CN113106212B - High-temperature heat treatment process for high-strength steel pipe - Google Patents

High-temperature heat treatment process for high-strength steel pipe Download PDF

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CN113106212B
CN113106212B CN202110381724.5A CN202110381724A CN113106212B CN 113106212 B CN113106212 B CN 113106212B CN 202110381724 A CN202110381724 A CN 202110381724A CN 113106212 B CN113106212 B CN 113106212B
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steel pipe
temperature
heating
time
cooling
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CN113106212A (en
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姚闻天
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Wuxi Fuhui Steel Pipe Co ltd
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Wuxi Fuhui Steel Pipe Co ltd
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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
    • C21D1/34—Methods of heating
    • 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
    • C21D11/00—Process control or regulation for heat treatments
    • C21D11/005—Process control or regulation for heat treatments for cooling
    • 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
    • C21D9/08—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes
    • C21D9/085—Cooling or quenching
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
    • C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
    • C23G1/08—Iron or steel
    • C23G1/085—Iron or steel solutions containing HNO3
    • 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
    • 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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • 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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Heat Treatment Of Articles (AREA)
  • Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)

Abstract

The invention relates to a high-temperature heat treatment process for a high-strength steel pipe, which is characterized by comprising the following steps of: the method comprises the following steps: acid washing; the pickling process comprises the following steps: acid washing for the first time; cleaning for the first time; acid washing for the second time; cleaning for the second time; preheating; preheating the steel pipe; a first heating step; a second heating zone; a third heating zone; a fourth heating zone; a fifth hot zone; a cooling step; the cooling process comprises the following steps: cooling for the first time; cooling for the second time; cooling for the third time; a second heating step; the steel pipe is cooled after being heated. The method solves the problems that the heat treatment process of the steel pipe is simple in the existing scheme, so that the comprehensive performance of the steel pipe is low, and the service life of the steel pipe is influenced.

Description

High-temperature heat treatment process for high-strength steel pipe
Technical Field
The invention relates to the field of heat treatment, in particular to a high-temperature heat treatment process for a high-strength steel pipe.
Background
Steel pipe is a hollow, long, steel material used in large quantities as pipes for transporting fluids, such as oil, natural gas, water, gas, steam, etc. Steel pipes are not only used for transporting fluids and powdery solids, exchanging heat energy, manufacturing mechanical parts and containers, but also are economical steels. The steel pipe is used for manufacturing the building structure net rack support and the mechanical support, so that the weight can be reduced, the metal can be saved by 20-40%, and the industrialized mechanical construction can be realized. The steel pipe is used for manufacturing the highway bridge, so that steel can be saved, the construction is simplified, the area of a coating protective layer can be greatly reduced, and the investment and the maintenance cost are saved.
In actual production, steel pipes are mostly subjected to heat treatment in order to improve the properties of the steel pipes. The steel pipe is heated to about 1150 ℃ during heat treatment of the steel pipe, and then water cooling is carried out. The heat treatment process of the steel pipe is simple, so that the comprehensive performance of the steel pipe is low, and the service life of the steel pipe is influenced. How to solve this problem becomes crucial.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a high-temperature heat treatment process for a high-strength steel pipe, so as to solve the problems that the comprehensive performance of the steel pipe is low and the service life of the steel pipe is influenced due to the simple heat treatment process of the steel pipe in the prior art.
In order to achieve the purpose, the technical scheme of the invention is as follows:
high-temperature heat treatment process for high-strength steel pipe
The method comprises the following steps:
the steel pipe comprises the following chemical elements in percentage by weight: c: 0.1-0.4%, Si: 0.2-0.6%, Mn: 1.0-1.8%, Ni: 0.35-0.75%, P: less than or equal to 0.05 percent, S: less than or equal to 0.03 percent, Cr: 0.55-1.25%, and the balance of Fe and impurities;
acid washing; the pickling process comprises the following steps:
acid washing for the first time; placing the steel pipe in a first pickling tank for pickling;
cleaning for the first time; placing the steel pipe in a water tank for cleaning;
acid washing for the second time; placing the steel pipe in a second pickling tank for pickling;
cleaning for the second time; washing the steel pipe;
preheating; preheating the steel pipe;
a first heating step; the first heating process includes five heating zones:
a first heating zone; the heating temperature is 700-800 ℃; the temperature rising speed is 10-15 ℃/min; the heat preservation time is 30-40 min;
a second heating zone; the heating temperature is 800-900 ℃; the temperature rising speed is 8-12 ℃/min; the heat preservation time is 20-30 min;
a third heating zone; the heating temperature is 900-1000 ℃; the temperature rising speed is 6-9 ℃/min; the heat preservation time is 15-20 min;
a fourth heating zone; the heating temperature is 1010-1150 ℃; the temperature rising speed is 5-7 ℃/min; the heat preservation time is 12-15 min;
a fifth hot zone; the heating temperature is 1175-1200 ℃; the temperature rising speed is 3-5 ℃/min; heat preservation is not carried out;
a cooling step; the cooling process comprises the following steps:
cooling for the first time; cooling the steel pipe to 900-1000 ℃ along with the furnace;
cooling for the second time; cooling the steel pipe to room temperature by water;
cooling for the third time; drying the steel pipe in an air cooling mode;
a second heating step; heating the steel pipe and then cooling;
the second heating step specifically includes: heating the steel pipe to 525-545 ℃ along with the furnace; the heat preservation time is positively correlated with the wall thickness of the steel pipe, the heat preservation is carried out for 1-1.5 min every 0.1mm of steel pipe wall thickness, and then the steel pipe is cooled to the room temperature.
The further technical scheme is as follows: in the pickling step, the chemical elements in the first pickling tank comprise the following components in percentage by weight: hydrofluoric acid: 5-8%, nitric acid: 10-15% and the balance of pure water.
The further technical scheme is as follows: in the acid washing step, the chemical elements in the second acid washing tank comprise the following components in percentage by weight: nitric acid: 8-15% and the balance of pure water.
The further technical scheme is as follows: the temperature in the second pickling tank in the pickling step is 20-50 ℃; the temperature in the second pickling bath is positively correlated with the room temperature.
The further technical scheme is as follows: washing by a high-pressure water gun for the second time in the acid washing step; the water pressure is more than or equal to 0.6 Mpa.
The further technical scheme is as follows: the steel pipe is obliquely arranged in the first pickling tank, and the steel pipe is obliquely taken out of the first pickling tank; the steel pipe is obliquely arranged in the second acid washing tank, and the steel pipe is obliquely taken out of the second acid washing tank.
The further technical scheme is as follows: the preheating step specifically comprises: placing the steel pipes in a heating furnace at intervals, wherein the preheating temperature is 300-350 ℃; the temperature rising speed is 5-7 ℃/min; the heat preservation time is 20-25 min.
The further technical scheme is as follows: the cooling mode in the second heating step is air cooling.
Compared with the prior art, the invention has the following beneficial technical effects: (1) in the first pickling, the steel pipe is obliquely arranged in the first pickling tank to avoid splashing of a medium in the first pickling tank, and after the steel pipe is cleaned, the steel pipe is obliquely taken out of the first pickling tank to flow out the medium in the steel pipe to avoid residue; (2) the steel pipe surface is pickled by mixed liquid of hydrofluoric acid and nitric acid, the hydrofluoric acid has a rust removal effect on the steel pipe surface, the steel pipe is placed in a water tank, the residual hydrofluoric acid and nitric acid on the steel pipe surface are cleaned, and the medium of a first pickling tank and the medium of a second pickling tank are prevented from being mixed and influenced; (3) in the second pickling, the steel pipe is obliquely arranged in a second pickling tank to avoid splashing of a medium in the second pickling tank, and after the steel pipe is cleaned, the steel pipe is obliquely taken out of the second pickling tank to flow out the medium in the steel pipe to avoid residue; (4) in the second cleaning, the surface of the steel pipe is washed by a high-pressure water gun, so that nitric acid on the surface of the steel pipe can be washed clean, and impurities on the surface of the steel pipe can be washed clean; (5) the temperature of the steel pipe rises along with the temperature in the furnace, the temperature rising speed in the preheating step is slow, and the heat preservation time is long, so that the inside and the outside of the steel pipe can be uniformly heated, and the internal structure of the steel pipe is uniform; (6) the heating speed and the heat preservation time are adjusted according to different heating zones by adopting the fifth heating zone process, so that the steel pipe can be uniformly heated, and the metallographic structure in the steel pipe is uniform; (7) the temperature of the steel pipe is reduced along with the furnace, so that the internal crystallization of the steel pipe is more refined, the metallographic structure in the steel pipe is more uniform, and the rapid temperature reduction is realized through water cooling in the secondary cooling process; (8) the cooling time of the steel pipe in the second cooling is short, so that the inner temperature and the outer temperature of the steel pipe are inconsistent, the steel pipe is cooled by air cooling in the third cooling process, the temperature in the steel pipe is conducted on the surface of the steel pipe, the cooling is realized on the steel pipe, meanwhile, the air cooling can remove the residual moisture on the surface of the steel pipe, and the steel pipe is dried by air; (9) the hardness, strength, plasticity and toughness of the steel pipe can be adjusted through the second heating step, the comprehensive performance of the steel pipe is improved, the metallographic structure of the steel pipe tends to be stable, the steel pipe is not easy to deform, and the service life of the steel pipe is prolonged; (10) the heat preservation time of the steel pipes with different wall thicknesses is different, and the thicker the wall thickness of the steel pipe is, the longer the heat preservation time is, so that the internal and external temperatures of the steel pipe are consistent, and the metallographic structures of the steel pipe are uniform and consistent.
Drawings
Fig. 1 shows a flowchart of a high-temperature heat treatment process for a high-strength steel pipe according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the following detailed description of the present invention is provided with reference to the accompanying drawings and the detailed description. The advantages and features of the present invention will become more apparent from the following description. It is to be noted that the drawings are in a very simplified form and are all used in a non-precise scale for the purpose of facilitating and distinctly aiding in the description of the embodiments of the present invention. To make the objects, features and advantages of the present invention comprehensible, reference is made to the accompanying drawings. It should be understood that the structures, ratios, sizes, and the like shown in the drawings and described in the specification are only used for matching with the disclosure of the specification, so as to be understood and read by those skilled in the art, and are not used to limit the implementation conditions of the present invention, so that the present invention has no technical significance, and any structural modification, ratio relationship change or size adjustment should still fall within the scope of the present invention without affecting the efficacy and the achievable purpose of the present invention.
Fig. 1 shows a flowchart of a high-temperature heat treatment process for a high-strength steel pipe according to an embodiment of the present invention. Referring to fig. 1, the present invention discloses a high temperature heat treatment process for a high strength steel pipe.
The high-temperature heat treatment process for the high-strength steel pipe comprises the following steps of:
and (4) acid washing. The pickling process comprises the following steps:
and (5) carrying out acid washing for the first time. And placing the steel pipe in a first pickling tank for pickling.
And (5) cleaning for the first time. And (5) cleaning the steel pipe in a water tank.
And (5) carrying out acid washing for the second time. And placing the steel pipe in a second pickling tank for pickling.
And (5) cleaning for the second time. And (5) washing the steel pipe.
The steel pipe comprises the following chemical elements in percentage by weight: c: 0.1-0.4%, Si: 0.2-0.6%, Mn: 1.0-1.8%, Ni: 0.35-0.75%, P: less than or equal to 0.05 percent, S: less than or equal to 0.03 percent, Cr: 0.55-1.25%, and the balance of Fe and impurities.
Before the steel pipe is pickled, the components of each chemical element of the steel pipe need to be strictly controlled. In order to ensure the comprehensive performance of the steel pipe, the contents of C, Si, Mn, Ni and Cr are strictly controlled, and the contents of harmful elements S and P are also controlled.
In the pickling step, the chemical elements in the first pickling tank comprise the following components in percentage by weight: hydrofluoric acid: 5-8%, nitric acid: 10-15% and the balance of pure water.
In the acid washing step, the chemical elements in the second acid washing tank comprise the following components in percentage by weight: nitric acid: 8-15% and the balance of pure water.
The temperature in the second pickling tank in the pickling step is 20-50 ℃. The temperature in the second pickling bath is positively correlated with the room temperature.
And in the acid washing step, the second cleaning is carried out by adopting a high-pressure water gun. The water pressure is more than or equal to 0.6 Mpa.
The steel pipe is obliquely arranged in the first pickling tank, and the steel pipe is obliquely taken out of the first pickling tank. The steel pipe is obliquely arranged in the second acid washing tank, and the steel pipe is obliquely taken out of the second acid washing tank.
The pickling step can remove scale and rust on the surface of the steel pipe.
The steel pipe is obliquely arranged in the first pickling tank in the first pickling, so that the splashing of a medium in the first pickling tank is avoided. And after the steel pipe is cleaned, the steel pipe is obliquely taken out of the first pickling tank, and the medium in the steel pipe flows out to avoid residue.
The surface of the steel pipe is pickled by a mixed solution of hydrofluoric acid and nitric acid. The hydrofluoric acid has the function of removing rust on the surface of the steel pipe. The steel pipe is placed in a water tank, and the residual hydrofluoric acid and the residual nitric acid on the surface of the steel pipe are cleaned, so that the medium in the first pickling tank and the medium in the second pickling tank are prevented from being mixed and influenced.
And the steel pipe is obliquely arranged in the second pickling tank in the second pickling process, so that the splashing of a medium in the second pickling tank is avoided. And after the steel pipe is cleaned, the steel pipe is obliquely taken out of the second pickling tank, and the medium in the steel pipe flows out to avoid residue.
The surface of the steel pipe is clean and uniform after being cleaned by the nitric acid solution.
Wash the steel pipe surface through the high-pressure squirt in the washing of secondary, can wash the nitric acid on steel pipe surface totally, can wash the impurity on steel pipe surface totally simultaneously.
The solution temperature in the second pickling bath is positively correlated with the room temperature. When the room temperature is higher, a higher temperature value within the range of 20-50 ℃ is selected. When the room temperature is lower, a lower temperature value within the range of 20-50 ℃ is selected.
And (4) preheating. And preheating the steel pipe.
The preheating step specifically comprises: the steel pipes are placed in a heating furnace at intervals, and the preheating temperature is 300-350 ℃. The temperature rising speed is 5-7 ℃/min. The heat preservation time is 20-25 min.
A gap exists between the adjacent steel pipes, so that the steel pipes are convenient to heat. So that the steel pipe can be uniformly heated and the local temperature rise of the steel pipe is avoided.
The temperature of the steel pipe rises along with the temperature in the furnace. In the preheating step, the temperature rising speed is low, and the heat preservation time is long, so that the inside and the outside of the steel pipe can be uniformly heated, and the internal structure of the steel pipe is uniform.
A first heating step. The first heating process includes five heating zones:
a first heating zone. The heating temperature is 700-800 ℃. The temperature rising speed is 10-15 ℃/min. The heat preservation time is 30-40 min.
A second heating zone. The heating temperature is 800-900 ℃. The temperature rising speed is 8-12 ℃/min. The heat preservation time is 20-30 min.
A third heating zone. The heating temperature is 900-1000 ℃. The temperature rise speed is 6-9 ℃/min. The heat preservation time is 15-20 min.
A fourth heating zone. The heating temperature is 1010-1150 ℃. The temperature rising speed is 5-7 ℃/min. The heat preservation time is 12-15 min.
The fifth hot zone. The heating temperature is 1175-1200 ℃. The temperature rising speed is 3-5 ℃/min. The temperature is not preserved.
The first heating step adopts five times of temperature rise steps, the interval of heating temperature is gradually shortened, the temperature rise speed is gradually increased, and the heat preservation time is gradually shortened in the process from the first heating area to the fifth heating area.
The heating zone process is adopted for five times, and the heating rate and the heat preservation time are adjusted according to different heating zones, so that the steel pipe can be uniformly heated, and the metallographic structure in the steel pipe is uniform.
After the first heating step, the distorted crystal lattice of the steel pipe is recovered, the elongated and broken crystal grains are recrystallized, and the internal stress of the steel pipe is eliminated.
And (5) cooling. The cooling process comprises the following steps:
and (6) cooling for the first time. And cooling the steel pipe to 900-1000 ℃ along with the furnace.
And (5) cooling for the second time. The steel tube is cooled to room temperature by water.
And cooling for the third time. And (5) air cooling and drying the steel pipe.
The steel pipe is cooled along with the furnace in the first cooling process, so that a heat preservation process does not exist in the fifth heating area in the first heating step, and the time of a high-temperature heat treatment process for the high-strength steel pipe is shortened.
The steel pipe is cooled along with the furnace, so that the internal crystallization of the steel pipe is more refined, and the metallographic structure in the steel pipe is more uniform. And the rapid cooling is realized by water cooling in the second cooling process.
And the cooling time of the steel pipe is shorter in the second cooling, so that the internal temperature and the external temperature of the steel pipe are inconsistent. And in the third cooling process, air cooling is adopted for the steel pipe. And cooling the steel pipe by cooling the surface of the steel pipe with temperature conduction in the steel pipe. Meanwhile, residual moisture on the surface of the steel pipe can be removed through air cooling, and the steel pipe is air-dried.
And a second heating step. The steel pipe is cooled after being heated.
The second heating step specifically includes: the temperature of the steel pipe rises to 525-545 ℃ along with the furnace. The heat preservation time is positively correlated with the wall thickness of the steel pipe, the heat preservation is carried out for 1-1.5 min every 0.1mm of steel pipe wall thickness, and then the steel pipe is cooled to the room temperature.
The cooling mode in the second heating step is air cooling.
The hardness, strength, plasticity and toughness of the steel pipe can be adjusted through the second heating step, the comprehensive performance of the steel pipe is improved, the metallographic structure of the steel pipe tends to be stable, the steel pipe is not prone to deformation, and the service life of the steel pipe is prolonged.
The heat preservation time of the steel pipes with different wall thicknesses is different, and the thicker the wall thickness of the steel pipe is, the longer the heat preservation time is. So that the internal and external temperatures of the steel pipe are consistent, and the metallographic structures of the steel pipe are uniform and consistent.
The process of the invention is illustrated below by means of three examples:
the first embodiment:
the high-temperature heat treatment process for the high-strength steel pipe comprises the following steps of:
the steel pipe comprises the following chemical elements in percentage by weight: c: 0.1%, Si: 0.2%, Mn: 1.0%, Ni: 0.35%, P: 0.01%, S: 0.01%, Cr: 0.55%, the balance being Fe and impurities.
And (4) acid washing. The pickling process comprises the following steps:
and (5) carrying out acid washing for the first time. And placing the steel pipe in a first pickling tank for pickling.
And (5) cleaning for the first time. And (5) cleaning the steel pipe in a water tank.
And (5) carrying out acid washing for the second time. And placing the steel pipe in a second pickling tank for pickling.
And (5) cleaning for the second time. And (5) washing the steel pipe.
In the pickling step, the chemical elements in the first pickling tank comprise the following components in percentage by weight: hydrofluoric acid: 5%, nitric acid: 10 percent of pure water, and the balance of pure water.
In the acid washing step, the chemical elements in the second acid washing tank comprise the following components in percentage by weight: nitric acid: 8 percent of pure water, and the balance of pure water.
The temperature in the second pickling tank in the pickling step is 20 ℃. The temperature in the second pickling bath is positively correlated with the room temperature.
And in the acid washing step, the second cleaning is carried out by adopting a high-pressure water gun. The water pressure was 0.6 MPa.
The steel pipe is obliquely arranged in the first pickling tank, and the steel pipe is obliquely taken out of the first pickling tank. The steel pipe is obliquely arranged in the second acid washing tank, and the steel pipe is obliquely taken out of the second acid washing tank.
And (4) preheating. And preheating the steel pipe.
The preheating step specifically comprises: the steel pipes are placed in a heating furnace at intervals, and the preheating temperature is 300 ℃. The temperature rise rate was 5 ℃/min. The holding time is 20 min.
A first heating step. The first heating process includes five heating zones:
a first heating zone. The heating temperature was 700 ℃. The temperature rise rate is 10 ℃/min. The holding time is 30 min.
A second heating zone. The heating temperature was 800 ℃. The temperature rise rate is 8 ℃/min. The holding time is 20 min.
A third heating zone. The heating temperature was 900 ℃. The temperature rise rate was 6 ℃/min. The holding time is 15 min.
A fourth heating zone. The heating temperature was 1010 ℃. The temperature rise rate was 5 ℃/min. The holding time is 12 min.
The fifth hot zone. The heating temperature was 1175 ℃. The temperature rise rate was 3 ℃/min. The temperature is not preserved.
And (5) cooling. The cooling process comprises the following steps:
and (6) cooling for the first time. The steel pipe is cooled to 900 ℃ along with the furnace.
And (5) cooling for the second time. The steel tube is cooled to room temperature by water.
And cooling for the third time. And (5) air cooling and drying the steel pipe.
And a second heating step. The steel pipe is cooled after being heated.
The second heating step specifically includes: the steel tube is heated to 525 ℃ along with the furnace. The heat preservation time is positively correlated with the wall thickness of the steel pipe, the steel pipe with the wall thickness of 2mm is subjected to heat preservation for 20min, and then the steel pipe is cooled to the room temperature.
The cooling mode in the second heating step is air cooling.
The second embodiment:
the high-temperature heat treatment process for the high-strength steel pipe comprises the following steps of:
the steel pipe comprises the following chemical elements in percentage by weight: c: 0.25%, Si: 0.4%, Mn: 1.5%, Ni: 0.55%, P: 0.03%, S: 0.02%, Cr: 0.85%, and the balance of Fe and impurities.
And (4) acid washing. The pickling process comprises the following steps:
and (3) acid washing for the first time. And (3) pickling the steel pipe in a first pickling tank.
And (5) cleaning for the first time. And (5) cleaning the steel pipe in a water tank.
And (5) carrying out acid washing for the second time. And placing the steel pipe in a second pickling tank for pickling.
And (5) cleaning for the second time. And (5) washing the steel pipe.
In the pickling step, the chemical elements in the first pickling tank comprise the following components in percentage by weight: hydrofluoric acid: 7%, nitric acid: 13 percent of pure water and the balance of pure water.
In the acid washing step, the chemical elements in the second acid washing tank comprise the following components in percentage by weight: nitric acid: 11 percent of pure water, and the balance of pure water.
The temperature in the second pickling tank in the pickling step is 30 ℃. The temperature in the second pickling bath is positively correlated with the room temperature.
And in the acid washing step, the second cleaning is carried out by adopting a high-pressure water gun. The water pressure is 0.8 Mpa.
The steel pipe is obliquely arranged in the first pickling tank, and the steel pipe is obliquely taken out of the first pickling tank. The steel pipe is obliquely arranged in the second acid washing tank, and the steel pipe is obliquely taken out of the second acid washing tank.
And (4) preheating. And preheating the steel pipe.
The preheating step specifically comprises: the steel pipes are placed in a heating furnace at intervals, and the preheating temperature is 330 ℃. The temperature rise rate is 6 ℃/min. The holding time is 23 min.
A first heating step. The first heating process includes five heating zones:
a first heating zone. The heating temperature was 750 ℃. The temperature rise rate is 12 ℃/min. The holding time is 35 min.
A second heating zone. The heating temperature was 850 ℃. The temperature rise rate is 10 ℃/min. The holding time is 25 min.
A third heating zone. The heating temperature was 950 ℃. The temperature rise rate is 8 ℃/min. The holding time is 17 min.
A fourth heating zone. The heating temperature was 1030 ℃. The temperature rise rate was 6 ℃/min. The holding time is 14 min.
The fifth hot zone. The heating temperature was 1190 ℃. The temperature rise rate was 4 ℃/min. The temperature is not preserved.
And (5) cooling. The cooling process comprises the following steps:
and (6) cooling for the first time. The steel pipe is cooled to 950 ℃ along with the furnace.
And (5) cooling for the second time. The steel tube is cooled to room temperature by water.
And cooling for the third time. And (5) air cooling and drying the steel pipe.
And a second heating step. The steel pipe is cooled after being heated.
The second heating step specifically includes: the steel tube is heated to 535 ℃ with the furnace. The heat preservation time is positively correlated with the wall thickness of the steel pipe, the heat preservation is carried out on the steel pipe with the wall thickness of 3mm for 36min, and then the steel pipe is cooled to the room temperature.
The cooling mode in the second heating step is air cooling.
The third embodiment:
the high-temperature heat treatment process for the high-strength steel pipe comprises the following steps of:
the steel pipe comprises the following chemical elements in percentage by weight: c: 0.4%, Si: 0.6%, Mn: 1.8%, Ni: 0.75%, P: 0.05%, S: 0.03%, Cr: 1.25%, the balance being Fe and impurities.
And (4) acid washing. The pickling process comprises the following steps:
and (5) carrying out acid washing for the first time. And placing the steel pipe in a first pickling tank for pickling.
And (5) cleaning for the first time. And (5) cleaning the steel pipe in a water tank.
And (5) carrying out acid washing for the second time. And placing the steel pipe in a second pickling tank for pickling.
And (5) cleaning for the second time. And (5) washing the steel pipe.
In the pickling step, the chemical elements in the first pickling tank comprise the following components in percentage by weight: hydrofluoric acid: 8%, nitric acid: 15 percent of pure water in balance.
In the acid washing step, the chemical elements in the second acid washing tank comprise the following components in percentage by weight: nitric acid: 15 percent of pure water in balance.
The temperature in the second pickling tank in the pickling step is 50 ℃. The temperature in the second pickling bath is positively correlated with the room temperature.
And in the acid washing step, the second cleaning is carried out by adopting a high-pressure water gun. The water pressure is 1.0 Mpa.
The steel pipe is obliquely arranged in the first pickling tank, and the steel pipe is obliquely taken out of the first pickling tank. The steel pipe is obliquely arranged in the second acid washing tank, and the steel pipe is obliquely taken out of the second acid washing tank.
And (4) preheating. And preheating the steel pipe.
The preheating step specifically comprises: the steel pipes are placed in a heating furnace at intervals, and the preheating temperature is 350 ℃. The temperature rise rate is 7 ℃/min. The holding time is 25 min.
A first heating step. The first heating process includes five heating zones:
a first heating zone. The heating temperature was 800 ℃. The temperature rise rate is 15 ℃/min. The holding time is 40 min.
A second heating zone. The heating temperature was 900 ℃. The temperature rise rate is 12 ℃/min. The holding time is 30 min.
A third heating zone. The heating temperature was 1000 ℃. The temperature rise rate was 9 ℃/min. The holding time is 20 min.
A fourth heating zone. The heating temperature was 1150 ℃. The temperature rise rate was 7 ℃/min. The holding time is 15 min.
The fifth hot zone. The heating temperature was 1200 ℃. The temperature rise rate was 5 ℃/min. The temperature is not preserved.
And (5) cooling. The cooling process comprises the following steps:
and (6) cooling for the first time. The steel pipe is cooled to 1000 ℃ along with the furnace.
And (5) cooling for the second time. The steel tube is cooled to room temperature by water.
And cooling for the third time. And (5) air cooling and drying the steel pipe.
And a second heating step. The steel pipe is cooled after being heated.
The second heating step specifically includes: the steel pipe is heated to 545 ℃ along with the furnace. The heat preservation time is positively correlated with the wall thickness of the steel pipe, the heat preservation is carried out on the steel pipe with the wall thickness of 4mm for 6min, and then the steel pipe is cooled to the room temperature.
The cooling mode in the second heating step is air cooling.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims (8)

1. A high-temperature heat treatment process for a high-strength steel pipe is characterized by comprising the following steps of: the method comprises the following steps:
the steel pipe comprises the following chemical elements in percentage by weight: c: 0.1-0.4%, Si: 0.2-0.6%, Mn: 1.0-1.8%, Ni: 0.35-0.75%, P: less than or equal to 0.05 percent, S: less than or equal to 0.03 percent, Cr: 0.55-1.25%, and the balance of Fe and impurities;
acid washing; the pickling process comprises the following steps:
acid washing for the first time; placing the steel pipe in a first pickling tank for pickling;
cleaning for the first time; placing the steel pipe in a water tank for cleaning;
acid washing for the second time; placing the steel pipe in a second pickling tank for pickling;
cleaning for the second time; washing the steel pipe;
preheating; preheating the steel pipe;
a first heating step; the first heating process includes five heating zones:
a first heating zone; the heating temperature is 700-800 ℃; the temperature rising speed is 10-15 ℃/min; the heat preservation time is 30-40 min;
a second heating zone; the heating temperature is 800-900 ℃; the temperature rising speed is 8-12 ℃/min; the heat preservation time is 20-30 min;
a third heating zone; the heating temperature is 900-1000 ℃; the temperature rising speed is 6-9 ℃/min; the heat preservation time is 15-20 min;
a fourth heating zone; the heating temperature is 1010-1150 ℃; the temperature rising speed is 5-7 ℃/min; the heat preservation time is 12-15 min;
a fifth hot zone; the heating temperature is 1175-1200 ℃; the temperature rising speed is 3-5 ℃/min; heat preservation is not carried out;
a cooling step; the cooling process comprises the following steps:
cooling for the first time; cooling the steel pipe to 900-1000 ℃ along with the furnace;
cooling for the second time; cooling the steel pipe to room temperature by water;
cooling for the third time; drying the steel pipe in an air cooling mode;
a second heating step; heating the steel pipe and then cooling;
the second heating step specifically includes: heating the steel pipe to 525-545 ℃ along with the furnace; the heat preservation time is positively correlated with the wall thickness of the steel pipe, the heat preservation is carried out for 1-1.5 min every 0.1mm of steel pipe wall thickness, and then the steel pipe is cooled to the room temperature.
2. The high temperature heat treatment process for a high strength steel pipe according to claim 1, wherein: in the pickling step, the chemical elements in the first pickling tank comprise the following components in percentage by weight: hydrofluoric acid: 5-8%, nitric acid: 10-15% and the balance of pure water.
3. The high temperature heat treatment process for a high strength steel pipe according to claim 1, wherein: in the acid washing step, the chemical elements in the second acid washing tank comprise the following components in percentage by weight: nitric acid: 8-15% and the balance of pure water.
4. The high temperature heat treatment process for a high strength steel pipe according to claim 3, wherein: the temperature in the second pickling tank in the pickling step is 20-50 ℃; the temperature in the second pickling bath is positively correlated with the room temperature.
5. The high temperature heat treatment process for a high strength steel pipe according to claim 1, wherein: washing by a high-pressure water gun for the second time in the acid washing step; the water pressure is more than or equal to 0.6 Mpa.
6. The high temperature heat treatment process for a high strength steel pipe according to claim 1, wherein: the steel pipe is obliquely arranged in the first pickling tank, and the steel pipe is obliquely taken out of the first pickling tank; the steel pipe is obliquely arranged in the second acid washing tank, and the steel pipe is obliquely taken out of the second acid washing tank.
7. The high temperature heat treatment process for a high strength steel pipe according to claim 1, wherein: the preheating step specifically comprises: placing the steel pipes in a heating furnace at intervals, wherein the preheating temperature is 300-350 ℃; the temperature rising speed is 5-7 ℃/min; the heat preservation time is 20-25 min.
8. The high temperature heat treatment process for a high strength steel pipe according to claim 1, wherein: the cooling mode in the second heating step is air cooling.
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