EP4074858A1

EP4074858A1 - Hot-rolled h-beam steel based on special-shaped billet rolling and forming, and manufacturing method therefor

Info

Publication number: EP4074858A1
Application number: EP20899696.7A
Authority: EP
Inventors: Peilin ZHAO; Zhongxue WANG; Jianjun Wang; Wenxi Han; Chengzhi WEI; Qiang Ma; Bo Lu; Chao Li; Huiliang WU; Feng Lu
Original assignee: Shandong Iron and Steel Co Ltd
Current assignee: Shandong Iron and Steel Co Ltd
Priority date: 2019-12-09
Filing date: 2020-12-08
Publication date: 2022-10-19
Also published as: EP4074858A4; WO2021115263A1; JP2023505172A; CN110938778A; KR20220085820A

Abstract

Disclosed in the present invention is a manufacturing method for hot-rolled H-beam steel based on special-shaped billet rolling and forming. The H-beam steel comprises the chemical components in percentage by weight: C: 0.04-0.08; Si: ≤ 0.25; Mn: 1.25-1.45; V: 0.04-0.10; Ni: 0.2-1.0; P ≤ 0.02; S ≤ 0.01; Nb: 0.02-0.06, Al: 0.02-0.06; N ≤ 0.015; O ≤ 0.005; with the balance being Fe and inevitable impurities. The H-beam steel has the yield strength of the upper and lower flanges being greater than or equal to 420 MPa; the -40°C transverse impact energy being greater than or equal to 34 J, and the -60°C longitudinal impact energy being greater than or equal to 120 J. The manufacturing method for the H-beam steel comprises the following steps: 1) a smelting and continuous casting process: smelting using a converter, LF refining, and casting into a special-shaped continuous casting billet; and 2) a rolling process: heating; rolling; and cooling after the rolling. The low temperature-resistant H-beam steel product for marine engineering provided in the present invention has good mechanical properties, is easy to industrially manufacture, reduces the requirements for rolling equipment; and is suitable for use in an area under extreme temperature conditions.

Description

Cross Reference to Related Applications

This application claims the priority to Chinese Patent Application No. 2019112501386, filed on December 9, 2019 , which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention belongs to the field of metallurgical technology. In particular, the present invention relates to a hot-rolled H-beam steel based on special-shaped billet rolling and forming and a manufacturing method therefor. According to the manufacturing process and the forming method.

BACKGROUND

As the demand for oil and gas resources increases, marine oil platforms are gradually expanding to complex climatic regions, and the quality and requirements of platform construction are more demanding. As a result, the hot-rolled H-beam steels that must be used to build the platforms are not only in increased demand, but also there are higher requirements for their toughness in low-temperature environments. With regard to the hot-rolled H-beam steels currently used at home and abroad, the requirements for the impact toughness are mainly for the longitudinal impact that is detected along the rolling direction. There are generally no specific requirements for the transverse impact due to the complex shape of the H-beam steel, the complex structural changes, and the large structural differences of the flanges along the transverse part. However, with the development of engineering, the platform structures become more complex. Combined with the changes in the conditions of regions for use, higher requirements are also gradually being put forward to the indicators of transverse impact toughness. And profiles with good transverse impact toughness are promoted to use in part of standards and projects.
For medium and large size H-beam steel, the special-shaped billet rolling and forming is mostly used. In addition, it is more difficult to ensure the microstructures for the application of micro-alloying in the manufacturing field of H-beam steel. For a combination of the many factors, the transverse impact toughness is eventually affected. Especially for industrial manufacturing, stability is a problem. In order to ensure the transverse impact, different patents provide different technical ideas.
The patent CN103556055B discloses a hot-rolled H-beam steel used in the structure of marine gas exploitation platforms and a manufacturing method thereof. One aspect of the present invention provides a hot-rolled H-beam steel used in the structure of marine gas exploitation platforms, which includes the following components in percentage by weight: C: 0.10-0.17, Si: 0.10-0.40, Mn: 1.00-1.60, P ≤ 0.025, S ≤ 0.015, Nb: 0.02-0.05, Ti ≤ 0.025, with the balance being Fe and inevitable impurities. The mechanical properties, -20°C transverse and longitudinal impact energy, surface quality of the hot-rolled H-beam steel used in the structure of marine gas exploitation platforms concerned in the present invention can fully meet the technical requirements for the H-beam steel used in the structure of marine gas exploitation platforms. This invention mainly employs medium carbon and a composite microalloying composition design of Nb and Ti. Due to the influence of Nb and Ti composite microalloying mechanism, the rolling force in the actual rolling process is higher, thus proposing higher requirements for the rolling equipment.
The patent application CN1421286A discloses a rolling method of a niobium-containing H-beam steel. By utilizing the principle of physical metallurgy of metals, this method adjusts and optimizes the conventional process conditions, and controls the deformation amount of a single pass by employing controlled rolling in the recrystallization zone and controlled rolling in the insubrecrystallization zone, so as to enable the nucleation of ferrite in the deformation zone to obtain fine ferrite grains, thereby uniformly refining the metallographic structure, and obtaining H-beam steel with high strength, high toughness, and good weldability. The obtained H-beam steel has a tensile strength of 490-610 MPa and a -20°C transverse impact energy of 34-98 J, meeting the American Petroleum Institute's requirements for Class II steel in platform design specifications. In this invention, the conditions for controlling the deformation temperature and deformation amount are very harsh, which also increase the load of the rolling mill. It is extremely difficult to adjust reduction in real time, thus having great impact on the performance of the product. Therefore, there are fluctuations in the performance of the product, and the qualification rate of the product is significantly reduced.
In summary, it is necessary to specifically design the smelting and rolling processes for H-beam steel rolled from special-shaped billets, so that it not only meets the smelting requirements and reduces the rolling load, but also at the same time, the structure state after rolling can meet the requirement of having high transverse impact toughness under certain low temperature conditions.

SUMMARY OF THE INVENTION

In order to meet the needs of marine oil platform construction in different regions and under harsh and complex environments, the present invention provides a hot-rolled H-beam steel based on special-shaped billet rolling and forming and a manufacturing method therefor. The technical scheme of the present invention is as follows:
A manufacturing method for hot-rolled H-beam steel based on special-shaped billet rolling and forming, which includes the chemical components in percentage by weight: C: 0.04-0.08; Si: ≤ 0.25; Mn: 1.25-1.45; V: 0.04-0.10; Ni: 0.2-1.0; P ≤ 0.02; S ≤ 0.01; Nb: 0.02-0.06, Al: 0.02-0.06; N ≤ 0.015; O ≤ 0.005; with the balance being Fe and inevitable impurities.
Preferably, the chemical components of molten steel are preferably (wt%): C: 0.05-0.07; Si: ≤ 0.25; Mn: 1.25-1.45; V: 0.04-0.06; Ni: 0.2-0.7; P ≤ 0.02; S ≤ 0.01; Nb: 0.02-0.04, Al: 0.02-0.05; N ≤ 0.015; O ≤ 0.005.
The manufacturing process mainly includes converter smelting, LF refining, continuous casting and hot-rolling and forming, the steps of which are as follows:

1) smelting and continuous casting process:
smelting using a converter, LF refining and casting into a special-shaped continuous casting billet, with the balance being Fe and inevitable impurities; the liquid height of tundish during the continuous casting being 900 mm to 950 mm, employing a full protection pouring process; with the casting speed being controlled at 0.7-1.3 m/min;
2) a rolling process:
- heating: heating the special-shaped continuous casting billet in a digitally controlled heating furnace, and descaling by high pressure water after discharging out of the furnace;
- rolling: rough rolling with water cooling for controlled cooling, finish rolling by temperature-holding rolling and water-cooling controlled rolling, the reduction rate of an insubrecrystallization zone being greater than 30%, preferably 30%-45%; starting pre- and post-cooling equipment for forced cooling of lower legs of the H-beam steel, so as to control the final rolling temperature at 750°C-820°C;
- cooling: according to different specifications, the rolled beam steel being cooled by air or water, then entering a cooling bed for centralized cooling, thus enabling the full precipitation of carbonitride, and at the same time ensuring the grain size after rolling being over grade 8.5; and being straightened in a straightener after the temperature of the beam steel drops below 100°C, and finally cutting the beam steel into materials with specified lengths, stacking and bundling.

Preferably, the heating temperature in the step 2) is controlled at 1220°C-1260°C for a heating period of 90-180 min.
Preferably, the initial rolling temperature of the rough rolling in the step 2) is controlled at 1030°C-1130°C, and the number of rolling passes is 5-7.
Preferably, the initial rolling temperature of the finish rolling in the step 2) is controlled at 900°C-1000°C; and the number of finish rolling passes is 3-5.
Preferably, a water nozzle is used in the step 2) for forced cooling of the lower legs of the H-beam steel, controlling the temperature difference between upper and lower legs within a range of ≤ 10°C, and controlling the final rolling temperature at 780°C-810°C. The present invention employs low carbon and a microalloying process design of V, Nb, and Al, combined with controlled rolling of the hole pattern of beam steel, to achieve low temperature-resistant H-beam steel products with good transverse impact toughness based on special-shaped billet rolling and forming, and achieve the industrial manufacturing of H-beam steel products with a specification of flange thickness of 18 mm-24 mm. According to the embodiments of the present invention, the manufacturing method for low temperature-resistant H-beam steel with good transverse impact toughness used for marine engineering includes converter smelting, LF refining, full protection continuous casting, rolling process of rough rolling and finish rolling and on-line water-cooling control process.
In the present invention, a low carbon and a V and Nb microalloying controlled rolling process is employed for the industrial manufacturing of H-beam steel products with a specification of flange thickness of 18 mm-24 mm; the matrix structure is refined by controlling the recrystallization rolling with Nb combined with controlling the temperature during the finish rolling process, so as to obtain fine and uniform ferrite structure; meanwhile, nanoscale carbonitride is precipitated by V in the cooling stage so as to enhance the strength of steel, ultimately ensuring that the hot-rolled H-beam steel of such a specification has good transverse impact toughness.
Other processes not mentioned in the present invention can also employ the existing technology.
Compared with the current low temperature-resistant H-beam steel with transverse impact toughness requirements and the manufacturing method therefor, the technical scheme of the present invention has the following advantages:

1. By using fine grain strengthening and precipitation strengthening mechanisms, the composite microalloying composition design is more suitable for manufacturing fine grain structures, thereby obtaining hot-rolled H-beam steels with a tensile strength of over 510 MPa used for marine engineering;
2. By using a whole-process on-line controlled cooling process, combined with rolling of recrystallization and insubrecrystallization zones, as well as a microalloying composition design of Nb, V, Al, Ni, it is suitable for manufacturing low temperature-resistant hot-rolled H-beam steel while ensuring good transverse impact toughness;
3. Compared with the chemical component designs in other patents, the average rolling force is reduced by 10%-30%, so it is easy to industrially manufacture, and the requirements for rolling equipment are reduced.
4. The low temperature-resistant H-beam steel product for marine engineering provided in the present invention has good mechanical properties, its tensile strength is greater than 510 MPa, especially its -40°C transverse impact energy is greater than 34 J, and its -60°C longitudinal impact energy is greater than 120 J, so it is suitable for use in an area under extreme temperature conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a diagram showing the microstructure of a flange with a thickness of 24 mm according to the present invention.

DETAILED DESCRIPTION

The following specific examples are given to illustrate the present invention. It should be noted that, the examples are only for further illustration of the present invention, rather than restricting the protection scope of the present invention. Any non-essential modifications and adjustments made by any other people to the invention are still within the protection scope of the present invention
The continuous casting billets in the following examples were all manufactured following the process below: according to the set chemical component range (Table 1), the chemical components C, Si, Mn, S, P and Fe, as the raw materials, were subjected to converter smelting, refining, continuous casting, direct heating or uniform heating of cast billets. The manufacturing steps of Examples 1-4 are as below:

1. Smelting:
The contents of As and Sn in the molten iron in the furnace were both less than 80 ppm; the slag material must all be added 3 minutes before the end. The final slag alkalinity was controlled in the range of 2.9-3.9. The slag amount of the converter was controlled at 55 mm by employing a double slag retaining process for steelmaking. The bottom-argon-blowing for stirring was implemented during the whole refining process so as to ensure the full floatation of inclusions; the time for soft argon blowing during refining was not less than 20 minutes. To ensure smooth production, 100 m of calcium line was fed before the end of refining.
2. Continuous casting: A full protection pouring process was employed; and the casting speed was controlled at 0.7-1.3 m/min.
3. Rolling during hot-rolling process and controlled cooling: The rolling during hot-rolling process and the controlled cooling after rolling adopted temperature controlling as the main means. The outside of the flanges was detected at the final rolling temperature. And the rolled materials after rolling were subjected to centralized slow cooling in a cooling bed, so as to enable the full precipitation of carbonitride of V. Fig. 1 is a diagram showing the microstructure of a flange with a thickness of 24 mm according to the present invention. The chemical components and specific processes of Examples 1-4 were listed in the table below.

Table 1 Chemical components (wt%, with the balance being Fe)

Item	C	Si	Mn	P	s	Nb	V	Ni	Al
Example 1	0.05	0.25	1.40	0.02	0.006	0.02	0.08	0.25	0.020
Example 2	0.06	0.22	1.25	0.019	0.007	0.04	0.07	0.23	0.033
Example 3	0.07	0.23	1.45	0.018	0.008	0.04	0.05	0.28	0.028
Example 4	0.08	0.20	1.35	0.017	0.005	0.03	0.09	0.35	0.036

The hot-rolling process conditions of Examples 1-4 were listed in Table 2. BS EN ISO 377-1997-Location and preparation of test pieces for mechanical testing was used as the standard; the testing methods of yield strength, tensile strength, and elongation referred to the standard ISO6892-1-2009-Metallic materials--Tensile testing at ambient temperature; and the testing method of impact energy referred to the standard ISO 148-1-Metallic materials-Charpy pendulum impact test, with the results shown in Table 2.

Table 2 Hot-rolling process parameters and specifications

Item	Heating temperature (°C)	Holding time (min)	Final rolling temperature (°C)	Flange thickness t mm
Example 1	1220	120	780	18
Example 2	1230	130	830	20
Example 3	1250	140	820	22
Example 4	1260	150	800	24

As can be seen from the above table, the yield strength of the upper and lower flanges in Examples 1-4 of the present invention all maintained above 420 MPa, indicating good impact toughness, which all meet the use conditions of components for marine engineering of marine oil platforms in extremely low environment.

Table 3 Mechanical properties

Item	Yield strength of upper flange (MPa)	Yield strength of lower flange (MPa)	Tensile strength (MPa)	Elongation (%)	-40°C transverse average impact energy (J)	-60°C longitudinal average impact energy (J)
Example 1	425	435	565	29	120	180
Example 2	435	450	576	31	105	185
Example 3	442	448	580	30	95	170
Example 4	450	460	595	29	90	155

Finally, it should be noted that, the above examples are only intended to illustrate the technical scheme of the present invention, rather than restricting. Although the present invention has been illustrated in detail with reference to the above examples, any person with ordinary skills in the art should understand that, all modifications or equivalent substitutions made to the technical scheme of the present invention do not depart from the spirit and scope of the technical scheme of the present invention, and should all be encompassed within the scope of the claims of the present invention.

Claims

A hot-rolled H-beam steel based on special-shaped billet rolling and forming, wherein, comprising chemical components in percentage by weight: C: 0.04-0.08; Si: ≤ 0.25; Mn: 1.25-1.45; V: 0.04-0.10; Ni: 0.2-1.0; P ≤ 0.02; S ≤ 0.01; Nb: 0.02-0.06, Al: 0.02-0.06; N ≤ 0.015; O ≤ 0.005; with the balance being Fe and inevitable impurities;
said H-beam steel has a thickness specification of flanges being 18-24 mm, a yield strength of upper and lower flanges being greater than or equal to 420 MPa; a -40°C transverse impact energy being greater than or equal to 34 J, and a -60°C longitudinal impact energy being greater than or equal to 120 J.
The H-beam steel according to claim 1, wherein, comprising chemical components in percentage by weight: C: 0.05-0.07; Si: ≤ 0.25; Mn: 1.25-1.45; V: 0.04-0.06; Ni: 0.2-0.7; P ≤ 0.02; S ≤ 0.01; Nb: 0.02-0.04, Al: 0.02-0.05; N ≤ 0.015; O ≤ 0.005; with the balance being Fe and inevitable impurities.
A manufacturing method for hot-rolled H-beam steel based on special-shaped billet rolling and forming, comprising the following steps:
1) a smelting and continuous casting process:
smelting using a converter, LF refining and casting into a special-shaped continuous casting billet, the liquid height of tundish during the continuous casting being greater than or equal to 900 mm, employing a full protection pouring process; with the casting speed being controlled at 0.7-1.3 m/min;

2) a rolling process:
heating: heating the special-shaped continuous casting billet, and descaling after discharging out of the furnace;

rolling: rough rolling with water cooling, finish rolling by temperature-holding rolling and water-cooling rolling, the reduction rate of an insubrecrystallization zone being greater than 30%; starting pre- and post-cooling equipment for forced cooling of lower legs of the H-beam steel, so as to control the final rolling temperature at 750°C-820°C;

cooling after the rolling: the rolled beam steel being cooled by air or water, then entering a cooling bed for centralized cooling, and being straightened in a straightener after the temperature drops below 100°C.
The manufacturing method according to claim 3, wherein, the heating temperature in the step 2) is controlled at 1220°C-1260°C for a heating period of 90-180 min.
The manufacturing method according to claim 3, wherein, the initial rolling temperature of the rough rolling in the step 2) is controlled at 1030°C-1130°C, and the number of rolling passes is 5-7.
The manufacturing method according to claim 3, wherein, the initial rolling temperature of the finish rolling in the step 2) is controlled at 900°C-1000°C; and the number of finish rolling passes is 3-5.
The manufacturing method according to claim 3, wherein, in the step 2), a water nozzle is used for forced cooling of the lower legs of the H-beam steel, controlling the temperature difference between upper and lower legs within a range of ≤ 10°C.