CN111485074B - Heating temperature-control type slow cooling dehydrogenation method for alloy steel casting blank - Google Patents
Heating temperature-control type slow cooling dehydrogenation method for alloy steel casting blank Download PDFInfo
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- CN111485074B CN111485074B CN202010265089.XA CN202010265089A CN111485074B CN 111485074 B CN111485074 B CN 111485074B CN 202010265089 A CN202010265089 A CN 202010265089A CN 111485074 B CN111485074 B CN 111485074B
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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
- C21D1/40—Direct resistance heating
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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
- C21D1/84—Controlled slow cooling
Abstract
The invention discloses a heating temperature-control slow cooling dehydrogenation method for alloy steel casting blanks. The invention can overcome the defects that the continuous casting blank for crack sensitive steel grade is slowly cooled to prevent stress cracks in the cooling process, the hydrogen induced crack sensitive steel grade is dehydrogenated to prevent white spots, and the common heavy rail steel is slowly cooled to dehydrogenate to prevent hydrogen induced cracks on the steel rail.
Description
Technical Field
The invention relates to the technical field of continuous casting processes, in particular to a heating temperature-control slow cooling dehydrogenation method for an alloy steel casting blank.
Background
The hydrogen content in the alloy steel casting blank has an important influence on the quality of a final product, and in the current continuous casting process, the alloy steel casting blank is dehydrogenated in a natural cooling mode of a common slow cooling pit, so that the dehydrogenation efficiency is low, the dehydrogenation effect is unstable, and the requirement of process design cannot be met. One of the high-strength and high-toughness alloy steel products mainly adopts Mn-Mo-Ni alloy and has bainite as a structure. The steel grade has high sensitivity to hydrogen element, the industry standard requires that the hydrogen content is less than 0.0025 percent (mass percent), and the enterprise internal control standard is less than 0.0017 percent (mass percent). Because the hydrogen content of the high-strength and high-toughness alloy steel (the components are shown in table 1) is required to be as low as possible, the target requirements cannot be met by adopting the traditional slow cooling technology dehydrogenation process.
TABLE 1 high-strength alloy steel main alloy chemical composition range (%)
| Si | Mn | Ni | Mo |
| 0.70-1.00 | 2.10-2.50 | 0.45-0.85 | 0.30-0.60 |
Disclosure of Invention
The invention aims to provide a heating temperature-control slow cooling dehydrogenation method for an alloy steel casting blank, which overcomes the defect of slow cooling of the continuous casting blank for crack sensitive steel so as to prevent stress cracks in the cooling process; the method is used for dehydrogenation of hydrogen induced crack sensitive steel grade to prevent white spots; the method is used for slow cooling dehydrogenation of common heavy rail steel so as to prevent the hydrogen induced cracks of the steel rail.
In order to solve the technical problems, the invention adopts the following technical scheme:
a heating temperature-control slow cooling dehydrogenation method for alloy steel casting blanks is characterized in that the alloy steel casting blanks directly enter a slow cooling pit on line, the slow cooling pit is preheated to a set temperature in advance, and a heating compensation type slow cooling process is controlled in a grading mode according to the alloy types of the casting blanks and the purposes of steel types.
Further, according to the slow cooling purpose and the characteristics of different steel grades, the heating compensation type slow cooling process comprises the following three slow cooling modes:
the common heavy rail steel is slowly cooled and is divided into the following 9 sections:
1) a heating section: heating to 720 ℃;
2) a primary soaking section: the temperature difference between adjacent thermocouples after soaking is not more than 10 ℃;
3) a primary heat preservation section: the temperature is controlled at 710-730 ℃;
4) a primary cooling section: cooling to 650 ℃;
5) a secondary soaking section: the temperature difference between adjacent thermocouples after soaking is not more than 10 ℃;
6) a secondary heat preservation section: the temperature is controlled at 640-660 ℃;
7) a secondary cooling section: cooling to 400 ℃;
8) a secondary heat preservation section: the temperature is controlled at 390-410 ℃;
9) a third cooling section: slowly cooling, the solubility of hydrogen in steel is reduced along with the reduction of temperature, the diffusion coefficient is increased, and the slow cooling is beneficial to the removal of hydrogen;
ordinary medium and high alloy steel and crack sensitive alloy steel are slowly cooled and divided into the following 4 sections:
1) a heating section: heating to 680 ℃;
2) a soaking section: the temperature difference between adjacent thermocouples after soaking is not more than 10 ℃;
3) a heat preservation section: the heat preservation temperature is controlled at 670-;
4) a cooling section: cooling the temperature in the slow cooling pit to 200 ℃, and then air cooling;
the high-strength and high-toughness alloy steel (bainite) is slowly cooled and is divided into 16 sections as follows:
1) a cooling section: cooling to the supercooling temperature of 350 ℃;
2) a primary soaking section: the temperature difference between adjacent thermocouples after soaking is not more than 10 ℃;
3) a primary heat preservation section: the heat preservation temperature is controlled to be 340-;
4) a primary heating section: heating to 650 ℃;
5) a secondary soaking section: the temperature difference between adjacent thermocouples after soaking is not more than 10 ℃;
6) a secondary heat preservation section: the heat preservation temperature is controlled to be 640-660 ℃, and the heat preservation time is 1 h;
7) a secondary heating section: heating to 920 ℃;
8) and (3) third soaking section: the temperature difference between adjacent thermocouples after soaking is not more than 10 ℃;
9) a third heat preservation section: the heat preservation temperature is controlled at 910-;
10) a secondary cooling section: cooling to the supercooling temperature of 350 ℃;
11) four soaking sections: the temperature difference between adjacent thermocouples after soaking is not more than 10 ℃;
12) a fourth heat preservation section: the heat preservation temperature is controlled to be 340-;
13) a third heating section: heating to 670 deg.C;
14) and (4) five soaking sections: the temperature difference between adjacent thermocouples after soaking is not more than 10 ℃;
15) and (5) five heat preservation sections: the temperature is controlled at 640-660 ℃;
16) a third cooling section: and cooling the temperature in the slow cooling pit to 200 ℃, and then carrying out air cooling.
Also discloses application of the heating compensation type slow cooling process in dehydrogenation of casting blank slow cooling by using an annealing principle.
Compared with the prior art, the invention has the beneficial technical effects that:
1) the method is reliable to implement, and can stably ensure that the hydrogen content of the high-strength and high-toughness alloy steel is controlled within 0.8 ppm;
2) the method quantifies the key technical requirements, so the method is easy to popularize and implement and can ensure the implementation effect;
3) the method can be popularized and applied to the continuous casting billet alloy steel slow cooling process.
Detailed Description
A heating temperature-control slow cooling dehydrogenation method for alloy steel casting blanks is characterized in that the alloy steel casting blanks directly enter a slow cooling pit on line, the slow cooling pit is preheated to a set temperature in advance, and a heating compensation type slow cooling process is controlled in a grading mode according to the alloy types of the casting blanks and the purposes of steel types.
According to the slow cooling purpose and the characteristics of different steel grades, the heating compensation type slow cooling process comprises the following three slow cooling modes:
the common heavy rail steel is slowly cooled and is divided into the following 9 sections:
1) a heating section: heating to 720 ℃;
2) a primary soaking section: the temperature difference between adjacent thermocouples after soaking is not more than 10 ℃;
3) a primary heat preservation section: the temperature is controlled at 710-730 ℃;
4) a primary cooling section: cooling to 650 ℃;
5) a secondary soaking section: the temperature difference between adjacent thermocouples after soaking is not more than 10 ℃;
6) a secondary heat preservation section: the temperature is controlled at 640-660 ℃;
7) a secondary cooling section: cooling to 400 ℃;
8) a secondary heat preservation section: the temperature is controlled at 390-410 ℃;
9) a third cooling section: slowly cooling, the solubility of hydrogen in steel is reduced along with the reduction of temperature, the diffusion coefficient is increased, and the slow cooling is beneficial to the removal of hydrogen;
ordinary medium and high alloy steel and crack sensitive alloy steel are slowly cooled and divided into the following 4 sections:
1) a heating section: heating to 680 ℃;
2) a soaking section: the temperature difference between adjacent thermocouples after soaking is not more than 10 ℃;
3) a heat preservation section: the heat preservation temperature is controlled at 670-;
4) a cooling section: cooling the temperature in the slow cooling pit to 200 ℃, and then air cooling;
the high-strength and high-toughness alloy steel is slowly cooled and is divided into the following 16 sections:
1) a cooling section: cooling to the supercooling temperature of 350 ℃;
2) a primary soaking section: the temperature difference between adjacent thermocouples after soaking is not more than 10 ℃;
3) a primary heat preservation section: the heat preservation temperature is controlled to be 340-;
4) a primary heating section: heating to 650 ℃;
5) a secondary soaking section: the temperature difference between adjacent thermocouples after soaking is not more than 10 ℃;
6) a secondary heat preservation section: the heat preservation temperature is controlled to be 640-660 ℃, and the heat preservation time is 1 h;
7) a secondary heating section: heating to 920 ℃;
8) and (3) third soaking section: the temperature difference between adjacent thermocouples after soaking is not more than 10 ℃;
9) a third heat preservation section: the heat preservation temperature is controlled at 910-;
10) a secondary cooling section: cooling to the supercooling temperature of 350 ℃;
11) four soaking sections: the temperature difference between adjacent thermocouples after soaking is not more than 10 ℃;
12) a fourth heat preservation section: the heat preservation temperature is controlled to be 340-;
13) a third heating section: heating to 670 deg.C;
14) and (4) five soaking sections: the temperature difference between adjacent thermocouples after soaking is not more than 10 ℃;
15) and (5) five heat preservation sections: the temperature is controlled at 640-660 ℃;
16) a third cooling section: and cooling the temperature in the slow cooling pit to 200 ℃, and then carrying out air cooling.
Example 1
1. Determination of production Process
Taking A alloy steel as an example, the production flow is KR molten iron desulphurization, No. 9 converter smelting, No. 3 LF refining, No. 4 LF refining, VD vacuum treatment, No. 5 bloom continuous casting and slow cooling cover stacking cooling. According to the requirements of quality plan issued by the technical center, the production adopts a low-aluminum-silicon-calcium-barium deoxidation process, adopts double refining production, simultaneously carries out VD degassing process, and finally carries out compensation type casting blank slow cooling.
2. Description of compensated casting blank slow cooling process
Alloy steel A belongs to common medium-carbon low-alloy steel in Table 2, and is slowly cooled according to a slow cooling curve of a second slow cooling mode, namely common medium-carbon and high-carbon alloy steel and crack sensitive alloy steel:
(1) heating of casting blanks
Heating the casting blank to 680 ℃ in a slow cooling pit, wherein the heating speed is not more than 20 ℃/h;
(2) casting blank soaking
Heating the casting blank to 680 ℃, and then soaking for 2.5h, wherein the temperature difference between adjacent thermocouples after soaking does not exceed 10 ℃;
(3) casting blank heat preservation
After soaking, the casting blank is subjected to heat preservation for 9 hours, and the heat preservation temperature is controlled at 670-;
(4) casting blank cooling
And after the heat preservation time is up, cooling the casting blank, firstly cooling the casting blank to 200 ℃ in a slow cooling pit, and then cooling the casting blank by air.
Temperature control process requirements:
(1) the heating speed is not more than 20 ℃/h, and the temperature difference of the thermocouple after soaking is not more than 10 ℃;
(2) the heat preservation temperature is controlled to be 670-690 ℃, the heat preservation time is calculated according to an empirical formula, and 12min is needed when hydrogen diffuses 1 mm;
(3) the cooling section requires slow cooling, the solubility of hydrogen in steel is reduced along with the temperature reduction, the diffusion coefficient is increased, and the slow cooling is beneficial to the removal of hydrogen.
3. H content detection of casting blank after slow cooling
And after the casting blank is slowly cooled, sampling on the casting blank for hydrogen content detection. And drilling an effective sample from the reserved casting blank at a target position by using a special sampling drill to obtain a cylindrical sample with the diameter of about 4-8mm, protecting hydrogen by using liquid nitrogen to prevent hydrogen from escaping, and carrying out inspection analysis within 2 hours. Through detection, the content of H in the casting blank after compensation type slow cooling is less than 0.8PPM, and the quality requirement is met.
The invention realizes the control of low hydrogen, and the H content of the casting blank after slow cooling is controlled within 0.8 PPM; the components of the finished product are controlled in a narrow range, and the quality requirements are met at low times.
The invention adopts a heating compensation type slow cooling process, the annealing principle is utilized to be applied to the slow cooling of the casting blank for the first time, the continuous casting blank directly enters a slow cooling pit on line, the slow cooling pit is preheated to a set temperature in advance, the slow cooling process is controlled in a grading way according to the alloy type and the steel type application of the casting blank, the temperature, the slow cooling time and the casting blank offline close arrangement mode are optimized according to a set slow cooling process control curve, a good dehydrogenation effect is obtained, and the dehydrogenation rate reaches more than 40 percent at present.
The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.
Claims (1)
1. A heating temperature-control slow cooling dehydrogenation method for alloy steel casting blanks is characterized in that the continuous casting blanks directly enter a slow cooling pit on line, the slow cooling pit is preheated to a set temperature in advance, and a heating compensation type slow cooling process is controlled in a grading mode according to the alloy types and the steel types of the casting blanks;
according to the slow cooling purpose and the characteristics of different steel grades, the heating compensation type slow cooling process comprises the following three slow cooling modes:
the common heavy rail steel is slowly cooled and is divided into the following 9 sections:
1) a heating section: heating to 720 ℃;
2) a primary soaking section: the temperature difference between adjacent thermocouples after soaking is not more than 10 ℃;
3) a primary heat preservation section: the temperature is controlled at 710-730 ℃;
4) a primary cooling section: cooling to 650 ℃;
5) a secondary soaking section: the temperature difference between adjacent thermocouples after soaking is not more than 10 ℃;
6) a secondary heat preservation section: the temperature is controlled at 640-660 ℃;
7) a secondary cooling section: cooling to 400 ℃;
8) a secondary heat preservation section: the temperature is controlled at 390-410 ℃;
9) a third cooling section: slowly cooling, the solubility of hydrogen in steel is reduced along with the reduction of temperature, the diffusion coefficient is increased, and the slow cooling is beneficial to the removal of hydrogen;
ordinary medium and high alloy steel and crack sensitive alloy steel are slowly cooled and divided into the following 4 sections:
1) a heating section: heating to 680 ℃;
2) a soaking section: the temperature difference between adjacent thermocouples after soaking is not more than 10 ℃;
3) a heat preservation section: the heat preservation temperature is controlled at 670-;
4) a cooling section: cooling the temperature in the slow cooling pit to 200 ℃, and then air cooling;
the high-strength and high-toughness alloy steel is slowly cooled and is divided into the following 16 sections:
1) a cooling section: cooling to the supercooling temperature of 350 ℃;
3) a primary heat preservation section: the heat preservation temperature is controlled to be 340-;
4) a primary heating section: heating to 650 ℃;
6) a secondary heat preservation section: the heat preservation temperature is controlled to be 640-660 ℃, and the heat preservation time is 1 h;
7) a secondary heating section: heating to 920 ℃;
8) and (3) third soaking section: the temperature difference between adjacent thermocouples after soaking is not more than 10 ℃;
9) a third heat preservation section: the heat preservation temperature is controlled at 910-;
10) a secondary cooling section: cooling to the supercooling temperature of 350 ℃;
11) four soaking sections: the temperature difference between adjacent thermocouples after soaking is not more than 10 ℃;
12) a fourth heat preservation section: the heat preservation temperature is controlled to be 340-;
13) a third heating section: heating to 670 deg.C;
14) and (4) five soaking sections: the temperature difference between adjacent thermocouples after soaking is not more than 10 ℃;
15) and (5) five heat preservation sections: the temperature is controlled at 640-660 ℃;
16) a third cooling section: cooling the temperature in the slow cooling pit to 200 ℃, and then air cooling;
the application of the heating compensation type slow cooling technology in dehydrogenation of casting blank slow cooling by using the annealing principle is disclosed.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102732674A (en) * | 2012-06-05 | 2012-10-17 | 舞阳钢铁有限责任公司 | Production method of heavy-gauge large-single-weight low-alloy high-strength structural steel plates |
| CN103468887A (en) * | 2013-08-02 | 2013-12-25 | 浙江吉利汽车研究院有限公司 | Heat treatment method of alloy steel after forging |
| CN105385938A (en) * | 2015-12-11 | 2016-03-09 | 钢铁研究总院 | Alloy system, heat treatment method for Bainite steel rail of alloy system and Bainite steel rail |
| CN107287399A (en) * | 2016-04-04 | 2017-10-24 | 鞍钢股份有限公司 | A kind of slow cooling method after less than 30 tons steel ingot coggings |
| CN110592355A (en) * | 2019-09-27 | 2019-12-20 | 武汉钢铁有限公司 | Production method for reducing residual stress of heat-treated steel rail and steel rail obtained by production method |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2011094179A (en) * | 2009-10-29 | 2011-05-12 | Jfe Steel Corp | Apparatus for heating end part and method for slowly cooling thick steel plate |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102732674A (en) * | 2012-06-05 | 2012-10-17 | 舞阳钢铁有限责任公司 | Production method of heavy-gauge large-single-weight low-alloy high-strength structural steel plates |
| CN103468887A (en) * | 2013-08-02 | 2013-12-25 | 浙江吉利汽车研究院有限公司 | Heat treatment method of alloy steel after forging |
| CN105385938A (en) * | 2015-12-11 | 2016-03-09 | 钢铁研究总院 | Alloy system, heat treatment method for Bainite steel rail of alloy system and Bainite steel rail |
| CN107287399A (en) * | 2016-04-04 | 2017-10-24 | 鞍钢股份有限公司 | A kind of slow cooling method after less than 30 tons steel ingot coggings |
| CN110592355A (en) * | 2019-09-27 | 2019-12-20 | 武汉钢铁有限公司 | Production method for reducing residual stress of heat-treated steel rail and steel rail obtained by production method |
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