CN112143863B - Anti-decarbonization heat treatment method for shield machine hob ring - Google Patents

Anti-decarbonization heat treatment method for shield machine hob ring Download PDF

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CN112143863B
CN112143863B CN202011021892.5A CN202011021892A CN112143863B CN 112143863 B CN112143863 B CN 112143863B CN 202011021892 A CN202011021892 A CN 202011021892A CN 112143863 B CN112143863 B CN 112143863B
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heat treatment
oxidation
coating
shield machine
ring
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CN112143863A (en
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袁志钟
韦家波
张琰琳
袁飞
曹赟
段旭斌
罗锐
程晓农
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Guangzhou Xinrun Fengdong Heat Treatment Co.,Ltd.
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Jiangsu University
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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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/68—Temporary coatings or embedding materials applied before or during heat treatment
    • C21D1/70—Temporary coatings or embedding materials applied before or during heat treatment while heating or quenching
    • 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
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • 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
    • C21D1/68—Temporary coatings or embedding materials applied before or during heat treatment
    • C21D1/72—Temporary coatings or embedding materials applied before or during heat treatment during chemical change of surfaces
    • 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/22—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for drills; for milling cutters; for machine cutting tools

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Abstract

The invention belongs to the technical field of shield machine cutters, and particularly relates to an anti-decarbonization heat treatment method for a shield machine hob ring. The invention provides an anti-decarbonization heat treatment method for a shield machine hob ring, which comprises the following steps: placing a shield machine hobbing cutter ring coated with an oxidation coating on the surface in a cavity of heat treatment equipment, heating to a final temperature under normal pressure, preserving heat, and performing heat treatment, wherein a briquette is placed in the cavity of the heat treatment equipment, and the oxidation coating sequentially comprises a first oxidation-resistant coating and a second oxidation-resistant coating from inside to outside; the first oxidation-preventing coating includes Na 2 O·2SiO 2 、Al 2 O 3 、Cr 2 O 3 、NaF、TiO 2 And V 2 O 5 (ii) a The second oxidation-resistant coating comprises SiC, graphite powder and poly-internal olefin. Test results show that the surface structure of the hob ring obtained by the anti-decarbonization heat treatment method provided by the invention is a large amount of lath martensite, the surface has obvious relief, and the hardness reaches 54HRC.

Description

Anti-decarbonization heat treatment method for shield machine hob ring
Technical Field
The invention belongs to the technical field of shield machine cutters, and particularly relates to an anti-decarbonization heat treatment method for a shield machine hob ring.
Background
The shield machine is an ultra-large mechanical device specially used for hard rock layer tunneling. Replaceable disc cutters are regularly arranged on a cutter head of the shield tunneling machine, and through rotation and propulsion of the cutter head, rocks are broken and peeled off by rolling and impacting of a cutter ring on the outermost side of the cutters, and then the tunnel is gradually penetrated. As a key consumable material of the shield machine, the use cost and the working efficiency of the shield machine are directly determined by the processing performance of the hob ring of the shield machine.
At present, the heat treatment process of the shield machine hob ring is divided into two types, namely full-hard heat treatment and gradient-hard heat treatment. The hob ring is usually made of die steel and tool steel, the decarburization phenomenon of the hob ring occurs when the hob ring is heated and insulated above 600 ℃, and the quenching temperature of the hob ring is usually higher than 1000 ℃, therefore, no matter which heat treatment process is adopted, the decarburized layer can all appear on hobbing cutter ring surface after heat treatment, and the tissue of decarburized layer is thick, and the hardness is low, reduces hobbing cutter ring intensity, shortens hobbing cutter ring life-span, leads to that the tool changing frequency is high, with high costs. In order to solve the problem of coarse decarburized layer structure, the hob ring is subjected to heat treatment in a mode of quenching and tempering under a vacuum condition in most industries. For example, the Chinese invention patent (CN 107060789A) discloses a cutter ring material of a shield cutter and a heat treatment process, the cutter ring is integrally heated in a vacuum furnace in a grading way, and then quenched and tempered twice, so that the problems of decarburization and poor strength of the cutter ring in the heat treatment are solved. However, the vacuum heat treatment in the method has high cost, complicated parameter design and operation, increased cost of cutter ring processing and manufacturing, and no consideration of both cutter changing cost and processing and manufacturing cost.
Disclosure of Invention
In view of the above, the invention aims to provide a decarbonization preventing heat treatment method for a shield machine hob cutter ring, which can inhibit the generation of a decarbonization layer, has simple process and low cost, and can obtain the hob cutter ring with a large amount of lath martensite on the surface, high hardness and long service life.
In order to achieve the purpose of the invention, the invention provides the following technical scheme:
the invention provides an anti-decarbonization heat treatment method for a shield machine hob ring, which comprises the following steps:
placing a shield machine hobbing cutter ring coated with an oxidation coating on the surface in a cavity of heat treatment equipment, heating to a final temperature under normal pressure, preserving heat, and performing heat treatment, wherein a briquette is placed in the cavity of the heat treatment equipment, and the oxidation coating sequentially comprises a first oxidation-resistant coating and a second oxidation-resistant coating from inside to outside;
the first oxidation preventing coating comprises Na 2 O·2SiO 2 、Al 2 O 3 、Cr 2 O 3 、NaF、TiO 2 And V 2 O 5 (ii) a The second anti-oxidation coating comprises SiC, graphite powder and poly-internal olefin;
the final temperature is more than or equal to 1000 ℃, and the heat preservation time is more than or equal to 30min.
Preferably, the first oxidation-resistant coating comprises the following components in percentage by mass:
Figure BDA0002700924560000021
preferably, the second oxidation-resistant coating comprises the following components in percentage by mass:
SiC 3～5％；
30-60% of graphite powder;
30 to 40 percent of poly-internal olefin;
the balance being water.
Preferably, the particle size of the graphite powder is more than or equal to 1000 meshes.
Preferably, the first oxidation preventing coating is coated to a thickness of 0.5 to 1mm.
Preferably, the second oxidation preventing coating is coated to a thickness of 0.3 to 0.8mm.
Preferably, the briquette comprises the following components in percentage by mass:
25 to 30 percent of sodium nitrate, 2 to 5 percent of potassium nitrate, 10 to 30 percent of charcoal powder, 25 to 30 percent of anthracite, 10 to 15 percent of carbonized sawdust, 1 percent of tungsten oxide and 3 to 5 percent of yellow mud.
Preferably, the diameter of the coal briquette is 100-120 mm, and the height of the coal briquette is 65-75 mm;
the number of the coal balls is 2-4 per hob ring.
Preferably, after the heat treatment, the method further comprises the step of sequentially quenching and tempering the obtained heat-treated hob ring.
Preferably, the quenching is oil quenching; the tempering temperature is 460-580 ℃, and the time is 2-4 h.
The invention provides an anti-decarbonization heat treatment method for a shield machine hob cutter ring, which comprises the following steps: placing a hob ring of a shield machine, the surface of which is coated with an oxidation coating, in a cavity of heat treatment equipment, heating to a final temperature under normal pressure, and carrying out heat treatment by keeping the temperature, wherein a briquette is placed in the cavity of the heat treatment equipment, and the oxidation coating sequentially comprises a first oxidation-resistant coating and a second oxidation-resistant coating from inside to outside; the first oxidation preventing coating comprises Na 2 O·2SiO 2 、Al 2 O 3 、Cr 2 O 3 、NaF、TiO 2 And V 2 O 5 (ii) a The second anti-oxidation coating comprises SiC, graphite powder and poly-internal olefin; the final temperature is more than or equal to 1000 ℃, and the heat preservation time is more than or equal to 30min. The invention coats the anti-oxidation coating on the surface of the hob ring to form the anti-oxidation coating, when the heat treatment temperature is raised to 300 ℃ in the heating process of the heat treatment, the carbon contained in the coal briquette can react with the oxygen in the air to generate CO 2 The oxygen content in the air is reduced, and the oxidation and decarburization behaviors of the hob ring at high temperature are relieved; na in the first oxidation preventing coating when the heat treatment temperature is raised to 600 DEG C 2 O·2SiO 2 、Al 2 O 3 、Cr 2 O 3 The coating reacts with active gases such as oxygen and the like near the surface of the steel in a large amount, the high-temperature closed oxidation coating forms a compact film with an extremely high melting point, the film has high hardness, abrasion resistance and good heat conductivity, and a vacuum area of the active gases is formed, so that the surface of the steel is well protected from being corroded, and Na are contained in the vacuum area 2 O·2SiO 2 、Al 2 O 3 And Cr 2 O 3 TiO as film-forming substance for isolating oxygen in air from contact with metal substrate 2 And NaF as coloring matter to make the anti-oxidation paint in milk white, V 2 O 5 Is an accelerant to promote the film forming process. The invention helps to avoid the oxidation and decarburization of the hob ring in the heat treatment process through the anti-oxidation coating and the briquettes.
The test results of the embodiment show that the surface structure of the hob ring processed by the anti-decarbonization heat treatment method provided by the invention is a large amount of lath martensite, the surface has obvious relief and the hardness is high.
Drawings
FIG. 1 is an optical microscopic metallographic image of the surface structure of a hob ring obtained by heat treatment in comparative example 1;
FIG. 2 is an optical microscopic metallographic image of a surface structure of a hob ring obtained by the decarburization heat treatment method in example 1;
FIG. 3 is an optical microscopic metallographic image of the surface structure of the hob ring obtained by heat treatment in comparative example 2;
FIG. 4 is an optical microscopic metallographic image of a surface structure of a hob ring obtained by the decarburization heat treatment method in example 2;
FIG. 5 is an optical microscopic metallographic image of the surface structure of the hob ring obtained by heat treatment in comparative example 3;
FIG. 6 is an optical microscopic metallographic image of the surface structure of the hob ring obtained by the decarburization heat treatment method in example 3.
Detailed Description
The invention provides an anti-decarbonization heat treatment method for a shield machine hob cutter ring, which comprises the following steps:
placing a shield machine hobbing cutter ring coated with an oxidation coating on the surface in a cavity of heat treatment equipment, heating to a final temperature under normal pressure, preserving heat, and performing heat treatment, wherein a briquette is placed in the cavity of the heat treatment equipment, and the oxidation coating sequentially comprises a first oxidation-resistant coating and a second oxidation-resistant coating from inside to outside;
the first oxidation-preventing coating includes Na 2 O·2SiO 2 、Al 2 O 3 、Cr 2 O 3 、NaF、TiO 2 And V 2 O 5 (ii) a The second anti-oxidation coating comprises SiC, graphite powder and poly-internal olefin;
the final temperature is more than or equal to 1000 ℃, and the heat preservation time is more than or equal to 30min.
In the present invention, the components are commercially available products well known to those skilled in the art unless otherwise specified.
The shield machine hob cutter ring with the surface coated with the oxidation coating is placed in a cavity of heat treatment equipment, and the temperature is raised to the final temperature under normal pressure and is preserved for heat treatment. In the invention, the oxidation coating is sequentially a first oxidation-resistant coating and a second oxidation-resistant coating from inside to outside. The method comprises the steps of sequentially coating a first anti-oxidation coating and a second anti-oxidation coating on the surface of the shield machine hob cutter ring to be subjected to heat treatment to respectively form a first oxidation coating and a second oxidation coating, and drying to obtain the shield machine hob cutter ring with the surface coated with the oxidation coatings.
The material of the hob ring of the shield machine is not particularly limited, and the material of the hob ring of the shield machine, which is well known to those skilled in the art, can be adopted, such as tool steel or die steel, specifically, 4Cr5MoSiV1 steel. In the present invention, the chemical composition of the 4Cr5MoSiV1 steel is preferably: 0.32 to 0.45wt.% of C, 0.80 to 1.20wt.% of Si, 0.20 to 0.50wt.% of Mn, less than or equal to 0.030wt.% of S, less than or equal to 0.030wt.% of P, 4.75 to 5.50wt.% of Cr, 0.80 to 1.20wt.% of V, 1.10 to 1.7wt.% of Mo, less than or equal to 0.25wt.% of allowable residual content of Ni, less than or equal to 0.30wt.% of allowable residual content of Cu, and the balance of Fe and inevitable impurities. In the embodiment of the invention, the chemical composition of the 4Cr5MoSiV1 steel is as follows: c0.42 wt.%, cr 5.36wt.%, mo 1.40wt.%, si 1.14wt.%, V0.83 wt.%, mn 0.35wt.%, and the balance Fe and unavoidable impurities.
In the present invention, the first oxidation preventing coating layer includes Na 2 O·2SiO 2 、Al 2 O 3 、Cr 2 O 3 、NaF、TiO 2 And V 2 O 5 。
The first anti-oxidation coating preferably comprises 10-30% of Na by mass percentage 2 O·2SiO 2 More preferably 13 to 27%, and still more preferably 15 to 25%.
The first oxidation-preventing coating preferably comprises 10-20% of Al by mass 2 O 3 More preferably 12 to 19%, and still more preferably 14 to 18%.
The first oxidation-proof coating preferably comprises 10-15% of Cr by mass 2 O 3 More preferably 11 to 14%, and still more preferably 12 to 13%.
The first oxidation prevention coating preferably includes 5 to 15% by mass of NaF, more preferably 7 to 14%, and further preferably 9 to 12%.
The first anti-oxidation coating preferably comprises 5-10% of TiO by mass percentage 2 More preferably 6 to 9%, and still more preferably 7 to 8%.
The first oxidation-preventing coating preferably comprises 2-10% by mass of V 2 O 5 More preferably 3 to 9%, and still more preferably 4 to 8%.
The first oxidation preventing coating preferably includes the balance of water by mass percentage.
In the invention, the first anti-oxidation coating is prepared by coating and drying a first anti-oxidation coating.
In the present invention, the first oxidation preventing coating layer is preferably applied to a thickness of 0.5 to 1mm, more preferably 0.6 to 0.9mm, and still more preferably 0.7 to 0.8mm.
In the present invention, the second oxidation preventing coating includes SiC, graphite powder, poly-internal-olefin, and water.
The second oxidation prevention coating preferably includes 3 to 5% by mass of SiC, more preferably 3.5 to 4.5%, and further preferably 3.5 to 4%.
The second oxidation prevention coating preferably includes 30 to 60% of graphite powder by mass, more preferably 35 to 55% by mass, and further preferably 40 to 50% by mass. In the invention, the particle size of the graphite powder is preferably more than or equal to 1000 meshes.
The second oxidation preventing coating preferably includes 30 to 40% by mass of a poly (internal olefin), more preferably 32 to 38%, and still more preferably 34 to 36%.
The second oxidation preventing coating preferably includes the balance of water by mass percentage.
In the present invention, the second oxidation preventing coating layer is preferably applied to a thickness of 0.3 to 0.8mm, more preferably 0.4 to 0.7mm, and still more preferably 0.5 to 0.6mm.
The drying is not particularly limited, and the coating of the first oxidation-preventing coating and the coating of the second oxidation-preventing coating are completely dried, specifically, the drying is carried out at room temperature.
After the shield machine hob ring with the surface coated with the oxidation coating is obtained, the shield machine hob ring with the surface coated with the oxidation coating is placed in an equipment cavity with the coal balls for heat treatment.
In the invention, the components of the coal briquette comprise the following components in percentage by mass: 25 to 30 percent of sodium nitrate, 2 to 5 percent of potassium nitrate, 10 to 30 percent of charcoal powder, 25 to 30 percent of anthracite, 10 to 15 percent of carbonized sawdust, 1 percent of tungsten oxide and 3 to 5 percent of yellow mud.
The source of the yellow mud in the coal briquette is not particularly limited in the invention, and the source known by the person skilled in the art can be adopted. In the invention, the yellow mud preferably comprises the following components in percentage by mass: siO 2 2 65.18～71.86％，Al 2 O 3 15.02～17.99％，Fe 2 O 3 3.27～6.61％，CaO 0.75～1.68％，MgO 0.89～2.07％。
In the present invention, the briquette is preferably a honeycomb briquette. In the present invention, the honeycomb briquette preferably has a diameter of 100 to 120mm, more preferably 105 to 115mm; the height is preferably 65 to 75mm, more preferably 70 to 75mm; the pore diameter of the honeycomb is preferably 12 to 14mm, and more preferably 13 to 14mm; the number of holes is preferably 12.
The number of the briquettes is preferably 2-4 per hob ring.
In the invention, the heat treatment is that the shield machine hob ring with the surface coated with the oxidation coating and the briquette are heated together with the furnace and then are subjected to heat preservation. The rate of temperature rise is not particularly limited in the present invention, and may be a rate of temperature rise known to those skilled in the art. In the invention, the temperature of the heat preservation is preferably more than or equal to 1000 ℃, and more preferably 1000-1200 ℃; the time for heat preservation is preferably not less than 30min, more preferably 30-60 min.
In the present invention, the heat treatment apparatus is preferably a box furnace, specifically, an SXL-1700 box furnace.
After the heat treatment, the invention preferably further comprises the step of sequentially quenching and tempering the obtained heat-treated hob ring.
In the present invention, the quenching is preferably oil quenching. In the present invention, the tempering temperature is preferably 460 to 580 ℃, more preferably 480 to 560 ℃; the time is preferably 2 to 4 hours, more preferably 2 to 3 hours.
In order to further illustrate the invention, the method for decarburization preventing heat treatment of a shield machine hob ring provided by the invention is described in detail below with reference to the following embodiments, but they should not be construed as limiting the scope of the invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
The material of the hob ring of the shield machine is 4Cr5MoSiV1, the element composition comprises 0.42% of C, 5.36% of Cr, 1.40% of Mo, 1.14% of Si, 0.83% of V, and the balance of Fe and inevitable impurities;
the first anti-oxidation coating comprises the following components: na (Na) 2 O·2SiO 2 20％；Al 2 O 3 20％；Cr 2 O 3 10％；NaF 5％；TiO 2 5％；V 2 O 5 4 percent; the balance of water;
the second anti-oxidation coating comprises the following components: 3% of SiC; 30% of graphite powder (1000 meshes); 30% of poly-internal olefin; the balance of water;
the composition of the briquette is as follows: 30% of sodium nitrate, 2% of potassium nitrate, 20% of charcoal powder, 30% of anthracite, 15% of carbonized sawdust, 1% of tungsten oxide and 2% of yellow mud;
the briquette is a honeycomb briquette, and the size conditions are as follows: the diameter is 120mm, the height is 75mm, the honeycomb aperture is 12mm, and the number of holes is 12.
Coating a first anti-oxidation coating with the thickness of 1mm on the surface of the shield machine hob cutter ring to be subjected to heat treatment, then coating a second anti-oxidation coating with the thickness of 2mm, and drying at room temperature to obtain the shield machine hob cutter ring with the surface coated with an oxidation coating;
and (3) placing the obtained shield machine hob ring with the surface coated with the oxidation coating and 2 briquettes in an SXL-1700 box furnace, simultaneously heating to 1100 ℃, preserving heat for 40min, performing oil cooling after heat preservation, and tempering at 500 ℃ in the box furnace for 2h to finish the decarburization-preventing heat treatment of the shield machine hob ring.
Testing the hardness of the surface of the shield machine hob ring to be subjected to heat treatment, wherein the hardness is 24HRC; and testing the hardness of the surface of the shield machine hob ring subjected to the decarburization heat treatment, wherein the hardness is 57HRC.
Comparative example 1
The material of the hob ring of the shield machine is 4Cr5MoSiV1, the element composition comprises 0.42% of C, 5.36% of Cr, 1.40% of Mo, 1.14% of Si, 0.83% of V, and the balance of Fe and inevitable impurities;
directly placing the shield machine hobbing cutter ring to be heat treated in an SXL-1700 box furnace, simultaneously heating to 1100 ℃, preserving heat for 40min, performing oil cooling after the heat preservation is finished, and then tempering in the box furnace at 500 ℃ for 2h to finish the heat treatment of the shield machine hobbing cutter ring.
The hardness of the hob ring treated by the heat treatment method is tested, and the hardness is 42HRC.
Carrying out optical microscopic observation on the metallographic structure on the surface of the hob ring obtained in comparative example 1 and example 1, wherein the test chart is shown in figures 1-2, wherein figure 1 is an optical microscopic metallographic chart of the surface structure of the hob ring obtained by carrying out heat treatment on the hob ring obtained in comparative example 1; FIG. 2 is an optical microscopic metallographic image of the surface structure of the hob ring obtained by the decarburization heat treatment method in example 1.
As can be seen from fig. 1, the quenched structure on the surface of the cutter ring directly subjected to heat treatment without being coated with the oxidation-resistant coating is ferrite plus pearlite, and hardenability is reduced due to decarburization of the surface of the cutter ring, so that martensite is not formed on the surface; as can be seen from FIG. 2, the surface of the hob ring processed by the anti-decarbonization heat treatment method provided by the invention is a typical martensite structure, the surface has obvious embossment which is a phenomenon caused by the increase of specific volume when austenite is transformed into martensite, and is one of the characteristics of martensite phase transformation.
Example 2
The material of the hob ring of the shield machine is 4Cr5MoSiV1, the element composition comprises 0.39% of C, 5.1% of Cr, 1.20% of Mo, 1.1% of Si, 0.9% of V, and the balance of Fe and inevitable impurities; the remaining technical means are the same as in application example 1.
Comparative example 2
The material of the hob ring of the shield machine is 4Cr5MoSiV1, the element composition comprises 0.39% of C, 5.1% of Cr, 1.20% of Mo, 1.1% of Si, 0.9% of V, and the balance of Fe and inevitable impurities; the remaining technical measures are in accordance with comparative example 1.
The hardness of the hob ring surface obtained by the heat treatment of comparative example 2 and example 2 was tested, and the hardness of the hob ring surface obtained in comparative example 2 was 44HRC, and the hardness of the hob ring surface obtained in example 2 was 56.5HRC.
Performing optical microscopic observation on the metallographic structure of the surface of the hob ring obtained by the heat treatment of the comparative example 2 and the example 2, wherein the test chart is shown in fig. 3-4, wherein fig. 3 is an optical microscopic metallographic structure of the surface of the hob ring obtained by the heat treatment of the comparative example 2; FIG. 4 is an optical microscopic metallographic image of the surface structure of the hob ring obtained by the decarburization heat treatment method in example 2.
As can be seen from fig. 3, the quenched structure on the surface of the cutter ring without the anti-oxidation coating is ferrite plus pearlite, and the hardenability of the cutter ring due to the surface decarburization is reduced, so that no martensite is formed on the surface; as can be seen from FIG. 4, the surface of the hob ring treated by the anti-decarbonization heat treatment method provided by the invention is a typical martensite structure, and the hardness of the hob ring is improved.
Example 3
The material of the hob ring of the shield machine is 4Cr5MoSiV1, the element composition is C0.47%, cr 4.9%, mo 1.0%, si 1.1%, V1%, and the balance is Fe and inevitable impurities; the remaining technical means are the same as in application example 1.
Comparative example 2
The material of the hob ring of the shield machine is 4Cr5MoSiV1, the element composition is C0.47%, cr 4.9%, mo 1.0%, si 1.1%, V1%, and the balance is Fe and inevitable impurities; the remaining technical means correspond to comparative example 1.
The hardness of the surface of the hob ring obtained by the heat treatment of comparative example 3 and example 3 was tested, and the hardness of the surface of the hob ring obtained in comparative example 3 was 47HRC, and the hardness of the surface of the hob ring obtained in example 3 was 59HRC.
Performing optical microscopic observation on the metallographic structure of the surface of the hob cutter ring obtained by the heat treatment of the comparative example 3 and the example 3, wherein the test chart is shown in fig. 5-6, wherein fig. 5 is an optical microscopic metallographic structure of the surface of the hob cutter ring obtained by the heat treatment of the comparative example 3; FIG. 6 is an optical microscopic metallographic image of the surface structure of the hob ring obtained by the decarburization heat treatment method in example 3.
As can be seen from fig. 5, the quenched structure on the surface of the cutter ring without the anti-oxidation coating is ferrite plus pearlite, and the hardenability of the cutter ring due to the surface decarburization is reduced, so that no martensite is formed on the surface; as can be seen from FIG. 6, the surface of the hob ring treated by the anti-decarbonization heat treatment method provided by the invention is a typical martensite structure, and the hardness of the hob ring is improved.
The results show that the decarbonization preventing heat treatment method for the shield machine hob cutter ring provided by the invention can inhibit the generation of a decarbonization layer of the hob cutter ring, has the advantages of simple process and low cost, can obtain the heat treatment effect of the hob cutter ring with a large number of lath martensite on the surface, high hardness and long service life, can control the cutter changing cost and the manufacturing cost of the hob cutter ring, and has extremely high application value and economic value.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and amendments can be made without departing from the principle of the present invention, and these modifications and amendments should also be considered as the protection scope of the present invention.

Claims (6)

1. An anti-decarbonization heat treatment method for a shield tunneling machine hob ring comprises the following steps:
placing a shield machine hobbing cutter ring coated with an oxidation coating on the surface in a cavity of heat treatment equipment, heating to a final temperature under normal pressure, preserving heat, and performing heat treatment, wherein a briquette is placed in the cavity of the heat treatment equipment, and the oxidation coating sequentially comprises a first oxidation-resistant coating and a second oxidation-resistant coating from inside to outside;
the first anti-oxidation coating comprises the following components in percentage by mass:
Figure FDF0000018947930000011
the balance of water;
the second anti-oxidation coating comprises the following components in percentage by mass:
SiC 3～5％；
30-60% of graphite powder;
30% -40% of poly-internal olefin;
the balance of water;
the heat treatment is that the shield machine hob ring with the surface coated with the oxidation coating and the briquette are heated together with the furnace, and then heat preservation is carried out;
the final temperature is more than or equal to 1000 ℃, and the heat preservation time is more than or equal to 30min;
the coating thickness of the first anti-oxidation coating is 0.5-1 mm;
the coating thickness of the second anti-oxidation coating is 0.3-0.8 mm.
2. The decarbonization preventing heat treatment method according to claim 1, wherein the particle size of the graphite powder is not less than 1000 meshes.
3. The anti-decarbonization heat treatment method according to claim 1, wherein the coal briquette comprises the following components in percentage by mass:
25 to 30 percent of sodium nitrate, 2 to 5 percent of potassium nitrate, 10 to 30 percent of charcoal powder, 25 to 30 percent of anthracite, 10 to 15 percent of carbonized sawdust, 1 percent of tungsten oxide and 3 to 5 percent of yellow mud.
4. The decarbonization preventing heat treatment method according to any one of claims 1 or 3, wherein the diameter of the briquette is 100 to 120mm, and the height is 65 to 75mm;
the number of the coal balls is 2-4 per hob ring.
5. The decarburization heat treatment method according to claim 1, wherein after the heat treatment, the quenching and tempering are sequentially performed on the obtained heat-treated hob ring.
6. The decarburization heat treatment process of claim 5, wherein the quenching is oil quenching; the tempering temperature is 460-580 ℃, and the time is 2-4 h.
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