CN111455143A - Heat treatment method for low-temperature 9Ni steel two-phase region quenching - Google Patents
Heat treatment method for low-temperature 9Ni steel two-phase region quenching Download PDFInfo
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- CN111455143A CN111455143A CN202010331343.1A CN202010331343A CN111455143A CN 111455143 A CN111455143 A CN 111455143A CN 202010331343 A CN202010331343 A CN 202010331343A CN 111455143 A CN111455143 A CN 111455143A
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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
- C21D1/18—Hardening; Quenching with or without subsequent tempering
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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
- C21D11/00—Process control or regulation for heat treatments
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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
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/0081—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for slabs; for billets
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
- G01N23/20—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by using diffraction of the radiation by the materials, e.g. for investigating crystal structure; by using scattering of the radiation by the materials, e.g. for investigating non-crystalline materials; by using reflection of the radiation by the materials
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
- G01N23/22—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material
- G01N23/225—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material using electron or ion
- G01N23/2251—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material using electron or ion using incident electron beams, e.g. scanning electron microscopy [SEM]
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/30—Investigating strength properties of solid materials by application of mechanical stress by applying a single impulsive force, e.g. by falling weight
Abstract
The invention discloses a heat treatment method for quenching a low-temperature 9Ni steel two-phase region, which comprises the following steps of S1, processing a 9Ni steel block into 4 steel plates with the sizes of 70mm, × 80mm, × 14mm and × mm, S2, carrying out heat treatment on the steel plates, S3, cutting the sample into metallographic samples with the sizes of 14mm, × 14mm, 14mm and × 3mm, embedding the metallographic samples into cylindrical blocks with the diameters of 32mm by cold embedding, S4, carrying out surface treatment on the samples, S5, observing the phase composition of a microstructure of the samples after the surface treatment on a scanning electron microscope, S6, scanning martensite (200) and austenite (200), (211) and (220) and (311) by XRD to calculate the content of rotary austenite, S7, processing the workpieces after the heat treatment into an impact sample and a tensile sample according to national standards, and searching the quenching temperature of the two-phase region, so that the obtained microstructure achieves the optimal heat preservation toughness and the even low-temperature ratio under the condition that the temperature of the temperature region is 640 ℃ for 30 min.
Description
Technical Field
The invention relates to the technical field of heat treatment processes, in particular to a heat treatment method for low-temperature 9Ni steel two-phase region quenching.
Background
However, the geographic location of storing large quantities of natural gas in the world is generally far from the primary consumption area, and therefore large-scale storage and long-distance transportation are required.
The 9Ni steel is a steel grade with 9 percent of Ni which is firstly developed by the United states in the 40 th century, the use temperature can reach-196 ℃ at the lowest, and the 9Ni steel is a steel grade which is widely used for building liquefied natural gas internationally. Under the condition of low temperature, the high-strength steel can meet the high strength requirement and has good toughness and fracture resistance. In recent years, 9Ni steel has been studied for its properties, including strength, toughness, tensile, compressive properties, and the like. The 9Ni steel after heat treatment has better performance. Therefore, the selection of an appropriate heat treatment method is particularly important for the properties of the 9Ni steel.
The prior art is that 9Ni steel has two types: one is firstly quenching and tempering; the other is quenching, two-phase zone quenching and tempering. Studies have shown that the first mode of heat treated material does not perform as well as the second. Many researchers have conducted researches on the second heat treatment mode, including selection of quenching temperature, selection of quenching temperature in the two-phase region, selection of heat preservation time in the two-phase region, and selection of tempering temperature. The stability of the 9Ni steel depends on the content of the rotary austenite, and the tempering temperature, the tempering heat preservation time, the two-phase zone quenching and the like have certain influence on the content of the rotary austenite.
The two existing methods have the defects that the heat treatment mode of the former method is simple, only quenching and tempering are carried out, the obtained strength and low-temperature toughness are low, and the material performance obtained by the heat treatment mode of the latter method is good, but researchers have shallow research on the aspect, and the change of the quenching and tempering temperature has little influence on the performance of the material and does not achieve the best performance. And the optimal heat treatment process parameters selected for the 9Ni steel with different compositions are slightly different.
Disclosure of Invention
The invention aims to provide a heat treatment method for low-temperature 9Ni steel two-phase region quenching, which aims to solve the problems in the background technology.
In order to achieve the purpose, the invention provides the following technical scheme:
a heat treatment method for low-temperature 9Ni steel two-phase zone quenching specifically comprises the following steps:
s1, firstly, processing the 9Ni steel block into 4 steel plates with the thickness of 70mm, × 80mm, × 14mm and the thickness of 3914 mm;
s2, carrying out heat treatment on the steel plate: the heat treatment protocol was:
s2.1, heating the four steel plates to 800 ℃, preserving heat for 1h, and cooling with water;
s2.2, respectively heating the quenched sample to 610-700 ℃, preserving heat for 30min, and cooling with water;
and S2.3, heating the four samples to 570 ℃, preserving heat for 1 hour, tempering, and air cooling.
S3, cutting the sample into metallographic samples with the size of 14mm × 14mm × 3mm, and then embedding the metallographic samples into cylindrical blocks with the diameter of 32mm by cold embedding;
s4, carrying out surface treatment on the sample;
s5, observing the microstructure phase composition of the sample after surface treatment on a scanning electron microscope;
s6, scanning martensite (200), (211) and austenite (200), (220) and (311) by XRD, and calculating the content of the rotary austenite;
s7, processing the heat-treated workpiece into an impact sample and a tensile sample according to national standards, soaking the impact sample in liquid nitrogen, taking out the impact sample, completing an impact test by using an impact tester, collecting data, and stretching the processed tensile sample by using a universal fatigue tester at the speed of 0.01S-1。
Further, in S2.2, the sample after quenching is heated to 610 ℃, 640 ℃, 670 ℃ and 700 ℃ respectively, and is kept warm for 30min, and then is cooled by water.
Further, the heat-treated sample to be processed in step S1 is ensured to have the same size.
Further, the surface treatment in step S4 includes steps of grinding the sample surface with 250, 400, 1000, 1500 # sandpaper until the scratches on the sample surface are distributed on the sample surface at substantially equal intervals and in the same direction, polishing the sample surface on a mechanical polisher with 2.5 # water-soluble grinding paste until no scratches are formed, and then etching the sample with 7% nital solution until the surface is matte.
Further, in the step S7, the tensile test sample and the impact test sample are processed according to the national standard, and when the low-temperature impact test is performed, the test sample is ensured to be soaked in liquid nitrogen for more than 10min, and the test is completed within 5S after being taken out.
Further, the preparation, characterization and measurement instruments used in the present invention: a medium-speed wire cutting machine tool; a heat treatment resistance furnace; grinding and polishing machine; a scanning electron microscope; an X-ray diffractometer; an impact testing machine; a fatigue testing machine.
Compared with the prior art, the invention has the beneficial effects that:
the invention explores the L stage with key factors in the Q L T three-stage heat treatment process of 9Ni steel, and compares the grain size and distribution condition, the content and distribution condition of the rotary austenite, the tensile property and the low-temperature impact toughness of the 9Ni steel through different process parameters, thereby obtaining the process parameters with the best performance.
By exploring the quenching temperature of the two-phase region, the microstructure obtained is fine and uniform under the condition that the temperature of the two-phase region is 640 ℃ and the heat preservation time is 30min, and the strength and the low-temperature toughness reach the optimal proportion.
Drawings
FIG. 1 is a process flow diagram of a heat treatment method of two-phase zone quenching of low-temperature 9Ni steel.
Detailed Description
The technical solution of the present patent will be described in further detail with reference to the following embodiments.
Referring to fig. 1, the main process of the present invention is as follows: the first quenching is carried out for 1h at the temperature of Ac3, and then water quenching treatment is carried out rapidly; the second time is that two-phase regions with different temperature parameters are selected between Ac1 and Ac3 for quenching, the temperature is kept for 30min, and then water quenching treatment is rapidly carried out; and thirdly, keeping the temperature below Ac1 for 1h, and then performing air cooling treatment.
A heat treatment method for low-temperature 9Ni steel two-phase zone quenching specifically comprises the following steps:
s1, firstly, processing the 9Ni steel block into 4 steel plates with the thickness of 70mm, × 80mm, × 14mm and the thickness of 3914 mm;
s2, the heat treatment protocol is as follows:
s2.1, heating the four steel plates to 800 ℃, preserving heat for 1h, and cooling with water;
s2.2, respectively heating the quenched samples to 640 ℃, preserving heat for 30min, and cooling with water;
and S2.3, heating the four samples to 570 ℃, preserving heat for 1 hour, tempering, and air cooling.
S3, cutting the sample into metallographic samples with the size of 14mm × 14mm × 3mm, and then embedding the metallographic samples into cylindrical blocks with the diameter of 32mm by cold embedding;
s4, grinding the surfaces of the samples by No. 250, No. 400, No. 1000 and No. 1500 abrasive papers respectively until scratches on the surfaces of the samples are distributed on the surfaces of the samples at the same direction and basically equal intervals, polishing the surfaces of the samples on a mechanical polishing machine by No. 2.5 water-soluble grinding paste until no scratches exist, and then corroding the samples by 7% nital solution until the surfaces are matt;
s5, observing the phase composition of the microstructure of the corroded sample on a scanning electron microscope;
s6, the martensite (200), (211) and the austenite (200), (220), and (311) were scanned by XRD, and the content of the austenite turned was calculated.
S7, processing the heat-treated workpiece into an impact sample and a tensile sample according to national standards, soaking the impact sample in liquid nitrogen for more than 10min, taking out, completing an impact test in 5S by using an impact tester, collecting data, and stretching the processed tensile sample by using a universal fatigue tester at a speed of 0.01S-1。
Finally, the indexes of the 9Ni steel in all aspects, which are achieved by adopting the invention, are as follows:
the preparation, characterization and measurement instrument used in the invention:
a medium-speed wire cutting machine tool;
a heat treatment resistance furnace;
grinding and polishing machine;
a scanning electron microscope;
an X-ray diffractometer;
an impact testing machine;
a fatigue testing machine;
the invention explores the temperature of the two-phase zone quenching (L) stage through the heat treatment mode of Q L T, thereby obtaining the best tensile strength and low-temperature impact toughness;
by exploring the quenching temperature of the two-phase region, the microstructure obtained is fine and uniform under the condition that the temperature of the two-phase region is 640 ℃ and the heat preservation time is 30min, and the strength and the low-temperature toughness reach the optimal proportion.
Although the preferred embodiments of the present patent have been described in detail, the present patent is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present patent within the knowledge of those skilled in the art.
Claims (7)
1. A heat treatment method for low-temperature 9Ni steel two-phase zone quenching is characterized by comprising the following steps:
s1, firstly, processing the 9Ni steel block into 4 steel plates with the thickness of 70mm, × 80mm, × 14mm and the thickness of 3914 mm;
s2, carrying out heat treatment on the steel plate: the heat treatment protocol was:
s2.1, heating the four steel plates to 800 ℃, preserving heat for 1h, and cooling with water;
s2.2, respectively heating the quenched sample to 610-700 ℃, preserving heat for 30min, and cooling with water;
and S2.3, heating the four samples to 570 ℃, preserving heat for 1 hour, tempering, and air cooling.
S3, cutting the sample into metallographic samples with the size of 14mm × 14mm × 3mm, and then embedding the metallographic samples into cylindrical blocks with the diameter of 32mm by cold embedding;
s4, carrying out surface treatment on the sample;
s5, observing the microstructure phase composition of the sample after surface treatment on a scanning electron microscope;
s6, scanning martensite (200), (211) and austenite (200), (220) and (311) by XRD, and calculating the content of the rotary austenite;
s7, processing the heat-treated workpiece into an impact sample and a tensile sample according to national standards, soaking the impact sample in liquid nitrogen, taking out the impact sample, completing an impact test by using an impact tester, collecting data, and stretching the processed tensile sample by using a universal fatigue tester at the speed of 0.01S-1。
2. The heat treatment method for the two-phase zone quenching of the low-temperature 9Ni steel as claimed in claim 1, wherein the step S2.2 is to heat the quenched sample to 610 ℃, 640 ℃, 670 ℃ and 700 ℃ respectively, keep the temperature for 30min, and cool the sample with water.
3. The heat treatment method for the two-phase zone quenching of the low-temperature 9Ni steel as claimed in claim 1, wherein the heat treatment samples to be performed in the step S1 are guaranteed to have the same size.
4. The heat treatment method for low-temperature 9Ni steel two-phase zone quenching as claimed in claim 1, wherein the surface treatment in step S4 comprises the steps of grinding with 250, 400, 1000 and 1500 # sand papers respectively until scratches on the sample surface are distributed on the sample surface in substantially equal intervals and directions, polishing the sample surface on a mechanical polishing machine with 2.5 # water-soluble grinding paste until no scratches are formed, and then corroding the sample to have matte color.
5. The heat treatment method for the two-phase zone quenching of the low-temperature 9Ni steel as claimed in claim 1, wherein a 7% nital solution is used for corrosion samples.
6. The heat treatment method for the two-phase zone quenching of the low-temperature 9Ni steel as claimed in claim 1, wherein in the step S7, the tensile test sample and the impact test sample are processed according to national standards, and when the low-temperature impact test is carried out, the test samples are soaked in liquid nitrogen for more than 10min and taken out to complete the test within 5S.
7. The heat treatment method for the two-phase zone quenching of the low-temperature 9Ni steel as claimed in claim 1, wherein the preparation, characterization and measurement instruments used in the invention are as follows: a medium-speed wire cutting machine tool, a heat treatment resistance furnace, a grinding and polishing machine, a scanning electron microscope, an X-ray diffractometer, an impact tester and a fatigue tester.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101717887A (en) * | 2009-11-13 | 2010-06-02 | 北京科技大学 | Rotary austenite toughening-based low-temperature steel and method for preparing same |
| CN103343202A (en) * | 2013-07-11 | 2013-10-09 | 太原理工大学 | Quenching/subzero treatment method for heat treatment of low-temperature nickel steel |
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- 2020-04-24 CN CN202010331343.1A patent/CN111455143A/en active Pending
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101717887A (en) * | 2009-11-13 | 2010-06-02 | 北京科技大学 | Rotary austenite toughening-based low-temperature steel and method for preparing same |
| CN103343202A (en) * | 2013-07-11 | 2013-10-09 | 太原理工大学 | Quenching/subzero treatment method for heat treatment of low-temperature nickel steel |
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Application publication date: 20200728 |