CN113061811A - LNG (liquefied Natural gas) marine structural steel and preparation method thereof - Google Patents
LNG (liquefied Natural gas) marine structural steel and preparation method thereof Download PDFInfo
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- CN113061811A CN113061811A CN202110285249.1A CN202110285249A CN113061811A CN 113061811 A CN113061811 A CN 113061811A CN 202110285249 A CN202110285249 A CN 202110285249A CN 113061811 A CN113061811 A CN 113061811A
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- 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
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
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- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
The invention provides a structural steel for LNG ships, which comprises: 0.010-0.040 wt% of Nb, 0.020-0.050 wt% of Al, 0.10-0.15 wt% of C, 0.10-0.30 wt% of Si, 1.30-1.60 wt% of Mn, 0.15-0.30 wt% of Ni, less than or equal to 0.010 wt% of P, less than or equal to 0.005 wt% of S, less than or equal to 0.005 wt% of Ti and the balance of Fe. The application also provides a preparation method of the LNG marine structural steel. The invention refines material crystal grains by a microalloying process, controls the carbon and the residual elements such as phosphorus, sulfur, titanium and the like, improves the low-temperature impact toughness of the material, improves the material strength by controlling the contents of manganese and nickel elements, and improves the impact toughness of the material while ensuring the material strength under the environment condition of minus 55 ℃ by matching with a controlled rolling and controlled cooling process method.
Description
Technical Field
The invention relates to the technical field of metal materials, in particular to LNG (liquefied natural gas) marine structural steel and a preparation method thereof.
Background
The LNG ship is a special ship for transporting liquefied gas at low temperature, and in the design, the material for preparing the LNG ship is mainly a material capable of adapting to the low-temperature environment, and particularly the material needs to keep higher impact toughness in the low-temperature environment so as to prevent brittle fracture and ensure the safety of the ship. Such materials also have greater application in cold winter areas. In order to meet the performance requirements, it is critical to provide a special component structural steel and control the preparation method thereof.
Disclosure of Invention
The invention aims to provide the structural steel for the LNG ship, and the structural steel provided by the invention still keeps higher impact toughness and prevents brittle fracture when working in a low-temperature environment.
In view of this, the present application provides a structural steel for LNG ships, including:
P≤0.010wt％；
S≤0.005wt％；
Ti≤0.005wt％；
the balance of Fe.
Preferably, the content of Nb is 0.015-0.035 wt%.
Preferably, the content of Al is 0.025 to 0.045 wt%.
Preferably, the content of C is 0.13-0.15 wt%.
Preferably, the content of Si is 0.20-0.30 wt%.
Preferably, the content of Mn is 1.42-1.57 wt%.
The application also provides a preparation method of the LNG marine structural steel, which comprises the following steps:
mixing the components according to the component ratio and then smelting to obtain a steel billet;
and heating and rolling the steel billet, controlling the finish rolling temperature, cooling and carrying out online normalizing treatment to obtain the LNG marine structural steel.
Preferably, the heating temperature is 1100-1200 ℃, the total heating time is more than or equal to 180min, and the soaking and heat preservation time is more than or equal to 45 min.
Preferably, the finishing rolling temperature is 900-930 ℃, the cooling is air cooling, and the air cooling is carried out until the temperature is less than or equal to 300 ℃.
The application provides a marine structural steel of LNG, it carries out microalloying through adopting Nb and Al, and the control of C content is under the prerequisite of assurance intensity to reduce brittle transition temperature, the control of manganese, nickel content has guaranteed that the material can reach the intensity level, and the further control participates in the content of element phosphorus, sulphur and titanium, in order to reduce non-metallic inclusion, improves material purity, reduces the brittle transition temperature of material. Therefore, the content of the alloy elements is controlled, so that the structural steel can still keep high impact toughness when working in a low-temperature environment, and brittle fracture is prevented.
Furthermore, in the preparation process of the LNG marine structural steel, the strength and the low-temperature impact toughness of the material are ensured by establishing a reasonable heating system and a finish rolling temperature.
Detailed Description
For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.
In order to meet the performance requirements of LNG marine materials, the invention refines material grains by a microalloying process, controls the carbon, the residual elements such as phosphorus, sulfur, titanium and the like, improves the low-temperature impact toughness of the material, improves the material strength by controlling the contents of manganese and nickel elements, and is matched with a controlled rolling and controlled cooling process method to realize the improvement of the impact toughness of the material while ensuring the material strength under the environment condition of-55 ℃. Specifically, the embodiment of the invention firstly discloses a structural steel for an LNG ship, which comprises the following components:
P≤0.010wt％；
S≤0.005wt％；
Ti≤0.005wt％；
the balance of Fe.
For the components of the structural steel, microalloying of Nb and Al is utilized, wherein the content of Nb is 0.010-0.040 wt%, and the content of Al is 0.020-0.050 wt%; specifically, the content of Nb is 0.015-0.035 wt%, and the content of Al is 0.025-0.045 wt%; more specifically, the content of Nb is 0.018 wt%, 0.020 wt%, 0.023 wt%, 0.025 wt%, 0.028 wt%, 0.030 wt%, or 0.032 wt%, and the content of Al is 0.027 wt%, 0.029 wt%, 0.032 wt%, 0.035 wt%, 0.038 wt%, 0.040 wt%, 0.042 wt%, or 0.044 wt%. When Nb exists in the form of carbide and oxide particles in steel, the main purpose is to refine the grains, improve the impact toughness of the steel and reduce the brittle transition temperature thereof; the main functions of Al in steel are to refine crystal grains and fix nitrogen in steel, thereby obviously improving the impact toughness of steel and reducing the cold brittleness tendency and the aging tendency. The refined crystal grains can simultaneously improve the strength and the plasticity of the material and improve the impact toughness. Nb and Al are out of the control range, so that the low-temperature impact is easily unqualified, and the strength is lower than the standard requirement.
The content of C is 0.10-0.15 wt%, specifically, the content of C is 0.10 wt%, 0.11 wt%, 0.12 wt%, 0.13 wt%, 0.14 wt% or 0.15 wt%. The C element directly influences the strength, the plasticity and the toughness of steel in the steel, when the carbon content in the steel is below 0.8 percent, the strength and the hardness of the steel are improved along with the increase of the carbon content, and the plasticity and the toughness are reduced; studies have shown that the brittle transition temperature increases by 7 ℃ per 0.01% C increase. Therefore, the C content is reduced as much as possible to lower the brittle transition temperature while ensuring the strength. The C content is lower than the control target, so that the strength is low easily, and the C content exceeds the control target, so that the low-temperature impact is unqualified easily.
The Si content is 0.10 to 0.30 wt%, specifically 0.20 to 0.30 wt%, more specifically 0.22 wt%, 0.24 wt%, 0.25 wt%, 0.26 wt%, 0.27 wt%, 0.28 wt%, or 0.30 wt%. Si is an important reducing agent and deoxidizing agent in the steel-making process: silicon is soluble in ferrite and austenite to increase the hardness and strength of the steel.
The Mn content is 1.30 to 1.60 wt%, specifically 1.42 to 1.57 wt%, more specifically 1.45 wt%, 1.46 wt%, 1.48 wt%, 1.50 wt%, 1.52 wt%, 1.55 wt%, or 1.56 wt%. The Ni content is 0.15-0.30 wt%, specifically 0.18 wt%, 0.20 wt%, 0.21 wt%, 0.24 wt%, 0.26 wt%, 0.28 wt%, or 0.30 wt%. Mn can improve the strength of steel and can be infinitely dissolved with Fe; the influence on plasticity is relatively small while the strength of the steel is improved. Therefore, manganese is widely used as a reinforcing element in steel. Meanwhile, Mn can form MnS with a high melting point with S in steel smelting, so that the adverse effect of S is weakened and eliminated. Adding a certain amount of Ni, on one hand, the strength of the steel is strongly improved, on the other hand, the toughness of the iron is always kept at a very high level, and the brittle transition temperature is reduced. When the Ni content is less than 0.3%, the embrittlement temperature is below-100 ℃, and when the Ni content is increased, the embrittlement temperature can be reduced to-180 ℃. The content of Mn and Ni is lower than the control target, and the yield strength is easily lower than the standard requirement.
P, S and Ti as the participating elements, wherein the phosphorus content is less than or equal to 0.010 percent, the sulfur content is less than or equal to 0.005 percent, and the titanium content is less than or equal to 0.005 percent. Phosphorus can increase the strength and hardness of steel, but causes remarkable reduction of plasticity and impact toughness; particularly at low temperatures, it makes the steel significantly brittle, so that controlling the P content lower is better. Sulfur is a harmful element in steel and generally exists in the form of iron sulfide (FeS) in steel, reducing the ductility and toughness of the steel. Titanium has strong affinity with nitrogen, oxygen and carbon; titanium can improve the plasticity and the toughness in common low alloy steel; since titanium is a strong carbide former and forms titanium carbide. The titanium carbide fine particles have an effect of preventing the growth of crystal grains. Carbide is precipitated through normalizing to refine grains, so that the strength of the steel is improved, and the plasticity and impact toughness of the steel are obviously improved; however, TiN in the steel is square particles, cracks are easy to form and propagate at sharp edges, and the influence is more obvious particularly under low-temperature conditions, so that the impact toughness is greatly reduced, and the lower the Ti content is, the better the impact toughness is. P, S, Ti exceed control targets, easily resulting in lower than standard low temperature impact work.
The application also provides a preparation method of the LNG marine structural steel, which comprises the following steps:
mixing the components according to the component ratio and then smelting to obtain a steel billet;
and heating and rolling the steel billet, controlling the finish rolling temperature, cooling and carrying out online normalizing treatment to obtain the LNG marine structural steel.
In the process, the heating temperature of the steel billet is 1100-1200 ℃, more specifically is controlled at 1160 +/-10 ℃, the total heating time is more than or equal to 180min, and the soaking heat preservation time is more than or equal to 45min, so that the temperature and the tissue of the heated billet are uniform, and conditions are provided for ensuring the uniform tissue of the rolled billet; if the microstructure of the bar is not uniform, the stability of the low-temperature impact toughness result of the bar is seriously influenced.
In the application, a water-through cooling mode is adopted in a final rolling mill group for final rolling, the final rolling temperature is controlled to be 900-930 ℃, and then air cooling is carried out until the temperature is less than or equal to 300 ℃ for collection; and (3) controlling the Ac3 of the steel grade at 900 ℃, controlling the finish rolling temperature at 900-930 ℃, performing air cooling for on-line normalizing treatment, and refining the bar grains to obtain the LNG marine structural steel.
For further understanding of the present invention, the structural steel for LNG ship and the method for manufacturing the same according to the present invention will be described in detail with reference to the following examples, and the scope of the present invention is not limited by the following examples.
Example 1
Mixing various alloy elements and then smelting to obtain a steel billet, wherein the steel billet comprises the following components: 0.14 wt%, Mn: 1.50 wt%, Si: 0.25 wt%, P: 0.006 wt%, S: 0.0015 wt%, Ni: 0.24 wt%, Ti: 0.005 wt%, Nb: 0.020 wt%, Al: 0.025 wt%;
heating the steel billet to 1100-1200 ℃, carrying out total heating time of 200min, carrying out soaking and heat preservation time of 60min, then rolling, carrying out finish rolling at 900-930 ℃, and then carrying out air cooling to 300 ℃ for on-line normalizing treatment to obtain the LNG marine structural steel.
Detecting the performance of the LNG marine structural steel, wherein the yield strength is 412MPa, the tensile strength is 565MPa, and the impact toughness AKv2 is detected at the temperature of minus 55 ℃, and the result is 52J; the structural steel meets the requirements that the yield strength is more than or equal to 345MPa, the tensile strength is 470-630 MPa, and the impact toughness AKv2 at 55 ℃ is more than or equal to 41J.
Comparative example 1
The preparation method is the same as that of the embodiment 1, except that the content of Ti is 0.04-0.06 wt%.
The impact toughness AKv2 is detected at-20 deg.C, and the structure is below 10J.
Comparative example 2
The preparation method is the same as example 1 except that the Mn content is less than 1.4 wt%.
Through detection, the yield strength of the structural steel is distributed between 300 and 340MPa, and the requirement that the yield strength is not less than or equal to 345MPa is not met.
The above description of the embodiments is only intended to facilitate the understanding of the method of the invention and its core idea. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (9)
1. A structural steel for LNG ships, comprising:
P≤0.010wt％；
S≤0.005wt％；
Ti≤0.005wt％；
the balance of Fe.
2. The LNG ship structural steel of claim 1, wherein the Nb content is 0.015 to 0.035 wt%.
3. The structural steel for LNG ships according to claim 1, wherein the Al content is 0.025 to 0.045 wt%.
4. The structural steel for LNG ships according to claim 1, wherein the content of C is 0.13 to 0.15 wt%.
5. The structural steel for LNG ships according to claim 1, wherein the content of Si is 0.20 to 0.30 wt%.
6. The structural steel for LNG ships according to claim 1, wherein the content of Mn is 1.42 to 1.57 wt%.
7. The method for preparing structural steel for LNG ships as set forth in claim 1, comprising the steps of:
mixing the components according to the component ratio and then smelting to obtain a steel billet;
and heating and rolling the steel billet, controlling the finish rolling temperature, cooling and carrying out online normalizing treatment to obtain the LNG marine structural steel.
8. The preparation method according to claim 7, wherein the heating temperature is 1100-1200 ℃, the total heating time is not less than 180min, and the soaking and heat preservation time is not less than 45 min.
9. The preparation method according to claim 7, wherein the temperature of the finish rolling is 900-930 ℃, and the cooling is air cooling to be less than or equal to 300 ℃.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202110285249.1A CN113061811A (en) | 2021-03-17 | 2021-03-17 | LNG (liquefied Natural gas) marine structural steel and preparation method thereof |
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| CN202110285249.1A CN113061811A (en) | 2021-03-17 | 2021-03-17 | LNG (liquefied Natural gas) marine structural steel and preparation method thereof |
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Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2013245360A (en) * | 2012-05-23 | 2013-12-09 | Nippon Steel & Sumitomo Metal Corp | Steel sheet for lpg tank |
| CN106467951A (en) * | 2016-09-12 | 2017-03-01 | 武汉钢铁股份有限公司 | For 70 DEG C of high intensity, high tenacity, low yield strength ratio low-temperature steel and its manufacture method |
| CN107805755A (en) * | 2016-09-09 | 2018-03-16 | 中国石化工程建设有限公司 | A kind of low temperature thick walled steel tube and preparation method thereof |
| CN107805756A (en) * | 2016-09-09 | 2018-03-16 | 中国石化工程建设有限公司 | A kind of cryogenic steel, low-temperature pressure container and steel for pipe pipe and preparation method thereof |
| CN108004465A (en) * | 2017-11-23 | 2018-05-08 | 南阳汉冶特钢有限公司 | A kind of 130mm thickness low-temperature pressure container 16MnDR steel plates and its production method |
| CN110100027A (en) * | 2016-12-21 | 2019-08-06 | 株式会社Posco | The steel plate and its manufacturing method of low yielding ratio with excellent low-temperature flexibility |
| KR20200064511A (en) * | 2018-11-29 | 2020-06-08 | 주식회사 포스코 | High-strength steel sheet having excellent ductility and low-temperature toughness and method for manufacturing thereof |
-
2021
- 2021-03-17 CN CN202110285249.1A patent/CN113061811A/en active Pending
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2013245360A (en) * | 2012-05-23 | 2013-12-09 | Nippon Steel & Sumitomo Metal Corp | Steel sheet for lpg tank |
| CN107805755A (en) * | 2016-09-09 | 2018-03-16 | 中国石化工程建设有限公司 | A kind of low temperature thick walled steel tube and preparation method thereof |
| CN107805756A (en) * | 2016-09-09 | 2018-03-16 | 中国石化工程建设有限公司 | A kind of cryogenic steel, low-temperature pressure container and steel for pipe pipe and preparation method thereof |
| CN106467951A (en) * | 2016-09-12 | 2017-03-01 | 武汉钢铁股份有限公司 | For 70 DEG C of high intensity, high tenacity, low yield strength ratio low-temperature steel and its manufacture method |
| CN110100027A (en) * | 2016-12-21 | 2019-08-06 | 株式会社Posco | The steel plate and its manufacturing method of low yielding ratio with excellent low-temperature flexibility |
| CN108004465A (en) * | 2017-11-23 | 2018-05-08 | 南阳汉冶特钢有限公司 | A kind of 130mm thickness low-temperature pressure container 16MnDR steel plates and its production method |
| KR20200064511A (en) * | 2018-11-29 | 2020-06-08 | 주식회사 포스코 | High-strength steel sheet having excellent ductility and low-temperature toughness and method for manufacturing thereof |
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Application publication date: 20210702 |