A method for super-long shaft double-end secondary nitriding

Abstract

The application discloses a double-end secondary nitriding method for an ultralong shaft, and comprises the following steps: S01, pretreatment of the ultralong shaft; S02, single-end ultrasonic cleaning of the ultralong shaft; S03, single-end cleaning of the ultralong shaft; S04, mounting a lifting hook in a second lifting thread hole of the ultralong shaft; S05, baking the ultralong shaft; S06, single-end nitriding of the ultralong shaft; S07, single-end oxidation of the ultralong shaft; S08, cleaning of the ultralong shaft after oxidation; S09, cleaning of the surface oxide skin of the ultralong shaft; and S10, double-end nitriding of the ultralong shaft. The double-end secondary nitriding method for the ultralong shaft can be used for double-end separate nitriding of the ultralong shaft with a relatively long size, and surface treatment of the ultralong shaft is completed.

Description

Technical Field

[0001] This invention belongs to the field of metal surface treatment technology, and particularly relates to an ultra-long shaft double-head secondary nitriding method. Background Technology

[0002] Secondary nitriding is a surface treatment technology to improve the surface hardness and wear resistance of mold steel. Secondary nitriding requires the use of QPQ (Quench-Polish-Quench) technology, which includes cleaning (degreasing, derusting) - mounting - preheating - salt bath nitriding - salt bath oxidation - cleaning (desalting) - drying - polishing - mounting - preheating - oxidation - cleaning (desalting) - drying - oil immersion. This process requires some related equipment, such as nitriding furnaces and oxidation furnaces. Traditional processing methods involve completely immersing the workpiece to be treated in the nitriding liquid of the nitriding furnace and the oxidation liquid of the oxidation furnace.

[0003] The current maximum working size of commonly used nitriding furnaces is 1.6m in diameter and 1.8m in height. However, in actual production, it is necessary to surface treat some extra-long workpieces (longer than 1.8m). Conventional nitriding furnaces cannot process extra-long workpieces. If the furnace body is modified or customized, it will not only require redesign but also testing, which will incur huge costs. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned problems in the prior art and provide a dual-head secondary nitriding method for ultra-long shafts, which can perform dual-head separate nitriding on ultra-long shafts of relatively long dimensions to complete the surface treatment of ultra-long shafts.

[0005] To achieve the above-mentioned technical objectives and effects, the present invention is implemented through the following technical solution:

[0006] A method for dual-head secondary nitriding of ultra-long shafts, comprising the following steps:

[0007] S01: Take an extra-long shaft and open a first lifting threaded hole and a second lifting threaded hole at both ends of the extra-long shaft respectively;

[0008] S02: Use a crane to lift the extra-long shaft. Specifically, connect the crane's lifting hook threaded into the first lifting threaded hole, so that the end of the extra-long shaft with the second lifting threaded hole faces downwards. Clean the oil stains and rust on the outside of the extra-long shaft. After cleaning, immerse the lower part of the extra-long shaft in ultrasonic cleaning solution for ultrasonic cleaning.

[0009] S03: After ultrasonic cleaning, remove the extra-long shaft from the ultrasonic cleaning solution and rinse it repeatedly with clean water 2-3 times. After rinsing it clean, blow it dry and wrap it with steel foil near the middle of the extra-long shaft.

[0010] S04: Install a lifting hook in the second lifting threaded hole of the extra-long shaft;

[0011] S05: Place the extra-long shaft above the nitriding furnace for baking;

[0012] S06: Immerse the baked extra-long shaft into the nitriding liquid in the nitriding furnace for nitriding. The distance between the liquid level of the nitriding liquid in the nitriding furnace and the bottom of the steel foil on the extra-long shaft is 40-60mm.

[0013] S07: Quickly move the nitrided ultra-long shaft into the oxidation furnace for oxidation. The distance between the liquid level in the oxidation furnace and the bottom of the steel foil on the ultra-long shaft is 40-60mm.

[0014] S08: Move the extra-long shaft with one end oxidized into the clean water tank, remove the steel foil paper from the surface of the extra-long shaft, and clean the extra-long shaft;

[0015] S09: Clean the middle area of ​​the ultra-long shaft after cleaning in step S08, and remove the oxide scale from the middle area.

[0016] S10: Remove the cleaned ultra-long shaft from the crane in step S9, connect the lifting hook in the second lifting threaded hole to the crane, so that the end of the ultra-long shaft with the first lifting threaded hole is facing down, immerse the lower part of the ultra-long shaft in ultrasonic cleaning solution for ultrasonic cleaning, repeat steps S03-S09 to prepare the ultra-long shaft after secondary nitriding.

[0017] Furthermore, in step S02, the middle position of the ultra-long shaft is located below the surface of the ultrasonic cleaning fluid, and the distance between the middle position of the ultra-long shaft and the surface of the ultrasonic cleaning fluid is 100-200mm.

[0018] Furthermore, in step S02, the ultrasonic cleaning time is 3-5 minutes.

[0019] Furthermore, in step S03, steel foil is wrapped around the outer end of the extra-long shaft near the second lifting threaded hole, and the distance between the lower end of the steel foil and the middle position of the extra-long shaft is 100-200mm.

[0020] Furthermore, in step S05, the baking time is 40-50 minutes and the baking temperature is 180-220℃.

[0021] Furthermore, in step S05, the distance between the bottom of the extra-long shaft and the surface of the nitriding liquid in the nitriding furnace is 180-220 mm.

[0022] Furthermore, in step S06, the nitriding time is 8-10 hours and the nitriding temperature is 500-600℃.

[0023] Furthermore, in step S07, the oxidation time is 10-20 min and the oxidation temperature is 360-400℃.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] 1. This invention provides a method for dual-head secondary nitriding of ultra-long shafts. Through the design of this method, ultra-long shafts of relatively long dimensions can be nitrided separately at both ends to complete the surface treatment of ultra-long shafts, reducing the requirements for nitriding furnaces and reducing equipment investment costs.

[0026] 2. This invention effectively reduces the color difference in the middle region of the ultra-long shaft during the double-head nitriding process by wrapping steel foil at a specific position in the middle region of the ultra-long shaft. Attached Figure Description

[0027] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0028] Figure 1 This is a flowchart of the ultra-long shaft double-head secondary nitriding method provided by the present invention;

[0029] Figure 2 This is a schematic diagram of the structure of the ultra-long shaft double-head secondary nitriding equipment provided by the present invention.

[0030] The attached diagram is labeled as follows: 1. Extra-long shaft; 2. Crane; 3. Lifting hook; 4. Nitriding furnace; 5. Steel foil. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] like Figure 1 As shown, an ultra-long shaft dual-head secondary nitriding method includes the following steps:

[0033] S01: Pre-processing for extra-long shafts

[0034] Take an extra-long shaft, measure its length, and mark the measurement result as L. Make a first lifting threaded hole and a second lifting threaded hole at both ends of the extra-long shaft.

[0035] S02: Ultra-long shaft single-head ultrasonic cleaning

[0036] Use a crane to lift the extra-long shaft. Specifically, connect the crane's lifting hook threaded into the first lifting threaded hole, so that the end of the extra-long shaft with the second lifting threaded hole is facing down. Clean the oil stains and rust on the outside of the extra-long shaft. After cleaning, immerse the lower part of the extra-long shaft in ultrasonic cleaning solution for ultrasonic cleaning. The ultrasonic cleaning time is 3-5 minutes.

[0037] In this step, the middle position of the extra-long shaft is below the surface of the ultrasonic cleaning fluid, and the distance between the middle position of the extra-long shaft and the surface of the ultrasonic cleaning fluid is 100-200mm.

[0038] The workpieces are cleaned before entering the furnace to remove grease and deposits from their surfaces;

[0039] S03: Extra-long shaft single-head cleaning

[0040] After ultrasonic cleaning, rinse the extra-long shaft repeatedly with clean water 2-3 times. After rinsing, blow dry the water and wrap steel foil around the outside of the extra-long shaft near the middle position.

[0041] In this step, in step S03, the steel foil is wrapped around the outside of the extra-long shaft near the middle position of the extra-long shaft. That is, when the extra-long shaft is in the lifting state and the end of the extra-long shaft with the second lifting threaded hole is facing down, the distance between the lower end of the steel foil on the extra-long shaft and the middle position of the extra-long shaft is 100-200mm.

[0042] The purpose of wrapping with steel foil is to protect the end of the ultra-long shaft that is close to the nitriding liquid surface and the end that is close to the oxidation liquid surface during subsequent nitriding and oxidation treatments, so as to prevent discoloration of this section under high temperature baking and affect the overall surface treatment effect of the ultra-long shaft.

[0043] S04: Install a lifting hook in the second lifting threaded hole of the extra-long shaft;

[0044] The purpose of installing a lifting hook in the second lifting threaded hole of the extra-long shaft is to protect the second lifting threaded hole and pre-install the lifting hook, so as to prevent nitride salt from entering the second lifting threaded hole during nitriding, which would cause the lifting hook to fail to be installed later.

[0045] S05: Place the extra-long shaft above the nitriding furnace for baking;

[0046] The baking time is 40-50 minutes, and the baking temperature is 180-220℃.

[0047] In step S05, the distance between the bottom of the ultra-long shaft and the surface of the nitriding liquid in the nitriding furnace is 180-220 mm;

[0048] Baking the extra-long shaft serves two purposes: first, it dries the surface moisture of the workpiece, preventing it from entering the nitriding furnace with water and causing a hazard; second, it prevents cold workpieces from directly entering the nitriding furnace, which would lower the furnace temperature too much, and also reduces workpiece deformation.

[0049] S06: Immerse the baked extra-long shaft into the nitriding liquid in the nitriding furnace for nitriding. The distance between the liquid level of the nitriding liquid and the bottom of the steel foil on the extra-long shaft is 40-60mm.

[0050] The nitriding time is 8-10 hours, and the nitriding temperature is 500-600℃.

[0051] S07: Quickly move the nitrided ultra-long shaft into the oxidation furnace for oxidation. The distance between the liquid level in the oxidation furnace and the bottom of the steel foil on the ultra-long shaft is 40-60mm.

[0052] The oxidation time is 10-20 min, and the oxidation temperature is 360-400℃.

[0053] S08: Move the extra-long shaft with one end oxidized into the clean water tank, remove the steel foil paper from the surface of the extra-long shaft, and clean the extra-long shaft;

[0054] S09: Clean the middle area of ​​the ultra-long shaft after cleaning in step S08, and remove the oxide scale from the middle area, that is, remove the oxide scale from the outside of the connection end of the unnitrided part and the nitrided part. Due to the influence of actual production, the temperature of the connection end is not stable enough compared with other parts when nitriding. After cleaning and nitriding treatment of the other end of the ultra-long shaft in step S10, the surface treatment effect of the connection end is guaranteed to be uniform with the treatment effect of both ends of the ultra-long shaft.

[0055] S10: Remove the cleaned ultra-long shaft from the crane in step S9, connect the lifting hook in the second lifting threaded hole to the crane, so that the end of the ultra-long shaft with the first lifting threaded hole is facing down, immerse the lower part of the ultra-long shaft in ultrasonic cleaning solution for ultrasonic cleaning, repeat steps S03-S09 to prepare the ultra-long shaft after secondary nitriding.

[0056] This invention provides a dual-head secondary nitriding method for ultra-long shafts, which is used for surface treatment of long workpieces. It is low-cost and the performance parameters of the treated workpieces meet the requirements of actual production processes. The method provided in this embodiment offers ideas and directions for nitriding other types of ultra-long parts.

[0057] The following section will further explain the double-head secondary nitriding method for ultra-long shafts by taking the double-head nitriding treatment in actual production as an example:

[0058] like Figure 2 As shown, the method for double-head secondary nitriding of an ultra-long shaft with a length of 2.8m includes the following steps:

[0059] S01: Pre-processing for extra-long shafts

[0060] Take an extra-long shaft 1 with a length of 2.8m, and open the first lifting threaded hole and the second lifting threaded hole at both ends of the extra-long shaft 1 respectively;

[0061] S02: Ultra-long shaft single-head ultrasonic cleaning

[0062] Use crane 2 to lift the extra-long shaft 1. Specifically, connect the lifting hook 3 of crane 2 to the first lifting threaded hole, so that the end of the extra-long shaft 1 with the second lifting threaded hole is facing down. Clean the oil stains and rust on the outside of the extra-long shaft. After cleaning, immerse the lower part of the extra-long shaft 1 in ultrasonic cleaning solution for ultrasonic cleaning. The ultrasonic cleaning time is 3-5 minutes.

[0063] In this step, the middle position of the extra-long shaft 1 is below the surface of the ultrasonic cleaning fluid. The distance between the middle position of the extra-long shaft 1 and the surface of the ultrasonic cleaning fluid is 100-200mm. That is, when the extra-long shaft 1 is vertically suspended, the lower 1.5-1.6m length of the extra-long shaft 1 is immersed in the ultrasonic cleaning fluid.

[0064] The ultrasonic cleaning fluid uses QPQ's proprietary water-based cleaning agent.

[0065] The extra-long shaft 1 is cleaned before entering the furnace to remove grease and deposits from the surface of the workpiece;

[0066] S03: Rinse the extra-long shaft

[0067] After ultrasonic cleaning, rinse the extra-long shaft 1 repeatedly with clean water 3 times. After rinsing, blow dry the water and wrap steel foil 5 around the outside of the extra-long shaft 1 near the second lifting threaded hole.

[0068] In this step, the steel foil 5 is wrapped around the outside of the extra-long shaft 1 at one end near the second lifting threaded hole. The distance between the end of the steel foil 5 away from the second lifting threaded hole and the middle position of the extra-long shaft 1 is 100mm. That is, when the extra-long shaft 1 is in a vertically lifted state, the steel foil 5 is wrapped 100mm above the middle position of the extra-long shaft 1.

[0069] The purpose of covering the steel foil paper 5 is to protect the end of the ultra-long shaft 1 that is close to the nitriding liquid surface and the end that is close to the oxidation liquid surface during the subsequent nitriding and oxidation treatments, so as to prevent discoloration of this section under high temperature baking and affect the overall surface treatment effect of the ultra-long shaft 1.

[0070] S04: Install a lifting hook in the second lifting threaded hole of the extra-long shaft;

[0071] The purpose of installing the lifting hook 3 in the second lifting threaded hole of the extra-long shaft 1 is to protect the second lifting threaded hole and pre-install the lifting hook 3, so as to prevent the nitride salt from entering the second lifting threaded hole during nitriding, which would cause the lifting hook 3 to fail to be installed later.

[0072] S05: Place the extra-long shaft above nitriding furnace 4 for baking;

[0073] The baking time is 45 minutes and the baking temperature is 200℃.

[0074] In step S05, the distance between the bottom of the extra-long shaft 1 and the surface of the nitriding liquid in the nitriding furnace 4 is 200mm;

[0075] Baking the extra-long shaft 1 serves two purposes: first, to dry the moisture on the surface of the workpiece and prevent it from entering the nitriding furnace 4 with water, which could cause danger; second, to prevent the cold workpiece from directly entering the nitriding furnace 4 and causing the furnace temperature to drop too much, while also reducing workpiece deformation.

[0076] S06: Immerse the baked extra-long shaft 1 into the nitriding liquid in the nitriding furnace 4 for nitriding. The distance between the liquid surface of the nitriding liquid and the bottom of the steel foil 5 on the extra-long shaft 1 is 40-60mm. Ensure that the steel foil 5 on the extra-long shaft 1 does not contact the liquid surface of the nitriding liquid in the nitriding furnace 4, that is, ensure that there is a certain distance between the steel foil 5 on the extra-long shaft 1 and the liquid surface of the nitriding liquid in the nitriding furnace 4.

[0077] The nitriding time was 8 hours and the nitriding temperature was 550℃.

[0078] S07: Quickly move the nitrided ultra-long shaft 1 into the oxidation furnace for oxidation. The distance between the liquid surface in the oxidation furnace and the bottom of the steel foil 5 on the ultra-long shaft 1 is 40-60mm. Similar to the nitriding steps of the ultra-long shaft 1, ensure that the steel foil 5 on the ultra-long shaft 1 does not contact the liquid surface in the oxidation furnace, that is, ensure that there is a certain distance between the steel foil 5 on the ultra-long shaft 1 and the liquid surface in the oxidation furnace.

[0079] The oxidation time was 15 minutes and the oxidation temperature was 380℃.

[0080] S08: Move the ultra-long shaft 1, which has been oxidized at one end, into the clean water tank, remove the steel foil paper 5 from the surface of the ultra-long shaft 1, and clean the ultra-long shaft 1.

[0081] S09: Clean the middle area of ​​the ultra-long shaft 1 after cleaning in step S08, and clean the oxide scale in the middle area.

[0082] S10: Remove the cleaned ultra-long shaft 1 from the crane 2 in step S9, connect the lifting hook 3 in the second lifting threaded hole to the crane 2, so that the end of the ultra-long shaft 1 with the first lifting threaded hole faces down, immerse the lower part of the ultra-long shaft 1 in ultrasonic cleaning solution for ultrasonic cleaning, repeat steps S03-S09 to prepare the ultra-long shaft 1 after secondary nitriding;

[0083] S11: Performance Testing of Ultra-Long Shafts After Secondary Nitriding

[0084] Among them, a white bright layer with a thickness of 6-12μm is formed on the surface of the ultra-long shaft 1 after secondary nitriding through steps S01-S10;

[0085] The total diffusion depth of the ultra-long shaft 1 surface after secondary nitriding is 130-170 μm;

[0086] The hardened layer thickness of the ultra-long shaft 1 after secondary nitriding is 20 mm;

[0087] The ultra-long shaft 1 after secondary nitriding was divided into three equal segments along its height: the upper segment, the middle segment, and the lower segment. The upper, middle, and lower segments of the ultra-long shaft 1 after secondary nitriding were tested respectively, and the test results are shown in Table 1.

[0088] Table 1

[0089] data upper section middle section Lower section Whitening layer hardness HV 816 820 817 Hardness of hardened layer HRC 36.2 37 36.4

[0090] Data from destructive testing shows that the performance parameters of the ultra-long shaft 1 treated by the dual-head secondary nitriding method provided by this invention meet the requirements of actual production. This indicates that the dual-head secondary nitriding method for ultra-long shafts provided by this invention has important reference value for dual-head surface treatment of ultra-long shafts 1, provides a basis for dual-head treatment of ultra-long shafts 1, and is conducive to the promotion and use of the dual-head secondary nitriding method for ultra-long shafts, reducing equipment investment, lowering production costs, and increasing enterprise profits.

[0091] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0092] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for dual-head secondary nitriding of ultra-long shafts, characterized in that, The method includes the following steps: S01: Pre-processing for extra-long shafts Take an extra-long shaft and open a first lifting threaded hole and a second lifting threaded hole at both ends of the extra-long shaft, respectively; S02: Ultra-long shaft single-head ultrasonic cleaning Connect the crane's lifting hook threaded into the first lifting threaded hole, use the crane to lift the extra-long shaft, so that the end of the extra-long shaft with the second lifting threaded hole is facing down, clean the oil stains and rust on the outside of the extra-long shaft, and after cleaning, immerse the lower part of the extra-long shaft in ultrasonic cleaning solution for ultrasonic cleaning. S03: Extra-long shaft single-head cleaning After ultrasonic cleaning, rinse the extra-long shaft repeatedly with clean water 2-3 times. After rinsing, blow dry the water and wrap steel foil around the outside of the extra-long shaft near the middle position. S04: Install a lifting hook in the second lifting threaded hole of the extra-long shaft; S05: Baking Extra Long Shaft The extra-long shaft is placed above the nitriding furnace for baking; S06: Ultra-long shaft single-head nitriding The baked extra-long shaft is immersed in the nitriding liquid in the nitriding furnace for nitriding. The distance between the liquid level of the nitriding liquid in the nitriding furnace and the bottom of the steel foil on the extra-long shaft is 40-60mm. S07: Extra-long shaft single-head anodizing The ultra-long shaft with one end nitrided is quickly moved into the oxidation furnace for oxidation. The distance between the liquid level in the oxidation furnace and the bottom of the steel foil on the ultra-long shaft is 40-60mm. S08: Cleaning the oxidized extra-long shaft The extra-long shaft with one end oxidized was moved into a clean water tank, the steel foil on the surface of the extra-long shaft was removed, and the extra-long shaft was cleaned. S09: Clean the oxide scale from the surface of the extra-long shaft The middle area of ​​the ultra-long shaft after cleaning in step S08 is cleaned to remove the oxide scale from the middle area. S10: Dual-head Nitrided Ultra-long Shaft Remove the cleaned ultra-long shaft from the crane in step S9, connect the lifting hook in the second lifting threaded hole to the crane, so that the end of the ultra-long shaft with the first lifting threaded hole is facing down, immerse the lower part of the ultra-long shaft in ultrasonic cleaning solution for ultrasonic cleaning, repeat steps S03-S09 to prepare the ultra-long shaft after secondary nitriding. In step S03, the distance between the lower end of the steel foil and the middle position of the extra-long shaft is 100-200mm; In step S05, the baking time is 40-50 minutes and the baking temperature is 180-220℃. In step S05, the distance between the bottom of the extra-long shaft and the surface of the nitriding liquid in the nitriding furnace is 180-220mm.

2. The ultra-long shaft double-head secondary nitriding method according to claim 1, characterized in that: In step S02, the middle position of the ultra-long shaft is located below the surface of the ultrasonic cleaning fluid, and the distance between the middle position of the ultra-long shaft and the surface of the ultrasonic cleaning fluid is 100-200mm.

3. The ultra-long shaft double-head secondary nitriding method according to claim 1, characterized in that: In step S02, the ultrasonic cleaning time is 3-5 minutes.

4. The ultra-long shaft double-head secondary nitriding method according to claim 1, characterized in that: In step S06, the nitriding time is 8-10 hours and the nitriding temperature is 500-600℃.

5. The method for dual-head secondary nitriding of ultra-long shafts according to claim 1, characterized in that: In step S07, the oxidation time is 10-20 min and the oxidation temperature is 360-400℃.

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