Low-coefficient-of-thermal expansion steel with improved low-temperature impact strength and method for its production

Abstract

FIELD: metallurgy.SUBSTANCE: production of steel sheets used as a material for the manufacture of products for the transportation and storage of liquefied natural gas. The sheet is made of steel containing, wt.%: more than 0 and 0.04 or less carbon (C), 0.1 or more and 0.5 or less silicon (Si), 0.1 or more and 0.4 or less manganese (Mn), 0.003 or less phosphorus (P), 0.003 or less sulfur (S), more than 0 and 0.5 or less chromium (Cr), 34 or more and 37.1 or less nickel (Ni), more than 0 and 2.0 or less cobalt (Co), the rest is iron (Fe) and unavoidable impurities. The contents of elements in steel satisfy the following ratios: 15Cr+3Ni+3Co≤ 112 and 3Cr+2Ni-50Mn-2Co≥ 56, where Cr, Ni, Co and Mn represent the content, wt.%, of the corresponding elements.EFFECT: sheet has a low coefficient of thermal expansion of 1.0×10-6 / ° C or less in the range from room temperature to 100 °C, and improved low temperature impact strength of 140 J / cm2 or more at -196°C.8 cl, 2 tbl

Description

[0001] Field of technology to which the invention relates

[0002] The present disclosure relates to a low thermal expansion steel having improved low temperature impact toughness and a production method thereof.

[0003] Technology Level

[0004] Recently, the growing demand for the transportation and storage of liquefied natural gas has led to a significant increase in the need for tank materials that can store liquids at extremely low temperatures.

[0005] Since the brittleness of materials increases in extremely low temperature environments, cracks may easily occur in the material of the storage container, resulting in leakage.

[0006] Meanwhile, cracks in the material can be caused by stress due to thermal expansion of the material with temperature changes or due to a decrease in the impact toughness of the material in an extremely low temperature environment.

[0007] Therefore, it is necessary to develop materials with low thermal expansion coefficient and excellent low temperature impact toughness to prevent cracking even in extremely low temperature environments.

[0008] Prior Art

[0009] (Patent Document 1) Korean Patent Publication 10-1995-0032674 A (December 22, 1995)

[0010] Essence of the invention

[0011] Technical task

[0012] The present disclosure provides a low thermal expansion steel having a low thermal expansion coefficient and excellent impact toughness at low temperatures by optimizing the steel composition and adjusting the production method, and a production method thereof.

[0013] Technical solution

[0014] According to one embodiment of the present disclosure, a low thermal expansion steel having improved low temperature impact toughness comprises, in percentage by weight (wt%): more than 0% and 0.04% or less of carbon (C); 0.1% or more and 0.5% or less of silicon (Si); 0.1% or more and 0.4% or less of manganese (Mn); 0.003% or less of phosphorus (P); 0.003% or less of sulfur (S); more than 0% and 0.5% or less of chromium (Cr); 34% or more and 38% or less of nickel (Ni); more than 0% and 2.0% or less of cobalt (Co); the rest is iron (Fe) and inevitable impurities, and the value of Formula (1), shown below, can be 112 or less.

[0015] Formula (1): 15Cr + 3Ni + 3Co

[0016] In formula (1), Cr, Ni and Co represent the contents (wt%) of the corresponding elements.

[0017] A steel with a low coefficient of thermal expansion having improved impact toughness at low temperatures, according to one embodiment, may have a value of Formula (2) shown below of 56 or more.

[0018] Formula (2): 3Cr + 2Ni - 50Mn - 2Co

[0019] In Formula (2), Cr, Ni, Mn and Co represent the contents (wt%) of the corresponding elements.

[0020] A low thermal expansion steel having improved impact toughness at low temperatures, according to one embodiment, may have a thermal expansion coefficient from room temperature to 100°C of 1.0 × 10 -6 / °C or less.

[0021] A low thermal expansion steel having improved low temperature impact toughness, according to one embodiment, may have an impact toughness of 140 J / cm 2 or more at -196°C.

[0022] A low thermal expansion steel having improved impact toughness at low temperatures, according to one embodiment, may have an impact toughness at room temperature of 300 J / cm 2 or more.

[0023] According to one embodiment of the present disclosure, a method for producing a steel with a low coefficient of thermal expansion having improved low-temperature impact toughness includes: producing a slab containing, in percentage by weight (wt%): more than 0% and 0.04% or less of carbon (C); 0.1% or more and 0.5% or less of silicon (Si); 0.1% or more and 0.4% or less of manganese (Mn); 0.003% or less of phosphorus (P); 0.003% or less of sulfur (S); more than 0% and 0.5% or less of chromium (Cr); 34% or more and 38% or less of nickel (Ni); more than 0% and 2.0% or less of cobalt (Co); the remainder is iron (Fe) and unavoidable impurities; and hot rolling the slab at a temperature of 1200 to 1350°C and hot rolling annealing at a temperature of 800 to 1000°C to produce a hot-rolled steel sheet, wherein the slab has a value of Formula (1) shown below of 112 or less.

[0024] Formula (1): 15Cr + 3Ni + 3Co

[0025] In formula (1), Cr, Ni and Co represent the contents (wt%) of the corresponding elements.

[0026] The slab may have a value of Formula (2) shown below of 56 or more.

[0027] Formula (2): 3Cr + 2Ni - 50Mn - 2Co

[0028] In Formula (2), Cr, Ni, Mn and Co represent the contents (mass%) of the corresponding elements.

[0029] The method may further include cold rolling the hot rolled steel sheet with a reduction ratio of 50% or more and cold rolling annealing at a temperature of 800 to 950°C to produce a cold rolled steel sheet.

[0030] Advantageous effects

[0031] According to one embodiment of the present solution, by adjusting the alloying components and the production method, a low thermal expansion steel having a low thermal expansion coefficient and excellent impact toughness at low temperatures can be provided, and a production method thereof.

[0032] Optimal mode for carrying out the invention

[0033] Below, embodiments of the present disclosure are described in detail with reference to the accompanying drawings. The following embodiments are intended to fully disclose the essence of the present disclosure to those skilled in the art and are not limited to those presented herein, but may be embodied in other forms. Figures irrelevant to the description may be omitted in the drawings for a better understanding of the present disclosure, and the dimensions of the structures may be exaggerated for illustrative purposes.

[0034] In this specification, when a part "includes" a certain component, it means that the part may further include other components, and not exclude other components, unless otherwise specified.

[0035] It should be understood that the singular also implies the plural, unless the context clearly indicates otherwise.

[0036] The reasons for the numerical limitations on the alloying component content in the embodiments of the present disclosure will be described below. Hereinafter, unless otherwise specified, the unit of measurement is percentage by mass (wt%).

[0037] According to one embodiment, a steel with a low coefficient of thermal expansion having improved impact toughness at low temperatures may contain, in percentage by weight (wt%): more than 0% and 0.04% or less C; 0.1% or more and 0.5% or less Si; 0.1% or more and 0.4% or less Mn; 0.003% or less P; 0.003% or less S; more than 0% and 0.5% or less Cr; 34% or more and 38% or less Ni; more than 0% and 2.0% or less Co; the rest is Fe and unavoidable impurities.

[0038] The carbon (C) content can be more than 0% and 0.04% or less.

[0039] C is an element effective in improving strength, so it is desirable to add an appropriate amount for use as a thin sheet material. However, since C can degrade the coefficient of thermal expansion due to the formation of carbides, it is advantageous to keep the C content low. However, excessively low C content can lead to increased production costs. Therefore, the C content should be controlled at a level of more than 0% and less than 0.04% to ensure a competitive price while maintaining low thermal expansion properties. It is preferable for the C content to be 0.003% or more to 0.037% or less.

[0040] The silicon (Si) content can be 0.1% or more to 0.5% or less.

[0041] Si is an element effective in reducing oxygen content and controlling inclusions by facilitating deoxidation during alloy refining. However, since the addition of Si increases the coefficient of thermal expansion, the Si content is traditionally controlled at 0.1% or less. According to the disclosure, the Si content can be controlled at 0.1% or more to 0.5% or less to facilitate deoxidation while suppressing thermal expansion. Preferably, the Si content should be 0.11% or more to 0.42% or less.

[0042] The content of manganese (Mn) can be 0.1% or more to 0.4% or less.

[0043] Mn is an element effective for solid solution strengthening and improving hot workability. In particular, Mn can be used as a deoxidizer together with Si during alloy refining. However, the Mn content has traditionally been controlled at 0.1% or less to suppress thermal expansion. According to the disclosure, the Mn content can be controlled at 0.1% or more to 0.4% or less to suppress thermal expansion even when the Mn content increases by adjusting the Cr, Ni, and Co components. Preferably, the Mn content is 0.12% or more to 0.34% or less.

[0044] The phosphorus (P) content may be 0.003% or less or more than 0% and 0.003% or less.

[0045] P is an undesirable impurity inevitably contained in steel, and it is an element that causes grain boundary corrosion and impairs machinability during hot working. Therefore, it is advantageous to keep the P content low. However, excessively low P content can lead to increased production costs. Based on the above, the P content can be 0.003% or less. It is preferable for the P content to be 0.001% or more to 0.003% or less.

[0046] The sulfur (S) content may be 0.003% or less, or more than 0% and 0.003% or less.

[0047] S is an undesirable impurity inevitably contained in steel. It concentrates at grain boundaries, impairing machinability during hot working. In particular, since S can cause shape defects during welding and cracks, it is advantageous to keep the S content low. Based on the above, the upper limit of the S content can be limited to 0.003% or less. It is desirable for the S content to be 0.0004% or more to 0.0022% or less.

[0048] The content of chromium (Cr) can be more than 0% and 0.5% or less.

[0049] In the conventional stainless steel production process, Cr may be introduced into steel with a low coefficient of thermal expansion during the production of other steel grades, making Cr removal difficult. However, Cr is an element that increases the coefficient of thermal expansion, so it is desirable to keep the Cr content as low as possible. In the present disclosure, by adjusting the Ni content, the Cr content can be controlled to a level greater than 0% and less than 0.5% to suppress thermal expansion even as the Cr content increases.

[0050] The nickel (Ni) content can be 34% or more to 38% or less.

[0051] Ni is a necessary element for achieving low thermal expansion properties by reducing thermal expansion. Typically, to achieve low thermal expansion properties, elements other than Ni and Fe are kept at extremely low levels, which leads to increased production costs. In this disclosure, the Ni content is controlled within a range of 34% or more to 38% or less, and the Cr and Co components are adjusted to lower the coefficient of thermal expansion. It is desirable to control the Ni content within a range of 34.6% or more to 37.1% or less.

[0052] The cobalt (Co) content can be more than 0% and 2.0% or less.

[0053] In general, Co is known as a component that reduces the coefficient of thermal expansion when added in an amount of 4% or less, and increases the coefficient of thermal expansion when added in an amount of more than 4%. In addition, as the Co content increases, cryogenic impact toughness may decrease. In the disclosure, the Co content is controlled at more than 0% and 2.0% or less, and the Cr and Ni contents are adjusted to lower the coefficient of thermal expansion. It is preferable that the Co content be more than 0% and 0.5% or less, and it is even more preferable that the Co content be 0.01% or more to 0.5% or less.

[0054] The remaining component of the composition in the present disclosure is iron (Fe). However, since undesirable impurities from the starting material or the environment may inevitably be introduced during typical manufacturing, they cannot be excluded. Since such impurities are well known to those skilled in the art of typical manufacturing, details regarding them are not described herein.

[0055] A steel with a low coefficient of thermal expansion having improved impact toughness at low temperatures, according to one embodiment, may have a value of Formula (1) below of 112 or less.

[0056] Formula (1): 15Cr + 3Ni + 3Co

[0057] In Formula (1), Cr, Ni and Co represent the contents (mass%) of the corresponding elements.

[0058] The purpose of the present disclosure is to suppress thermal expansion by optimizing alloying components to lower the coefficient of thermal expansion. Accordingly, according to the present disclosure, Formula (1) is obtained by combining alloying components that can affect the coefficient of thermal expansion. If the value of Formula (1) exceeds 112, the coefficient of thermal expansion from room temperature to 100°C can exceed 1.0 × 10 -6 / °C. That is, if the value of Formula (1) exceeds 112, the ability to suppress thermal expansion may be insufficient.

[0059] The value of Formula (1) may be, in particular, from 102 to 112, more specifically, from 105 to 112, and even more specifically, from 108 to 112. Within the above range, a steel with a low coefficient of thermal expansion having improved impact toughness at low temperatures, according to one embodiment of the present disclosure, may be more preferable for achieving both a low coefficient of thermal expansion and excellent impact toughness at low temperatures.

[0060] A steel with a low coefficient of thermal expansion having improved impact toughness at low temperatures, according to one embodiment, may have a value of Formula (2) below of 56 or more.

[0061] Formula (2): 3Cr+2Ni - 50Mn - 2Co

[0062] In Formula (2), Cr, Ni, Mn and Co represent the contents (mass%) of the corresponding elements.

[0063] The purpose of the disclosure is to improve the low-temperature impact toughness by adjusting the composition. Accordingly, according to the disclosure, Formula (2) is obtained by combining alloying components that can affect the low-temperature impact toughness. If the value of Formula (2) is less than 56, the impact toughness at -196°C may be less than 140 J / cm 2 . That is, if the value of Formula (2) is less than 56, the impact toughness at low temperatures may be insufficient.

[0064] The value of Formula (2) may be, in particular, from 56 to 72.5 or less, from 56 to 70, more specifically from 56 to 65, and even more specifically from 58 to 60. Within the specified range, a steel with a low coefficient of thermal expansion having improved impact toughness at low temperatures, according to one embodiment of the present disclosure, may be more preferable for achieving both a low coefficient of thermal expansion and excellent impact toughness at low temperatures. Also, even more excellent impact toughness properties can be achieved by further improving the balance between the impact toughness value at room temperature and the impact toughness value at -196°C.

[0065] A low thermal expansion steel having improved impact toughness at low temperatures, according to one embodiment, may have a thermal expansion coefficient from room temperature to 100°C of 1.0 × 10 -6 / °C or less by adjusting the alloy composition and production method. That is, the low-thermal-expansion steel having improved impact toughness at low temperatures, according to one embodiment, has low thermal expansion with a change in temperature, and therefore this low-thermal-expansion steel can be used as a steel for storing low-temperature liquids.

[0066] Furthermore, the low thermal expansion steel having improved impact toughness at low temperatures, according to one embodiment, may have an impact toughness of 140 J / cm 2or more at -196°C and impact strength at room temperature of 300 J / cm 2 or more. That is, a steel with a low coefficient of thermal expansion having improved impact toughness at low temperatures, according to one embodiment, has low crack formation even in cryogenic environments, and therefore this steel with a low coefficient of thermal expansion can be used as a steel for storing low-temperature liquids.

[0067] The following describes a method for producing a steel with a low coefficient of thermal expansion having improved impact toughness at low temperatures, according to another aspect of the disclosure.

[0068] A method for producing steel with a low coefficient of thermal expansion having improved low-temperature impact toughness, according to one embodiment, includes: producing a slab containing, in percentage by weight (wt%): more than 0% and 0.04% or less C; 0.1% or more and 0.5% or less Si; 0.1% or more and 0.4% or less Mn; 0.003% or less P; 0.003% or less S; more than 0% and 0.5% or less Cr; 34% or more and 38% or less Ni; more than 0% and 2.0% or less Co; the rest is Fe and unavoidable impurities; and hot rolling the slab at a temperature of 1200 to 1350°C and hot rolling annealing at a temperature of 800 to 1000°C to produce a hot-rolled steel sheet, wherein the slab may have a Formula (1) value of 112 or less.

[0069] Formula (1): 15Cr + 3Ni + 3Co

[0070] In Formula (1), Cr, Ni and Co represent the contents (mass%) of the corresponding elements.

[0071] In addition, the slab may have a Formula (2) value of 56 or more.

[0072] Formula (2): 3Cr+2Ni - 50Mn - 2Co

[0073] In Formula (2), Cr, Ni, Mn and Co represent the contents (mass%) of the corresponding elements.

[0074] The reasons for the numerical limitations of the component ranges of the corresponding alloy compositions, Formula (1) and Formula (2) are described above, and each production step is described in more detail below.

[0075] After producing a slab that meets the requirements of the alloy composition, Formula (1) and Formula (2), the hot rolling process, the hot rolling annealing process can be carried out, and optionally, cold rolling and cold rolling annealing can also be carried out further.

[0076] The slab can first be hot rolled at 1200 to 1350°C and hot rolling annealed at 800 to 1000°C to produce hot rolled steel sheet.

[0077] If the hot rolling temperature is low, it may be difficult to re-dissolve the coarse inclusions formed during slab production. However, if the hot rolling temperature is too high, the internal grains may become excessively coarse.

[0078] If the annealing temperature during hot rolling is low, inclusions formed during casting may remain, resulting in insufficient elongation. However, if the annealing temperature during hot rolling is too high, strength may decrease due to grain coarsening.

[0079] Further, if necessary, the method may further include cold rolling the hot-rolled steel sheet with a reduction ratio of not less than 50% and cold rolling annealing at a temperature of 800 to 950°C to produce a cold-rolled steel sheet.

[0080] When the reduction ratio is less than 50%, recrystallization may be reduced during rolling annealing, resulting in grain coarsening.

[0081] If the annealing temperature during cold rolling is low, recrystallization may be insufficient, resulting in reduced elongation. However, if the annealing temperature during cold rolling is too high, grain coarsening occurs and the depth of oxides formed at grain boundaries increases, resulting in insufficient surface quality after pickling.

[0082] The present disclosure is hereinafter described in more detail by means of embodiments. However, the descriptions of the embodiments serve only to illustrate the implementation of the present disclosure, and the present disclosure is not limited to the descriptions of the embodiments. This is because the scope of the present disclosure is determined by the claims and the features reasonably derived therefrom.

[0083] {Implementation options}

[0084] A slab with different alloying component ranges, as shown in Table 1 below, was produced in a vacuum induction furnace. The resulting slab was hot-rolled at 1250°C and annealed at 900°C to produce hot-rolled steel sheets. The hot-rolled steel sheets were then cold-rolled with a reduction ratio of 60% and annealed at 900°C to produce specimens.

[0085] [Table 1]

[0086] Alloying elements (wt.%) C Si Mn P S Cr Ni Co Example 1 0,028 0,17 0,15 0,0010 0,0005 0,5 34,7 0,10 Example 2 0,035 0,11 0,26 0,0012 0,0005 0,0 37,1 0,12 Example 3 0,033 0,20 0,32 0,0010 0,0004 0,2 36,0 0,30 Example 4 0,029 0,15 0,34 0,0017 0,0008 0,1 36,7 0,10 Example 5 0,021 0,18 0,27 0,0023 0,0004 0,1 36,2 0,50 Example 6 0,027 0,20 0,25 0,0014 0,0005 0,3 35,7 0,02 Example 7 0,024 0,37 0,19 0,0013 0,0005 0,0 36,0 0,01 Example 8 0,003 0,32 0,26 0,0018 0,0012 0,0 36,1 0,01 Example 9 0,037 0,19 0,12 0,0014 0,0011 0,5 34,6 0,20 Example 10 0,018 0,23 0,26 0,0014 0,0020 0,0 36,5 0,02 Example 11 0,026 0,42 0,25 0,0015 0,0022 0,0 36,1 0,01 Example 12 0,031 0,20 0,29 0,0030 0,0019 0,1 35,6 0,01 Comparative example 1 0,017 0,18 0,28 0,0031 0,0008 0,2 35,1 0,98 Comparative example 2 0,027 0,17 0,27 0,0014 0,0004 0,1 34,7 1,02 Comparative example 3 0,030 0,20 0,35 0,0026 0,0005 0,2 34,2 1,90 Comparative example 4 0,029 0,19 0,27 0,0015 0,0006 0,1 34,0 1,90 Comparative example 5 0,026 0,19 0,26 0,0016 0,0007 0,1 36,0 2,10 Comparative example 6 0,022 0,16 0,31 0,0014 0,0006 0,2 36,5 1,48 Comparative example 7 0,020 0,36 0,28 0,0027 0,0004 0,1 36,2 0,95 Comparative example 8 0,039 0,20 0,25 0,0030 0,0005 0,3 36,3 0,03 Comparative example 9 0,002 0,23 0,30 0,0014 0,0005 0,3 36,5 0,01 Comparative example 10 0,027 0,41 0,24 0,0015 0,0010 0,5 36,0 0,04 Comparative example 11 0,026 0,37 0,27 0,0014 0,0004 0,9 35,7 0,12 Comparative example 12 0,036 0,20 0,10 0,0031 0,0004 1,0 36,1 0,01

[0087] Table 2 below shows the values ​​of Formula (1), the values ​​of Formula (2), the coefficient of thermal expansion, the impact strength at room temperature and the impact strength at -196°C. The value of Formula (1) was calculated according to Formula (1) below.

[0088] Formula (1): 15Cr + 3Ni + 3Co

[0089] In Formula (1), Cr, Ni and Co represent the contents (mass%) of the corresponding elements.

[0090] The value of Formula (2) was calculated by Formula (2) below.

[0091] Formula (2): 3Cr + 2Ni - 50Mn - 2Co

[0092] In Formula (2), Cr, Ni, Mn and Co represent the contents (mass%) of the corresponding elements.

[0093] The coefficient of thermal expansion was measured using a dilatometer. First, the change in sample length was measured as a function of temperature when heated from room temperature to 120°C at a rate of 1°C / s. Then, the linear coefficient of thermal expansion from 25 to 100°C was calculated using Formula (3) below.

[0094] Formula (3):

[0095] In Formula (3) α m is the coefficient of thermal expansion, L0 is the initial length, ΔL is the change in length, and ΔT is the change in temperature.

[0096] Room-temperature impact strength and -196°C impact strength were measured at low temperatures of 25°C and -196°C using a Zwick Roell impact tester. Impact strength at -196°C was assessed by immersing the sample in liquid nitrogen for 5 minutes.

[0097] [Table 2]

[0098] Formula (1) Formula (2) Coefficient of thermal expansion (x10-6 / °) Impact strength at room temperature (J / cm2, room temperature) Impact strength at -196°C (J / cm2, -196°C) Example 1 111,9 63,2 1,0 306 172 Example 2 111,7 61,0 1,0 314 164 Example 3 111,9 56,0 0,8 310 155 Example 4 111,9 56,5 0,9 309 168 Example 5 111,6 58,2 0,9 319 157 Example 6 111,7 59,8 0,9 312 161 Example 7 108,0 62,5 0,8 308 168 Example 8 108,3 59,2 0,9 302 166 Example 9 111,9 64,3 0,8 303 179 Example 10 109,6 60,0 0,9 310 157 Example 11 108,3 59,7 0,9 309 156 Example 12 108,3 57,0 0,8 304 152 Comparative example 1 111,2 54,8 0,7 298 119 Comparative example 2 108,7 54,2 0,8 304 123 Comparative example 3 111,3 47,7 0,6 297 100 Comparative example 4 109,2 51,0 0,8 311 105 Comparative example 5 115,8 55,1 1,5 307 135 Comparative example 6 116,9 55,1 1,5 306 130 Comparative example 7 113,0 56,8 1,1 308 140 Comparative example 8 113,5 60,9 1,1 307 183 Comparative example 9 114,0 58,9 1,2 307 188 Comparative example 10 115,6 61,4 1,3 309 191 Comparative example 11 121,0 60,4 1,8 303 199 Comparative example 12 123,3 70,2 1,8 306 194

[0099] According to Table 2, Examples 1-12 satisfied the requirements for alloying components, the values ​​of Formula (1), the values ​​of Formula (2), and the production method described in this disclosure. Therefore, Examples 1-12 satisfied the requirement for the coefficient of thermal expansion from room temperature to 100°C of 1.0 × 10 -6 / °C or less, impact strength of 140 J / cm or more 2 at -196°C and impact strength at room temperature of 300 J / cm 2 or more. That is, Examples 1-12 had a low coefficient of thermal expansion and excellent impact toughness at low temperatures. However, Comparative Examples 1-6 did not satisfy the condition of the value of Formula (2) of 56 or more. Therefore, Comparative Examples 1-6 did not meet the requirement for an impact toughness of 140 J / cm 2 or more at -196°C. That is, comparative examples 1-6 had insufficient impact toughness properties at low temperatures.

[0100] Comparative Examples 5-12 did not satisfy the condition of the value of Formula (1) of 112 or less. Therefore, Comparative Examples 5-12 did not satisfy the requirement of the coefficient of thermal expansion from room temperature to 100°C of 1.0×10 -6 / °C or less. That is, comparative examples 5-12 exhibited relatively high thermal expansion.

[0101] According to the embodiment of the disclosure, by adjusting the alloying components and the production method, it is possible to provide a low thermal expansion coefficient steel having a low thermal expansion coefficient value and excellent impact toughness at low temperatures, as well as a production method thereof.

Claims

1. Steel containing, by mass %: more than 0% and 0.04% or less carbon (C); 0.1% or more and 0.5% or less silicon (Si); 0.1% or more and 0.4% or less manganese (Mn); 0.003% or less phosphorus (P); 0.003% or less sulfur (S); more than 0% and 0.5% or less chromium (Cr); 34% or more and 37.1% or less nickel (Ni); more than 0% and 2.0% or less cobalt (Co); the balance is iron (Fe) and inevitable impurities, and in this case, the value of Formula (1) is 112 or less, Formula (1): 15Cr + 3Ni + 3Co, where Cr, Ni and Co represent the content, in wt.%, of the corresponding elements.

2. Steel according to paragraph 1, characterized in that the value of Formula (2) is 56 or more, Formula (2): 3Cr + 2Ni - 50Mn - 2Co, where Cr, Ni, Mn and Co represent the content, in wt.%, of the corresponding elements.

3. Steel according to paragraph 1, characterized in that the coefficient of thermal expansion from room temperature to 100°C is 1.0 × 10 -6 / °C or less.

4. Steel according to paragraph 1, characterized in that the impact toughness is 140 J / cm 2 or more at -196°C.

5. Steel according to paragraph 1, characterized in that the impact strength at room temperature is 300 J / cm 2 or more.

6. A method for manufacturing a steel sheet, comprising: the production of a slab containing, by mass %: more than 0% and 0.04% or less carbon (C); 0.1% or more and 0.5% or less silicon (Si); 0.1% or more and 0.4% or less manganese (Mn); 0.003% or less phosphorus (P); 0.003% or less sulfur (S); more than 0% and 0.5% or less chromium (Cr); 34% or more and 37.1% or less nickel (Ni); more than 0% and 2.0% or less cobalt (Co); the remainder is iron (Fe) and unavoidable impurities; and hot rolling of the slab at a temperature of 1200 to 1350°C and hot rolling annealing at a temperature of 800 to 1000°C to produce hot rolled steel sheet, in this case the slab has a Formula (1) value of 112 or less, Formula (1): 15Cr + 3Ni + 3Co, where Cr, Ni and Co represent the content, in wt.%, of the corresponding elements.

7. The method according to paragraph 6, characterized in that the slab has a value of Formula (2) of 56 or more, Formula (2): 3Cr + 2Ni - 50Mn - 2Co, where Cr, Ni, Mn and Co represent the content, in wt.%, of the corresponding elements.

8. The method according to paragraph 6, further comprising: cold rolling the hot rolled steel sheet to a reduction ratio of 50% or more and cold rolling annealing at a temperature of 800 to 950°C to produce cold rolled steel sheet.