CN116987850A - Method and device for reducing surface decarburization of forging - Google Patents
Method and device for reducing surface decarburization of forging Download PDFInfo
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- CN116987850A CN116987850A CN202310929224.XA CN202310929224A CN116987850A CN 116987850 A CN116987850 A CN 116987850A CN 202310929224 A CN202310929224 A CN 202310929224A CN 116987850 A CN116987850 A CN 116987850A
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- 238000005242 forging Methods 0.000 title claims abstract description 74
- 238000005261 decarburization Methods 0.000 title claims abstract description 61
- 238000000034 method Methods 0.000 title claims abstract description 60
- 230000006698 induction Effects 0.000 claims abstract description 91
- 238000010438 heat treatment Methods 0.000 claims abstract description 69
- 230000008569 process Effects 0.000 claims abstract description 20
- 238000004519 manufacturing process Methods 0.000 claims abstract description 10
- 230000000630 rising effect Effects 0.000 claims abstract description 8
- 230000003111 delayed effect Effects 0.000 claims abstract description 3
- 238000005192 partition Methods 0.000 claims description 30
- 238000013461 design Methods 0.000 claims description 14
- 230000006835 compression Effects 0.000 claims description 5
- 238000007906 compression Methods 0.000 claims description 5
- 230000001276 controlling effect Effects 0.000 claims description 5
- 230000002500 effect on skin Effects 0.000 claims description 5
- 230000000694 effects Effects 0.000 claims description 5
- 230000001105 regulatory effect Effects 0.000 claims description 5
- 239000003990 capacitor Substances 0.000 claims description 3
- 238000005520 cutting process Methods 0.000 claims description 3
- 239000000463 material Substances 0.000 claims description 3
- 238000005262 decarbonization Methods 0.000 claims 1
- 239000011261 inert gas Substances 0.000 abstract description 12
- 229910000831 Steel Inorganic materials 0.000 abstract description 8
- 239000010959 steel Substances 0.000 abstract description 8
- 239000003973 paint Substances 0.000 abstract description 4
- 239000010410 layer Substances 0.000 description 26
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 14
- 239000011248 coating agent Substances 0.000 description 8
- 238000000576 coating method Methods 0.000 description 8
- 230000004048 modification Effects 0.000 description 7
- 238000012986 modification Methods 0.000 description 7
- 229910052757 nitrogen Inorganic materials 0.000 description 7
- 230000005540 biological transmission Effects 0.000 description 6
- 238000002791 soaking Methods 0.000 description 6
- 238000007254 oxidation reaction Methods 0.000 description 5
- 230000009471 action Effects 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 238000005422 blasting Methods 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 238000007689 inspection Methods 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 238000011049 filling Methods 0.000 description 2
- 230000003137 locomotive effect Effects 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000005554 pickling Methods 0.000 description 2
- 238000010080 roll forging Methods 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000010301 surface-oxidation reaction Methods 0.000 description 2
- 238000009966 trimming Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
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- 239000007769 metal material Substances 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 238000009740 moulding (composite fabrication) Methods 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000004080 punching Methods 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/34—Methods of heating
- C21D1/42—Induction heating
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
- B21J1/00—Preparing metal stock or similar ancillary operations prior, during or post forging, e.g. heating or cooling
- B21J1/06—Heating or cooling methods or arrangements specially adapted for performing forging or pressing operations
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D11/00—Process control or regulation for heat treatments
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Forging (AREA)
Abstract
The application relates to a method and a device for reducing surface decarburization of a forging piece; by controlling the surface temperature rise of the blank, the surface temperature rise speed of the blank is delayed in the initial heating stage so as to reduce surface decarburization; adjusting the power of each part of the inductor in the induction furnace, controlling and designing the surface temperature rising speed of the blank in the inductor through an induction heating furnace temperature rising curve, keeping the surface temperature of the blank in the inductor within a period of about 1/4 to 3/8 of the whole heating period at the initial stage of entering the induction furnace, forming a low-temperature oxide skin protection layer on the surface of a forging piece, gradually rising the temperature, and enabling the surface temperature to reach about 1230 ℃ required by the process at the final stage; the application saves a great deal of cost for purchasing inert gas or paint; the surface decarburization problem of the quenched and tempered steel forging is solved at one time, the automatic operation of the whole forging production line is ensured, and the cost of purchasing a large amount of inert gas and paint is saved.
Description
Technical Field
The application belongs to the technical field of forging processing, and relates to a method and a device for reducing surface decarburization of a forging.
Background
The quenched and tempered steel crankshaft is very easy to generate surface decarburization phenomenon in the forging heating and forming processes. The forging production process needs links such as blank heating, forging forming, trimming, heat treatment, subsequent surface shot blasting treatment and the like. In the induction heating stage of the blank, the forging forming stage and the heat treatment stage, the surface of the blank or the forging is in a high-temperature state, and the surface of the forging can be continuously subjected to oxidation reaction with oxygen in the air, so that carbon elements on the surface layer of the forging and the oxygen in the air are subjected to oxidation reaction, and a decarburized layer on the surface part is gradually deepened. The forging with higher requirements for the surface decarburized layer can cause the technical index to be unsatisfied. In order to realize automation, the forging blank is heated by an intermediate frequency power supply induction heating method in recent years at home and abroad, the surface decarburization is not required or not required by various manufacturers in the previous years, and when the forging is heated by the intermediate frequency power supply induction heating, indexes such as core surface temperature difference of the blank, head-tail temperature difference of the blank, heating beat, heating efficiency and the like are often focused, so that a high-power rapid heating method is often used in the initial stage of heating the blank, as much energy as possible is input to the blank as soon as possible, and due to the skin effect of induction heating, current is concentrated on the outer surface of the blank, so that the outer surface is always near the target temperature in the whole heating process, and the surface serious decarburization is caused although the heat conduction efficiency is improved. In an automobile engine, if the surface decarburized layers of a crankshaft and a connecting rod are too thick, stress concentration occurs at corresponding positions, and metal fatigue at the positions is caused by long-term operation, so that the crankshaft and the connecting rod are broken firstly, and the service life of the whole engine is influenced.
The forging and forming and subsequent processes of the crankshaft forging product are as follows: … … blank induction heating stage, forging forming stage, heat treatment stage, surface shot blasting stage, flaw detection … …, wherein the surface temperature of the blank is increased from room temperature to about 1200-1260 ℃ in the induction heating stage; in the forging stage, the surface temperature is gradually reduced from 1260 ℃ to below 900 ℃; in the heat treatment stage, the temperature is up to 890 ℃. In the three stages, the surface decarburization condition is gradually deepened due to the fact that the surface of the blank or the forging is in a high-temperature state, and the practice proves that the decarburization caused in the heat treatment stage is lighter, and the surface decarburization of the rest part below is lightened because the surface of the forging is also taken away by the fallen oxide skin although the oxide skin is generated by the combustion of natural gas and oxygen at the relatively lower temperature. In the forging forming stage of the second stage, the whole process is in the open stage, and the increase of surface decarburization is unavoidable. So in order to reduce surface decarburization, the best strategy is to take measures during the induction heating phase of the blank in the first phase. The prior art has two methods for reducing surface decarburization, one is a method for adding a surface coating to a blank or a forging, and the method has higher cost and is not suitable for mass production occasions; another method is to charge inert gas such as nitrogen or alcohol into the hearth of the induction furnace in the induction heating stage to reduce the oxidation speed of the surface of the blank, as shown in fig. 1.
The method for filling inert gas into the hearth is suitable for the conditions of smaller forging, smaller induction furnace power and better sealing of the two ends of the hearth. In order to ensure the production beat, the high-power induction furnace consists of a plurality of sections of inductors, and in order to ensure the transmission of blanks, a plurality of press rolls are arranged in the middle of the inductors, so that the whole inductor is in a relative semi-open state, and the inflation method for isolating the forge piece from being contacted with air is difficult to achieve the expected effect.
Patent document CN114196809a discloses a method for reducing the heating decarburization of a billet, which is carried out according to the following steps: 1) A set of nitrogen pipeline is designed and arranged, nitrogen is introduced into a gas burner of a soaking section of the heating furnace, so that the nitrogen is uniformly arranged in the soaking section, and a set of exhaust type smoke analyzer 2 is newly added in the soaking section; 2) A pipeline main valve, a pressure reducing valve and a pneumatic regulating valve are arranged on the newly added nitrogen pipeline; 3) Newly adding a nitrogen nozzle at the side of the gas burner of the soaking section to ensure that nitrogen uniformly enters a hearth of the soaking section; 4) Optimizing the soaking section temperature of the heating furnace and the heating process system of the atmosphere in the furnace in the rolling stop state. The internal atmosphere of the heating furnace can be forcedly regulated, and the thickness of surface decarburization during billet heating can be effectively reduced by combining reasonable heating parameter control, so that the overall performance of steel is improved.
The above patent documents have a low degree of correlation as compared with the present application, which reduces decarburization by an inert gas.
Patent document CN113444864a discloses a control process for surface decarburization of a hollow transmission shaft tube of an automobile and the hollow transmission shaft tube, comprising the following steps: heating a tube blank, rolling the tube, pickling, drying, performing controlled atmosphere heat treatment, cold working, finishing, checking and warehousing; the pickling is to clean oxide skin and lubricant on the inner surface of the steel pipe; the drying is to clean H2O on the inner surface of the steel pipe; the controllable atmosphere heat treatment adopts a controllable atmosphere heat treatment furnace, the concentration of CO in the furnace is controlled to be 5%, the concentration of CO2 is 0.16%, and the concentration ratio Kp1 of CO and CO2 is more than 30; the H2 concentration in the furnace is controlled to be 11%, the H2O concentration is 0.4%, and the concentration ratio Kp2 of H2 to H2O is more than 27. The application can effectively control the generation of decarburization on the surface of the steel pipe, the decarburization depth is controlled to be 0-0.07 mm, and the torsion fatigue performance of the transmission shaft is improved
More than or equal to 30 ten thousand times, and meets the design requirement of the transmission shaft.
The above patent documents have a low degree of correlation as compared with the present application, which is controlled by the atmosphere in the furnace.
Patent document CN104057263a discloses a large locomotive connecting rod forging process, comprising the following steps: blanking, turning, coating an anti-decarburization coating, heating a blank, removing a surface oxidation layer, forging a blank by roll forging, pre-forging, final forging, trimming, punching and correcting, coating the anti-decarburization coating and performing heat treatment; according to the large locomotive connecting rod forging process, only one-time heating forming is needed, compared with two or more times of heating, the surface oxidation and decarburization of the connecting rod are effectively reduced, the mechanical properties of the connecting rod are ensured, and meanwhile, the working time and energy are saved; the roll forging blank is adopted, so that the speed and the labor are saved, the blank making consistency effect is good, and the later forging time and the labor are saved; the high-temperature-resistant, oxidation-resistant and decarburization-resistant coating is coated twice in the whole process, so that the surface decarburization layer of the final forging is smaller than 0.3mm, and the quality of the product is effectively improved; during heat treatment, the connecting rod forging is vertically hoisted for heat treatment, so that bending deformation in the heat treatment process is effectively prevented.
The patent documents have a low degree of correlation as compared with the present application, which is to apply a high temperature resistant, oxidation resistant, decarburization resistant coating to prevent decarburization.
Disclosure of Invention
The application aims to solve the technical problems in the prior art and provides a method and a device for reducing the surface decarburization of a forging.
According to the method for reducing the surface decarburization of the forging by controlling the temperature rise speed of the blank, the surface decarburization of the forging is reduced, simplicity and convenience are realized, after the inductor is designed according to the method provided by the application, the blank can be heated at a frequency not higher than the design beat, and even though the subsequent forging and heat treatment stages are performed, the surface shot blasting treatment is performed, and the level that the thickness of the decarburization layer on the surface of the forging is less than or equal to 0.1mm can be basically ensured.
It is noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
In order to solve the technical problems, the application is realized by adopting the following technical scheme:
a method for reducing decarburization on the surface of a forging, which is characterized by comprising the following steps:
by controlling the surface temperature rise of the blank, the surface temperature rise speed of the blank is delayed in the initial heating stage so as to reduce surface decarburization.
Further, the power of each part of the inductor in the induction furnace is regulated, the temperature rising speed of the blank surface in the inductor is controlled and designed through the temperature rising curve of the induction heating furnace, the temperature of the blank surface is raised and kept at about 700-900 ℃ in the inductor in a period of about 1/4 to 3/8 of the whole heating period at the initial stage of entering the induction furnace, a low-temperature oxide skin protection layer is formed on the surface of a forging, then the temperature is gradually raised, and the surface temperature reaches about 1230 ℃ required by the process at the final stage.
Further, the induction furnaces are divided into an integrated induction furnace and a split induction furnace which can be controlled in a partition mode.
Integrated induction furnace: the whole induction furnace is controlled by a single power supply, after one-time design, manufacture and molding, the proportion of the power of each part of the inductor from front to back is fixed, and the power and the frequency of all the inductors can be simultaneously regulated only through a unique power supply.
The split type inductors controlled by the partition are respectively controlled by independent power supplies from front to back, so that the power and the frequency of each inductor can be respectively adjusted.
The integrated induction furnace designs each section of inductor coil according to a blank surface temperature rise curve;
the split induction furnace controlled by the partition directly adjusts the power of each partition according to the surface temperature rise curve of the blank;
under the condition of constant total power, the input power of the first part of inductors is reduced, the power of the subsequent inductors is properly increased, and under the condition of meeting the temperature difference of the core surface of the final discharge port, the surface temperature of the initial stage is kept below 900 ℃ for as long as possible.
Further, the oxide scale formed at the surface temperature of 700 to 900 ℃ in the initial stage can protect the deepening of the internal decarburized layer.
A method of reducing decarburization of a forging surface comprising the steps of:
step 1, determining a blank temperature rise curve;
setting a target temperature rise curve, wherein the surface temperature in the inductor with the length of the first 1/4 is increased to be close to 900 ℃, and the surface temperature in the inductor with the length of the first 3/8-1/2 is not higher than 1000 ℃;
step 2, distributing power of each section of inductor according to a set temperature rise curve, and calculating the number of turns of coils of each section of inductor;
step 3, simulating the surface and core temperature of the blank heating process according to experience or iHaz software, and if the core surface temperature difference of the final outlet blank meets the design requirement and the surface temperature is close to an ideal surface temperature rise curve, starting to manufacture the inductor; if the surface temperature does not meet the requirement, repeating the steps 1-2 until the surface temperature meets the requirement; the newly manufactured inductor is used for actually heating the forging, the surface temperature of each stage in the heating process is measured, and compared with an ideal surface temperature rise curve, the surface temperature rise curve is used for verifying the design effect;
the iHaz software is development software applied to induction heating, which is developed by an induction heating group in the United states, and can simulate and calculate continuously-changed core, surface and average temperature curves in the whole induction furnace according to preset power, frequency, beat and power and turns of each inductor of a setter according to metal materials of blanks with different diameters.
And 4, cutting the actual sample forging, taking a metallographic photograph of a surface decarburized layer of a process required point, and observing whether the surface decarburized layer meets the requirement of the thickness dimension of the decarburized layer.
A method of reducing decarburization of a forging surface, further comprising:
for the integrated induction furnace, the cooperation between the total inductance of the inductor and the compensation capacitor should be paid attention to when the inductor is designed, so that the resonance frequency of the induction furnace is ensured to meet the requirement of the heating thickness caused by the skin effect and to be suitable for reality;
for a split induction furnace capable of being controlled in a partitioned mode, the steps 1-2 can be simplified as follows: and adjusting the power and frequency settings of all the partition control power supplies from front to back according to the ideal temperature rise curve, and finally enabling the surface temperature of the actual blank to be close to the ideal temperature rise curve. The number of turns of each partition does not have to be changed.
Preferably, the blank material is 42CrMoHA.
A device for reducing decarburization on the surface of a forging piece comprises an induction furnace;
the induction furnaces are divided into an integrated induction furnace and a partition-controlled induction furnace;
the integrated induction furnace comprises: each section of the inductor of the whole induction furnace is controlled by a single power supply.
The split induction furnace controlled by the subareas comprises a plurality of subareas, each subarea comprises one or more sections of inductors, and each subarea is controlled by a power supply which is independent.
Preferably, the sensor is provided with eight sections.
The device for reducing the decarburization on the surface of the forging piece further comprises a compression roller;
the three press rollers are respectively a first press roller, a second press roller and a third press roller.
Compared with the prior art, the application has the beneficial effects that:
the application relates to a method for reducing the surface decarburization of a forging by controlling the surface temperature rise of a blank, which is characterized in that the method is different from the prior method for filling inert gas into a hearth of an inductor and smearing a decarburization preventing coating, and has the following maximum characteristics:
1. saving a lot of cost for purchasing inert gas or paint.
2. For a high-power semi-closed inductor with multiple pressing rollers in the middle, the problem of decarburization on the surface of the quenched and tempered steel forging is solved at one time by redesigning the inductor according to the method, so that the automatic operation of the whole forging production line is ensured, and the cost for purchasing a large amount of inert gas and paint can be saved.
3. For the induction furnace which can be controlled in a partition mode, the aim of reducing surface decarburization can be achieved by directly adjusting the power and the frequency of each partition according to the method provided by the application.
Drawings
In order to more clearly illustrate the embodiments of the application or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a prior art method for reducing surface decarburization of a billet by charging an inert gas into a furnace of an inductor;
FIG. 2 is a version of an induction heating furnace modified in accordance with an example of the present application, with two intermediate rolls in between;
FIG. 3 shows a blank temperature rise curve of the original sensor before improvement, wherein the measured value is the same as the simulation value;
FIG. 4 is a metallographic view of a decarburized layer thickness of 0.3mm detected at a prescribed inspection position of a sample 1 before modification;
FIG. 5 is a metallographic view of a decarburized layer thickness of 0.23mm detected at a prescribed inspection position of a sample piece 2 before modification;
FIG. 6 is a metallographic view of a decarburized layer thickness of 0.18mm detected at a prescribed inspection position of a sample 3 before modification;
FIG. 7 is a schematic diagram of an ideal temperature rise profile provided in example 1 of the present application;
FIG. 8 is a metallographic photograph of a decarburized layer thickness of 0.05mm of forging 1 after the inductor is modified;
FIG. 9 is a metallographic view of the thickness of the decarburized layer of forging 2 after sensor modification of 0.1mm;
in the figure:
1. an induction furnace inlet;
2. a first press roller;
3. a second press roller;
4. a third press roller;
5. an induction furnace outlet;
6. eight sections of sensors;
7. an inert gas nozzle;
8. an induction furnace inlet of the prior art;
9. an inlet press roll;
10. the valve is made into an inert gas valve;
11. a high-pressure gas cylinder for storing inert gas;
12. two sections of inductors;
13. is an induction furnace outlet in the prior art.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application become more apparent, the technical solutions in the embodiments of the present application will be described in more detail below with reference to the accompanying drawings in the embodiments of the present application. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are some, but not all, embodiments of the application. The embodiments described below by referring to the drawings are illustrative and intended to explain the present application and should not be construed as limiting the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application. Embodiments of the present application will be described in detail below with reference to the accompanying drawings.
In the description of the present application, it should be understood that the terms "center," "longitudinal," "lateral," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, merely to facilitate describing the present application and simplify the description, and do not indicate or imply that the devices or elements being referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the scope of the present application.
The application is described in detail below with reference to the attached drawing figures:
the application relates to a method for reducing decarburization on the surface of a forging piece, which is characterized in that the temperature rising speed of the surface of a blank in a design sensor is controlled, the surface temperature of the blank is kept at about 900 ℃ in a first section of sensor or a sensor which occupies about 1/4 to 3/8 of the whole heating period at the initial stage of the blank entering an induction furnace, a low-temperature oxide skin protection layer is formed on the surface of the forging piece, then the temperature is gradually raised, and the surface temperature reaches about 1230 ℃ required by the process at the final stage.
The medium frequency induction furnace can be divided into an integrated induction furnace and a split induction furnace which can be controlled in a partition mode. For a split induction furnace which can be controlled in a partition mode, in order to meet the requirement of a temperature rise curve, the heating power of each partition can be simply adjusted. For the integrated intermediate frequency furnace, namely, each section of inductor of the induction furnace should be redesigned, the number of turns and the wire diameter of each section of inductor are redesigned under the condition of unchanged total power, the input power of a first section of inductor is reduced, the power of a subsequent section of inductor is properly increased, the surface temperature rise means of the blank is achieved, and the purpose of keeping the surface temperature of the initial stage at about 800-900 ℃ for as long as possible under the condition of meeting the temperature difference of a core meter is achieved. Experiments prove that the oxide scale formed at the intermediate temperature of 700-900 ℃ can protect the deepening of the internal decarburized layer.
Blank materials suitable for use in the present application: 42CrMoHA.
The chemical composition is shown in Table 1.
Table 1 shows the chemical compositions of the elements of 42CrMoHA in the present application;
TABLE 1
According to multiple practical experiences, the application can completely realize the surface decarburization requirement when the content of each element is not necessarily the same as or close to the above table.
Examples:
blank size: phi 160mm x 980mm blank weight: 157kg
Eight sections of inductors of the integral medium-frequency induction heating furnace have total power: 3000KW;
frequency 490HZ;
the required beat: 65S/root;
blank heating temperature: 1230 ℃;
core surface temperature difference: (+ -50 ℃;
decarburization requirement: thickness of decarburized layer: less than or equal to 0.1mm;
the layout situation of the induction furnace to be improved is shown in fig. 2; the temperature rise curve of the induction furnace before modification is shown in fig. 3.
In fig. 3, the red line is a surface temperature rise curve; the blue line is the core temperature rise curve; the green line is the average temperature rise curve. Because the skin effect and temperature are below the curie point, in the first-section induction furnace, the surface temperature rapidly rises to above 1000 ℃ and is always in a high temperature state after that, making the surface decarburization phenomenon particularly serious.
FIGS. 4, 5 and 6 show that the thickness of the decarburized layer at the prescribed position of the three samples before the improvement of the inductor is 0.18 to 0.3mm. It is obvious that the decarburized layer is far higher than the process requirement.
The method comprises the following implementation steps:
1. determination of a blank temperature rise curve
The target temperature rise profile is first set, as shown in fig. 7, with the surface temperature in the first two-section inductor desirably being around 900 c, and the surface temperature in the first three-section inductor not being higher than 1000 c.
2. According to the set temperature rise curve, the power of each section of inductor is distributed, the number of turns of the coil of each section of inductor is calculated, the result is shown in table 2, and table 2 is the data of each section of inductor of the 3000KW induction furnace designed according to the temperature rise curve in the example.
TABLE 2
| Sequence number of each section of sensor | 1# | 2# | 3# | 4# | 5# | 6# | 7# | 8# |
| Inductor power duty cycle | 30.3％ | 15.3％ | 12.3％ | 12.7％ | 6.7％ | 7.0％ | 7.8％ | 7.8％ |
| Inductor power distribution (KW) | 910 | 460 | 370 | 380 | 200 | 210 | 235 | 235 |
| Number of turns of inductor design | 47 | 68 | 68 | 68 | 44 | 44 | 47 | 47 |
3. Simulating the surface and core temperature of the blank heating process according to experience or iHaz software, and if the core surface temperature difference meets the design requirement and the surface temperature is close to an ideal surface temperature rise curve, starting to manufacture the inductor; if the surface temperature does not meet the requirement, repeating the steps 1-2 until the requirement is met. The newly manufactured inductor is used for actually heating the forging, the surface temperature of each stage in the heating process is measured, and compared with an ideal surface temperature rise curve, the surface temperature rise curve is used for verifying the design effect.
4. Cutting an actual sample forging, taking a metallographic photograph of a surface decarburized layer of a process required point, and observing whether the surface decarburized layer meets the requirement of the thickness dimension of the decarburized layer.
5. For the integrated induction furnace, the cooperation between the total inductance of the inductor and the compensation capacitor should be paid attention to when the inductor is designed, so that the resonance frequency of the induction furnace is ensured to meet the requirement of the heating thickness caused by the skin effect and to be suitable for reality.
6. For an intermediate frequency power supply that can be controlled in zones, the power and frequency settings for all zones from front to back can be adjusted according to the ideal temperature rise curve of fig. 5. And finally, the surface temperature of the actual blank is close to an ideal temperature rise curve.
The application relates to a method for reducing decarburization on the surface of a forging piece by controlling the temperature rise of the surface of a blank through adjusting the power of each part of an inductor in an induction furnace.
The method comprises the steps of redesigning an inductor coil according to a blank surface temperature rise curve of an integrated induction furnace and adjusting the power of each partition of the induction furnace controlled in a partition mode according to the blank surface temperature rise curve.
FIG. 8 is a metallographic photograph of a decarburized layer thickness of 0.05mm of forging 1 after the inductor is modified;
FIG. 9 is a metallographic view of the thickness of the decarburized layer of forging 2 after sensor modification of 0.1mm;
the method is successfully tried on the heating of the quenched and tempered steel engine crankshaft with the blank diameter phi of 160, and good effect is obtained.
The application provides another embodiment, a device for reducing the surface decarburization of a forging piece, which comprises an induction furnace and a compression roller;
the induction furnaces are divided into an integrated induction furnace and a partition-controlled induction furnace;
integrated induction furnace: each section of the inductor of the whole induction furnace is controlled by a single power supply. Once the inductor design and manufacture is completed, the power ratio of each inductor is fixed, and the corresponding surface temperature rise curve is also fixed. The internal power duty cycle cannot be adjusted during use.
The split induction furnace with the partition control comprises a plurality of partitions, wherein each partition comprises one or more sections of inductors, and each partition is controlled by a separate power supply.
The power and the frequency of each partition can be set according to the process requirement in the use process;
the high-power induction furnace has longer furnace type and can be designed into an integrated multi-section inductor or a plurality of inductor groups controlled in a partitioning way; the interior of each inductor is designed to have a uniformly arranged turn pitch.
Because the furnace type of the low-power induction furnace is shorter, the low-power induction furnace is designed into an integrated one-section at most two-section inductor, and in order to realize power distribution change, the front-back turn intervals are designed to be different in the same section of inductor, so that the power distribution of each front part and each back part is adjusted, and the requirement of meeting a temperature rise curve is met.
Eight sections of sensors are arranged.
The three press rolls are respectively a first press roll, a second press roll and a third press roll.
The compression roller in the middle of the induction furnace is a relay power source designed for facilitating the blank transmission of the high-power induction furnace. The arrangement of the middle press roller accelerates the surface decarburization. The induction furnace with small power and composed of a two-section inductor is not provided with an intermediate compression roller.
All methods which attempt to retard the rate of surface temperature rise of the billet during the initial heating phase by means of the induction furnace temperature rise profile to reduce surface decarburization are within the scope of the present application.
The foregoing is merely illustrative of specific embodiments of the present application, and the scope of the application is not limited thereto, but any modifications, equivalents, improvements and alternatives falling within the spirit and principles of the present application will be apparent to those skilled in the art within the scope of the present application. And all that is not described in detail in this specification is well known to those skilled in the art.
Claims (10)
1. A method for reducing decarburization on the surface of a forging, which is characterized by comprising the following steps:
by controlling the surface temperature rise of the blank, the surface temperature rise speed of the blank is delayed in the initial heating stage so as to reduce surface decarburization.
2. A method of reducing decarburization of a forging surface as set forth in claim 1, wherein:
the power of each part of the inductor in the induction furnace is regulated, the temperature rising speed of the surface of the blank in the inductor is controlled and designed through the temperature rising curve of the induction heating furnace, the surface temperature of the blank is raised and kept at about 700-900 ℃ in the inductor in a period which is about 1/4 to 3/8 of the whole heating period at the initial stage of entering the induction furnace, a low-temperature oxide skin protection layer is formed on the surface of a forging, then the temperature is gradually raised, and the surface temperature reaches about 1230 ℃ required by the process at the final stage.
3. A method of reducing decarburization of a forging surface as set forth in claim 2, wherein:
the induction furnace is divided into an integrated induction furnace and a split induction furnace which can be controlled in a partition mode;
the integrated induction furnace designs each section of inductor coil according to a blank surface temperature rise curve;
the power of each partition is directly adjusted according to the temperature rise curve of the surface of the blank by the partition-controlled split induction furnace.
4. A method of reducing decarburization of a forging surface as set forth in claim 3, wherein:
the surface temperature in the initial stage is kept at 700-900 ℃ to form oxide scale, so that the deepening of the internal decarburized layer is protected.
5. A method of reducing decarburization of a forging surface as set forth in claim 1, comprising the steps of:
step 1, determining a blank temperature rise curve;
setting a target temperature rise curve, wherein the surface temperature in the inductor with the length of the first 1/4 is increased to be close to 900 ℃, and the surface temperature in the inductor with the length of the first 3/8-1/2 is not higher than 1000 ℃;
step 2, distributing power of each section of inductor according to a set temperature rise curve, and calculating the number of turns of coils of each section of inductor;
step 3, simulating the surface and core temperature of the blank heating process according to experience or iHaz software, and if the core surface temperature difference of the final outlet blank meets the design requirement and the surface temperature is close to an ideal surface temperature rise curve, starting to manufacture the inductor; if the surface temperature does not meet the requirement, repeating the steps 1-2 until the surface temperature meets the requirement; the newly manufactured inductor is used for actually heating the forging, the surface temperature of each stage in the heating process is measured, and compared with an ideal surface temperature rise curve, the surface temperature rise curve is used for verifying the design effect;
and 4, cutting the actual sample forging, taking a metallographic photograph of a surface decarburized layer of a process required point, and observing whether the surface decarburized layer meets the requirement of the thickness dimension of the decarburized layer.
6. The method of reducing decarburization of a forging surface of claim 5, further comprising:
for an integrated induction furnace, the total inductance of the inductor is matched with the compensation capacitor, so that the resonance frequency of the induction furnace is ensured to meet the requirement of the heating thickness caused by the skin effect and is suitable for reality;
for the split induction furnace capable of being controlled in a partitioned mode, the steps 1-2 are simplified as follows: according to the ideal temperature rise curve, the power and frequency settings of all the front-to-back partition control power supplies are adjusted, and finally the surface temperature of the actual blank is close to the ideal temperature rise curve, so that the number of turns of each partition does not need to be changed.
7. A method of reducing decarburization of a forging surface according to any one of claims 1 to 6, wherein:
the blank material adopts 42CrMoHA.
8. The utility model provides a reduce device of forging surface decarbonization which characterized in that: comprises an induction furnace;
the induction furnaces are divided into an integrated induction furnace and a partition-controlled induction furnace;
the integrated induction furnace comprises: each section of sensor of the whole induction furnace is controlled by a single power supply;
the split induction furnace controlled by the partition comprises a plurality of partitions, each partition comprises one or more sections of inductors, and each partition is controlled by a power supply independently.
9. The apparatus for reducing surface decarburization of a forging as recited in claim 8, wherein:
the inductor is provided with eight sections.
10. The apparatus for reducing surface decarburization of a forging as recited in claim 8, wherein:
the device also comprises a compression roller;
the three press rollers are respectively a first press roller, a second press roller and a third press roller.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310929224.XA CN116987850A (en) | 2023-07-27 | 2023-07-27 | Method and device for reducing surface decarburization of forging |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310929224.XA CN116987850A (en) | 2023-07-27 | 2023-07-27 | Method and device for reducing surface decarburization of forging |
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| CN116987850A true CN116987850A (en) | 2023-11-03 |
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| CN202310929224.XA Pending CN116987850A (en) | 2023-07-27 | 2023-07-27 | Method and device for reducing surface decarburization of forging |
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