JPS5891151A - Steel for high-temperature and high-pressure apparatus - Google Patents

Abstract

PURPOSE:To obtain an economical steel equal to a C-Mo steel or an Mn-Mo steel in creep characteristics and having superior weldability and toughness by reducing the amount of Mo in the C-Mo steel corresponding to ASTM A204-B or the Mn-Mo steel corresponding to ASTM A302-B and by adding Nb or V. CONSTITUTION:This steel for an apparatus which is operated frequently or sometimes at 400-530 deg.C creep temp. under <=50kg/cm<2> partial pressure of H2 consists of 0.02-0.22% C, 0.02-0.80% Si, 0.6-2.00% Mn, 0.1-0.4% Mo, 0.005- 0.1% Al, 0.005-0.07% Nb and/or 0.005-0.07% V and the balance essentially Fe or further contains one or more among 0.03-0.5% each of Cu, Ni and Cr. This steel is subjected to normalizing or normalizing and tempering. Nb and V produce an effect of increasing the creep strength especially in the presence of Mo, yet excess Nb and V increases the reheating crack sensitivity during stress relief annealing after welding. Cu, Ni and Cr increase the creep strength.

Description

Detailed Description of the Invention The present invention relates to steel materials for high-temperature and high-pressure equipment, and in particular, the present invention relates to steel materials for high-temperature and high-pressure equipment. This invention relates to low MO steel materials used in high-temperature, high-pressure equipment.

A high-temperature, high-pressure boiler used for thermal power generation, etc. Specifically, it is a boiler that heats water by filling it with water and transmitting combustion heat from the outside.
In order to improve operational efficiency, in the die 2 main body that generates steam at a predetermined pressure, and the superheater that heats the saturated steam generated in the die 2 main body to a saturation temperature or higher to turn it into superheated steam, For example, 0jAWIL is qoo~jiO℃, pressure is /20yu/Ca1 (however, 62 partial pressure is!;Okg 7
C-M is the steel used to manufacture containers used under such conditions.

Conventionally, Mn-Mo steel is used.

In addition, in the chemical industry, operations are carried out in the creep temperature range.
and equipment with a partial pressure of 5Ok417cd or less in the creep temperature range, such as terephthalic acid manufacturing equipment, which does not contain Hg
The reaction chamber is operated at 100~300℃ using as a catalyst! (However, H2 is not used in this reaction.) O-MO steel and Mn-Mo steel have been conventionally used.

Furthermore, in petroleum refining, it is operated or must be operated in the creep temperature range, and there is a partial pressure of 62 in the creep temperature range! Okg/cd! O-Mo also applies to the following containers.
Conventionally, Mn-MO steel has been used. Equipment operated in the creep temperature range includes, for example, naphtha gas dehydration towers, and equipment that may be operated in creep fjArtL is refining equipment. Some reaction vessels are normally operated at temperatures below 320°C, which does not cause creep, but during catalyst regeneration (drying) the temperature is raised to 500°C and maintained for 1 oz. Because overcast containers are used for over 10 years, the regeneration temperature is important when selecting materials for these containers.

Cumulative regeneration time must be considered, and high temperature materials that can be used in the creep temperature range must be selected.

In addition to the above, the above-mentioned 0
-Mo steel and Mn-Mo steel are used, and if there is a concern about hydrogen corrosion, an internal opening cover made of stainless steel 11K is used.

C-Mo steel, which has been conventionally used in the above-mentioned equipment.

Mn-MO steel has a composition as shown in Table 1 below, and is a steel corresponding to A8TM Standard A 2011-B and A3Q Co-B.

In other words, 00~! For equipment such as boilers that operate in the creep temperature range of r, 30 °C, O-Mo steel and Mn-Mo steel, which contain approximately 10% Mo, are widely used, and have been used for several decades to date. It has been used as a steel that has both creep properties and economic efficiency, and although new steels that are more economical than these Mo steels have never been developed, it is extremely unlikely that such a development will be realized. It has been considered a difficult proposition and has been given up on until now.

By the way, the conventionally used hsTMA: 104I
B.

The M3Q Co-B and its equivalent products had the following technical and economical difficulties and drawbacks.

(() MO is an extremely expensive element.0-1
Necessary for improving creep characteristics at 30°C. , s-
The addition of Mo has the disadvantage of significantly impeding economic efficiency, and therefore, there is a strong desire to develop a steel that reduces MOt and improves economic efficiency and has creep characteristics similar to those of the conventional steel.

←) The C equivalent defined by the Japan Welding Association, which indicates the weld hardenability of C-MO steel and Mn-Mo steel, is Oeg, -0+Mn
/A + EH/29 + Or/j + MO/4'
When calculated using the formula: 10N1%η+v//41, it is usually more than O,S@, and often exceeds 0.6-. In addition to the large amount of MO, this is due to the unimaginably high C content in recent welded structural steels, often 0. λcol 0. This is because it is influenced by the fact that it contains Kosti.

Therefore, as a matter of course, the welding hardenability and welding susceptibility are extremely high, and preheating to 200° C. or higher is unavoidably performed during welding. A gas burner is used for this preheating, which consumes a considerable amount of energy. As we enter an era of energy conservation, there is a strong desire to reduce preheating temperature and, in turn, achieve energy conservation by improving the weldability of steel. Furthermore, reducing the preheating temperature is an issue that cannot be avoided from the viewpoint of improving the working environment, which is increasingly required these days.

(c) Conventionally, since this type of plant is operated at high temperatures, it has been thought that it is only important for plant materials to have high-temperature properties, especially creep properties, and low-temperature toughness has been neglected, or even ignored in many cases. It is no exaggeration to say that this has been the case. However, recently it has been recognized that low-temperature toughness is extremely important for K, which is used to safely perform airtightness tests during periodic inspections of plants. Regarding the above-mentioned O-Mo steel and Mn-Mo steel, Ri I
From the point of view of emphasizing J-p properties, many conventional metallurgists and those skilled in the art believed that the coarser the crystal grains, the better to ensure creep properties, and the addition of AJ, which is a grain refining element, was also refrained from being added. Painting is generally a material with extremely low toughness. In terms of grain size, creep properties and toughness can be said to be contradictory properties, and it has been said that it is extremely difficult to achieve both, but today O-Mo
MAwIA: Improving steel toughness is inevitable
It has come to be said that

The present invention is based on A8TM standard A used for high temperature and high pressure equipment.
204 I-B or A 30 Cor BK Comparable C-M
The object of the present invention is to provide a material for high-temperature, high-pressure equipment that eliminates and improves the above-mentioned problems and drawbacks of O steel or Mn-Mo steel, and the steel described in the scope of the request for special FF11iJ. The above objective can be achieved by providing a material.

Next, the present invention will be explained in detail.

The present inventors have discovered that the conventional C-Mo #1 or Mn
-Although it has creep properties equivalent to Mo steel, it has a lower 10 content compared to them, so it has excellent economic efficiency.
Furthermore, it has better weldability, saves energy during construction, improves the working environment, and has higher toughness.
It is made of steel that is highly safe even in periodic airtightness tests, and is used for high-temperature, high-pressure equipment that has low construction costs, is very safe, and has long durability, such as Boi 2. We have discovered a new low-MO steel material that can be used for manufacturing towers, tanks, heat exchangers, and other equipment. In other words, the present inventors found that in steel materials for high temperature and high pressure equipment and steel materials for boilers, Mo is at least O,
It was newly discovered that low-Mo steel can be used for high-temperature and high-pressure equipment, breaking the stereotype that steel is required.

Conventionally, steel materials for medium- and room-temperature pressure equipment below 1I00"C, which do not cause creep, require a trace amount of precipitation-hardening elements such as Nb--V and trace amounts of Cu and Ni to improve high-temperature properties, especially yield strength. Although it is known that solid solution elements such as Or are extremely useful, common sense suggests that these elements strengthen in the creep temperature range.

Traditionally, it has been considered invalid. However, when the present inventors conducted a creep test, they newly discovered that these elements are effective in strengthening in the creep temperature range and can serve as a substitute for MO, and have come up with the present invention.

Next, the behavior when the steel of the present invention is used in the following applications will be explained.

(a) Many equipment used in the chemical industry or petroleum refining use H2 or are subject to H2 corrosion due to the generation of H2, but the steel of the present invention has relatively low H2 corrosion resistance, so it cannot be used for damage. It is necessary to limit the use to equipment in which the H2 partial pressure is 5θkg/a11 or less in the creep temperature range of OO to 530°C. H2 partial pressure! ;0)cp
/cs1 or less, if H2 invasion is still a concern, it is advantageous to coat the inner surface with stainless steel.

(b) Use of the steel of the present invention in place of the aforementioned conventional O-Mo steel or Mn-Mo steel in equipment that is or will be operated in the creep temperature range of 4Ioo -z3θ°C. Since this is the orthodox usage and the intended effect of the present invention is best exhibited, the steel of the present invention may be used for equipment that is operated or may be operated in the creep temperature range of 1 degree. It is advantageous to use

(c) ＾High-temperature and high-pressure boilers are operated in the creep temperature range, and it is necessary to use steel with excellent creep characteristics as the zeira material.
2) Since there is no need to worry about erosion at all,
Not only is the requirement stated in (b) most clearly met, but the number of boiler units installed in the fcs is also relatively large. Therefore, it is extremely advantageous to fabricate the high-temperature pressure boiler 2 using the steel of the invention.

By the way, there are some devices in the chemical industry and oil refining industry that are operated or can be operated in the creep temperature range without worrying about H2 corrosion, and our copper material can also be used in devices in such fields. can be used. In reaction vessels in these industrial fields, the H2 partial pressure is so kg
/ d or less, and containers using conventional O-Mo steel or Mn-MO steel are often coated on the inside with stainless steel, but containers using the steel of the present invention are similarly coated with stainless steel. Internal coating with steel is preferred.

Next, the reason for limiting the composition of the steel material of the present invention will be explained.

C is an element that increases the strength of steel and contributes to improving high-temperature strength, especially creep strength, but if C#'i is less than 0.0, the strength required for structural steel cannot be obtained. - If the amount is more than 0.000, the creep strength will improve, but weld hardening and weld crack sensitivity will become excessive, so 0 should be within the range of 0.0 to Q, 29. .

81 is an element that is necessary for steelmaking and contributes to improved strength and oxidation resistance, but if it is less than 0.02-, it is preferable in terms of the toughness of the weld heat affected zone, but is disadvantageous in steelmaking; If it is more than 0.10, the toughness of the base material will be impaired, so 81 must be within the range of 0.0 to o,tto.

Mn is an element that contributes to giving ductility and strength to the base metal, but if it is less than 0.44, the necessary ductility and strength cannot be obtained, while if it exceeds QO or QO, weld hardenability increases significantly. Note that Mn #'i must be within the range of 0.4 to J, oo*.

MO is a typical hardening element, and in normalized materials, it is used during stress relief annealing after welding, or in normalized and tempered materials. In fact, it is the element that contributes most to the increase in strength during tempering. Mo. ,/4Io
High-temperature strength, especially creep strength, cannot be secured in the creep temperature range of θ~z3o "C," on the other hand, if it is greater than θ, lIl, the creep properties will improve, but it will not only be expensive but also increase weld hardenability. Therefore, MO is 0.7~θ
, l1%. However, in the steel of the present invention, at least /l of either Nb or V, which will be described later.
ASTM Muko0der B (0-MO steel) or Mo8
This makes it easier to obtain creep characteristics similar to those of TM A 30 Co B (Mn-Mo steel).

A4 is an element that contributes to making crystal grains finer and improving toughness, but 0. -001- If there is less, the necessary toughness cannot be obtained, and -00,000. Even if the amount is more than l-, the toughness will not be particularly improved and will be saturated, so Aj is o, oor ~ 0, /
- Must be within the range.

Nb and V are precipitation hardening elements, and are effective in increasing strength 1, especially in increasing creep strength when coexisting with MO, but at least one of nb and v is
*If the value is less than 0007, the required leap strength cannot be obtained, while if it exceeds 0007-, the creep stiffness will be greatly improved compared to the required value, but the susceptibility to reheating during stress annealing after welding will increase. At least one of them must be within the ranges o, oos-o, and o7-, respectively. Note that at least one of Nb and/or V is within the above content range, and MoO,/~
0. A major feature of the steel of the present invention is that when it coexists with MODA, its creep properties are equivalent to those of steel containing O.S% of MODA.

Ou, Ni, and Or are substitutional elements, and are elements that particularly contribute to improving creep strength through solid solution strengthening. If it is less than 0.03%, the target creep strength cannot be obtained, while if it is more than o, s%, weldability will be impaired. In addition, at least one selected from Ou, Ni, and Or improves the strength, especially creep strength, toughness, weldability, and economic efficiency of steel containing Mb and/or V. It is advantageous to add it when it becomes necessary to further improve the properties.

In the steel of the present invention, there is no problem with the amount of unavoidable impurities contained in the normal steelmaking process, and as a general limit of the content, P, 8 is a value that reduces the susceptibility to high temperature cracking of the weld zone. Therefore, it is preferable to reduce the O heat treatment to 0.0 or less because of the disadvantage of increasing the O.S. In many cases, it is necessary to perform a tempering treatment to soften the hardened structure formed during the precipitation hardening of Mo, Wb, V, etc. and normalization. The above-mentioned normalizing treatment includes not only cooling in air from the normalizing heating temperature but also forced cooling using water or the like.

Next, the limiting conditions under which the nine devices can be used safely using the steel material of the present invention will be explained.

Equipment using the steel of the present invention must be operated, or may be operated, within the creep temperature range of dOO~JtJO℃, and when used under such conditions, ・Conventional steel The new size is advantageous in terms of economy, weldability, toughness, etc. compared to equipment manufactured with W.
Even if equipment used at temperatures lower than OO°C is manufactured using the steel of the present invention, there will be little effect on the above-mentioned characteristics, and it is believed that it will have more advanced and useful effects than equipment using conventional steel. However, when the steel of the invention is used in equipment used at temperatures higher than 330"C, problems arise in terms of creep strength.

In addition, in equipment manufactured using the steel of the present invention, if the 82 partial pressure exceeds so kg/csf, hydrogen corrosion will be significant, and even if the inner surface of the equipment is coated with stainless steel, it will not be usable. Partial pressure is so kg/d
It is necessary to use the steel material of the present invention in the following equipment.

Next, the properties of the steel material of the present invention will be explained using experimental data.

Room-temperature tensile properties, impact toughness, l!
Table 3 shows the results of an examination of sensitivity to contact, and Figure 1 shows the results of an examination of creep strength.

From Table 3, the toughness and weldability of the invented steel are superior to conventional steel.
It can be seen that it is advantageous in terms of safety in airtightness tests during periodic inspections and energy saving by reducing the preheating temperature during welding.

The horizontal axis in the '4% diagram represents the creep test conditions at the test temperature T.
It is expressed as Tc (Seijyu Jog tc) using c ('K) and rupture time tc (h), and is
It is called a mirror parameter. The same figure shows the results of the test materials, as well as the ASTM A-04I-B, KJO-B, M8ME B&P, V, Corle,
813 (!, V, DiV, 1) Maximum allowable stress at various temperatures shown in

times (safety factor) stress is compared to io h breaking stress at each temperature T(! (x + togto5)
is plotted to form a continuous line. When designing with the maximum allowable stress e max, the average value of many tests is J/2 times the stress t max, and the forging low value is ′/l.
It is said that it is preferable that the stress exceeds I times (the oil passage in the figure).

From the same figure, the steel material B of the present invention, which has economical efficiency, weldability, and toughness, is ASTM A jO (I-B
, A, and 30 Cor B steel materials show good creep properties that exceed the design standards for creep strength of BMH, and in this respect conventional steel materials 0. It is possible to use the steel materials A and B of the present invention as a substitute for D, and it is also seen that the steel materials A and B of the present invention have much superior properties compared to the comparative steel material E.

As described above, the steel materials of the present invention were used in conventional A, STM AλO'l-B,
Mainly replaced with steel material equivalent to A3θ Co. 00~! 30
It has been found that it can be advantageously used in medium to high temperature and high pressure equipment operated in the creep temperature range of °C.

[Brief explanation of drawings]

The figure shows the steel of the present invention, conventional steel, A-coder B steel, 13
It is a figure which shows the relationship between the rigid-frame mirror parameter and creep rupture stress of 02-B steel material and comparative steel material. Patent applicant Kawasaki Steel Corporation Kinsha

Claims (1)

[Claims] L co, o col0. , here %, 810.0 ~
oogos. Mn O,A ~yu00嗟, MOO,/ ~0.41
'lk, Ajθ, θθ! ~0. /-, and M
bO,003~0.07%, VO,00r~
0.07'1kf) containing the least of 7 types, the remainder being substantially IFe, and subjected to any of the following heat treatments: normalizing, normalizing and tempering% 4Ioo~S30℃
Steel materials for high-temperature, high-pressure equipment used in equipment that is operated with H2 partial pressure below sokg/d in the creep temperature range of 2. The equipment is die 2. The steel material according to claim 1, which is a tower, a cypress, a heat exchanger, etc. "s, ao, o ko ~ O, here, BLo, 0 ko ~ o, go chi. Mn O, 4-2.00%, 1100./ ~ 0.I
l*, A! Contains 0.00S to 0.7, and Nt)
0.00S~0.07%, VO,00! t-
0,07'Ikf) any of at least 7 species and CuO,
03~0.1%, NiO,OJ~0,! 94
．． Orθ, θJ −0, ji−, and the remainder is substantially 10 or more, and is subjected to one heat treatment of normalizing or normalizing and annealing. H in the creep temperature range of 4I00 to 330℃
2. Steel material for high-temperature and high-pressure equipment used in equipment that is operated or may be operated at a partial pressure of less than sokgbl. The steel material according to claim 3, wherein the equipment is a boiler, tower, oak, heat exchanger, etc.