 4 through the pressure sensor 22, and introducing nitrogen into the vacuum chamber 4 when the air pressure in the vacuum chamber 4 is less than a second set air pressure until the air pressure in the vacuum chamber 4 is equal to the second set air pressure.

When in actual use, the resistance furnace can be used for independently carrying out a chromizing procedure of a workpiece or a nitriding process of the workpiece.

In the embodiment, in step 603, when the workpiece to be chromized 16-1 is heated, the heating process of the workpiece is divided into N heating stages and N heat preservation stages according to the size of the workpiece to be chromized 16-1, wherein N is a positive integer and N is not less than 1 and not more than 5;

seventhly, when the workpiece 16-1 to be chromized is cooled, dividing the cooling process of the workpiece into N natural cooling stages and N-1 heat preservation stages according to the size of the workpiece 16-1 to be chromized;

in step S602, when heating the chromized workpiece 16-2, dividing the temperature rise process of the workpiece into N heating stages and N heat preservation stages according to the size of the chromized workpiece 16-2, wherein N is a positive integer and is not less than 1 and not more than 5;

in step S7, when cooling the chromized workpiece 16-2, the cooling process of the workpiece is divided into N natural cooling stages and N-1 heat preservation stages according to the size of the chromized workpiece 16-2.

When the device is actually used, the temperature rise process of a workpiece 16-1 to be chromized is the same as that of a workpiece 16-2 which is chromized, the temperature rise process is divided into 3 heating stages and 3 heat preservation stages, the cooling process of the workpiece 16-1 to be chromized is the same as that of the workpiece 16-2 which is chromized, the cooling process is divided into 3 natural cooling stages and 2 heat preservation stages, namely, the vacuum chamber 4 is heated for the first time by the heating body 3 at a certain heating rate, when the temperature measured by the hearth temperature measuring sensor 6 corresponding to one uniform temperature zone 5 reaches 500-650 ℃, the first heat preservation can be carried out on the vacuum chamber 4, and the temperature measured by the hearth temperature measuring sensors 6 corresponding to all the uniform temperature zones 5 is required to reach 500-650 ℃ before the first heat preservation time is finished; after the first heat preservation of the vacuum chamber 4 is finished, the vacuum chamber 4 is continuously heated for the second time at a stable heating rate through the heating body 3, and when the temperature measured by the hearth temperature measuring sensor 6 corresponding to one uniform temperature zone 5 reaches 800-950 ℃, the vacuum chamber 4 can be subjected to the second heat preservation; after the second heat preservation of the vacuum chamber 4 is finished, the vacuum chamber 4 is continuously heated for the third time at a stable heating rate through the heating body 3, and when the temperature measured by the hearth temperature measuring sensor 6 corresponding to one uniform temperature zone 5 reaches 1050-1150 ℃, the vacuum chamber 4 can be subjected to the third heat preservation; after the third heat preservation of the vacuum chamber 4 is finished, performing first cooling of the vacuum chamber 4, and when the temperature measured by the hearth temperature measuring sensor 6 corresponding to each uniform temperature zone 5 reaches 900-950 ℃, finishing the first cooling and starting heat preservation in the first cooling process; after the heat preservation in the first cooling process is finished, starting to carry out second cooling of the vacuum chamber 4, and when the temperature measured by the hearth temperature measuring sensor 6 corresponding to each uniform temperature zone 5 reaches 600-700 ℃, finishing the second cooling and starting to carry out heat preservation in the second cooling process; and after the heat preservation of the second cooling process is finished, starting the third cooling of the vacuum chamber 4, and finishing the third cooling when the temperature measured by the hearth temperature measuring sensor 6 corresponding to each uniform temperature zone 5 reaches the room temperature.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, changes and equivalent structural changes made to the above embodiment according to the technical spirit of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. The utility model provides an austenitic stainless steel work piece chromizing is resistance furnace for nitrogenize which characterized in that: comprises a furnace body with an opening at the upper part and a vacuum chamber (4) which is used as a furnace pipe and arranged in the furnace body, a uniform temperature zone (5) is arranged in the furnace body, furnace temperature sensors (6) are arranged in the uniform temperature zone (5), the furnace body comprises a furnace shell (1), a heat preservation layer (2) and a heating body (3) from outside to inside in sequence, the upper end of the vacuum chamber (4) is provided with an opening, the upper end of the vacuum chamber extends out to the top of the furnace body, the opening at the upper end of the vacuum chamber (4) is provided with a sealing and heat-insulating mechanism, a water cooling mechanism is arranged on the outer side of one end of the vacuum chamber (4) extending to the top of the furnace body, the sealed heat insulation mechanism is provided with an air outlet pipe (7), an air inlet pipe (8), a temperature measuring pipe (9) and a pressure measuring pipe (10) for connecting a vacuum measuring device (17), and the chromizing air inlet component and the nitriding air inlet component are arranged in the vacuum chamber (4);

and a welding flange (14) is further arranged on the outer side of one end, extending out of the top of the furnace body, of the vacuum chamber (4), the welding flange (14) is positioned at the lower part of the water cooling mechanism, and the vacuum chamber (4) is fixed in the furnace body through the welding flange (14).

2. The electric resistance furnace for chromizing and nitriding an austenitic stainless steel workpiece according to claim 1, wherein: the sealing heat insulation mechanism comprises a heat insulation plug (11) arranged inside the upper end of the vacuum chamber (4) and a furnace cover (12) used for sealing the upper end opening of the vacuum chamber (4).

3. The electric resistance furnace for chromizing and nitriding an austenitic stainless steel workpiece according to claim 2, wherein: and a limiting edge for limiting the heat insulation plug (11) is arranged in the vacuum chamber (4), and the furnace cover (12) is connected with the vacuum chamber (4) through a flange.

4. The electric resistance furnace for chromizing and nitriding an austenitic stainless steel workpiece according to claim 2, wherein: the upper end of buret for temperature measurement (9) is located bell (12) top, the lower extreme of buret for temperature measurement (9) from top to bottom passes bell (12) and thermal-insulated stopper (11) back in proper order and stretches into to vacuum chamber (4) in, the upper end of outlet duct (7), intake pipe (8) and ressure measurement buret (10) all is located bell (12) top, the lower extreme of outlet duct (7), intake pipe (8) and ressure measurement buret (10) all passes behind bell (12) and lies in bell (12) and thermal-insulated stopper (11) between.

5. The electric resistance furnace for chromizing and nitriding an austenitic stainless steel workpiece according to claim 1, wherein: the water cooling mechanism is a cooling water circulating pipe (13) wound on the vacuum chamber (4) and extending out of one end of the furnace body.

6. The electric resistance furnace for chromizing and nitriding an austenitic stainless steel workpiece according to claim 1, wherein: the chromizing air inlet component is of an annular air inlet structure, the annular air inlet structure comprises an annular air inlet pipe (20-1) tightly attached to the bottom of a vacuum chamber (4) and arranged, the annular air inlet pipe (20-1) is communicated with an air inlet pipe (8) through a first L-shaped air guide pipe (20-2), the lower end of the first L-shaped air guide pipe (20-2) is connected to the upper portion of one side of the annular air inlet pipe (20-1), the upper end of the first L-shaped air guide pipe (20-2) is connected with the air inlet pipe (8), a plurality of air vent groups are formed in the annular air inlet pipe (20-1), and the first L-shaped air guide pipe (20-2) is tightly attached to the inner side wall of the vacuum chamber (4).

7. The electric resistance furnace for chromizing and nitriding an austenitic stainless steel workpiece according to claim 6, wherein: the nitriding air inlet component is of a uniform annular multilayer air inlet structure, the uniform annular multilayer air inlet structure comprises an annular multilayer air inlet pipeline (23-1) tightly attached to the bottom of a vacuum chamber (4) and arranged, the annular multilayer air inlet pipeline (23-1) is communicated with an air inlet pipe (8) through a second L-shaped air guide pipe (23-2), the lower end of the second L-shaped air guide pipe (23-2) is connected to the upper portion of one side of the annular multilayer air inlet pipeline (23-1), the upper end of the second L-shaped air guide pipe (23-2) is connected with the air inlet pipe (8), a plurality of vent hole groups are formed in the annular multilayer air inlet pipeline (23-1), and the second L-shaped air guide pipe (23-2) is tightly attached to the inner side wall of the vacuum chamber (4) and arranged.

8. A method for chromizing and nitriding an austenitic stainless steel workpiece using the electric resistance furnace according to claim 7, comprising a chromizing method and a nitriding method, said chromizing method comprising the steps of:

step one, hoisting a vacuum chamber: hoisting a vacuum chamber (4) in the furnace body through a hoisting tool, and placing the chromizing gas inlet component in the vacuum chamber (4);

step two, arranging a workpiece and chromizing powder in a vacuum chamber, placing the workpiece (16-1) to be chromized in the vacuum chamber (4) through an assembled workpiece frame, filling a gap between the assembled workpiece frame and the workpiece (16-1) to be chromized through the chromizing powder, and sequentially hoisting the assembled workpiece frame into the vacuum chamber (4) through a bottom frame body (15-1), a middle frame body (15-2), an upper frame body (15-3) and an upper cover (15-4), wherein the specific process is as follows:

step 201, hoisting a bottom layer frame body: hoisting a bottom layer frame body (15-1) to the bottom of a vacuum chamber (4) through a lifting appliance, wherein the bottom of the bottom layer frame body (15-1) is closely arranged on the upper end surface of an annular air inlet pipe (20-1), and chromizing powder with the depth of 100-300 mm is poured into the bottom of the bottom layer frame body (15-1);

step 202, hoisting of the workpiece: hoisting a workpiece (16-1) to be chromized into a bottom layer frame body (15-1) through a lifting appliance, and simultaneously pouring chromizing powder into the bottom layer frame body (15-1);

step 203, hoisting the middle-layer frame body: hoisting the middle layer frame body (15-2) into the vacuum chamber (4) through a hoisting tool, clamping the middle layer frame body (15-2) on the upper part of the bottom layer frame body (15-1), and pouring chromium infiltration powder into the middle layer frame body (15-2);

step 204, hoisting the upper layer frame body: hoisting the upper layer frame body (15-3) into the vacuum chamber (4) through a hoisting tool, clamping the upper layer frame body (15-3) on the upper part of the middle layer frame body (15-2), and pouring the upper layer frame body (15-3) with the chromium infiltration powder;

step 205, hoisting the upper cover: hoisting an upper cover (15-4) into the vacuum chamber (4) through a hoisting tool, clamping the upper cover (15-4) on an upper frame body (15-3), and sealing a gap between the upper frame body (15-3) and the upper cover (15-4) by adopting glass powder;

step three, sealing the vacuum chamber: the upper end opening of the vacuum chamber (4) is sealed through the sealing and heat insulating mechanism, the upper end of the first L-shaped air guide pipe (20-2) is connected with the air inlet pipe (8), the sealing and heat insulating mechanism comprises a heat insulating plug (11) arranged at the upper end opening of the vacuum chamber (4) and a furnace cover (12) used for sealing the upper end opening of the vacuum chamber (4), a limiting edge for limiting the heat insulating plug (11) is arranged in the vacuum chamber (4), and the furnace cover (12) is in flange connection with the vacuum chamber (4);

step four, mounting a sensor: a vacuum measuring device (17) is connected to the pressure measuring tube (10) to measure the vacuum degree in the vacuum chamber (4), a vacuum gauge, a pressure sensor (22) and an exhaust valve are connected to the air outlet tube (7) in parallel, a vacuum gauge is installed on the vacuum gauge to display the vacuum degree in the vacuum chamber (4), the vacuum measuring device (17) and the pressure sensor (22) are both connected with a controller (18), a vacuum chamber internal temperature measuring sensor (19) is installed in the vacuum chamber (4) through a temperature measuring tube (9), the vacuum chamber internal temperature measuring sensor (19) is connected with the controller (18), and the vacuum chamber internal temperature measuring sensor (19) is closely attached to the upper end face of the upper cover (15-4) and is arranged;

step five, vacuumizing the interior of the vacuum chamber: the air outlet pipe (7) is connected with a vacuum pump through a vacuum pipeline, and the vacuum chamber (4) is vacuumized to 10 degrees by the vacuum pump⁰Pa～10¹Pa；

Step six, heating the workpiece, wherein the process is as follows:

step 601, preheating of the workpiece: a plurality of uniform temperature areas (5) are uniformly heated and preheated through a heating body (3), and a hearth temperature measuring sensor (6) in each uniform temperature area (5) is connected with a controller (18);

step 602, introducing protective gas: when the temperature value measured by a hearth temperature measuring sensor (6) in one uniform temperature zone (5) reaches 200-300 ℃, introducing argon into the vacuum chamber (4) through an air inlet pipe (8), monitoring the vacuum degree in the vacuum chamber (4) through a vacuum measuring device (17), monitoring the air pressure in the vacuum chamber (4) through a pressure sensor (22) when the vacuum degree in the vacuum chamber (4) is zero, and stopping introducing the argon into the vacuum chamber (4) when the air pressure in the vacuum chamber (4) reaches the set air pressure of chromizing;

step 603, temperature rise of the workpiece: in the process of introducing argon, the heating body (3) is continuously heated, the temperature of a workpiece (16-1) to be chromized in the vacuum chamber (4) is gradually increased along with the continuous heating of the heating body (3), the air pressure in the vacuum chamber (4) is monitored through the pressure sensor (22) in the temperature rising process of the workpiece (16-1) to be chromized, and when the air pressure in the vacuum chamber (4) is greater than the set air pressure of chromizing, the air is automatically exhausted through the exhaust valve (24) to release the pressure to the set air pressure of chromizing;

step 604, judging whether the temperature of the workpiece reaches a set temperature: measuring the surface temperature of the upper-layer frame body (15-3) through a temperature measuring sensor (19) in the vacuum chamber, and stopping heating the vacuum chamber (4) by the heating body (3) when the surface temperature of the upper-layer frame body (15-3) reaches a set temperature; when the surface temperature of the upper layer rack body (15-3) does not reach the set temperature, continuing to execute step 503;

step seven, cooling the workpiece: lifting the vacuum chamber (4) provided with the workpiece (16-1) to be chromized out of the furnace body, naturally cooling to room temperature, completing chromizing of the workpiece (16-1) to be chromized and forming a chromized workpiece (16-2); in the process of naturally cooling the chromized workpiece (16-2) to room temperature, monitoring the air pressure in the vacuum chamber (4) through the pressure sensor (22), and introducing argon into the vacuum chamber (4) when the air pressure in the vacuum chamber (4) is less than the set chromized air pressure until the air pressure in the vacuum chamber (4) is equal to the set chromized air pressure;

the nitriding method comprises the following steps:

step S1, preparation: replacing a new vacuum chamber (4) in the furnace body through a lifting appliance, disassembling a sealing heat insulation mechanism on the vacuum chamber (4) after chromizing is finished, and taking out the chromized workpiece (16-2) from the vacuum chamber (4) after chromizing is finished;

step S2, hoisting the workpiece in the vacuum chamber: the chromized workpiece (16-2) is placed in a vacuum chamber (4) in a furnace body through a fabricated workpiece rack, and the specific process is as follows:

step S201, hoisting the bottom layer frame body, the middle layer frame body and the upper layer frame body: sequentially hoisting a bottom layer frame body (15-1), a middle layer frame body (15-2) and an upper layer frame body (15-3) into a vacuum chamber (4) through a hoisting tool, wherein the bottom of the bottom layer frame body (15-1) is provided with a plurality of air passing holes, and the bottom of the bottom layer frame body (15-1) is closely attached to the upper end face of an annular multilayer air inlet pipeline (23-1) to be distributed;

step S202, hoisting of the workpiece: after floating ash removal treatment is carried out on the surface of the chromized workpiece (16-2), the chromized workpiece (16-2) is hoisted into the bottom layer frame body (15-1) through a hoisting tool;

step S203, hoisting of the upper cover: the upper cover (15-4) is hoisted into the vacuum chamber (4) through a hoisting tool, and the upper cover (15-4) is clamped on the upper layer frame body (15-3);

step S3, closing of the vacuum chamber: the upper end opening of the vacuum chamber (4) provided with the chromized workpiece (16-2) is closed through the sealed heat insulation mechanism detached in the step S1, and the upper end of the second L-shaped air duct (23-2) is connected with the air inlet pipe (8);

step S4, replacement of gas inside the vacuum chamber: the air outlet pipe (7) is connected with a vacuum pump through a vacuum pipeline, and the vacuum chamber (4) is vacuumized to 10 degrees by the vacuum pump⁰Pa～10¹After Pa, introducing nitrogen into the vacuum chamber (4) through an air inlet pipe (8), monitoring the vacuum degree in the vacuum chamber (4) through a vacuum measuring device (17), monitoring the air pressure in the vacuum chamber (4) through a pressure sensor (22) when the vacuum degree in the vacuum chamber (4) is zero, and stopping introducing the nitrogen into the vacuum chamber (4) when the air pressure in the vacuum chamber (4) reaches a first set air pressure;

step S6, heating the workpiece, the process is as follows:

step S601, pressurization in the vacuum chamber: introducing nitrogen into the vacuum chamber (4) through the air inlet pipe (8), monitoring the air pressure in the vacuum chamber (4) by the pressure sensor (22), and stopping introducing the nitrogen into the vacuum chamber (4) when the air pressure in the vacuum chamber (4) reaches a second set air pressure;

step S602, heating of the workpiece: the temperature of a plurality of uniform temperature areas (5) is uniformly increased through a heating body (3), a hearth temperature measuring sensor (6) in each uniform temperature area (5) is connected with a controller (18), the temperature of a chromized workpiece (16-2) in a vacuum chamber (4) is gradually increased along with the continuous heating of the heating body (3), the air pressure in the vacuum chamber (4) is monitored through a pressure sensor (22) in the temperature increasing process of the chromized workpiece (16-2), and when the air pressure in the vacuum chamber (4) is greater than a second set air pressure, the air is automatically exhausted through an exhaust valve (24) to be released to the second set air pressure;

step S603, determining whether the temperature of the workpiece reaches a set temperature: measuring the surface temperature of the upper part of the bottom layer frame body (15-1) through a temperature measuring sensor (19) in the vacuum chamber, and stopping heating the vacuum chamber (4) by the heating body (3) when the surface temperature of the bottom layer frame body (15-1) reaches a set temperature; when the surface temperature of the bottom layer shelf body (15-1) does not reach the set temperature, continuing to execute the step 602;

step S7, cooling of the workpiece: lifting the vacuum chamber (4) provided with the chromized workpiece (16-2) out of the furnace body, and naturally cooling to room temperature to finish the nitridation process of the chromized workpiece (16-2); in the process of naturally cooling the chromized workpiece (16-2) to room temperature, monitoring the air pressure in the vacuum chamber (4) through the pressure sensor (22), and introducing nitrogen into the vacuum chamber (4) when the air pressure in the vacuum chamber (4) is less than a second set air pressure until the air pressure in the vacuum chamber (4) is equal to the second set air pressure.

9. The method of claim 8, wherein: in step 603, when the workpiece (16-1) to be chromized is heated, the heating process of the workpiece is divided into N heating stages and N heat preservation stages according to the size of the workpiece (16-1) to be chromized, wherein N is a positive integer and is more than or equal to 1 and less than or equal to 5;

seventhly, when the workpiece (16-1) to be chromized is cooled, dividing the cooling process of the workpiece into N natural cooling stages and N-1 heat preservation stages according to the size of the workpiece (16-1) to be chromized;

in the step S602, when the chromized workpiece (16-2) is heated and heated, the heating process of the workpiece is divided into N heating stages and N heat preservation stages according to the size of the chromized workpiece (16-2), wherein N is a positive integer and is more than or equal to 1 and less than or equal to 5;

in step S7, when cooling the chromized workpiece (16-2), the cooling process of the workpiece is divided into N natural cooling stages and N-1 heat preservation stages according to the size of the chromized workpiece (16-2).