CN108504936B

CN108504936B - High-manganese medium plate with excellent ultralow-temperature toughness and preparation method thereof

Info

Publication number: CN108504936B
Application number: CN201810455448.0A
Authority: CN
Inventors: 刘振宇; 任家宽; 陈俊; 陈其源; 王国栋
Original assignee: Northeastern University China
Current assignee: Northeastern University China
Priority date: 2018-05-14
Filing date: 2018-05-14
Publication date: 2020-01-14
Anticipated expiration: 2038-05-14
Also published as: CN108504936A

Abstract

A high-manganese medium plate with excellent ultralow-temperature toughness and a preparation method thereof belong to the technical field of steel materials, and the medium plate comprises the following chemical components in percentage by weight: c: 0.31 to 0.67%, Si: 0.02 to 0.48%, Mn: 22.0-27.3%, P: less than or equal to 0.08 percent, S: less than or equal to 0.06 percent, Al: 1.5-4.64% and the balance of Fe and inevitable impurities; the preparation method comprises the following steps: 1) heating and insulating the steel billet; 2) carrying out one-stage rolling on the heated steel billet to obtain a hot rolled steel; 3) cooling the hot rolled steel to obtain a high-manganese medium plate with excellent toughness at the temperature of-196 ℃; the high-manganese medium plate can be used after being rolled, has excellent ultralow-temperature toughness and higher strength, does not need to add alloy elements, and has the cost far lower than that of 9Ni steel.

Description

High-manganese medium plate with excellent ultralow-temperature toughness and preparation method thereof

Technical Field

The invention belongs to the technical field of steel materials, and particularly relates to a high-manganese medium plate with excellent ultralow-temperature toughness and a preparation method thereof.

Background

With the improvement of environmental awareness of people, natural gas is regarded as the cleanest energy, and the development and utilization of natural gas are more and more valued by people and become the fastest-developing fossil fuel for decades in the future. Due to their wide geographical distribution, the distribution of liquefied natural gas resources is not balanced from place to place, and the transportation of Liquefied Natural Gas (LNG) is becoming increasingly important. The demand of natural gas resources in China increases rapidly, in 2001 + 2015, the natural gas in China increases by 15.9% in the year; in 2020, the liquefied natural gas needs to be imported 1400 hundred million m3 in China, and the Liquefied Natural Gas (LNG) imported at sea accounts for 50 percent of the imported quantity and reaches 700 hundred million m³Therefore, our country plans to build over 200 oversized LNG storage tanks, about 60 marine transport vessels, where the critical material for ultra-low temperature steel for storage and transportation facilities will be up to 60 million tons.

At present, most of traditional materials used for LNG storage tanks are aluminum alloy, austenitic stainless steel, 9% Ni steel, invar alloy and the like, but these materials have certain disadvantages, such as high price, too low strength, high welding material, difficult welding and the like, and therefore, development of economical high-performance LNG storage tank materials is urgently needed. High manganese steel has a good combination of strength and toughness at low temperatures, and is a relatively low cost, and is an attractive alternative to storage tank materials.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a high-manganese medium plate with excellent ultralow temperature toughness and a preparation method thereof.

The invention relates to a high-manganese medium plate with excellent ultralow-temperature toughness, which comprises the following chemical components in percentage by weight: c: 0.31 to 0.67%, Si: 0.02 to 0.48%, Mn: 22.0-27.3%, P: less than or equal to 0.08 percent, S: less than or equal to 0.06 percent, Al: 1.5-4.64%, and the balance of Fe and inevitable impurities.

The thickness of the high-manganese medium-thickness plate is 11-20 mm, the impact absorption energy (RD) in the rolling direction at the ultralow temperature of-196 ℃ is 116-212J, the impact absorption energy (TD) in the width direction is 89-173J, the yield strength (Rel) is 318-529 MPa, and the tensile strength (Rm) is 728-889 MPa.

A preparation method of a high-manganese medium plate with excellent ultralow-temperature toughness comprises the following specific steps:

(1) smelting molten steel according to the component design of the high-manganese medium plate, casting the molten steel into a steel billet, heating the steel billet to 1000-1200 ℃, and preserving heat for 2-3 hours;

(2) rolling the heated steel billet in one stage at the initial rolling temperature of 1030-1150 ℃, the final rolling temperature of 950-1070 ℃ and the total rolling reduction of 78-85% to obtain a hot rolled steel;

(3) and (3) cooling the hot rolled steel to room temperature by water to obtain the high-manganese medium plate with excellent ultralow-temperature toughness.

The preparation method of the high-manganese medium plate with excellent ultralow-temperature toughness comprises the following steps:

in the step 1, the thickness of the steel billet is 55-112 mm.

In the step 1, the billet is heated in a box-type resistance furnace.

In the step 2, the single-pass reduction rate is 18-29% after 5-9 passes of rolling.

In the step 2, the thickness of the hot rolled steel is 11-20 mm.

The high-manganese medium plate with excellent ultralow-temperature toughness and the preparation method thereof have the main ideas of the technical scheme that:

c is used as a basic strengthening element and can improve the stacking fault energy and the strength, and the content of C in the invention is controlled between 0.31 percent and 0.67 percent; mn is an austenite stabilizing element, and the Mn content of the invention is controlled between 22.0 percent and 27.3 percent; C. mn can reduce the martensite phase transformation point to be lower than the temperature of liquefied natural gas, and ensures that the martensite phase is a full austenite phase in the low-temperature use process. The austenite is in a face-centered cubic lattice structure, and has no obvious ductile-brittle transition phenomenon, so that the high-manganese austenitic steel has inherent advantages in the aspect of ultralow-temperature material development.

P, S are likely to segregate to grain boundaries or twin boundaries, causing brittleness, which greatly deteriorates the ultra-low temperature toughness of high manganese steel, and therefore, it is necessary to control the temperature within a low range.

Si is used as a stable ferrite element, the stacking fault energy can be reduced, the strength is improved, and the Si content is controlled to be 0.02-0.48%.

Al has the characteristics of improving the stacking fault energy, inhibiting hydrogen induced cracking and reducing the tensile strength, C and Al can also increase the stability of austenite at low temperature, the Al content of the invention is controlled to be between 1.5 and 4.64 percent, and a certain amount of Al is added into high manganese steel to inhibit the transformation of gamma to epsilon-martensite and promote the generation of deformation twin crystals in the deformation process. The high-temperature deformation is carried out in a higher temperature range, so that the deformed austenite structure is converted into an equiaxed austenite structure, and the water cooling treatment is adopted after the high-temperature deformation, so that the segregation of elements such as P, S at a grain boundary is weakened, the precipitation of carbide is reduced, and the toughness is improved.

Compared with the prior art, the high-manganese medium plate with excellent ultralow-temperature toughness and the preparation method thereof have the advantages and beneficial effects that:

1. the high-manganese medium plate can be used after being rolled, and has excellent ultralow-temperature toughness and higher strength.

2. No need of adding alloy elements and low cost far lower than that of 9Ni steel.

Drawings

FIG. 1A typical hot rolled optical microstructure of a # 1 steel prepared according to example 1 of the present invention.

FIG. 2A typical hot rolled optical microstructure of the 3# steel produced in example 2 of the present invention.

FIG. 3A typical hot rolled optical microstructure of 5# steel prepared according to example 3 of the present invention.

Detailed Description

The following examples 1-3 roll forming processes were carried out on a 450mm two roll reversible hot rolling pilot mill.

Example 1

A high-manganese medium plate with excellent ultralow-temperature toughness comprises the following chemical components in percentage by weight: c: 0.5%, Si: 0.146%, Mn: 23.96%, P: 0.004%, S: 0.002%, Al: 2.01%, and the balance of Fe and inevitable impurities.

(1) smelting molten steel according to component design, casting the molten steel into No. 1 and No. 2 billets with the thickness of 74mm, heating the billets to 1200 ℃, and preserving heat for 2 hours;

(2) respectively carrying out one-stage rolling on the heated 1# and 2# steel billets to obtain hot rolled steel, wherein the rolling pass, the initial rolling temperature, the final rolling temperature, the single-pass reduction rate and the total reduction rate are shown in a table 1, and the thickness of the hot rolled steel is shown in a table 2;

TABLE 1 control of the Rolling Process parameters

Numbering	The initial rolling temperature/. degree.C	Final Rolling temperature/. degree.C	Single pass reduction/%)	Total reduction/%)	Pass of rolling
						1075	956	18～29	84	7
2# Steel	1062	999	18～29	85	7

TABLE 2 thickness of hot rolled steel

Test specimen	1# Steel	2# Steel
			Thickness/mm of hot rolled steel	12	11

The impact test piece and the tensile test piece were taken along the rolling direction and the width direction of the high manganese medium plate with excellent ultralow temperature toughness prepared in this example, and the charpy V-notch impact absorption power at-196 ℃ and the room temperature tensile strength were shown in table 3.

Charpy V-notch impact absorption and room temperature tensile strength of the samples at temperatures of from 3 to 196 ℃.

Numbering	RD/J	TD/J	Rel/MPa	Rm/MPa
					1# Steel	199	156	339	765
2# Steel	203	158	328	740

The example results show that the high-manganese medium plate of the invention adopts controlled rolling and controlled cooling, so that the high-manganese medium plate in a hot rolling state can obtain excellent ultralow temperature impact toughness and simultaneously has higher strength, and the typical optical microstructure of the steel No. 1 in the hot rolling state is shown in figure 1.

Example 2

A high-manganese medium plate with excellent ultralow-temperature toughness comprises the following chemical components in percentage by weight: c: 0.67%, Si: 0.48%, Mn: 25.8%, P: 0.019%, S: 0.006%, Al: 3.64%, and the balance of Fe and inevitable impurities.

(1) smelting molten steel according to component design, casting the molten steel into No. 3 and No. 4 steel billets with the thickness of 112mm, heating the steel billets to 1000 ℃, and preserving heat for 2.5 hours;

(2) respectively carrying out one-stage rolling on the heated 3# and 4# steel billets to obtain hot rolled steel, wherein the rolling pass, the initial rolling temperature, the final rolling temperature, the single-pass reduction rate and the total reduction rate are shown in a table 4, and the thickness of the hot rolled steel is shown in a table 5;

TABLE 4 control of the Rolling Process parameters

Numbering	The initial rolling temperature/. degree.C	Final Rolling temperature/. degree.C	Single pass reduction/%)	Total reduction/%)	Pass of rolling
						3# Steel	1087	1017	20～29	82	9
4# Steel	1049	978	19～29	84	9

TABLE 5 thickness of hot rolled steel

Test specimen	3# Steel	4# Steel
			Thickness/mm of hot rolled steel	20	18

The impact test piece and the tensile test piece were taken from the high manganese medium plate with excellent ultra-low temperature toughness prepared in the examples in the rolling direction, and the impact test piece was taken in the width direction, and charpy V-notch impact absorption power at-196 ℃ and room temperature tensile strength were shown in table 6.

Charpy V-notch impact absorption and room temperature tensile strength of the samples at temperatures of from 6 to 196 ℃.

Numbering	RD/J	TD/J	Rel/MPa	Rm/MPa
					3# Steel	178	142	365	789
4# Steel	170	133	375	796

The example results show that the high-manganese medium plate of the invention adopts controlled rolling and controlled cooling, so that the high-manganese medium plate in a hot-rolled state can obtain excellent ultralow-temperature impact toughness and simultaneously has higher strength, and the typical optical microstructure of the 3# steel in the hot-rolled state is shown in figure 2.

Example 3

A high-manganese medium plate with excellent ultralow-temperature toughness comprises the following chemical components in percentage by weight: c: 0.31%, Si: 0.12%, Mn: 24.9%, P: 0.06%, S: 0.004%, Al: 1.96%, and the balance of Fe and inevitable impurities.

(1) smelting molten steel according to component design, casting into 5# and 6# steel billets with the thickness of 55mm, heating the steel billets to 1150 ℃, and preserving heat for 3 hours;

(2) respectively carrying out one-stage rolling on the heated 5# and 6# steel billets to obtain hot rolled steel, wherein the rolling pass, the initial rolling temperature, the final rolling temperature, the single-pass reduction rate and the total reduction rate are shown in a table 7, and the thickness of the hot rolled steel is shown in a table 8;

TABLE 7 control of the Rolling Process parameters

Numbering	The initial rolling temperature/. degree.C	Final Rolling temperature/. degree.C	Single pass reduction/%)	Total reduction/%)	Pass of rolling
						5# Steel	1061	990	20～29	78	5
6# Steel	1056	942	20～29	80	5

TABLE 8 thickness of hot rolled steel

Test specimen	5# Steel	6# Steel
			Thickness/mm of hot rolled steel	12	11

The impact test piece and the tensile test piece were taken from the high manganese medium plate with excellent ultralow temperature toughness prepared in this example in the rolling direction, and the impact test piece was taken in the width direction, and the charpy V-notch impact absorption power at-196 ℃ and the room temperature tensile strength were shown in table 9.

Charpy V-notch impact absorption and room temperature tensile strength of the samples at temperatures of from 9 to 196 ℃.

Numbering	RD/J	TD/J	Rel/MPa	Rm/MPa
					5# Steel	212	173	318	728
6# Steel	204	163	329	736

The example results show that the high-manganese medium plate of the invention adopts controlled rolling and controlled cooling, so that the high-manganese medium plate in a hot rolling state can obtain excellent ultralow temperature impact toughness and simultaneously has higher strength, and the typical optical microstructure of the 5# steel in the hot rolling state is shown in figure 3.

Example 4

A high-manganese medium plate with excellent ultralow-temperature toughness comprises the following chemical components in percentage by weight: c: 0.48%, Si: 0.15%, Mn: 27.3%, P: 0.004%, S: 0.005%, Al: 4.64%, and the balance of Fe and inevitable impurities.

(1) smelting molten steel according to the component design, casting the molten steel into a No. 7 steel billet with the thickness of 72mm, heating the steel billet to 1200 ℃, and preserving heat for 2 hours;

(2) carrying out one-stage rolling on the heated 7# billet to obtain a 12mm hot rolled steel, wherein the rolling pass, the initial rolling temperature, the final rolling temperature, the single-pass reduction rate and the total reduction rate are shown in a table 10;

TABLE 10 control of rolling process parameters

The impact test piece and the tensile test piece were taken from the high manganese medium plate with excellent ultralow temperature toughness prepared in this example in the rolling direction, and the impact test piece was taken in the width direction, and the charpy V-notch impact absorption power at-196 ℃ and the room temperature tensile strength were shown in table 11.

Charpy V-notch impact absorption and room temperature tensile strength of the samples at temperatures from 11 to 196 ℃.

Numbering	RD/J	TD/J	Rel/MPa	Rm/MPa
					7# Steel	116	89	529	889

The embodiment result shows that the high-manganese medium plate of the invention adopts controlled rolling and controlled cooling, so that the hot-rolled high-manganese medium plate can obtain excellent ultralow-temperature impact toughness and simultaneously has higher strength.

Claims

1. The high-manganese medium plate with excellent ultralow-temperature toughness is characterized by comprising 0.31 wt% of C, 0.12 wt% of Si, 24.9 wt% of Mn, 0.06 wt% of P, 0.004 wt% of S, 1.96 wt% of Al and the balance of Fe and inevitable impurities, wherein the thickness of the high-manganese medium plate is 11 ~ 20mm, the impact absorption power in the rolling direction at the ultralow temperature of-196 ℃ is 204 ~ 212J, the impact absorption power in the width direction is 163 ~ 173J, the yield strength is 318 ~ 329MPa, and the tensile strength is 728 ~ 736 MPa.

2. The preparation method of the high-manganese medium plate with excellent ultralow-temperature toughness as claimed in claim 1 is characterized by comprising the following specific steps:

(1) according to the component design of the high-manganese medium plate, molten steel is smelted and cast into a steel billet, the thickness of the steel billet is 55mm, and the steel billet is heated to 1150 ℃ and is kept warm for 3 hours;

(2) carrying out one-stage rolling on the heated billet, wherein the initial rolling temperature is 1056 ~ 1061 ℃, the final rolling temperature is 950 ~ 990 ℃, and the hot rolled steel is obtained through 5-pass rolling, the single-pass reduction rate is 20 ~ 29%, the total reduction rate is 78 ~ 80%, and the thickness is 11 ~ 20 mm;