阅读说明：本技术 一种低温设备用钢板及其生产方法 (Steel plate for low-temperature equipment and production method thereof ) 是由 邓建军 李样兵 赵国昌 李�杰 袁锦程 吴艳阳 龙杰 柳付芳 牛红星 尹卫江 侯 于 2019-09-19 设计创作，主要内容包括：一种低温设备用钢板及其生产方法,所述钢板化学成分组成为：C 0.06～0.12%,Si 0.4～0.5%,Mn 1.68～1.72%,P≤0.005%,S≤0.003%,Cr 0.3～0.34%,Mo 0.31～0.35%,Ni 0.71～0.73%,Cu 0.01～0.02%,Nb 0.055～0.06%,Nb+V 0.12～0.13%,Ti≤0.0007%,B 0.015～0.02%,Al 0.045～0.055%,其余为Fe及不可避免的杂质。所述生产方法包括初炼、LF炉精炼、VD炉真空处理、浇铸、清理、加热、轧制、探伤、正火、回火工序。本发明钢板纯净度高、组织细密,适于制造低温设备。(A steel plate for low-temperature equipment and a production method thereof are disclosed, wherein the steel plate comprises the following chemical components: 0.06-0.12% of C, 0.4-0.5% of Si, 1.68-1.72% of Mn, less than or equal to 0.005% of P, less than or equal to 0.003% of S, 0.3-0.34% of Cr, 0.31-0.35% of Mo, 0.71-0.73% of Ni, 0.01-0.02% of Cu, 0.055-0.06% of Nb, 0.12-0.13% of Nb + V, less than or equal to 0.0007% of Ti, 0.015-0.02% of B, 0.045-0.055% of Al, and the balance of Fe and inevitable impurities. The production method comprises the working procedures of primary smelting, LF furnace refining, VD furnace vacuum treatment, casting, cleaning, heating, rolling, flaw detection, normalizing and tempering. The steel plate has high purity and fine structure, and is suitable for manufacturing low-temperature equipment.)

1. A steel sheet for cryogenic equipment, characterized in that: the steel plate comprises the following chemical components in percentage by mass: 0.06-0.12% of C, 0.40-0.50% of Si, 1.68-1.72% of Mn, less than or equal to 0.005% of P, less than or equal to 0.003% of S, 0.30-0.34% of Cr, 0.31-0.35% of Mo, 0.71-0.73% of Ni, 0.01-0.02% of Cu, 0.055-0.060% of Nb, 0.12-0.13% of Nb + V, less than or equal to 0.0007% of Ti, 0.015-0.020% of B, 0.045-0.055% of Al, and the balance of Fe and inevitable impurities.

2. The steel plate for the cryogenic equipment as claimed in claim 1, wherein the thickness of the steel plate is 6-200 mm, the yield strength is not less than 530MPa, the tensile strength is 700-760 MPa, the elongation is not less than 24%, and the single value of the impact energy at-50 ℃ is not less than 150J.

3. The steel plate for cryogenic equipment as claimed in claim 2, wherein the steel plate is delivered in a state of accelerated cooling + tempering after normalizing, and the whole plate flaw detection meets the requirement of SA578/578M standard class C.

4. The method for producing a steel sheet for a cryogenic plant according to any one of claims 1 to 3, wherein the production method comprises primary smelting, LF furnace refining, VD furnace vacuum processing, casting, cleaning, heating, rolling, flaw detection, normalizing, and tempering; in the heating process, the highest heating temperature is 1290-1300 ℃, the soaking temperature is 1270-1280 ℃, and the whole closing of a certain section of burner is not allowed in the heating process.

5. The method for producing the steel plate for the cryogenic equipment according to claim 4, wherein in the LF furnace refining process, the total refining time is not less than 90min, the white slag retention time is not less than 45min, and the lime consumption is not less than 18kg/t steel; in the vacuum treatment process of the VD furnace, 1.7-2.0 kg/t of molten steel of Ca-Si blocks is added before vacuum, the vacuum degree is less than or equal to 65Pa, the vacuum retention time is 15-18 min, and the ladle is hoisted after soft blowing is carried out for 20-25 min.

6. The method according to claim 4, wherein the casting step comprises feeding molten steel having a uniform composition and a temperature of 1545 to 1575 ℃ to a die casting line to cast the molten steel into a flat ingot.

7. The method for producing a steel plate for a cryogenic device according to claim 4, wherein the rolling temperature of the rolling process is 1190 to 1200 ℃, the reduction per pass is 50 to 80mm, and the temperature of the red returning of the steel plate after the rolling is 760 to 770 ℃ after the water cooling.

8. The method for producing a steel sheet for a cryogenic plant according to any one of claims 4 to 7, wherein the flaw detection step is an ultrasonic flaw detection test performed according to ASME SA578/SA578M, and the qualification grade is class C.

9. The method for producing a steel sheet for a cryogenic device according to any one of claims 4 to 7, wherein the normalizing treatment step is performed at a normalizing temperature of 900 to 960 ℃ for a total heating time of 1.9H +35 to 40min, and after the normalizing treatment, the steel sheet is subjected to accelerated forced cooling by using an air mist at a cooling rate of 10 to 20 ℃/s and at a final cooling temperature of 180 to 350 ℃; and H is the thickness of the finished steel plate, and the unit is mm.

10. The method for producing a steel sheet for a cryogenic plant according to any one of claims 4 to 7, wherein the tempering treatment step is performed at a tempering temperature of not less than 595 ℃ and a total heating time of 4.6 to 4.8 min/mm.

Technical Field

The invention belongs to the technical field of metallurgy, and particularly relates to a steel plate for low-temperature equipment and a production method thereof.

Background

Pressure vessels leak or explode during use, which can cause catastrophic accidents. Therefore, under the premise of ensuring absolute safety, in order to make the pressure vessel achieve the purposes of advanced design, reasonable structure, easy manufacture, reliable use and the like, all countries actually establish relevant pressure vessel standards, specifications and technical conditions in combination with the country, and provide specific and mandatory regulations on the design, manufacture, inspection, use and the like of the pressure vessel. In recent years, with the increasing importance of China on the safety of pressure vessels for nuclear power and petrochemical industries, higher safety indexes and technical requirements are provided for the pressure vessels domestically, so that the further development of the pressure vessels is promoted. This trend has placed higher demands on the overall properties of most pressure vessel base materials, steel. Part of the carbon-silicon-manganese low-alloy steel plates even require that the-50 ℃ KV8 impact energy is more than or equal to 54J, and the steel can not meet the requirements at all by adopting the existing production process and mode because the alloy content is less.

Disclosure of Invention

In order to solve the technical problems, the invention provides a steel plate for low-temperature equipment and a production method thereof, and the invention adopts the following technical scheme:

the steel plate for the low-temperature equipment comprises the following chemical components in percentage by mass: 0.06-0.12% of C, 0.40-0.50% of Si, 1.68-1.72% of Mn, less than or equal to 0.005% of P, less than or equal to 0.003% of S, 0.30-0.34% of Cr, 0.31-0.35% of Mo, 0.71-0.73% of Ni, 0.01-0.02% of Cu, 0.055-0.060% of Nb, 0.12-0.13% of Nb + V, less than or equal to 0.0007% of Ti, 0.015-0.020% of B, 0.045-0.055% of Al, and the balance of Fe and inevitable impurities.

The thickness of the steel plate is 6-200 mm, the yield strength is larger than or equal to 530MPa, the tensile strength is 700-760 MPa, the elongation is larger than or equal to 24%, and the single value of the impact energy at the temperature of minus 50 ℃ is larger than or equal to 150J.

The delivery state of the steel plate is accelerated cooling and tempering after normalizing, and the flaw detection of the whole plate meets the C-grade requirement of the SA578/578M standard.

The functions of the chemical elements in the invention are as follows:

in the present invention, when the C content is 0.06-0.12% and the carbon content in the steel is 0.08% or less, the strength and hardness of the steel are improved and the plasticity and toughness are reduced as the carbon content increases. In the invention, C mainly forms carbide and plays roles of structure strengthening and precipitation strengthening, thereby regulating and controlling the strength and toughness of the steel.

The content of Mn is 1.68-1.72%, Mn can improve the strength of steel, can be infinitely dissolved with Fe, and has relatively small influence on plasticity while improving the strength of the steel. Therefore, manganese is a strengthening element widely used in steel. In the present invention, the solid solution strengthening and the strength improvement of the steel sheet are mainly performed.

Si element can be dissolved in ferrite and austenite, so that the strength, hardness and elasticity, elastic limit and wear resistance of the steel are improved, and the effect is stronger than common elements such as manganese, nickel, chromium, tungsten, molybdenum, vanadium and the like. Silicon has a moderate effect on the hardenability of steel, but has a great advantage in improving the tempering stability and oxidation resistance of steel.

The content of Ni is 0.71-0.73%, and the lattice constant of Ni is similar to that of gamma-iron, so that a continuous solid solution can be formed. The main effect in the present invention is on the one hand to strongly increase the strength of the steel and on the other hand to always maintain the toughness of the iron at an extremely high level. In addition, Ni lowers the critical point and increases the stability of austenite, so that the quenching temperature can be lowered and the hardenability is good.

The Nb element can improve the strength of the steel without affecting the plasticity or toughness of the steel. Meanwhile, the impact toughness of the steel can be improved and the brittle transition temperature of the steel can be reduced due to the effect of refining grains.

The main role of B in steel is to increase the hardenability of the steel.

P, S is a harmful element, so P is strictly controlled to be less than or equal to 0.005 percent and S is strictly controlled to be less than or equal to 0.003 percent, on one hand, the cleanliness of the steel is improved, and on the other hand, the negative temperature impact toughness of the steel is favorably improved.

The production method comprises the working procedures of primary smelting, LF furnace refining, VD furnace vacuum treatment, casting, cleaning, heating, rolling, flaw detection, normalizing treatment and tempering treatment.

According to the LF furnace refining process, the total refining time is more than or equal to 90min, the white slag holding time is more than or equal to 45min, and the lime consumption is more than or equal to 18kg/t steel.

According to the vacuum treatment process of the VD furnace, 1.7-2.0 kg/t of molten steel of Ca-Si blocks is added before vacuum, the vacuum degree is less than or equal to 65Pa, the vacuum retention time is 15-18 min, and the ladle is hung after soft blowing is carried out for 20-25 min.

According to the casting process, molten steel with uniform components and a temperature of 1545-1575 ℃ is sent to a die casting line for casting, and a flat cast ingot is obtained.

In the heating process of the method, the highest heating temperature is 1290-1300 ℃, the soaking temperature is 1270-1280 ℃, and the complete closing of a certain section of burner is not allowed in the heating process.

According to the rolling process, the rolling temperature is 1190-1200 ℃, the reduction per pass is 50-80 mm, and the temperature of water cooling and red returning after rolling of the steel plate is 760-770 ℃.

The flaw detection procedure of the method of the invention carries out ultrasonic flaw detection according to ASME SA578/SA578M, and the qualified grade is grade C.

In the normalizing treatment procedure of the method, after flaw detection is qualified, normalizing (accelerated cooling) is carried out, wherein the normalizing temperature is 900-960 ℃, the total heating time is 1.9H + 35-40 min, after normalizing, accelerated forced cooling is carried out by utilizing aerial fog, the cooling speed is 10-20 ℃/s, and the final cooling temperature is 180-350 ℃; and H is the thickness of the finished steel plate, and the unit is mm.

In the tempering treatment process of the method, the tempering temperature is more than or equal to 595 ℃, and the total heating time is 4.6-4.8 min/mm.

The invention optimizes the components and the proportion of each element in the steel plate, and the addition of the alloy elements is less; meanwhile, the heat treatment normalizing key point adopts the aerial fog to carry out forced accelerated cooling, so that the problems of inconsistent performance or uneven performance fluctuation caused by normalizing air cooling or direct cost rise caused by normalizing water cooling and the like of the steel plate are effectively avoided, and the production cost is obviously reduced on the premise of ensuring that all mechanical properties of the steel plate meet the requirements of the steel for low-temperature equipment.

The produced steel plate has the characteristics of high purity, uniform components, fine structure and the like, and is completely suitable for manufacturing key equipment such as low-temperature equipment and the like. The yield strength of the steel plate is more than or equal to 530MPa, the tensile strength is 700-760 MPa, the elongation is more than or equal to 24%, the single value of the impact energy at the temperature of minus 50 ℃ is more than or equal to 150J, and the flaw detection of the whole plate reaches the C-grade requirement of the SA578/578M standard.

Detailed Description

The present invention will be described in further detail with reference to specific examples.

A production method of a steel plate for low-temperature equipment comprises the working procedures of primary smelting, LF furnace refining, VD furnace vacuum treatment, casting, cleaning, heating, rolling, flaw detection, normalizing treatment and tempering treatment, and the specific process steps are as follows:

(1) primary smelting process: selecting high-quality raw materials to smelt in a primary smelting furnace, and avoiding slag in the tapping process;

(2) and (3) refining in an LF furnace: the total refining time is more than or equal to 90min, the white slag retention time is more than or equal to 45min, and good slagging is ensured. The lime consumption is more than or equal to 18kg/t steel so as to ensure the refining effect;

(3) and a VD furnace vacuum treatment process: adding 1.7-2.0 kg/t molten steel of Ca-Si blocks before vacuum, keeping the vacuum degree less than or equal to 65Pa, keeping the vacuum for 15-18 min, and hoisting after soft blowing for 20-25 min;

(4) a casting process: sending molten steel with uniform components and a temperature of 1545-1575 ℃ to a die casting line for casting to obtain a flat cast ingot;

(5) cleaning: the defects of cracks, subcutaneous bubbles and the like possibly existing on the shallow surface of the flat steel ingot are cleaned by utilizing flame;

(6) a heating procedure: heating in a soaking pit furnace, wherein the highest heating temperature is 1290-1300 ℃, the soaking temperature is 1270-1280 ℃, and a certain section of burner is not allowed to be completely closed in the heating process;

(7) a rolling procedure: the rolling temperature is 1190-1200 ℃, the reduction per pass is 50-80 mm, the steel plate is cooled after being rolled, and the temperature of red returning is 760-770 ℃;

(8) flaw detection: performing ultrasonic flaw detection according to ASME SA578/SA578M, wherein the qualified grade is grade C;

(9) normalizing treatment procedure: normalizing (accelerated cooling) after flaw detection is qualified, wherein the normalizing temperature is 900-960 ℃, the total heating time is 1.9H + 35-40 min, after normalizing, the accelerated forced cooling is carried out by utilizing aerial fog, the cooling speed is 10-20 ℃/s, and the final cooling temperature is 180-350 ℃; h is the thickness of the finished steel plate, and the unit is mm;

(10) tempering treatment: the tempering temperature is more than or equal to 595 ℃, the total heating time is 4.6-4.8 min/mm, and the steel plate for the low-temperature equipment is obtained after tempering.