CN112226692A

CN112226692A - Wear-resistant rack steel plate and manufacturing method thereof

Info

Publication number: CN112226692A
Application number: CN202011059392.0A
Authority: CN
Inventors: 朱隆浩; 赵坦; 金耀辉; 李家安; 于浩男; 任子平; 王�华; 肖青松; 陈华; 应传涛
Original assignee: Angang Steel Co Ltd
Current assignee: Angang Steel Co Ltd
Priority date: 2020-09-30
Filing date: 2020-09-30
Publication date: 2021-01-15
Anticipated expiration: 2040-09-30
Also published as: CN112226692B

Abstract

The invention discloses a wear-resistant rack steel plate and a manufacturing method thereof. The steel contains: 0.20 to 0.30 percent of C, 0.2 to 0.4 percent of Si, 0.6 to 0.9 percent of Mn, less than or equal to 0.02 percent of P, less than or equal to 0.01 percent of S, 0.01 to 0.03 percent of Als, 0.8 to 1.2 percent of Ni, 0.9 to 1.5 percent of Cr, 0.5 to 1.0 percent of Mo, 0.05 to 0.1 percent of V, 0.0015 to 0.0025 percent of B, 0.05 to 0.2 percent of W, and the balance of iron and inevitable impurities. When the furnace temperature is 400-700 ℃, steel ingots are loaded, the thickness of the steel billets after cogging is 2-3 times that of finished products, two-fire rolling is adopted, the cogging and finish rolling temperature is 900-1000 ℃, the remelting temperature is 1200-1300 ℃, and the heat preservation time is 100-200 min; the initial rolling temperature is 1150-1200 ℃, and the final rolling temperature is 900-1000 ℃; the heat treatment process comprises slow quenching and medium-low temperature tempering, the thickness of the finished steel plate is 128-260 mm, and the Rockwell hardness HRC is more than or equal to 45.

Description

Wear-resistant rack steel plate and manufacturing method thereof

Technical Field

The invention belongs to the field of steel material preparation, and particularly relates to a component design and a manufacturing method of a large-thickness high-use-frequency high-wear-resistance rack steel plate for a marine platform.

Background

The 21 st century is the ocean century, and with the development of science and technology and the improvement of the living standard of people, all countries in the world focus on huge resources stored in the ocean. In recent years, the maritime work equipment industry is continuously and rapidly developed, the massive demand of steel for maritime work platforms and the upgrading and updating of products are promoted, and the market urgently needs ultrahigh-strength and extra-thick maritime work steel plates with good comprehensive performance.

The ocean engineering platform has a severe service environment, besides conventional stress, the influence of various factors such as strong wind, surge, tide, ice impact, earthquake and the like is also considered, so that the specificity of the steel for the ocean platform is determined, and the ocean engineering platform can adapt to various sea conditions in the aspect of material selection of platform construction. Meanwhile, the steel plate is in a humid and high-salinity marine environment for a long time, and the problems of paint film falling, corrosion of the surface of the steel plate, corrosion fatigue and the like caused by adhesion of humid air, seawater and marine organisms are solved, the mechanical property of the steel plate is reduced, the service life is shortened, and the normal use of the ocean engineering platform is seriously influenced. In addition, the ocean platform is far away from the coast and cannot be periodically docked for maintenance like a ship. In order to ensure that the ocean engineering platform can be safely used in a complex environment, a high-quality ultrahigh-strength steel for ocean engineering with excellent comprehensive performance is urgently needed to be developed, and the ultrahigh-strength steel plate for ocean engineering has the advantages of high strength, high and low temperature toughness, low yield ratio, high ductility, fatigue resistance, hydrogen induced cracking resistance, marine environmental corrosion resistance, marine organism adhesion resistance, excellent welding performance and the like.

At present, steel for ocean engineering can meet most of requirements of the market in the field of maritime work, but special steel with high strength level and excellent comprehensive performance is still the target of development of all countries in the world, wherein the rack steel plate for the maritime work platform with large thickness, high use frequency and high wear resistance has high difficulty in scientific research, strict production process, high requirement on equipment and high development difficulty.

The invention discloses a high-strength steel plate for large-thickness F690 ocean engineering and a production method thereof, which are published under the patent No. CN104711488B, and provides F690 ocean engineering steel with the maximum thickness of 180mm and a manufacturing method thereof.

Patent CN109881092A, a Large thickness Rack Steel plate and a production method thereof, proposes a Rack Steel plate with a maximum thickness of 180mm, the C content of which is 0.30-0.33%, the impact toughness of the produced Steel plate can only ensure that the thickness of the Steel plate is equal to or more than 35J at 1/4-30 ℃, and the requirement of the mechanical property of the Rack Steel cannot be met.

The patent CN104264064B entitled Q690 high-strength structural steel plate with extra-thick specification and manufacturing method thereof proposes an extra-thick Q690 steel plate with thickness of 160-180 mm, because the chemical composition of the steel plate is low, the production process only adopts conventional rolling quenching and tempering treatment, the impact toughness of the produced steel plate can only ensure that the impact energy at 0 ℃ is more than or equal to 51J, and the use requirement of the rack steel can not be met.

Patent CN109234643B entitled super-strength rack steel rolling method for ocean platform proposes a rolling method of rack steel for ocean platform, the yield strength of the produced steel plate is lower than 690MPa, no subsequent heat treatment process is provided, and no scheme for improving the hardness and wear resistance of the finished steel plate is provided.

Disclosure of Invention

The invention aims to overcome the defects in the prior art, and the wear-resistant rack steel plate with large thickness and high use frequency, which is suitable for the field of ocean engineering, is prepared, and has hardness, wear resistance and high service safety performance which meet the service conditions of the rack steel of the marine platform. Forming a set of specific components of the wear-resistant rack steel plate with large thickness and high use frequency and a corresponding production process.

The invention utilizes the component design of high C and Cr, Mo, V, Ni elements, combines with the key production technology of the large-thickness high-use-frequency wear-resistant rack steel plate, and carries out a large amount of systematic experimental researches through screening and proportioning of alloy elements, controlling steel cleanliness, optimizing and selecting parameters of an efficient rolling heat treatment process and the like, and finally determines the alloy element proportioning and the rolling heat treatment process which can meet the aim of the invention, and the specific technical scheme is as follows:

a wear-resistant rack steel plate comprises the following components in percentage by weight: 0.20 to 0.30 percent of C, 0.2 to 0.4 percent of Si, 0.6 to 0.9 percent of Mn, less than or equal to 0.02 percent of P, less than or equal to 0.01 percent of S, 0.01 to 0.03 percent of Als, 0.8 to 1.2 percent of Ni, 0.9 to 1.5 percent of Cr, 0.5 to 1.0 percent of Mo, 0.05 to 0.1 percent of V, 0.0015 to 0.0025 percent of B, 0.05 to 0.2 percent of W, and the balance of Fe and inevitable impurities.

The design reason of the chemical components of the steel grade is as follows:

(1) c is used as an element for basically improving the strength and the hardness of the steel plate in the steel, is a main element for ensuring the strength and the hardness in the scheme of the invention, and according to experience, in the field of ultrahigh-strength quenched and tempered marine steel, the yield strength of the steel plate is improved by 30-50 MPa by improving 0.1 percent of C element, and the hardenability of the steel plate are also obviously improved along with the increase of the content of C; however, the welding performance is deteriorated when the content of C is too high, so the content of C in the steel is accurately controlled by the invention, and the content of C is controlled to be 0.20-0.30%.

(2) Si improves strength in steel by solid solution strengthening, and Si as a deoxidizer can reduce O content, and Si content more than 0.4% can cause coarsening of structure, so that Si content is 0.2-0.4% in the invention.

(3) The Mn atoms have similar radiuses to the Fe atoms, can be greatly dissolved in the Fe matrix, and improve the strength of the steel plate. When the Mn content is lower than 0.6%, the contribution to the strength of the steel plate is small, and meanwhile, because the C content in the steel is too high, excessive Mn elements cannot be added for controlling the carbon equivalent of the steel plate to ensure the welding performance, the Mn content in the invention is 0.6-0.9%.

(4) P, S element has no benefit to the mechanical property and welding property of the steel plate, and the invention controls the content of P, S as P less than or equal to 0.02% and S less than or equal to 0.01% by comprehensively considering the cost factor.

(5) Al is a main deoxidizing element in steel, when the content of Al is too low, the deoxidizing effect is poor, and micro-alloy elements such as Ti and the like cannot achieve the purposes of refining grains and improving welding performance due to oxidation; on the contrary, since a large inclusion is formed when the Al element is too high, the content of Als in the present invention is 0.01 to 0.03%.

(6) Ni is effective in improving hot workability and improving toughness. Particularly, when a large amount of C is added to the steel, sufficient Ni must be added to improve the low temperature toughness of the steel sheet to obtain a low ductile-brittle transition temperature, and therefore, the Ni content in the present invention is 0.8% to 1.2%.

(7) The Cr element can improve the strength, hardness and wear resistance of the steel plate in the structural steel, and particularly, the Cr element is matched with high C and elements, so that the wear resistance improving effect is more obvious; however, since too high Cr content lowers plasticity and toughness and Ni is required to improve toughness and plasticity of the steel sheet, the Cr content in the present invention is 0.9 to 1.5%.

(8) Mo element can refine crystal grains of steel, improve hardenability of the steel plate and improve hardness of the steel plate; however, since the welding property of the steel sheet is deteriorated due to the excessively high content of Mo, the content of Mo in the present invention is 0.5 to 1.0%.

(9) The V element can form V (C, N) particles in the matrix, and can play a role in refining and strengthening crystal grains. Meanwhile, the C, N compound of V is not easy to dissolve at high temperature, so that the thermal stability and the martensite stability of the steel plate can be improved, part of V element is dissolved in the matrix in a solid way, so that the hardness of the steel plate can be increased, and the toughness of the steel plate can be obviously improved under the combined action of Ti and N elements. Therefore, the V content in the present invention is 0.05% to 0.1%.

(10) The element B can improve the hardenability of the steel plate, trace element B can obviously improve the hardenability, the brittleness of the steel plate is increased when the element B is excessive, the welding crack tendency is increased, and the element B is controlled to be 0.0015-0.0025 percent.

(11) The W element forms carbide in the steel, so that the wear resistance and hardness of the steel can be obviously improved, and the tempering stability is improved; however, since the steel contains too much W element to reduce the heat deformability of the steel sheet and the toughness and plasticity of the steel sheet, the W content in the steel sheet is 0.05-0.2%.

The invention also comprises a manufacturing method of the wear-resistant rack steel plate, which adopts high cleanliness, alloying smelting, die casting steel ingot, heating (high-temperature steel burning), rolling and heat treatment (including slow quenching and tempering), so that the yield strength of the obtained steel plate is more than or equal to 690MPa, the tensile strength is 770-940 MPa, and the Charpy impact energy single value at the position of 1/4 ℃ below zero of the steel plate core is more than or equal to 80J. The Rockwell hardness HRC of each position of the steel plate is more than or equal to 45. The thickness range of the large-thickness low-cost ultrahigh-strength marine steel finished product is 128-260 mm. The method specifically comprises the following steps:

(1) high cleanliness and alloying smelting

And refining the molten steel by a converter, an LF furnace and an RH or VD furnace to further reduce P, S and the content of nonmetallic inclusions. The obtained weight percentage composition is as follows: 0.20 to 0.30 percent of C, 0.2 to 0.4 percent of Si, 0.6 to 0.9 percent of Mn, less than or equal to 0.02 percent of P, less than or equal to 0.01 percent of S, 0.01 to 0.03 percent of Als, 0.8 to 1.2 percent of Ni, 0.9 to 1.5 percent of Cr, 0.5 to 1.0 percent of Mo, 0.05 to 0.1 percent of V, 0.0015 to 0.0025 percent of B, 0.05 to 0.2 percent of W, and the balance of Fe and inevitable impurities. Protecting and casting the cast steel ingot.

(2) Heating and rolling process

And (3) loading the ingot into a heating furnace at the furnace temperature of 400-700 ℃, so that the internal and external temperatures of the billet are kept consistent in the low-temperature stage, and preparation is made for the uniform structure of the high-temperature section. The temperature rise rate of the casting blank is controlled to be 5-7 ℃/min in the subsequent temperature rise process, so that the condition that the interior of the steel blank is heated unevenly due to the fact that the steel blank is heated too fast is avoided. Soaking temperature is 1200-1300 ℃, heat preservation is carried out for 240-480 min, the purpose of soaking and heat preservation at high temperature for a long time is to ensure thorough burning inside the steel ingot, and the temperature difference between the inside and the outside is controlled to be lowest.

The thickness of the steel billet after cogging is 2-3 t, wherein t is the thickness of a finished product, two-fire rolling is adopted for rolling, the cogging and finish rolling temperature is 900-1000 ℃, the return temperature is 1200-1300 ℃, and the temperature is kept for 100-200 min. The initial rolling temperature is 1150-1200 ℃, and the final rolling temperature is 900-1000 ℃. The high-temperature hot rolling aims to improve the cast structure of a slab and avoid rolling warpage caused by excessive deformation resistance of a large-thickness steel ingot at low temperature.

(3) Thermal treatment

The heat treatment process comprises slow quenching and tempering. The quenching temperature is 850-920 ℃, oil cooling or water cooling is adopted to ensure that the quenching cooling rate at the position 1/4 is 3-8 ℃/s, the steel plate is slowly cooled, the steel plate keeps continuously swinging in a cooling tank or a quenching machine, the steel plate is quenched to 150-300 ℃, and the steel plate is stacked and slowly cooled to the room temperature. The tempering temperature is 300-550 ℃, and the heat preservation time is 3-4.5 min/mm. The steel plate is slowly cooled by oil cooling or water cooling and continuously swings to prevent the steel plate from cracking caused by overlarge internal stress in the phase change process of high-carbon steel, the steel plate is quenched to 150-300 ℃ to be not cooled completely, and the steel plate is prevented from cracking caused by overlarge temperature difference. The purpose of long-time heat preservation by medium-low temperature tempering is to ensure that the hardness and the wear resistance of the steel plate are not reduced while the toughness of the steel plate is improved.

Has the advantages that:

compared with the prior art, the invention has the following beneficial effects:

(1) the key production technology of the large-thickness high-use-frequency wear-resistant rack steel plate is combined with the component design of high C, Cr, Mo, V, Ni and W elements, the Rockwell hardness HRC of each position of the steel plate is more than or equal to 45, and the steel plate is suitable for high-use-frequency and high-wear-resistance racks.

(2) The innovative alloy component system and production process can ensure that the yield strength of the quenched and tempered steel plate is more than or equal to 690MPa, the tensile strength is 770-940 MPa, and the Charpy impact energy single value at the position of 1/4 ℃ below zero of the core part of the steel plate is more than or equal to 80J.

(3) The key production technology of the large-thickness high-use-frequency wear-resistant rack steel plate with high C, Cr, Mo, V, Ni and W elements matched is utilized, and the ultrahigh-strength rack steel plate with the thickness of 128-260 mm can be produced.

Drawings

FIG. 1 shows a metallographic structure of a quenched and tempered state at a thickness of 1/4 of a steel sheet and a structure of tempered martensite at a thickness of 1/4 of the steel sheet in example 1; FIG. 2 shows the metallographic structure of the steel sheet in a quenched and tempered state at a thickness of 1/2 in example 1, and the structure of the steel sheet at a thickness of 1/2 is tempered martensite;

Detailed Description

The following examples are intended to illustrate the invention in detail, and are intended to be a general description of the invention, and not to limit the invention.

The chemical compositions of the steel of the embodiment of the invention are shown in table 1, the heating and rolling process of the steel casting blank of the embodiment of the invention is shown in table 2, the heat treatment process of the steel plate of the embodiment of the invention is shown in table 3, and the mechanical properties of the steel plate of the embodiment of the invention are shown in table 4.

TABLE 1 chemical composition wt% of steel of examples of the invention

Examples	C	Si	Mn	P	S	Als	Ni	Cr	Mo	V	B	W
													1	0.237	0.26	0.66	0.02	0.01	0.01	0.88	0.91	0.73	0.084	0.0018	0.07
2	0.261	0.22	0.89	0.01	0.009	0.02	1.12	1.21	0.86	0.093	0.002	0.1
													3	0.212	0.37	0.81	0.01	0.008	0.023	0.92	1.40	1.0	0.068	0.0019	0.09
4	0.251	0.39	0.72	0.02	0.006	0.022	0.99	1.32	0.97	0.061	0.0017	0.11
													5	0.278	0.21	0.79	0.01	0.007	0.03	0.96	1.19	0.51	0.052	0.0022	0.18
6	0.20	0.29	0.74	0.01	0.01	0.016	0.81	1.47	0.58	0.059	0.0024	0.19
													7	0.292	0.31	0.77	0.01	0.01	0.018	0.86	0.96	0.62	0.05	0.0021	0.14
8	0.204	0.28	0.86	0.02	0.009	0.029	0.83	1.04	0.64	0.074	0.0025	0.08
													9	0.245	0.4	0.83	0.01	0.01	0.024	1.08	1.11	0.77	0.071	0.0015	0.06
10	0.266	0.33	0.61	0.02	0.006	0.027	1.19	1.38	0.69	0.064	0.0016	0.12
													11	0.271	0.24	0.63	0.02	0.006	0.02	1.01	0.93	0.92	0.078	0.0017	0.1
12	0.28	0.3	0.68	0.02	0.01	0.012	0.94	1.26	0.81	0.099	0.0023	0.08

TABLE 2 heating and Rolling Process of Steel casting blank according to the examples of the present invention

TABLE 3 Heat treatment Process for Steel plates according to examples of the invention

TABLE 4 mechanical Properties of Steel sheets according to examples of the present invention

As can be seen from tables 1-4, the ocean engineering steel produced by the technical scheme of the invention has the yield strength of more than or equal to 690MPa, the tensile strength of 770-940 MPa, and the Charpy impact energy single value of the steel plate core part at the position of 1/4 ℃ below zero of more than or equal to 80J. The Rockwell hardness HRC of each position of the steel plate is more than or equal to 45. The steel sheet has excellent wear resistance.

Claims

1. The wear-resistant rack steel plate is characterized in that the steel comprises the following chemical components in percentage by mass: 0.20 to 0.30 percent of C, 0.2 to 0.4 percent of Si, 0.6 to 0.9 percent of Mn, less than or equal to 0.02 percent of P, less than or equal to 0.01 percent of S, 0.01 to 0.03 percent of Als, 0.8 to 1.2 percent of Ni, 0.9 to 1.5 percent of Cr, 0.5 to 1.0 percent of Mo, 0.05 to 0.1 percent of V, 0.0015 to 0.0025 percent of B, 0.05 to 0.2 percent of W, and the balance of iron and inevitable impurities.

2. A wear-resistant steel rack plate as claimed in claim 1, wherein the steel plate has a yield strength of 690MPa or more, a tensile strength of 770-940 MPa, a Charpy impact strength of 80J or more at-40 ℃ at 1/4 in the core of the steel plate, and Rockwell hardness HRC of 45 or more at each position of the steel plate.

3. A wear resistant rack steel plate as claimed in claim 1 or 2 wherein the finished steel plate has a thickness of 128 to 260 mm.

4. A method of manufacturing a wear resistant rack steel plate as claimed in claim 1 or 2 or 3, the steel plate being produced by the process of: smelting, die casting, heating, rolling and heat treatment, which is characterized in that,

(1) smelting and die casting

Refining the molten steel through a converter, an LF furnace and an RH or VD furnace, and casting into a die-cast steel ingot in a protective mode;

(2) heating and rolling

Loading the steel ingot into a heating furnace at the furnace temperature of 400-700 ℃, controlling the heating rate to be 5-7 ℃/min in the subsequent heating process, controlling the soaking temperature to be 1200-1300 ℃, and keeping the temperature for 240-480 min;

the thickness of the steel billet after cogging is 2-3 t, wherein t is the thickness of a finished product, the rolling is carried out by adopting two-fire rolling, the cogging and finish rolling temperature is 900-1000 ℃, the return temperature is 1200-1300 ℃, and the heat preservation time is 100-200 min; the initial rolling temperature is 1150-1200 ℃, and the final rolling temperature is 900-1000 ℃;

(3) thermal treatment

The heat treatment process comprises slow quenching and tempering, wherein the quenching temperature is 850-920 ℃, the quenching cooling rate at the 1/4-part steel plate thickness is 3-8 ℃/s, the steel plate keeps continuously swinging in a cooling tank or a quenching machine, the quenching is carried out to 150-300 ℃, and the stacking is slowly cooled to the room temperature; the tempering temperature is 300-550 ℃, and the heat preservation time is 3-4.5 min/mm.

5. A method of manufacturing a wear resistant steel rack plate according to claim 4 wherein said quenching is oil or water cooled.