JPH0112827B2 - - Google Patents
Info
- Publication number
- JPH0112827B2 JPH0112827B2 JP13062884A JP13062884A JPH0112827B2 JP H0112827 B2 JPH0112827 B2 JP H0112827B2 JP 13062884 A JP13062884 A JP 13062884A JP 13062884 A JP13062884 A JP 13062884A JP H0112827 B2 JPH0112827 B2 JP H0112827B2
- Authority
- JP
- Japan
- Prior art keywords
- valve steel
- present
- less
- fatigue strength
- valve
- 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
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 29
- 229910000831 Steel Inorganic materials 0.000 claims description 26
- 239000010959 steel Substances 0.000 claims description 26
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical group [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 14
- 239000011651 chromium Substances 0.000 claims description 10
- 229910052759 nickel Inorganic materials 0.000 claims description 10
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 9
- 229910052804 chromium Inorganic materials 0.000 claims description 9
- 229910000765 intermetallic Inorganic materials 0.000 claims description 8
- 239000010936 titanium Substances 0.000 claims description 8
- 229910001566 austenite Inorganic materials 0.000 claims description 7
- 229910052742 iron Inorganic materials 0.000 claims description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 6
- 229910052782 aluminium Inorganic materials 0.000 claims description 6
- 229910052799 carbon Inorganic materials 0.000 claims description 6
- 239000013078 crystal Substances 0.000 claims description 6
- 239000011572 manganese Substances 0.000 claims description 6
- 229910052758 niobium Inorganic materials 0.000 claims description 6
- 239000010955 niobium Substances 0.000 claims description 6
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 claims description 6
- 229910052719 titanium Inorganic materials 0.000 claims description 6
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 5
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 5
- 238000005520 cutting process Methods 0.000 claims description 5
- 229910052748 manganese Inorganic materials 0.000 claims description 5
- 229910052710 silicon Inorganic materials 0.000 claims description 5
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims description 4
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims description 4
- 229910052796 boron Inorganic materials 0.000 claims description 4
- 239000012535 impurity Substances 0.000 claims description 4
- 230000000149 penetrating effect Effects 0.000 claims description 4
- 239000010703 silicon Substances 0.000 claims description 4
- 229910045601 alloy Inorganic materials 0.000 description 14
- 239000000956 alloy Substances 0.000 description 14
- 239000000047 product Substances 0.000 description 8
- 229910000913 inconels 751 Inorganic materials 0.000 description 7
- 239000011159 matrix material Substances 0.000 description 7
- 230000032683 aging Effects 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 238000010438 heat treatment Methods 0.000 description 5
- 238000002485 combustion reaction Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 3
- 230000006698 induction Effects 0.000 description 3
- 230000007774 longterm Effects 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 238000010998 test method Methods 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 238000005242 forging Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 150000001247 metal acetylides Chemical class 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- 230000002411 adverse Effects 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- -1 chromium carbides Chemical class 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000009661 fatigue test Methods 0.000 description 1
- UGKDIUIOSMUOAW-UHFFFAOYSA-N iron nickel Chemical compound [Fe].[Ni] UGKDIUIOSMUOAW-UHFFFAOYSA-N 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 150000002736 metal compounds Chemical class 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 230000035882 stress Effects 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
Description
［技術分野］
本発明は、熱間疲労強度を大きくした弁用鋼に
関する。ここで弁用鋼とは、自動車などの内燃機
関に用いられる吸気弁や排気弁等を構成する材料
をいう。
［従来技術］
自動車等の内燃機関に用いられる排気弁や吸気
弁は、高温で弁座等にかなり激しくくりかえして
衝突する。従つて、排気弁や吸気弁を構成する弁
用鋼は、熱間疲労強度の大きいことが要請され
る。そのため従来より弁用鋼として、鉄基の耐熱
合金であるJIS―SUH35系合金が（Ｃが0.5％―
Crが21％―Niが４％―Mnが９％―Ｎが0.45％―
残部鉄）主に用いられていた。
ところで近年、熱効率の向上、出力の増大等の
要請から、過給機付きエンジン、１気筒複数バル
ブエンジン等が開発され、内燃機関の稼働温度は
より高温度、具体的には800〜850℃に上昇しつつ
ある。このように内燃機関の稼働温度がより高温
になりつつあるといつた情況を鑑みると、従来か
ら使用されているJIS―SUH35系合金では熱間疲
労強度が不足する。そのため鉄基耐熱合金である
JIS―SUH35系合金の代わりに、鉄をほとんど含
まないニツケル基の合金、例えばインコネル751
（Ni72.5％、C0.04％、Cr15.0％、Fe6.75％、
Ti2.50％、Al1.2％、Si0.20％、Mn0.70％、）を用
いることが近年考えられている。しかし、この場
合には750℃の程度における熱間疲労強度は
SUH35系合金に比してかなり大きいものの、よ
り高温領域である800〜850℃においては熱間疲労
強度がSUH35系合金とほとんど差がないといつ
た問題がある。又インコネル751は、主成分が鉄
ではなくニツケルのためニツケル含有量が高くコ
スト高となる問題もある。
［発明の目的］
本発明は上記した従来技術に鑑みなされたもの
である。本発明は、鉄―ニツケル基で熱間疲労強
度の大きな弁用鋼を提供することを目的とする。
［発明の構成］
本発明者は、800℃以上の温度でも熱間疲労強
度の大きな材料を得んと多数の合金を検討した結
果、本発明を完成したものである。
即ち、本発明の弁用鋼は、重量％で炭素が0.1
％以下、ケイ素が0.5％以下、マンガンが0.5％以
下、ニツケルが35.0〜45.0％、クロムが23％を越
えて25.0％、ニオブが0.5〜2.0％、チタンが2.0〜
3.0％、アルミニウムが1.0〜2.0％、ボロンが
0.001〜0.01％、および不可避の不純物が含まれ、
残部鉄の組成をもち、その組織はオーステナイト
を主体とし、オーステナイトの結晶粒をつらぬく
針状金属間化合物を有することを特徴とする熱間
疲労強度が大きく耐カツピング性が優れたもので
ある。
本発明に係る弁用鋼のマトリツクスは通常、オ
ーステナイト―相である。そして、時効によつ
て、Ni3（AlNb）、Ni3Tiといつた針状の金属間化
合物がマトリツクス中に析出している。この金属
間化合物はオーステナイトの結晶粒を貫いて存在
している。
以下、本発明に係る弁用鋼の組成の限定理由に
ついてのべる。
本発明の弁用鋼において、炭素はその一部がク
ロムやニオブと結合して炭化物を形成する。炭素
が0.1％を越えて含まれると、クロム炭化物がマ
トリツクスの粒界に析出し、強度を低下させる。
そのため炭素は0.1％以下にする。ケイ素及びマ
ンガン、溶解時の脱酸剤として有効であるが、両
元素共に0.5％を越えるとマトリツクスが脆くな
る。そのためケイ素やマンガンは0.5％以下にす
る必要がある。ニツケルは、オーステナイトを形
成する元素として不可欠である。ニツケルは35％
未満では高温に長時間加熱された場合にη相が肥
大凝集化して高温強度を低下させる。一方45％を
越えても、ニツケルによる高温強度の向上は頭打
ちとなり、逆に高価なNi含有量が増すためコス
ト高となる。クロムは耐食性を向上させる元素と
して弁用鋼には、不可欠である。その為クロムは
23％を越える含有量が必要である。但し25％を越
えると時効硬さが低下する。低下する理由は、シ
グマ相が肥大凝集化するためであると考えられ
る。本発明の弁用鋼の特徴の１つは、クロムの成
分範囲の規制にあり、23％以下では望ましい高温
疲労強度や引張り強さおよび長時間時効硬さが得
られない。しかし25％を越えると合金をぜい化さ
せるシグマ相が、長時間加熱により肥大凝集化す
る事によつて熱間における組織不安定化が起き、
弁座部のカツピング現象をひき起す。ニオブは炭
素と結合して微細な炭化物を形成し、結晶の粗大
化抑制に有効である。又ニオブは金属間化合物で
あるNi3（TiNb）を形成し、高温強度の維持に効
果がある。但し0.5％未満ではその効果が小さく
２％を越えると脆くなる。そのためニオブは0.5
〜2.0％にする必要がある。チタンおよびアルミ
ニウムは、ニツケルと結合して微細な金属間化合
物であるNi2（AlTi）を形成し、高温における強
度の確保に有効である。チタンは2.0〜3.0％必要
であり、アルミニウムは1.0〜2.0％必要である。
チタン及びアルミニウムはその含有量以下では高
温強度が得られず、それ以上では熱間における弁
用鋼の塑性加工性を阻害する。ボロンは高温の塑
性加工性の改善に有効であり、0.001〜0.01％の
範囲で有効である。不可避の不純物としては、
Ｐ、Ｓ、Ｎ、Ｏ等が考えられる。不可避の不純物
は一般的には0.01％以下がよい。
次に、本発明の弁用鋼の代表的な製造方法を説
明する。まず真空誘導炉にて吹製精練後、造魂
し、鍛造圧延で所定の棒鋼を製造する。次に約
1050℃に加熱し、ここで15分から60分間保持した
後、水冷し、これにより固溶元素をマトリツクス
に固溶させる。尚、1050℃とした理由は、加熱が
1000℃以下では固溶力元素の溶け込み不足とな
り、一方、1050℃を越える温度では、マトリツク
スの結晶粒が粗大化し、弁成形の際に悪影響を及
ぼすからである。前記したように水冷したら、再
び750℃に加熱し、ここで４時間保持しその後空
冷し、以て弁用鋼を製造した。
［発明の効果］
本発明の弁用鋼は、長時間高温に保持しても熱
間疲労強度が安定していることに特徴がある。特
に800℃以上において、熱間疲労強度、長時間保
持した後の時効硬さ、高温における引張り強さが
大きい。具体的には、850℃における熱間疲労強
度は17kgf／mm2以上であつた。
本発明の弁用鋼が上記のような効果を奏する主
たる理由は、本発明の弁用鋼では、針状の金属間
化合物がマトリツクスの結晶粒界を貫いて存在し
ているため、所謂ピン止めの働きをし、これによ
り結晶粒界移動が抑制されるからである。
又本発明の弁用鋼では、インコネル751の場合
よりもニツケル含有量が低いため、コストも抑え
得る。本発明の効果を以下の試験例で立証する。
［試験例］
(1) まず、真空誘導炉にて３Kgのインゴツトをつ
くり、鍛造・圧延によつて、７種類の外径10
mm、長さ2000mmの試料を作製した。本例ではイ
ンゴツト製造は具体的には以下のように行なつ
た。即ち、真空誘導炉にて、マグネシヤルツボ
を使用し、溶解後金型に鋳造し、外径50mmのイ
ンゴツトを得た。本例では鍛造や圧延は具体的
には以下のようにして行なつた。即ち、インゴ
ツトを1100℃に均一加熱後20mm角に鍛伸した
後、1150℃にて圧延し外径10mmの試料を得た。
このように作製した合金組成を第１表に示す。
ここでNo.１は本発明品であり、No.２〜No.７は
比較例である。比較例のうちNo.６は従来弁用鋼
として用いられているJIS―SUH35系合金を示
し、又No.７はNi基合金であるインコネル751を
示す。
次に、第１表に示すNo.１〜No.５の試料を1050
℃に加熱して15分間保持した後、又No.７の試料
を1000℃に15分保持した後、それぞれ水冷し
750℃に加熱して４時間保持し、その後空冷し
た。
(2) 次に本発明品および比較例の試料の熱間疲労
強度を調べた。試験温度は850℃で試験方法小
野式回転曲げ疲労試験である。試験結果を第２
表に示す。
第２表に示すように、850℃における熱間疲
労強度は本発明品であるNo.１は20.0kgf／mm2で
あつた。この値はインコネル751のNo.７より約
3kgf／mm2以上高い。
(3) 次に本発明品および比較例の試料の900℃に
おける熱間引張強さを調べた。試験方法は、
JISZ2201による14号試験片を用い、この試験
片を電気炉中で900℃で15分間加熱後、３mm／
分の速度でおこなつた。尚前記14号試験片の大
きさは具体的には平行部径５mm、標点距離25
mm、平行部長さ28mm、全長90mmである。試験結
果を第３表に示す。
第３表に示すように、本発明品であるNo.１の
場合熱間引張強さは33.2kgf／mm2であつた。こ
の値は、JIS―SUH35系合金であるNo.６よりも
10kgf／mm2以上大きく、又、インコネル751の
No.７よりも大きい。
(4) 次に本発明品おび比較例の試料を用いて、
850℃で500時間保持した場合の硬さを調べた。
試験方法は、電気炉で850℃で500時間加熱した
後、ロツクウエル硬度計のＣスケールて硬さを
測定した。試験結果を第４表に示す。
第４表に示すように、No.１の本発明品は、
500時間経過の時効によりその硬さはHRC30.2
であつた。この値はNo.７のインコネル751と同
等程度であつた。従つて本発明品は、弁座など
に衝突するため耐摩性が要請される弁用鋼とし
て好適する。
(5) 本発明品の顕微鏡組織では、針状の金属間化
合物であるNi3（AlNb）、Ni3Tiが、オーステナ
イトの結晶粒を貫いて存在している。この金属
化合物は、所謂ピン止めの働きを行なう。故
に、高温で長時間にわたつて繰り返し応力が弁
用鋼に作用した場合であつても、結晶粒界移動
は
[Technical Field] The present invention relates to valve steel with increased hot fatigue strength. Here, valve steel refers to a material that constitutes intake valves, exhaust valves, etc. used in internal combustion engines such as automobiles. [Prior Art] Exhaust valves and intake valves used in internal combustion engines such as automobiles repeatedly and violently collide with valve seats at high temperatures. Therefore, the valve steel constituting exhaust valves and intake valves is required to have high hot fatigue strength. Therefore, JIS-SUH35 series alloys, which are iron-based heat-resistant alloys (0.5% C-
Cr: 21% - Ni: 4% - Mn: 9% - N: 0.45% -
The remaining iron) was mainly used. However, in recent years, in response to demands for improved thermal efficiency and increased output, engines with superchargers, single-cylinder multiple-valve engines, etc. have been developed, and the operating temperature of internal combustion engines has increased to higher temperatures, specifically 800 to 850 degrees Celsius. It is rising. In view of the fact that the operating temperature of internal combustion engines is becoming higher, the JIS-SUH35 series alloys that have been used conventionally lack hot fatigue strength. Therefore, it is an iron-based heat-resistant alloy.
Instead of JIS-SUH35 series alloys, use nickel-based alloys that contain almost no iron, such as Inconel 751.
(Ni72.5%, C0.04%, Cr15.0%, Fe6.75%,
Recently, it has been considered to use 2.50% Ti, 1.2% Al, 0.20% Si, 0.70% Mn. However, in this case, the hot fatigue strength at about 750℃ is
Although it is considerably larger than SUH35 series alloys, there is a problem in that there is almost no difference in hot fatigue strength from SUH35 series alloys in the higher temperature range of 800 to 850°C. Furthermore, since the main component of Inconel 751 is nickel rather than iron, there is a problem in that the nickel content is high and the cost is high. [Object of the Invention] The present invention has been made in view of the above-mentioned prior art. An object of the present invention is to provide an iron-nickel based valve steel with high hot fatigue strength. [Structure of the Invention] The present inventor completed the present invention after studying a large number of alloys in order to obtain a material with high hot fatigue strength even at temperatures of 800° C. or higher. That is, the valve steel of the present invention has a carbon content of 0.1% by weight.
% or less, silicon 0.5% or less, manganese 0.5% or less, nickel 35.0-45.0%, chromium over 23% to 25.0%, niobium 0.5-2.0%, titanium 2.0-45.0%
3.0%, aluminum 1.0-2.0%, boron
Contains 0.001~0.01% and unavoidable impurities,
It has a composition with the remainder iron, its structure is mainly austenite, and it has acicular intermetallic compounds penetrating the austenite crystal grains, so it has high hot fatigue strength and excellent cupping resistance. The matrix of the valve steel according to the invention is usually an austenitic phase. Then, due to aging, acicular intermetallic compounds such as Ni 3 (AlNb) and Ni 3 Ti are precipitated in the matrix. This intermetallic compound exists through the crystal grains of austenite. The reasons for limiting the composition of the valve steel according to the present invention will be described below. In the valve steel of the present invention, a portion of carbon combines with chromium and niobium to form carbides. If the carbon content exceeds 0.1%, chromium carbides will precipitate at the grain boundaries of the matrix, reducing the strength.
Therefore, the carbon content should be 0.1% or less. Silicon and manganese are effective as deoxidizing agents during melting, but if both elements exceed 0.5%, the matrix becomes brittle. Therefore, silicon and manganese must be kept at 0.5% or less. Nickel is an essential element for forming austenite. Nickel is 35%
If it is less than that, the η phase becomes enlarged and agglomerated when heated at high temperature for a long period of time, resulting in a decrease in high-temperature strength. On the other hand, even if it exceeds 45%, the improvement in high-temperature strength due to nickel will reach a plateau, and on the contrary, the expensive Ni content will increase, resulting in higher costs. Chromium is essential for valve steel as an element that improves corrosion resistance. Therefore, chrome
A content of more than 23% is required. However, if it exceeds 25%, the aging hardness will decrease. The reason for the decrease is considered to be that the sigma phase becomes enlarged and aggregated. One of the features of the valve steel of the present invention is the regulation of the range of chromium content; if it is less than 23%, desired high temperature fatigue strength, tensile strength and long-term aging hardness cannot be obtained. However, if it exceeds 25%, the sigma phase that embrittles the alloy becomes enlarged and agglomerated due to long-term heating, resulting in structural instability during hot heating.
This causes a cutting phenomenon in the valve seat. Niobium combines with carbon to form fine carbides and is effective in suppressing crystal coarsening. Niobium also forms Ni 3 (TiNb), an intermetallic compound, which is effective in maintaining high-temperature strength. However, if it is less than 0.5%, the effect is small, and if it exceeds 2%, it becomes brittle. Therefore, niobium is 0.5
It needs to be ~2.0%. Titanium and aluminum combine with nickel to form Ni 2 (AlTi), a fine intermetallic compound, which is effective in ensuring strength at high temperatures. Titanium is required at 2.0-3.0% and aluminum is required at 1.0-2.0%.
If the content of titanium and aluminum is less than that, high-temperature strength cannot be obtained, and if the content is more than that, the plastic workability of the valve steel is inhibited. Boron is effective in improving high temperature plastic workability, and is effective in the range of 0.001 to 0.01%. As unavoidable impurities,
P, S, N, O, etc. are possible. Generally, unavoidable impurities should be 0.01% or less. Next, a typical manufacturing method of the valve steel of the present invention will be explained. First, the steel is blown and refined in a vacuum induction furnace, then forged and rolled into a specified steel bar. Then about
It is heated to 1050°C, held there for 15 to 60 minutes, and then cooled with water, thereby dissolving the solid solution elements in the matrix. The reason for setting the temperature to 1050℃ is that the heating
This is because if the temperature is below 1000°C, there will be insufficient dissolution of the solid solution elements, while if the temperature exceeds 1050°C, the crystal grains of the matrix will become coarse, which will have an adverse effect on valve forming. After cooling with water as described above, it was heated again to 750°C, kept there for 4 hours, and then cooled in air to produce valve steel. [Effects of the Invention] The valve steel of the present invention is characterized in that its hot fatigue strength is stable even when it is held at high temperatures for a long time. Especially at temperatures above 800°C, the hot fatigue strength, aging hardness after long-term storage, and tensile strength at high temperatures are large. Specifically, the hot fatigue strength at 850°C was 17 kgf/mm 2 or more. The main reason why the valve steel of the present invention has the above-mentioned effects is that in the valve steel of the present invention, acicular intermetallic compounds exist penetrating the grain boundaries of the matrix, so that so-called pinning occurs. This is because grain boundary movement is suppressed. Furthermore, since the valve steel of the present invention has a lower nickel content than Inconel 751, costs can also be reduced. The effects of the present invention will be demonstrated in the following test examples. [Test example] (1) First, a 3 kg ingot was made in a vacuum induction furnace, and by forging and rolling, it was made into 7 different outer diameters of 10
A sample with a length of 2000 mm was prepared. In this example, ingot production was specifically performed as follows. That is, in a vacuum induction furnace, using a magnetic crucible, the melted material was cast into a mold to obtain an ingot with an outer diameter of 50 mm. In this example, forging and rolling were specifically performed as follows. That is, the ingot was uniformly heated to 1100°C, forged into a 20 mm square, and then rolled at 1150°C to obtain a sample with an outer diameter of 10 mm.
The composition of the alloy thus produced is shown in Table 1. Here, No. 1 is the product of the present invention, and No. 2 to No. 7 are comparative examples. Among the comparative examples, No. 6 shows a JIS-SUH35 alloy conventionally used as valve steel, and No. 7 shows Inconel 751, which is a Ni-based alloy. Next, the samples No. 1 to No. 5 shown in Table 1 were
After heating to ℃ and holding for 15 minutes, and after holding sample No. 7 at 1000℃ for 15 minutes, they were cooled with water.
It was heated to 750°C and held for 4 hours, and then air cooled. (2) Next, the hot fatigue strength of the products of the present invention and samples of comparative examples was investigated. The test temperature was 850℃ and the test method was Ono type rotating bending fatigue test. Second test result
Shown in the table. As shown in Table 2, the hot fatigue strength at 850°C of No. 1, which is a product of the present invention, was 20.0 kgf/mm 2 . This value is approximately from No. 7 of Inconel 751.
Higher than 3kgf/ mm2 . (3) Next, the hot tensile strength at 900°C of the products of the present invention and samples of comparative examples was examined. The test method is
Using a No. 14 test piece according to JISZ2201, after heating this test piece at 900℃ for 15 minutes in an electric furnace,
I did it at a speed of 1 minute. Specifically, the size of the No. 14 test piece mentioned above is 5 mm in parallel part diameter and 25 gage length.
mm, parallel length 28mm, total length 90mm. The test results are shown in Table 3. As shown in Table 3, the hot tensile strength of No. 1, which is a product of the present invention, was 33.2 kgf/mm 2 . This value is higher than No. 6, which is a JIS-SUH35 series alloy.
Larger than 10kgf/ mm2 , and Inconel 751
It's bigger than No.7. (4) Next, using the samples of the present invention and comparative example,
The hardness was investigated when held at 850°C for 500 hours.
The test method was to heat the material in an electric furnace at 850°C for 500 hours, and then measure the hardness using the C scale of a Rockwell hardness tester. The test results are shown in Table 4. As shown in Table 4, the No. 1 product of the present invention is:
After 500 hours of aging, its hardness is HRC30.2
It was hot. This value was about the same as No. 7 Inconel 751. Therefore, the product of the present invention is suitable as valve steel that requires wear resistance because it collides with valve seats and the like. (5) In the microscopic structure of the product of the present invention, acicular intermetallic compounds such as Ni 3 (AlNb) and Ni 3 Ti exist penetrating the austenite crystal grains. This metal compound performs a so-called pinning function. Therefore, even when repeated stress is applied to valve steel at high temperatures over a long period of time, grain boundary movement will not occur.
【表】【table】
【表】【table】
【表】【table】
【表】【table】
【表】
抑制される。
(6) クロム量を変化させたバルブを形成し、その
バルブをエンジンに組み込み実機耐久試験をお
こなつた。試験は、エンジンとして過給機付き
デイーゼルエンジンを用い、エンジン回転数を
4500rpmとし、全負荷条件下で300時間エンジ
ンを駆動させて行なつた。そしてエンジン駆動
後のバルブのカツピング量の変化を第１図に示
した。第１図の特性線に示すようにカツピング
量はクロム23〜25％で最小値を示す。[Table] Suppressed. (6) We created valves with varying amounts of chromium, installed them into engines, and conducted durability tests on actual machines. The test used a diesel engine with a supercharger as the engine, and the engine speed was
The engine was operated at 4500 rpm for 300 hours under full load conditions. Figure 1 shows the change in the amount of valve cutting after the engine is driven. As shown in the characteristic line of FIG. 1, the amount of cutting shows a minimum value at 23 to 25% chromium.
第１図はクロム量を変化させた場合のカツピン
グ量の変化を示すグラフである。
FIG. 1 is a graph showing changes in the amount of cutting when the amount of chromium is changed.
Claims (1)
下、マンガンが0.5％以下、ニツケルが35.0〜45.0
％、クロムが23％を越えて25.0％、ニオブが0.5
〜2.0％、チタンが2.0〜3.0％、アルミニウムが
1.0〜2.0％、ボロンが0.001〜0.01％、および不可
避の不純物が含まれ、残部鉄の組成をもち、その
組織はオーステナイトを主体とし、オーステナイ
トの結晶粒をつらぬく針状金属間化合物を有する
ことを特徴とする熱間疲労強度が大きく耐カツピ
ング性が優れた弁用鋼。 ２ 850℃における疲労強度は、17kgf／mm2以上
である特許請求の範囲第１項記載の弁用鋼。 ３ 900℃における引張り強さは、30kgf／mm2以
上である特許請求の範囲第１項記載の弁用鋼。 ４ 850℃で500時間保持したときの硬さは、
HRC28以上である特許請求の範囲第１項記載の
弁用鋼。[Claims] 1. Carbon is 0.1% or less, silicon is 0.5% or less, manganese is 0.5% or less, and nickel is 35.0 to 45.0% by weight.
%, chromium over 23% 25.0%, niobium 0.5
~2.0%, titanium 2.0-3.0%, aluminum
It contains 1.0-2.0% boron, 0.001-0.01% boron, and unavoidable impurities, the balance is iron, and its structure is mainly austenite, with acicular intermetallic compounds penetrating the austenite crystal grains. Valve steel featuring high hot fatigue strength and excellent cutting resistance. 2. The valve steel according to claim 1, which has a fatigue strength of 17 kgf/mm 2 or more at 850°C. 3. The valve steel according to claim 1, which has a tensile strength at 900°C of 30 kgf/mm 2 or more. 4 The hardness when held at 850℃ for 500 hours is
The valve steel according to claim 1, which has an HRC of 28 or more.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13062884A JPS619548A (en) | 1984-06-25 | 1984-06-25 | Steel for valve |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13062884A JPS619548A (en) | 1984-06-25 | 1984-06-25 | Steel for valve |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS619548A JPS619548A (en) | 1986-01-17 |
| JPH0112827B2 true JPH0112827B2 (en) | 1989-03-02 |
Family
ID=15038786
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP13062884A Granted JPS619548A (en) | 1984-06-25 | 1984-06-25 | Steel for valve |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS619548A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0639654A2 (en) | 1993-08-19 | 1995-02-22 | Hitachi Metals, Ltd. | Fe-Ni-Cr-base super alloy, engine valve and knitted mesh supporter for exhaust gas catalyzer |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2963842B2 (en) * | 1994-06-15 | 1999-10-18 | 大同特殊鋼株式会社 | Alloy for exhaust valve |
-
1984
- 1984-06-25 JP JP13062884A patent/JPS619548A/en active Granted
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0639654A2 (en) | 1993-08-19 | 1995-02-22 | Hitachi Metals, Ltd. | Fe-Ni-Cr-base super alloy, engine valve and knitted mesh supporter for exhaust gas catalyzer |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS619548A (en) | 1986-01-17 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP5147037B2 (en) | Ni-base heat-resistant alloy for gas turbine combustor | |
| JP5302192B2 (en) | Abrasion resistant heat resistant alloy | |
| JP3058794B2 (en) | Fe-Ni-Cr based super heat resistant alloy, knit mesh for engine valve and exhaust gas catalyst | |
| EP0657558B1 (en) | Fe-base superalloy | |
| US5660938A (en) | Fe-Ni-Cr-base superalloy, engine valve and knitted mesh supporter for exhaust gas catalyzer | |
| JPH0826438B2 (en) | Ferritic heat-resistant cast steel with excellent thermal fatigue life | |
| JPS5834129A (en) | Heat-resistant metallic material | |
| US4871512A (en) | Alloys for exhaust valve | |
| JP3412234B2 (en) | Alloy for exhaust valve | |
| JPS6250542B2 (en) | ||
| EP0359085B1 (en) | Heat-resistant cast steels | |
| WO2010150795A1 (en) | Heat-resistant steel for engine valve having excellent high-temperature strength | |
| EP3589769B1 (en) | Nickel and chrome based iron alloy having enhanced high temperature oxidation resistance | |
| WO2010122969A1 (en) | Heat resistant steel for use in engine valve having excellent high-temperature strength | |
| JP3424314B2 (en) | Heat resistant steel | |
| JPH0112827B2 (en) | ||
| JP4180753B2 (en) | Fe-base heat-resistant alloy with excellent cold workability and high-temperature heat stability | |
| JP4057208B2 (en) | Fe-base heat-resistant alloy for engine valves with good cold workability and high-temperature strength | |
| JP3744084B2 (en) | Heat-resistant alloy with excellent cold workability and overaging characteristics | |
| JPH06256908A (en) | Heat resistant cast steel and exhaust system parts using the same | |
| JP3744083B2 (en) | Heat-resistant alloy with excellent cold workability | |
| JP6745050B2 (en) | Ni-based alloy and heat-resistant plate material using the same | |
| JPH11199987A (en) | Heat resistant alloy suitable for cold working | |
| JP3840762B2 (en) | Heat resistant steel with excellent cold workability | |
| JPH07113139B2 (en) | Exhaust manifold and automobile turbine housing with excellent castability and heat fatigue resistance |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EXPY | Cancellation because of completion of term |