CN113755756A

CN113755756A - Rare earth microalloyed hot-rolled round steel for 600 MPa-level mooring chain and production method thereof

Info

Publication number: CN113755756A
Application number: CN202111008919.1A
Authority: CN
Inventors: 惠治国; 宋振东; 卜向东; 赵晓敏; 张凤明; 陈镇方
Original assignee: Baotou Iron and Steel Group Co Ltd
Current assignee: Baotou Iron and Steel Group Co Ltd
Priority date: 2021-08-31
Filing date: 2021-08-31
Publication date: 2021-12-07

Abstract

The invention discloses a rare earth microalloyed 600 MPa-level hot-rolled round steel for a mooring chain, which comprises the following chemical components in percentage by mass: 0.20 to 0.30 percent of C, 0.15 to 0.30 percent of S i 0.15, 0.80 to 1.00 percent of Mn, less than or equal to 0.020 percent of P, less than or equal to 0.020 percent of S, 0.60 to 0.80 percent of Cr, 0.40 to 0.60 percent of Mo, N i0.40, 0.40 to 0.60 percent of Nb, 0.02 to 0.06 percent of Nb, 0.10 to 0.20 percent of Cu, 0.020 to 0.050 percent of Al t, 0.020 to 0.030 percent of Re, and the balance of Fe and inevitable trace impurities, wherein the mass fraction is 100 percent. Its preparing process is also disclosed. The invention successfully adopts and develops the rare earth microalloying 600MPa level hot rolling round steel for mooring chains with excellent comprehensive mechanical property.

Description

Rare earth microalloyed hot-rolled round steel for 600 MPa-level mooring chain and production method thereof

Technical Field

The invention relates to the technical field of smelting, in particular to a rare earth microalloyed hot-rolled round steel for a 600MPa mooring chain and a production method thereof.

Background

With the gradual decrease of land resources, the development of ocean resources is accelerating in all countries in the world, and the development of ocean oil and gas, particularly deep sea oil and gas, has become the main field of world energy. The primary means of securing engineering platforms, vessels, floating storage vessels (FPSO) and semi-submersible drilling vessels for oil exploration and production in marine environments is mooring chain mooring. The demand for steel for marine mooring chains is increasing. The mooring chain needs to be soaked in seawater for a long time, is acted by irregular stress of sea waves and sea winds, and needs to have a service life of more than 20 years, which puts high requirements on the performance of the mooring chain. Steel for mooring chains is required to have not only high strength and good toughness but also seawater corrosion resistance, fatigue failure resistance, wear resistance and the like. Depending on the strength level used, mooring chain products are mainly of grades R3, R3S, R4, R4S, R5, etc.

In order to ensure the high performance of the R4 mooring chains produced at home and abroad at present, the steel price is high by increasing the content of alloy elements such as Ni, Mo and the like. Some reports are made on the research of a four-level mooring chain in part of domestic journals at present, wherein the reports comprise the influence of a heat treatment process on the steel structure and corrosion resistance of a 22MnCrNiMo mooring chain in 2010-02, the development of round steel with the diameter of 140mm in an R4 marine mooring chain in 2006-5, the influence of the heat treatment on the structure and performance of the novel mooring chain steel 22MnCrNiMo and the like in 2009-2. These documents report steel grades for the production of a primary mooring chain, which have in common that their low-temperature impact toughness is ensured by adding a large amount of steel, and some of the steel grades contain steel up to 1.2% or more, which results in an increase in production cost. Therefore, the research and production of low-cost high-performance mooring chain steel are urgent.

Because a large amount of alloy elements are added into steel, the hot rolled structure of the material is a semi-martensite structure, the material needs to be annealed before delivery, otherwise, the material can generate martensite transformation in the placing process, and the structure stress is generated, so that the material is scrapped due to internal cracks. This increases the heat treatment cost and reduces the production efficiency.

Disclosure of Invention

The invention aims to provide a rare earth microalloyed 600 MPa-level hot-rolled round steel for mooring chains and a production method thereof, which utilize the principle of compound alloying of trace rare earth and a small amount of Cr, Mo, Ni, Cu and Nb to obviously improve the hardenability, corrosion resistance, fatigue resistance and low-temperature toughness of the steel for mooring chains on the premise of reducing the production cost, thereby obviously improving the overall service life and safety of the steel for mooring chains and producing the steel for mooring chains with low cost and high performance.

In order to solve the technical problems, the invention adopts the following technical scheme:

the rare earth microalloyed 600 MPa-level hot-rolled round steel for the mooring chain comprises the following chemical components in percentage by mass: 0.20 to 0.30 percent of C, 0.15 to 0.30 percent of Si, 0.80 to 1.00 percent of Mn, less than or equal to 0.020 percent of P, less than or equal to 0.020 percent of S, 0.60 to 0.80 percent of Cr, 0.40 to 0.60 percent of Mo, 0.40 to 0.60 percent of Ni, 0.02 to 0.06 percent of Nb, 0.10 to 0.20 percent of Cu, 0.020 to 0.050 percent of Alt, 0.020 to 0.030 percent of Re, and the balance of Fe and inevitable trace impurities, wherein the mass fraction is 100 percent.

Further, the chemical components comprise the following components in percentage by mass: 0.20 percent of C, 0.18 percent of Si, 0.90 percent of Mn, 0.0072 percent of P, 0.005 percent of S, 0.75 percent of Cr, 0.55 percent of Mo, 0.45 percent of Ni, 0.030 percent of Nb, 0.12 percent of Cu, 0.025 percent of Alt, 0.021 percent of Re, and the balance of Fe and inevitable trace impurities, wherein the mass fraction accounts for 100 percent.

Further, the chemical components comprise the following components in percentage by mass: 0.23% of C, 0.22% of Si, 0.88% of Mn, 0.0033% of P, 0.009% of S, 0.72% of Cr, 0.52% of Mo, 0.55% of Ni, 0.030% of Nb, 0.15% of Cu, 0.023% of Alt, 0.025% of Re, and the balance of Fe and inevitable trace impurities, wherein the mass fraction accounts for 100%.

Further, the chemical components comprise the following components in percentage by mass: 0.26% of C, 0.25% of Si, 0.92% of Mn, 0.0056% of P, 0.007% of S, 0.67% of Cr, 0.53% of Mo, 0.48% of Ni, 0.024% of Nb, 0.14% of Cu, 0.026% of Alt, 0.027% of Re, and the balance of Fe and inevitable trace impurities, wherein the mass fraction is 100% in total.

A production method of rare earth microalloyed hot-rolled round steel for a 600 MPa-level mooring chain comprises the steps of converter smelting, LF refining, VD vacuum degassing, continuous casting, heating of a casting blank heating furnace and rolling of round steel; wherein:

smelting in a combined blown converter, controlling the alkalinity of final slag according to 3.0, controlling the end point to control the target C to be more than or equal to 0.06 percent, controlling the T to be 1660 ℃, and carrying out deoxidation alloying by adopting SiMn, MnFe and CrFe, wherein Al deoxidation is adopted for final deoxidation;

white slag refining operation, dipping a slag sample after lifting the electrode each time, supplementing silicon, calcium and barium according to the color of the slag, supplementing lime according to the viscosity of the slag, and requiring white slag for final slag; carrying out Ar blowing operation in the whole process, carrying out desulfurization, component fine adjustment and temperature rise operation according to the components and the temperature of the molten steel of the converter, wherein S is less than or equal to 0.020 percent after desulfurization, the component contents are 0.20-0.30 percent of C, 0.15-0.30 percent of Si, 0.80-1.00 percent of Mn, less than or equal to 0.020 percent of P, less than or equal to 0.020 percent of S, and the temperature T is more than or equal to 1560 ℃ after temperature rise; adding Cr, Mo, Ni, Nb, Cu, Al and Re alloy at the later stage of refining, and ensuring that 0.60-0.80 percent of Cr0.40-0.60 percent of Mo, 0.40-0.60 percent of Ni, 0.02-0.06 percent of Nb, 0.10-0.20 percent of Cu0.020-0.050 percent of Alt and 0.020-0.030 percent of Re are subjected to soft blowing for 9 min;

the vacuum degree is 0.09Kpa, the deep vacuum time is 18min, after the vacuum is broken, a calcium silicon wire is fed for 150m, the soft blowing time is 12min, and molten steel cannot be exposed during the soft blowing;

the constant drawing speed control is adopted, the electromagnetic stirring process is adopted, and the superheat degree of molten steel is as follows: the delta T is 28 ℃, and the specification of a casting blank is 320mm multiplied by 415mm, and the casting blank is slowly cooled in a slow cooling pit for 48 h;

controlling the total heating time for 3.5h, controlling the initial rolling temperature to be 1100-1200 ℃, preventing overheating, overburning and decarburization, slowly raising the temperature, ensuring the uniform heating temperature of the steel billet, and reducing the temperature difference;

the conditions of the roller, the tilting gear, the guide plate, the roller way and the cover plate are noticed, smoothness is ensured, sharp edges and corners do not exist, the defects of scratching, gouging and the like on the surface of a rolled piece are avoided, and the specification of a rolled finished product is phi 123 mm.

Compared with the prior art, the invention has the beneficial technical effects that:

(1) the invention saves cost, adopts lower contents of Mn, Cr and Ni, and adds trace rare earth elements on the premise of reducing the total content of alloy elements, so that the material has higher low-temperature toughness and corrosion resistance and higher hardenability;

(2) the steel has the advantages of high strength, high toughness, lower yield ratio, good welding performance and low-temperature impact performance;

(3) the invention reduces the preparation cost by optimizing the preparation process and replacing the electric furnace with the converter, degasses and removes impurities, and improves the cleanliness of the material, thereby obviously improving the obdurability of the steel and the fatigue life of the material. The preparation method has simple process and lower energy consumption, and is suitable for the existing preparation technology of industrial equipment level.

Detailed Description

The hot rolled round steel for a micro-alloyed 600 MPa-level mooring chain and the production method thereof according to the present invention will be described in further detail below.

Example (b): this embodiment is one preferred embodiment of various embodiments of the present invention.

The rare earth microalloyed 600 MPa-level hot-rolled round steel for mooring chains and the production method thereof comprise the following chemical components in percentage by mass: 0.20 to 0.30 percent of C, 0.15 to 0.30 percent of Si, 0.80 to 1.00 percent of Mn, less than or equal to 0.020 percent of P, less than or equal to 0.020 percent of S, 0.60 to 0.80 percent of Cr, 0.40 to 0.60 percent of Mo, 0.40 to 0.60 percent of Ni, 0.02 to 0.06 percent of Nb, 0.10 to 0.20 percent of Cu, 0.020 to 0.050 percent of Alt, 0.020 to 0.030 percent of Re, and the balance of Fe and inevitable trace impurities, wherein the mass fraction is 100 percent.

The production method of the rare earth microalloyed 600 MPa-level hot-rolled round steel for the mooring chain comprises the following steps: converter smelting, LF refining, VD vacuum degassing, continuous casting, heating of a casting blank heating furnace and round steel rolling.

Further: smelting in a combined blown converter, controlling the alkalinity of final slag according to 3.0, controlling the end point to control the target C to be more than or equal to 0.06 percent, controlling the T to be 1660 ℃, and carrying out deoxidation alloying by adopting SiMn, MnFe and CrFe, wherein Al deoxidation is adopted for final deoxidation;

and (3) white slag refining operation, dipping a slag sample after lifting the electrode each time, supplementing silicon, calcium and barium according to the color of the slag, supplementing lime according to the viscosity of the slag, and requiring white slag for final slag. The Ar blowing operation is carried out in the whole process, the operations of desulfurization, fine adjustment of components and temperature rise are carried out according to the components and the temperature of the molten steel of the converter, the S is less than or equal to 0.020 percent after the desulfurization, the component contents are 0.20-0.30 percent of C, 0.15-0.30 percent of Si, 0.80-1.00 percent of Mn, less than or equal to 0.020 percent of P, less than or equal to 0.020 percent of S, and the temperature T is more than or equal to 1560 ℃ after the temperature rise. In the later stage of refining, adding Cr, Mo, Ni, Nb, Cu, Al, Re and other alloys, and ensuring that Cr is 0.60-0.80%, Mo is 0.40-0.60%, Ni is 0.40-0.60%, Nb is 0.02-0.06%, Cu is 0.10-0.20%, Alt is 0.020-0.050%, Re is 0.020-0.030%, and soft blowing time is 9 min;

further: the vacuum degree is 0.09Kpa, the deep vacuum time is 18min, after the vacuum is broken, a calcium silicon wire is fed for 150m, the soft blowing time is 12min, and molten steel cannot be exposed during the soft blowing;

further: the constant drawing speed control is adopted, the electromagnetic stirring process is adopted, and the superheat degree of molten steel is as follows: the delta T is 28 ℃, and the specification of a casting blank is 320mm multiplied by 415mm, and the casting blank is slowly cooled in a slow cooling pit for 48 h;

further: controlling the total heating time for 3.5h, controlling the initial rolling temperature to be 1100-1200 ℃, preventing overheating, overburning and decarburization, slowly raising the temperature, ensuring the uniform heating temperature of the steel billet, and reducing the temperature difference;

further: the conditions of the roller, the tilting gear, the guide plate, the roller way and the cover plate are noticed, smoothness is ensured, sharp edges and corners do not exist, the defects of scratching, gouging and the like on the surface of a rolled piece are avoided, and the specification of a rolled finished product is phi 123 mm.

The rare earth microalloyed 600 MPa-grade hot rolled round steel for mooring chains produced by adopting the chemical components and the process flow can be used for determining the longitudinal mechanical property of the steel, wherein Rm is more than or equal to 860MPa, Rp0.2 is more than or equal to 580MPa, Rp0.2/Rm is less than or equal to 0.92, A is more than or equal to 12 percent, Z is more than or equal to 50 percent, the impact power KV2 at minus 20 ℃ is more than or equal to 80J, the hydrogen brittleness performance Z1/Z2 is more than or equal to 0.85 (the reduction of area without slow cooling treatment, the reduction of area after heat preservation for 2 hours at 250 ℃), the austenite grain size of the steel is more than or equal to 8.0 grade, the qualified grade of the steel reaches the A grade in GB/T4162-2012 by ultrasonic flaw detection, and the surface quality detection is carried out by eddy current flaw detection, so that the surface of the steel has no cracks, scars, folds or inclusions on the surface.

Table 1 shows the chemical composition of three examples of the present invention, and tables 2 and 3 further illustrate the present invention.

TABLE 1 chemical composition of each example (mass%/%)

TABLE 2 mechanical Properties of the examples

TABLE 3 non-metallic inclusions and Austenitic grain size Properties of the examples

As can be seen from tables 1-3, the rare earth microalloyed hot-rolled round steel for 600MPa mooring chains has excellent mechanical property and low-temperature toughness.

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. The rare earth microalloying 600MPa level hot-rolled round steel for mooring chains is characterized in that: the chemical components of the material comprise the following components in percentage by mass: 0.20 to 0.30 percent of C, 0.15 to 0.30 percent of Si, 0.80 to 1.00 percent of Mn, less than or equal to 0.020 percent of P, less than or equal to 0.020 percent of S, 0.60 to 0.80 percent of Cr, 0.40 to 0.60 percent of Mo, 0.40 to 0.60 percent of Ni, 0.02 to 0.06 percent of Nb, 0.10 to 0.20 percent of Cu, 0.020 to 0.050 percent of Alt, 0.020 to 0.030 percent of Re, and the balance of Fe and inevitable trace impurities, wherein the mass fraction is 100 percent.

2. The rare earth microalloyed 600 MPa-grade hot-rolled round steel for mooring chains as claimed in claim 1, wherein: the chemical components of the material comprise the following components in percentage by mass: 0.20 percent of C, 0.18 percent of Si, 0.90 percent of Mn, 0.0072 percent of P, 0.005 percent of S, 0.75 percent of Cr, 0.55 percent of Mo, 0.45 percent of Ni, 0.030 percent of Nb, 0.12 percent of Cu, 0.025 percent of Alt, 0.021 percent of Re, and the balance of Fe and inevitable trace impurities, wherein the mass fraction accounts for 100 percent.

3. The rare earth microalloyed 600 MPa-grade hot-rolled round steel for mooring chains as claimed in claim 1, wherein: the chemical components of the material comprise the following components in percentage by mass: 0.23% of C, 0.22% of Si, 0.88% of Mn, 0.0033% of P, 0.009% of S, 0.72% of Cr, 0.52% of Mo, 0.55% of Ni, 0.030% of Nb, 0.15% of Cu, 0.023% of Alt, 0.025% of Re, and the balance of Fe and inevitable trace impurities, wherein the mass fraction accounts for 100%.

4. The rare earth microalloyed 600 MPa-grade hot-rolled round steel for mooring chains as claimed in claim 1, wherein: the chemical components of the material comprise the following components in percentage by mass: 0.26% of C, 0.25% of Si, 0.92% of Mn, 0.0056% of P, 0.007% of S, 0.67% of Cr, 0.53% of Mo, 0.48% of Ni, 0.024% of Nb, 0.14% of Cu, 0.026% of Alt, 0.027% of Re, and the balance of Fe and inevitable trace impurities, wherein the mass fraction is 100% in total.

5. The method for producing a rare earth microalloyed 600MPa grade hot rolled round steel for mooring chains according to any one of claims 1 to 4, characterized by comprising the following steps: comprises converter smelting, LF refining, VD vacuum degassing, continuous casting, heating of a casting blank heating furnace and round steel rolling; wherein: