JPH0128827B2 - - Google Patents
Info
- Publication number
- JPH0128827B2 JPH0128827B2 JP58134749A JP13474983A JPH0128827B2 JP H0128827 B2 JPH0128827 B2 JP H0128827B2 JP 58134749 A JP58134749 A JP 58134749A JP 13474983 A JP13474983 A JP 13474983A JP H0128827 B2 JPH0128827 B2 JP H0128827B2
- Authority
- JP
- Japan
- Prior art keywords
- toughness
- less
- cryogenic
- stainless steel
- present
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 229910000734 martensite Inorganic materials 0.000 claims description 8
- 229910001105 martensitic stainless steel Inorganic materials 0.000 claims description 5
- 239000002184 metal Substances 0.000 claims description 3
- 229910052751 metal Inorganic materials 0.000 claims description 3
- 239000012535 impurity Substances 0.000 claims description 2
- 229910052759 nickel Inorganic materials 0.000 claims description 2
- 230000000694 effects Effects 0.000 description 9
- 229910001220 stainless steel Inorganic materials 0.000 description 9
- 229910000831 Steel Inorganic materials 0.000 description 8
- 239000010959 steel Substances 0.000 description 8
- 238000002844 melting Methods 0.000 description 7
- 230000008018 melting Effects 0.000 description 7
- 238000005496 tempering Methods 0.000 description 6
- 238000005260 corrosion Methods 0.000 description 5
- 230000007797 corrosion Effects 0.000 description 5
- 238000010791 quenching Methods 0.000 description 5
- 230000000171 quenching effect Effects 0.000 description 5
- 239000010935 stainless steel Substances 0.000 description 5
- 239000000126 substance Substances 0.000 description 5
- 238000004090 dissolution Methods 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 238000003466 welding Methods 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 3
- 229910000859 α-Fe Inorganic materials 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- 229910001566 austenite Inorganic materials 0.000 description 2
- 238000011109 contamination Methods 0.000 description 2
- 239000002872 contrast media Substances 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 238000009863 impact test Methods 0.000 description 2
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 229910052750 molybdenum Inorganic materials 0.000 description 2
- 229910052758 niobium Inorganic materials 0.000 description 2
- 238000004881 precipitation hardening Methods 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000007872 degassing Methods 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
- 230000023556 desulfurization Effects 0.000 description 1
- 238000005242 forging Methods 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 238000009849 vacuum degassing Methods 0.000 description 1
Description
この発明は0.2%耐力が100Kgf/mm2級で極低温
衝撃値の大きな極低温用高靭性マルテンサイト系
ステンレス鋼に係る。
例えばコンプレツサ部品、化学プラント部品或
いは高力ボルト等には高強度、高靭性および耐食
性が同時に要求されることが多い。
このような用途に対する高強度ステンレス鋼と
してはマルテンサイト系ステンレス鋼と析出硬化
形ステンレス鋼とがあり、前者は13Cr系が代表
的な鋼種であつて安価であるが、比較的銹び易
く、また溶接性および低温靭性及び極低温靭性が
良好でない。
後者は17−4PH(JIS・SUS630)が代表的な
17Cr−4Ni−4Cu−Nb系およびFV520B(Firth
Vicker社規格)が代表的な14Cr−5Ni−2Mo−
1Cu−Nb系があり、13Cr系の鋼種よりは溶接性
や耐食性が良いが低温靭性及び極低温靭性が低い
のが問題であり、そのうえ引張特性のうち耐力比
(0.2%耐力/引張強さ)が大きく、使用上望まし
くない。またFV520BはMoを含有しているため
それだけコスト高になるのが問題である。
本発明は上記の事情に鑑み、100Kgf/mm2級の
0.2%耐力を有し、17−4PHあるいはFV520Bよ
りも極低温靭性の高い、安価なマルテンサイト系
ステンレス鋼を提供することを目的とし、
重量%で、C0.05〜0.1%、Si1%以下、Mn1%
以下、Ni4〜6%、Cr15〜17.5%、V0.1%以下、
Al0.005〜0.04%、残部実質的にFeおよび不純物
からなり、微細な針状のマルテンサイトを主体と
する金属組織を有し、焼入れ焼戻しを施した極低
温衝撃値の高いマルテンサイト系ステンレス鋼に
係る。なお本明細書においては化学組成は通例の
とおり重量%で示してある。
次に本発明に係るステンレス鋼の化学成分組成
について述べる。
従来から13Crマルテンサイト系ステンレス鋼
にNiを添加すると溶接性および靭性が改善され
ることが知られている。しかしながら耐食性が悪
いのでこれを改善するため、本発明においては
Crの含有量を増やして15〜17.5%とする。而して
オーステナイト化温度域からの焼入れによつてマ
ルテンサイトに変態し易い不安定なオーステナイ
トとするため更にNiを4〜6%含有させる。こ
のようにすると焼入れ、焼戻しによつて基地がマ
ルテンサイトで少量の微粒のフエライトが分散
し、同時に微量の残留オーステナイトも混在する
金属組織を得ることができる。
Cは含有量が多くなると溶接性を低下させるの
で上限値は0.1%とする。高い靭性を得るために
は大気溶解で得られる最低値のおよそ0.03%近く
とするのが望ましい。この0.03%は上記大気溶解
と真空溶解との境界であることから、下限値は
0.03%の近くである0.05%とする。
Siは通例の通り脱酸のため添加するが、フエラ
イト生成元素であり、基地強化の効果もある。し
かしその量が多くなると靭性を損なうようになる
から上限は1%を超えないものとし、望ましくは
0.2〜0.5%とする。
Mnは同様に脱酸と脱硫のため添加するが、オ
ーステナイト生成元素であり、その量が多くなる
とアノード溶解を加速し、耐食性を損なうように
なるので上限は1%を超えないものとし、望まし
くは0.4〜0.6%とする。
Vは顕著な焼戻軟化抵抗を示し、焼戻後の強度
保持に重要な元素である。更に結晶粒の微細化効
果もあり、靭性には寧ろ有効である。しかしなが
らその量を多くしても効果は変わらなくなるので
本発明においては上限を0.1%とし、0.02〜0.06%
程度添加するのが望ましい。
Alは周知の通り強力な脱ガス作用を有すると
共に結晶粒を細粒化させる作用を有するので、そ
の含有量を0.005〜0.04%、望ましくは0.02〜0.04
%とする。このようにすると大気溶解によつて溶
製して酸素、窒素の含有量が多くなつても充分に
所期の効果が得られる。
Cuは析出硬化性の合金元素であり、Moは焼戻
軟化抵抗を示す合金元素であつて焼戻後の硬さに
影響を及ぼすが、靭性を高める効果はないので少
ない方がよい。Nb+Taは炭化物生成元素であ
り、靭性を高める効果は小さいので少ない方がよ
い。本発明においてはCu,MoおよびNb+Taの
量は溶解のさい原材料からの混入を工業的に制御
できる許容量以下とし、Cuはおよそ0.3%以下、
望ましくは0.1%以下とし、Moはおよそ1%以
下、Nb+Taはおよそ0.1%以下、望ましくは0.05
%以下とする。
PおよびSについては通例の通り溶解の際に付
随的に混入する元素であつて、少ない方が良いか
ら、本発明においては大気溶解においてその混入
を工業的に制御できるおよそ0.025%以下とする
ことが望ましい。
溶製は通例の大気溶解でよく、特に真空溶解或
いは真空脱ガス等によらなくとも良い。
熱処理はFV520Bよりも単純で、焼入れ焼戻し
のみで良く、焼入れは930〜970℃、油冷、焼戻し
温度は430〜470℃とし、空冷が適当である。
溶接の際には予熱或いは後熱が不要であり、溶
接性が良いので補修溶接を行い易い。
次に実施例について対比材と共に化学成分組成
を第1表に、熱処理、引張特性を第2表に示す。
This invention relates to a high-toughness martensitic stainless steel for cryogenic use that has a 0.2% proof stress of 100 Kgf/mm 2 grade and a large cryogenic impact value. For example, compressor parts, chemical plant parts, high-strength bolts, etc. often require high strength, high toughness, and corrosion resistance at the same time. High-strength stainless steels for such applications include martensitic stainless steels and precipitation-hardening stainless steels. The former is typically 13Cr and is inexpensive, but is relatively easy to rust and Poor weldability, low-temperature toughness, and cryogenic toughness. The latter is typically 17−4PH (JIS/SUS630).
17Cr−4Ni−4Cu−Nb system and FV520B (Firth
Vicker standard) is a typical 14Cr−5Ni−2Mo−
There is a 1Cu-Nb series steel, which has better weldability and corrosion resistance than 13Cr series steels, but has a problem of low low temperature toughness and cryogenic toughness, and also has a low yield strength ratio (0.2% yield strength/tensile strength) among tensile properties. is large, making it undesirable for use. Another problem is that FV520B contains Mo, which increases the cost accordingly. In view of the above circumstances, the present invention has developed a 100Kgf/mm 2nd grade
The purpose is to provide an inexpensive martensitic stainless steel with 0.2% yield strength and higher cryogenic toughness than 17-4PH or FV520B, with weight percentages of C0.05~0.1%, Si1% or less, Mn1%
Below, Ni4~6%, Cr15~17.5%, V0.1% or less,
Martensitic stainless steel with Al0.005~0.04%, the balance substantially Fe and impurities, has a metal structure mainly composed of fine acicular martensite, and has a high cryogenic impact value that has been quenched and tempered. Pertains to. In this specification, chemical compositions are expressed in weight % as usual. Next, the chemical composition of the stainless steel according to the present invention will be described. It has been known that adding Ni to 13Cr martensitic stainless steel improves weldability and toughness. However, the corrosion resistance is poor, so in order to improve this, in the present invention,
Increase the Cr content to 15 to 17.5%. In order to form unstable austenite that is easily transformed into martensite by quenching from the austenitizing temperature range, 4 to 6% of Ni is further contained. In this way, by quenching and tempering, it is possible to obtain a metal structure in which the base is martensite, a small amount of fine ferrite is dispersed, and at the same time, a small amount of residual austenite is also mixed. As C content increases, weldability deteriorates, so the upper limit is set at 0.1%. In order to obtain high toughness, it is desirable that the content be approximately 0.03%, which is the lowest value obtained by atmospheric dissolution. Since this 0.03% is the boundary between atmospheric melting and vacuum melting, the lower limit is
Set it to 0.05%, which is close to 0.03%. Si is added for deoxidation as usual, but it is a ferrite-forming element and also has the effect of strengthening the base. However, if the amount increases, the toughness will be impaired, so the upper limit should not exceed 1%, and preferably
0.2-0.5%. Mn is also added for deoxidation and desulfurization, but it is an austenite-forming element, and if its amount increases, it accelerates anode dissolution and impairs corrosion resistance, so the upper limit should not exceed 1%, and preferably It should be 0.4-0.6%. V exhibits remarkable temper softening resistance and is an important element for maintaining strength after tempering. Furthermore, it also has the effect of making crystal grains finer, which is rather effective for improving toughness. However, even if the amount is increased, the effect will not change, so in the present invention, the upper limit is set at 0.1%, and 0.02 to 0.06%.
It is desirable to add some amount. As is well known, Al has a strong degassing effect and also has the effect of refining crystal grains, so the content should be 0.005 to 0.04%, preferably 0.02 to 0.04%.
%. In this way, even if the content of oxygen and nitrogen increases due to melting in the atmosphere, the desired effect can be sufficiently obtained. Cu is a precipitation-hardening alloying element, and Mo is an alloying element that exhibits resistance to temper softening and affects the hardness after tempering, but it has no effect on increasing toughness, so the smaller the amount, the better. Nb+Ta is a carbide-forming element and has a small effect on improving toughness, so the smaller the amount, the better. In the present invention, the amounts of Cu, Mo, and Nb+Ta are below the allowable amount that allows industrial control of contamination from raw materials during melting, and Cu is approximately 0.3% or below.
Desirably 0.1% or less, Mo approximately 1% or less, Nb+Ta approximately 0.1% or less, preferably 0.05
% or less. As for P and S, they are elements that are mixed incidentally during dissolution as usual, and the less the better, so in the present invention, the contamination in atmospheric dissolution is set to about 0.025% or less, which can be industrially controlled. is desirable. The melting may be carried out by ordinary atmospheric melting, and does not necessarily require vacuum melting or vacuum degassing. Heat treatment is simpler than FV520B, requiring only quenching and tempering, with quenching at 930-970°C, oil cooling, and tempering at 430-470°C, with air cooling being suitable. There is no need for preheating or postheating during welding, and the weldability is good, making it easy to perform repair welding. Next, Table 1 shows the chemical compositions of Examples along with the comparison materials, and Table 2 shows the heat treatment and tensile properties.
【表】【table】
【表】
第2表から判るように本発明に係る鋼は0.2%
耐力をおよそ100Kgf/mm2とした場合、引張強さ、
伸び、絞り共に対比鋼よりも大きな値を示してお
り、耐力比は最も小さくて使用上も有利である。
次に上記各試料から2mmVノツチシヤルピー衝
撃試験片を製作して極低温衝撃試験を行つた結果
を吸収エネルギーと試験温度に関連させて示した
のが第1図である。
第1図から判るように本発明に係る鋼の低温衝
撃値は従来品の17−4PH或いはFV520Bに比して
著しく優れており、0.2%耐力をおよそ100Kgf/
mm2とした場合−120℃においても2mmVノツチシ
ヤルピー衝撃値が5Kgf/mm2という高い靭性を示
している。
上記第2表に示す熱処理を施し硬さHv385とし
たNo.1試験片の顕微鏡組織を第2図に、同じく
Hv360のNo.2のそれを第3図に示す。対比材のNo.
2の17−4PHの組織はラス状のマルテンサイト
組織であるのに対し、本発明に係る鋼は焼入れ焼
戻しによつて微細な針状の焼戻マルテンサイトの
基地に少量の微粒のフエライトが混在する組織と
なつており、これが極低温靭性を改善しているも
のと考えられる。
以上説明したように本発明に係る鋼は従来の
13Cr系の高強度ステンレス鋼のCr含有量を増や
すと共に、Niを4〜6%含有させ、焼入れ焼戻
しによつて針状マルテンサイト組織に少量の微細
なフエライトを分散した組織としてあるので、極
低温靭性値が抜群に優れた値を示している。
また鍛造、切削、溶接、熱処理等の加工性が優
れ、大気溶解が可能なうえMoを含有しないので
安価であり、或いは溶接性が良いので溶接の際に
予熱、後熱を必要とせず、13Cr系のステンレス
鋼よりも耐食性が良いので実機に使用したとき錆
取りが不要であり、或いはまた単純な化学成分組
成であるためスクラツプとした場合管理が容易で
ある等、優れた極低温靭性と耐力比を有するうえ
に経済的な高力ステンレス鋼であつて、実用上の
効果がきわめて大きい。[Table] As can be seen from Table 2, the steel according to the present invention is 0.2%
When the proof stress is approximately 100Kgf/ mm2 , the tensile strength is
Both elongation and reduction of area are larger than the comparison steel, and the proof stress ratio is the smallest, making it advantageous in terms of use. Next, 2 mm V-notched pylon impact test pieces were prepared from each of the above samples and cryogenic impact tests were conducted. The results are shown in FIG. 1 in relation to absorbed energy and test temperature. As can be seen from Figure 1, the low-temperature impact value of the steel according to the present invention is significantly superior to that of conventional products 17-4PH or FV520B, and the 0.2% proof stress is approximately 100Kgf/
mm 2 , it shows high toughness with a 2 mm V notch shear py impact value of 5 Kgf/mm 2 even at -120°C. Figure 2 shows the microscopic structure of the No. 1 test piece that was heat-treated and had a hardness of Hv385 as shown in Table 2 above.
Figure 3 shows that of Hv360 No. 2. Contrast material No.
The structure of 17-4PH in No. 2 is a lath-like martensite structure, whereas the steel according to the present invention has a fine needle-like tempered martensite base mixed with a small amount of fine ferrite due to quenching and tempering. It is thought that this structure improves the cryogenic toughness. As explained above, the steel according to the present invention is different from the conventional steel.
In addition to increasing the Cr content of 13Cr-based high-strength stainless steel, it also contains 4 to 6% Ni, and is quenched and tempered to create a structure in which a small amount of fine ferrite is dispersed in the acicular martensite structure, so it can withstand extremely low temperatures. It shows an outstanding toughness value. In addition, it has excellent workability in forging, cutting, welding, heat treatment, etc., can be melted in the atmosphere, and does not contain Mo, so it is inexpensive.Also, it has good weldability, so it does not require preheating or postheating during welding, and 13Cr It has excellent cryogenic toughness and yield strength ratio, such as better corrosion resistance than other stainless steels, so no rust removal is required when used in actual equipment, and its simple chemical composition makes it easy to manage when scrapped. It is an economical high-strength stainless steel that has extremely high practical effects.
第1図は本発明に係るステンレス鋼の低温衝撃
特性を対比材の特性と比較して示したグラフ、第
2図は本発明に係るステンレス鋼の顕微鏡組織を
示す写真(100倍)、第3図は対比材の17−4PH
の顕微鏡組織(100倍)を示す写真である。
Fig. 1 is a graph showing the low-temperature impact properties of the stainless steel according to the present invention in comparison with the properties of a comparison material, Fig. 2 is a photograph (100x magnification) showing the microscopic structure of the stainless steel according to the present invention, and Fig. 3 The figure shows the contrast material 17−4PH.
This is a photograph showing the microscopic structure (100x magnification).
Claims (1)
%以下、Ni4〜6%、Cr15〜17.5%、V0.1%以
下、Al0.005〜0.04%、残部実質的にFeおよび不
純物からなり、微細な針状のマルテンサイトを主
体とする金属組織を有し、焼入れ焼戻しを施した
極低温衝撃値の高い極低温用高靭性マルテンサイ
ト系ステンレス鋼。1% by weight, C0.05-0.1%, Si1% or less, Mn1
% or less, Ni 4-6%, Cr 15-17.5%, V 0.1% or less, Al 0.005-0.04%, the remainder consisting essentially of Fe and impurities, with a metal structure mainly consisting of fine acicular martensite. A high-toughness martensitic stainless steel for cryogenic use that has been quenched and tempered and has a high cryogenic impact value.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP13474983A JPS6026645A (en) | 1983-07-23 | 1983-07-23 | Martensitic stainless steel with high toughness |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP13474983A JPS6026645A (en) | 1983-07-23 | 1983-07-23 | Martensitic stainless steel with high toughness |
Publications (2)
Publication Number | Publication Date |
---|---|
JPS6026645A JPS6026645A (en) | 1985-02-09 |
JPH0128827B2 true JPH0128827B2 (en) | 1989-06-06 |
Family
ID=15135674
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP13474983A Granted JPS6026645A (en) | 1983-07-23 | 1983-07-23 | Martensitic stainless steel with high toughness |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPS6026645A (en) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
MX2018005245A (en) | 2016-01-13 | 2018-08-01 | Nippon Steel & Sumitomo Metal Corp | Method for manufacturing stainless steel pipe for oil wells and stainless steel pipe for oil wells. |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS58174554A (en) * | 1982-04-07 | 1983-10-13 | Nippon Steel Corp | Stainless steel excellent in ductility and corrosion resistance at weld zone |
-
1983
- 1983-07-23 JP JP13474983A patent/JPS6026645A/en active Granted
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS58174554A (en) * | 1982-04-07 | 1983-10-13 | Nippon Steel Corp | Stainless steel excellent in ductility and corrosion resistance at weld zone |
Also Published As
Publication number | Publication date |
---|---|
JPS6026645A (en) | 1985-02-09 |
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