CN105886727A - Method for promoting graphitization of hypoeutectoid steel through adopting pulse current - Google Patents
Method for promoting graphitization of hypoeutectoid steel through adopting pulse current Download PDFInfo
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- CN105886727A CN105886727A CN201610293454.1A CN201610293454A CN105886727A CN 105886727 A CN105886727 A CN 105886727A CN 201610293454 A CN201610293454 A CN 201610293454A CN 105886727 A CN105886727 A CN 105886727A
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- 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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
-
- 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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
-
- 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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/006—Graphite
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
The invention discloses a method for promoting graphitization of hypoeutectoid steel through adopting a pulse current, and belongs to the field of methods for producing free-cutting steel for mechanical structures. The method is characterized by comprising the steps that the steel is put in a heat treatment furnace, and the two ends of the steel are connected with a pulse power supply outside the furnace through conducting wires; when the steel is heated to the graphitization temperature 620 to 680 DEG C (as the pulse current is introduced, the temperature can be 30 to 50 DEG C lower than the conventional graphitization temperature), the pulse power supply is switched on to input the pulse current of which the current density is 50 to 200 A/mm<2> and the frequency is 10 to 50 Hz for 30 to 120 min; and the steel is cooled to the room temperature along with the furnace, and the graphitization is achieved. According to the method, when the metal is heated to the temperature capable of meeting the thermodynamic condition, the low-density pulse current is input, so that the diffusion velocity and dislocation motion capacity of carbon atoms are improved, the graphitization can be achieved in a relatively short time, and ideal preparation tissues, namely, ferrite and graphite, are provided for follow-up processing (such as cutting processing).
Description
Technical field
The invention belongs to the field of manufacturing machine structure automatic steel method, being directed primarily to a kind of application pulse current has rapidly
Effect ground promotes sub-eutectoid steel graphitizing method.
Background technology
Along with the development of national economy, the quantity of automatic machine tool increases sharply, its range of application also expanding day.Simultaneously as
Use new-type cutter and new technology, make cutting speed increasingly improve, it is desirable to the surface roughness of various machined piece and precision are more
Adding strict, therefore, the machinability of steel is by most attention.Various countries competitively develop that to have the steel grade of excellent machinability easy
Cutting Steel.At present, automatic steel major consumers state is developed country, and the automatic steel consumption figure of China is also little, but not
Disconnected expansion.Automatic steel is at automobile, tractor, motorcycle, Aeronautics and Astronautics, satellite, strategic missile and conventional weapon zero
The fields such as part, office and electronic equipment are widely used.
Conventional is sulfur system and lead series free cutting steel, and when it is smelted, air is seriously polluted, and lead is poisonous, harmful.Lead is easy
The use of Cutting Steel will gradually be restricted, and Europe community has limited and reclaimed leaded automobile component.Therefore, develop and produce
Eco-friendly low-sulfur, lead free free-cutting steel are important developing direction.
Graphite automatic steel is complied with this development trend just and is proposed, and it mainly utilizes Dispersed precipitate in steel to play lubrication
Cutting ability is improved with the graphite particle of chip breaking effect.Utilize graphitization technology to develop automatic steel, broken and utilized fragility
Cutting free unit usually improves the traditional view of the cutting ability of steel, and Cutting free element, while bringing fragility to material, reduces
The processing performance of material and serviceability.Graphite automatic steel by industry be considered one have simultaneously higher cutting ability with cold become
The new steel of " environmental protection " of type performance.
Graphite automatic steel is the steel grade with hypo eutectoid composition.It is known that have the graphitizing process of the steel of hypo eutectoid composition
Slowly, commercial Application is difficult to always.Shorten graphitizing process, be the key that can this steel grade industrial.Therefore, one is sought
New approach accelerates the graphitizing process of this steel, will have extremely important theoretical and practical significance.
From the point of view of sub-eutectoid steel, its graphitization is mainly to be decomposed by cementite and realizes.The method used is main
Have: a kind of method is microalloying, and such as K.He, H.R.Daniels, A.Brown, R.Brydson, D.V.Edmonds are at Acta
Paper " the An electron microscopic study of spheroidal delivered on Materialia (2007,55:291-2927)
Graphite nodules formed in amedium-carbon steel by annealing utilizes the unit such as graphitization of adding Si, Al
Element, is promoted the decomposition of cementite by the stability reducing cementite and then is realized graphitizing process；Another kind of method is to increase
The quantity of the heterogeneous nuclei of graphite, if Takashi Iwamoto, Toshiyuki Hoshino is at JFE TECHNICAL REPORT
Paper " the Bar and Wire Steels for Gears and Valves of delivered on (2004, (4): 74-80)
Automobiles---Eco-friendly Free Cutting Steel without Lead Addition " in utilize the nitridation of alloying element B
The disperse educt of compound is used as the forming core core (BN has the hexagonal simple structure that same graphite is the same) of graphite, and graphite depends on
Grow up at BN.Graphitization time needed for utilizing these methods is the most relatively long, short the most several hours, long then ten several hours.
In view of pulse current has promotion atoms permeating and the effect of dislocation motion, therefore, pulse current is incorporated into sub-eutectoid steel
In graphitizing process, the decomposition of cementite can be promoted, the quantity of newborn graphite in increasing ferrite, and then promote sub-eutectoid steel
Graphitizing process.To utilizing pulse current to promote, the graphitizing process of sub-eutectoid steel yet there are no open report at present.
Summary of the invention
The graphitizing process of sub-eutectoid steel, its essence is i.e. situated between stable cementite and the ferritic structural transformation that coexists by thermodynamics
Coexist the process of tissue for stable graphite and ferrite, is i.e. mainly realized by the cementite decomposition in steel.In order to solve
Sub-eutectoid steel graphitizing process problem slowly, the present invention proposes a kind of application pulse current and promotes sub-eutectoid steel stone quickly and effectively
The method of inkization, the method to while meeting graphitization thermodynamic condition, then inputs low-density pulse current in METAL HEATING PROCESS,
The graphitization dynamic conditions of material is changed, by promoting carbon atom diffusion and dislocation motion and then improving cementite decomposition speed with this
Degree and the newborn graphite increased in ferrite, realize graphitization, for following process (such as cutting reaching within a short period of time
Processing) preferable Preparedness Directorate is provided.
The present invention is realized by techniques below measure:
A kind of application pulse current promotes sub-eutectoid steel graphitizing method quickly and effectively, is placed in heat-treatment furnace by steel, steel
The two ends of material and stove outer pulse power wire is connected, when heat steel to graphitization temperature 620～680 DEG C are (due to introducing pulse
Electric current, can more conventional graphitization temperature low 30～50 DEG C), open the pulse power, input current density is 50～200A/mm2、
Frequency is the pulse current of 10～50Hz, and after keeping 30～120min, steel cool down at stove.
The main alloy element of sub-eutectoid steel of the present invention has C, Si, Mn, S, P and B or Al etc..Wherein, carbon
Content range is 0.15～0.77%, and silicone content scope is 1.45～1.65%；Fe content scope is 0.40～0.50%；Sulfur content model
It is trapped among 0.004～0.010%；Phosphorus content scope is 0.004～0.010%；Boron 0.002～0.005%；Aluminum content range exists
0.020～0.060%.Remaining content is ferrum element.
Beneficial effects of the present invention:
Being shown by experimentation and theory analysis, sub-eutectoid steel is while graphitization temperature heating, insulation, and input is certain strong
Degree, certain frequency, the pulse current of certain time, provide extra activation energy △ E, be greatly increased forming core Phase Transition Systems
Rate N, hence it is evident that improve carbon atom and other diffusion of alloy elements speed, improve transition kinetics condition, improve cementite
Decomposition rate, adds the nucleation rate of graphite.On traditional, single graphitization processing Process ba-sis, input current density
It is 50～200A/mm2, frequency be 10～50Hz this new technology of pulse current, can operatively promote sub-eutectoid steel
Graphitizing process.Simultaneously as introducing pulse current, can more conventional graphitization temperature low 30～50 DEG C.The method will be for enterprise
The graphitization of commercial Application sub-eutectoid steel provides a new technique.
Accompanying drawing explanation
Fig. 1 is the experimental provision schematic diagram of the present invention.
The copper niproll of 1-；2-automatic temperature control instrument；3-thermocouple；4-steel sample；5-heating furnace；The 6-pulse power
Fig. 2 is embodiments of the invention 1, realizes the steel sample after graphitization in sub-eutectoid steel graphitizing process after input pulse electric current
In metallographic structure.
Fig. 3 is embodiments of the invention, realizes after graphitization in steel sample in sub-eutectoid steel graphitizing process after input pulse electric current
Graphite particle electronogram.
Fig. 4 is embodiments of the invention 2, realizes the steel after graphitization in sub-eutectoid steel graphitizing process after input pulse electric current
Metallographic structure in sample.
Detailed description of the invention
After now embodiments of the invention being specifically described in.
Below in conjunction with drawings and Examples, technical scheme is described further.Embodiment is merely to illustrate the present invention,
Rather than limit the present invention by any way.
It is as follows that the present invention realizes step: (1) sample prepares: prepares a steel sample 4 being suitable for heating furnace 5 shove charge dimensional requirement；
(2) sample and the connection of the pulse power: the one side polishing that copper niproll 1 is contacted with steel sample 4, and clamping steel sample as far as possible
4, to keep good electric conductivity；(3) sample shove charge: smoothly send into add being connected complete steel sample 4 with the pulse power 6
Hot stove 5, and make steel sample be centrally located at thermocouple 3, in order to measured by automatic temperature control instrument 2 and control at pulse current
The temperature of steel sample 4 during reason；(4) heating furnace heats up and is incubated: connect the power supply of heating furnace 5, according to the material of steel sample 4
Character heats up by certain firing rate, is incubated after being increased to assigned temperature；(5) make pulse electric current: adding
After hot stove 5 reaches assigned temperature, open the pulse power 6, adjust the parameter such as current peak, frequency and carry out graphitization isothermal processes,
And record the time；(6) sample cooling: after held for some time (after i.e. steel sample 4 realizes graphitization), disconnects heating furnace 5
Power supply and the pulse power 6, steel sample 4 furnace cooling；(7) sample is come out of the stove: after graphitization processing, from heating furnace 5
In take tapping sample 4, and remove fixture (copper niproll) 1；(8) graphitization effect detection: to the steel sample 4 after graphitization
Carry out graphitization Metallographic Analysis.
Embodiment 1
The steel sample of the present embodiment is to go out after fusing (in stove, vacuum is 1.33Pa), microalloying in vacuum induction furnace
Steel, then steel ingot carries out forging molding is diameter 20mm, the round steel of long 100mm.Its chemical composition (mass fraction/%) is
0.45C, 1.6Si, 0.46Mn, 0.009S, 0.008P, 0.003B.During experiment, the copper good by electric conductivity presss from both sides
Hold roller to be connected on two electrodes of pulse power outfan by two ends of steel sample, and steel sample is placed in heating furnace.Open heating furnace
On and off switch, heats up to heating furnace, in time being warming up to 650 DEG C, opens pulse power switch, input current density
100A/mm2, frequency is the pulse current of 20Hz, and this parameter makes steel sample temperature stabilization near 650 DEG C, and conduction time is 50min.
Steel sample is come out of the stove after being cooled to room temperature in heating furnace afterwards, and so far the graphitization processing of this steel terminates.
For detection graphitization effect, the steel sample after graphitization is carried out Metallographic Analysis.
Fig. 2 is the result of the metallographic structure test after steel sample graphitization.The microscopic structure of sample is mainly biphase by ferrite and graphite
Composition, graphite particle not only separates out on crystal boundary, and separates out at intracrystalline；In Dispersed precipitate, size is uniform, average-size
Less than 6 μm, graphite approximation is spherical in shape.
Fig. 3 is shown that the graphite particle electronogram after the graphitization observed under transmission electron microscope in steel sample.Can by figure
See, occur in that four road graphite diffraction rings around center diffraction spot (000).First diffraction ring is (002) of graphite C
Crystal face, second diffraction ring is (101) crystal face；3rd road diffraction ring is (104) crystal face, and the 4th road diffraction ring is (201)
Crystal face.
For contrasting, choose the graphitization experiment that same steel sample carries out under the no pulse function of current.The graphite of this experiment
Changing temperature is 700 DEG C, and graphitization time is 8h.
Embodiment 2
The steel sample of the present embodiment is to go out after fusing (in stove, vacuum is 1.33Pa), microalloying in vacuum induction furnace
Steel, then steel ingot carries out forging molding is diameter 20mm, the round steel of long 100mm.Its chemical composition (mass fraction/%) is
0.25C, 1.6Si, 0.50Mn, 0.008S, 0.008P, 0.005B.During experiment, steel sample is placed in heating furnace, logical
Cross the good copper niproll of electric conductivity to be connected on two electrodes of pulse power outfan by two ends of steel sample.Open heating furnace
On and off switch, heats up to heating furnace, in time being warming up to 650 DEG C, opens pulse power switch, input current density
180A/mm2, frequency is the pulse current of 40Hz, and this parameter makes steel sample temperature stabilization near 650 DEG C, and conduction time is
100min.Steel sample is come out of the stove after being cooled to room temperature in heating furnace afterwards, and so far the graphitization processing of this steel terminates.
For detection graphitization effect, the steel sample after graphitization is carried out Metallographic Analysis.
Fig. 4 is the result of the metallographic structure test after steel sample graphitization.The microscopic structure of sample is mainly biphase by ferrite and graphite
Composition, graphite particle the most not only separates out on crystal boundary, and separates out at intracrystalline；In Dispersed precipitate；Particle size is uniform, flat
All being smaller in size than 10 μm, graphite approximation is spherical in shape.
For contrasting, choose the graphitization experiment that same steel sample carries out under the no pulse function of current.The graphite of this experiment
Changing temperature is 700 DEG C, and graphitization time is 12h.
From embodiment, in the graphitizing process of sub-eutectoid steel, after introducing pulse current, choosing suitable pulse electricity
In the case of stream parameter, can accelerate to realize the graphitizing process of sub-eutectoid steel.
Claims (3)
1. an application pulse current promotes sub-eutectoid steel graphitizing method, it is characterised in that: the graphitization of described sub-eutectoid steel
Process realizes under conditions of introducing this outer field technology of pulse current；Concrete grammar is to be placed in heat-treatment furnace by steel sample,
The two ends of steel sample pulse power wire outer with stove couples, and when steel sample is heated to graphitization temperature 620～680 DEG C, opens pulse electricity
Source, input current density is 50～200A/mm2, frequency be 10～50Hz pulse current, keep after 30～120min, steel
Material cools to room temperature with the furnace can realize graphitization.
2. promote sub-eutectoid steel graphitizing method according to the application pulse current described in claim l, it is characterised in that described
The main alloy element of sub-eutectoid steel has C, Si, Mn, S, P and B or Al；Wherein, carbon content scope 0.15～0.77%,
Silicone content scope is 1.45～1.65%；Fe content scope is 0.40～0.50%；Sulfur content scope is 0.004～0.010%；Phosphorus contains
Weight range is 0.004～0.010%；Boron 0.002～0.005%；Aluminum content range is 0.020～0.060%, and remaining content is ferrum unit
Element.
3. promote sub-eutectoid steel graphitizing method according to the application pulse current described in claim l, it is characterised in that realize step
Rapid as follows:
(1) sample prepares: prepare a steel sample being suitable for heating furnace shove charge dimensional requirement；
(2) sample and the connection of the pulse power: the one side polishing that copper niproll 1 is contacted with steel sample, and clamping steel sample as far as possible,
With the electric conductivity that holding is good；
(3) sample shove charge: smoothly send being connected complete steel sample with the pulse power into heating furnace, and make steel sample be centrally located at thermoelectricity
At Ou, in order to measured by automatic temperature control instrument and control the temperature of steel sample during pulsed current annealing；
(4) heating furnace heats up and is incubated: connects the power supply of heating furnace, carries out by certain firing rate according to the material character of steel sample
Heat up, be incubated after being increased to assigned temperature；
(5) make pulse electric current: after heating furnace reaches assigned temperature, opens the pulse power, adjusts current peak, frequency parameter
Carry out graphitization isothermal processes, and record the time；
(6) sample cooling: after held for some time, after i.e. steel sample realizes graphitization, disconnects power supply and the pulse power of heating furnace,
Steel sample furnace cooling；
(7) sample is come out of the stove: after graphitization processing, takes tapping sample, and remove fixture from heating furnace.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114804877A (en) * | 2022-05-19 | 2022-07-29 | 李鑫 | Pulse current internal heating type intermediate temperature graphitized negative electrode material and manufacturing method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114804877A (en) * | 2022-05-19 | 2022-07-29 | 李鑫 | Pulse current internal heating type intermediate temperature graphitized negative electrode material and manufacturing method thereof |
| CN114804877B (en) * | 2022-05-19 | 2024-01-23 | 深圳市钢昱碳晶科技有限公司 | Pulse current internal heating type medium-temperature graphitized anode material and manufacturing method thereof |
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Application publication date: 20160824 |