JPS6213428B2 - - Google Patents
Info
- Publication number
- JPS6213428B2 JPS6213428B2 JP18565083A JP18565083A JPS6213428B2 JP S6213428 B2 JPS6213428 B2 JP S6213428B2 JP 18565083 A JP18565083 A JP 18565083A JP 18565083 A JP18565083 A JP 18565083A JP S6213428 B2 JPS6213428 B2 JP S6213428B2
- Authority
- JP
- Japan
- Prior art keywords
- present
- fatigue strength
- valve steel
- strength
- alloy
- 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
- 229910000831 Steel Inorganic materials 0.000 claims description 21
- 239000010959 steel Substances 0.000 claims description 21
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 19
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical group [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 16
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 10
- 229910052759 nickel Inorganic materials 0.000 claims description 9
- 229910052742 iron Inorganic materials 0.000 claims description 8
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims description 7
- 229910052748 manganese Inorganic materials 0.000 claims description 7
- 239000011572 manganese Substances 0.000 claims description 7
- 230000003647 oxidation Effects 0.000 claims description 7
- 238000007254 oxidation reaction Methods 0.000 claims description 7
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims description 6
- 229910052750 molybdenum Inorganic materials 0.000 claims description 6
- 239000011733 molybdenum Substances 0.000 claims description 6
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 5
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 5
- 229910052796 boron Inorganic materials 0.000 claims description 5
- 229910052799 carbon Inorganic materials 0.000 claims description 5
- 229910052757 nitrogen Inorganic materials 0.000 claims description 5
- 229910052710 silicon Inorganic materials 0.000 claims description 5
- 239000010703 silicon Substances 0.000 claims description 5
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 4
- 229910052804 chromium Inorganic materials 0.000 claims description 4
- 239000011651 chromium Substances 0.000 claims description 4
- 229910052758 niobium Inorganic materials 0.000 claims description 4
- 239000010955 niobium Substances 0.000 claims description 4
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 claims description 4
- 230000004584 weight gain Effects 0.000 claims description 3
- 235000019786 weight gain Nutrition 0.000 claims description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 2
- 229910052802 copper Inorganic materials 0.000 claims description 2
- 239000010949 copper Substances 0.000 claims description 2
- 239000012535 impurity Substances 0.000 claims description 2
- 229910045601 alloy Inorganic materials 0.000 description 16
- 239000000956 alloy Substances 0.000 description 16
- 230000000052 comparative effect Effects 0.000 description 7
- 229910000913 inconels 751 Inorganic materials 0.000 description 7
- 230000000694 effects Effects 0.000 description 5
- 238000010998 test method Methods 0.000 description 4
- 229910001566 austenite Inorganic materials 0.000 description 3
- 238000002485 combustion reaction Methods 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 150000001247 metal acetylides Chemical class 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 230000032683 aging Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- -1 Inconel 751 Chemical compound 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000003628 erosive effect Effects 0.000 description 1
- 238000005242 forging Methods 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000004881 precipitation hardening Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
Landscapes
- Heat Treatment Of Steel (AREA)
- Lift Valve (AREA)
Description
［技術分野］
本発明は、熱間疲労強度の大きな弁用鋼に関す
る。
［従来技術］
自動車等の内燃機関の排気弁や吸気弁は、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、特
に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対熱合金である
JIS―SUH35系合金が用いられていた。
ところで近年、熱効率の向上、出力の増大等の
要請から、内燃機関の稼働温度はより高温度、例
えば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
つた状況を鑑みると、弁用鋼としては、JIS―
SUH35系合金よりも熱間疲労強度の大きな材料
を用いる必要がある。そのため鉄基合金の代わり
に、鉄をほとんど含まないニツケル基合金、例え
ばインコネル751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、800〜850℃においてはSUH35系
合金とほとんど差がないといつた問題がある。又
主成分が鉄ではなくニツケルのためコスト高とな
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鉄基合金を検討し
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0.25
〜0.35％、珪素が0.1〜1.0％、マンガンが5.0〜
15.0％、ニツケルが5.0〜10.0％、クロムが18.0〜
25.0％、銅が0.2〜1.0％、モリブデンが1.0〜3.0
％、ニオブが0.5〜1.5％、窒素が0.35〜0.55％、
ボロンが0.0005〜0.01％、および不可避の不純物
が含まれ、残部鉄の組成の合金からなることを特
徴とする熱間疲労強度の大きなものである。
本発明の弁用鋼は、時効によつて炭窒化物等を
組織中に析出させ、これによつて機械的性質が強
化される析出硬化型合金である。
本発明において炭素は、炭窒化物を生成して組
織を強化するために不可欠である。炭素は少なす
ぎても多すぎても、弁用鋼の強度は低下する。そ
のため炭素は0.25〜0.35％にする必要がある。
珪素は高温酸化に対する抵抗を増すため、又溶
解時における脱酸剤として必要である。そのため
珪素は最低限0.1％は必要である。但し珪素が１
％を越えると、弁用鋼は脆くなる。
ニツケルはオーステナイト生成元素であり、オ
ーステナイト組織を常温で安定させるものであ
る。そのためニツケルは最低限５％は必要であ
る。但しニツケルが10％を越えると、高温におけ
る硬さの低下を招く。
マンガンはニツケルと同様にオーステナイト生
成元素であり、高価なニツケルの代替元素として
使用されている。又、マンガンはイオウによる浸
食を軽減する。更にマンガンは有鉛ガソリンによ
るPbo浸食の防止に効果的である。そのためマン
ガンは最低限５％必要である。但し、マンガンは
15％を越えると、弁用鋼は高温酸化しやすくな
る。
クロムは耐食性を向上させる元素として弁用鋼
では不可欠である。そのためクロムは最低限18％
必要である。但し、25％を越えると、高温におけ
る塑性変形が困難となる。
モリブデンは、基地に固溶して基地を強化す
る。又、モリブデンは、安定炭窒化物や炭化物を
形成する作用がある。そのためモリブデンは最低
限1.0％〜3.0％は必要である。但し、モリブデン
の添加による効果は３％で飽和に達する。尚上記
した安定炭窒化物としては（MoW）2（CN）があ
る。
ニオブは微細な炭窒化物や炭化物を形成する作
用がある。そのため高温におけるオーステナイト
結晶の成長抑制に有効で高温における強度低下を
防ぐ。そのためニオブは0.5〜1.5％にする必要が
ある。
窒素は炭窒化物形成の基礎となる。従つて、窒
素は高温における強度低下を防ぐ。そのため窒素
は最低限0.35％必要である。但し、0.55％以上は
含有しにくい。
ボロンは、高温における強度の確保、高温にお
ける塑性加工の改善に有効である。そのためボロ
ンは最低限0.0005％必要である。但し、0.01％を
越えると、ボロンは結晶粒界に凝集し、この結果
加工性を劣化させたり、高温における強度を低下
させたりする。
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、大気溶解炉にて吹精精錬後、造塊
し、鍛造圧延で所定の棒鋼を製造する。次に1100
℃に加熱し、ここで15分から60分保持する。1100
℃で保持する理由は、主として、合金元素、炭窒
化物、炭化物を高温のオーステナイトに固溶する
ためである。次に水冷する。水冷した後再び750
℃に加熱し、ここで４時間保持し、その後空冷す
る。
［発明の効果］
本発明の弁用鋼は、熱間疲労強度が大きなもの
となる。特に800℃以上においては、疲労強度は
インコネル751よりも大きい。即ち、850℃におけ
る熱間疲労強度は17Kgｆ／mm2以上である。
更に本発明の弁用鋼は、高温における引張り強
さも大きい。又高温酸化い少ない。更に高温にお
ける加工性も優れている。
本発明の効果を以下の試験例で立証する。
［試験例］
まず、大気高周波炉にて３Kgのインゴツトをつ
くり、鍛造、圧延によつて９種類の試料を作製し
た。９種類の試料の合金組成は第１表に示す。こ
こでNo.１〜No.３は本発明品であり、No.４〜No.９は
比較例である。比較例のうち、No.８は従来弁用鋼
として用いられているJIS―SUH35系合金であ
り、又、No.９はNi基合金であるインコネル751で
ある。そして第１表に示す組成の試料を、約1100
℃に30分保持した後、水冷した。次に再び750℃
に加熱して４時間保持した。そしてその後空冷し
た。
まず、本発明品及び比較例を用いて熱間疲労強
度を調べた。試験温度は750℃と850℃である。試
験方法は、小野式回転曲げ疲労である。試験結果
を第２表に示す。750℃における熱間疲労強度
は、本発明品であるNo.１〜No.３の場合いずれも21
Kgｆ／mm2以上であつた。この値は、No.８とNo.９の
場合の中間の値である。850℃における熱間疲労
強度は、本発明品であるNo.１〜No.３の場合いずれ
も17Kgｆ／mm2以上であつた。
これに対して850℃における熱間疲労強度はNo.
８の場合は15.3Kgｆ／mm2であり、No.９の場合には
16.3Kgｆ／mm2であつた。このことから、本発明品
では、JIS―SUH35系合金よりも750℃における
熱間疲労強度、850℃における熱間疲労強度が大
きいことがわかる。又、本発明では、750℃にお
ける熱間疲労強度はインコネル751の場合よりも
小さいが、850℃における熱間疲労強度は、溶体
化処理を省略したインコネル751の場合よりも10
％程度大きいことがわかる。
次に本発明及び比較例を用いて900℃における
熱間引張り強さを調べた。試験方法は平行部φ５
のJISZ2201による14A号試験片を電気炉中で900
℃15分加熱保持後３mm／分の速度でおこなつた。
試験結果を第３表に示す。本発明品であるNo.１〜
No.３の場合、熱間引張り強さはいずれも22Kgｆ／
mm2以上であつた。この値は、JIS―SUH35系合金
であるNo.８の場合よりも大きい。
次に本発明品及び比較例を用いて、850℃で100
時間保持した場合の時効の硬さを調べた。試験方
法は、電気炉で加熱した後ロツクウエル硬度計の
Ｃスケールにて硬さを測定した。試験結果を第４
表に示す。本発明品であるNo.１〜No.３の場合、い
ずれもHRC29以上であつた。この値はNo.８の場
合よりも大きい。従つて本発明品は、弁座に衝突
するため耐摩滅性が要請される弁用鋼として適す
る。
次に本発明品及び比較例を用いて、900℃で300
時間保持した場合の酸化度合いを調べた。試験方
法はφ８×15mm形状の試料を1000℃１時間空焼き
した磁性ルツボに入れ、電気炉にて大気中所定の
時間加熱後取り出して秤量し、試料の酸化増量を
算出した。試験結果を第５表に示す。本発明品で
あるNo.１〜No.３の場合、酸化増量は2.20〜3.22
mg／cm2であつた。これに対してNo.８の場合には
3.73mg／cm2と大きかつた。
次に本発明品及び比較例（No.８及びNo.９）を用
いて、限界加工率を調べた。この場合、直径10
mm、高さ10mmの丸棒状の試料を製造し、その試料
の両面から32Kgのハンマーで叩いて圧縮加工を行
つた。そしてハンマーの振り上げ角度を順次変
え、試料に割れが発生したときの圧縮加工率を限
界加工率とした。この試験は、弁の加工温度であ
る950℃〜1200℃の範囲内で温度を種々変更して
行つた。試験結果を図に示す。図に示すように、
本発明品であるNo.１の場合には、試験温度が1050
℃以上ならば、限界加工率は70％以上の値を示し
た。図から明らかなようにこの値はJIS―SUH35
系合金であるNo.８の値よりもかなり大きい。一
方、インコネル751であるNo.９の場合には、限界
加工率は48〜64％程度とかなり低い。特にインコ
ネル751であるNo.９の限界加工率は、最高値でも
64％しかなかつた。
[Technical Field] The present invention relates to valve steel with high hot fatigue strength. [Prior Art] Exhaust valves and intake valves of internal combustion engines such as automobiles are exposed to high temperatures and repeatedly and violently collide with valve seats.
Therefore, the valve steel constituting exhaust valves and intake valves is required to have particularly high hot fatigue strength. For this reason, iron-based heat-resistant alloys have traditionally been used as valve steels.
JIS-SUH35 series alloy was used. However, in recent years, due to demands for improved thermal efficiency, increased output, etc., the operating temperature of internal combustion engines has been rising to higher temperatures, for example, 800 to 850°C. In view of the fact that the operating temperature of internal combustion engines is becoming higher, JIS-
It is necessary to use a material with higher hot fatigue strength than SUH35 alloy. Therefore, in recent years, it has been considered to use a nickel-based alloy containing almost no iron, such as Inconel 751, instead of an iron-based alloy. However, in this case, there is a problem in that although the hot fatigue strength at about 750°C is considerably higher than that of the SUH35 alloy, at 800 to 850°C there is almost no difference from the SUH35 alloy. There is also the problem of high cost because the main component is nickel rather than iron. [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-based valve steel having high hot fatigue strength. [Structure of the Invention] The present inventor completed the present invention after studying a large number of iron-based 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 0.25% by weight.
~0.35%, silicon 0.1~1.0%, manganese 5.0~
15.0%, Nickel 5.0~10.0%, Chromium 18.0~
25.0%, copper 0.2~1.0%, molybdenum 1.0~3.0
%, niobium 0.5-1.5%, nitrogen 0.35-0.55%,
It has a high hot fatigue strength and is characterized by being composed of an alloy with a composition of 0.0005 to 0.01% boron and unavoidable impurities, with the balance being iron. The valve steel of the present invention is a precipitation hardening alloy in which carbonitrides and the like are precipitated into the structure through aging, thereby strengthening mechanical properties. In the present invention, carbon is essential to generate carbonitrides and strengthen the structure. If the carbon content is too low or too high, the strength of the valve steel will decrease. Therefore, carbon needs to be 0.25 to 0.35%. Silicon is necessary to increase resistance to high temperature oxidation and as a deoxidizer during melting. Therefore, a minimum amount of silicon of 0.1% is required. However, silicon is 1
%, the valve steel becomes brittle. Nickel is an austenite-forming element that stabilizes the austenite structure at room temperature. Therefore, a minimum of 5% nickel is required. However, if the nickel content exceeds 10%, the hardness will decrease at high temperatures. Like nickel, manganese is an austenite-forming element and is used as a substitute for the expensive nickel. Manganese also reduces sulfur attack. Furthermore, manganese is effective in preventing Pbo erosion caused by leaded gasoline. Therefore, a minimum of 5% manganese is required. However, manganese
If it exceeds 15%, valve steel becomes susceptible to high-temperature oxidation. Chromium is essential in valve steel as an element that improves corrosion resistance. Therefore, the minimum chromium content is 18%.
is necessary. However, if it exceeds 25%, plastic deformation at high temperatures becomes difficult. Molybdenum strengthens the base by forming a solid solution in the base. Furthermore, molybdenum has the effect of forming stable carbonitrides and carbides. Therefore, molybdenum is required at a minimum of 1.0% to 3.0%. However, the effect of adding molybdenum reaches saturation at 3%. The stable carbonitride mentioned above is (MoW) 2 (CN). Niobium has the effect of forming fine carbonitrides and carbides. Therefore, it is effective in suppressing the growth of austenite crystals at high temperatures and prevents strength loss at high temperatures. Therefore, niobium needs to be 0.5 to 1.5%. Nitrogen is the basis for carbonitride formation. Therefore, nitrogen prevents strength loss at high temperatures. Therefore, a minimum nitrogen content of 0.35% is required. However, it is difficult to contain more than 0.55%. Boron is effective in ensuring strength at high temperatures and improving plastic working at high temperatures. Therefore, a minimum amount of boron of 0.0005% is required. However, if it exceeds 0.01%, boron aggregates at grain boundaries, resulting in poor workability and reduced strength at high temperatures. Next, a typical manufacturing method of the valve steel of the present invention will be explained. First, the steel is blown and refined in an atmospheric melting furnace, then ingot-formed and forged and rolled to produce a specified steel bar. then 1100
Heat to °C and hold here for 15 to 60 minutes. 1100
The reason for maintaining the temperature at °C is mainly to dissolve alloying elements, carbonitrides, and carbides in the high-temperature austenite. Next, cool with water. 750 again after water cooling
℃ and held there for 4 hours, then air cooled. [Effects of the Invention] The valve steel of the present invention has high hot fatigue strength. Especially at temperatures above 800°C, the fatigue strength is greater than Inconel 751. That is, the hot fatigue strength at 850°C is 17 kgf/mm 2 or more. Furthermore, the valve steel of the present invention has high tensile strength at high temperatures. Also, there is less oxidation at high temperatures. Furthermore, it has excellent workability at high temperatures. The effects of the present invention will be demonstrated in the following test examples. [Test Example] First, a 3 kg ingot was made in an atmospheric high frequency furnace, and nine types of samples were made by forging and rolling. The alloy compositions of the nine types of samples are shown in Table 1. Here, No. 1 to No. 3 are products of the present invention, and No. 4 to No. 9 are comparative examples. Among the comparative examples, No. 8 is a JIS-SUH35 alloy conventionally used as valve steel, and No. 9 is Inconel 751, which is a Ni-based alloy. Then, approximately 1100 samples with the composition shown in Table 1 were
After being kept at ℃ for 30 minutes, it was cooled with water. Then again 750℃
and held for 4 hours. Then it was air cooled. First, hot fatigue strength was investigated using the products of the present invention and comparative examples. The test temperatures are 750℃ and 850℃. The test method is Ono rotary bending fatigue. The test results are shown in Table 2. The hot fatigue strength at 750°C is 21 for all products No. 1 to No. 3 of the present invention.
Kgf/ mm2 or more. This value is an intermediate value between No. 8 and No. 9. The hot fatigue strength at 850° C. was 17 Kgf/mm 2 or more in all of the products No. 1 to No. 3 of the present invention. On the other hand, the hot fatigue strength at 850℃ is No.
In the case of No. 8, it is 15.3Kgf/mm 2 , and in the case of No. 9, it is 15.3Kgf/mm 2.
It was 16.3Kgf/ mm2 . From this, it can be seen that the product of the present invention has higher hot fatigue strength at 750°C and higher hot fatigue strength at 850°C than the JIS-SUH35 series alloy. In addition, in the present invention, the hot fatigue strength at 750°C is lower than that of Inconel 751, but the hot fatigue strength at 850°C is 10% lower than that of Inconel 751 without solution treatment.
It can be seen that it is about % larger. Next, hot tensile strength at 900°C was investigated using the present invention and comparative examples. The test method is parallel part φ5
A No. 14A test piece according to JISZ2201 was heated at 900°C in an electric furnace.
After heating and holding at °C for 15 minutes, heating was carried out at a speed of 3 mm/min.
The test results are shown in Table 3. No. 1~ which is the product of this invention
In the case of No. 3, the hot tensile strength is 22Kgf/
mm 2 or more. This value is larger than that of No. 8, which is a JIS-SUH35 series alloy. Next, using the product of the present invention and the comparative example,
The hardness of aging when held for a certain period of time was investigated. The test method was to heat the product in an electric furnace and then measure the hardness using a Rockwell hardness meter C scale. 4th test result
Shown in the table. In the case of Nos. 1 to 3, which are products of the present invention, all had an HRC of 29 or higher. This value is larger than the case of No.8. Therefore, the product of the present invention is suitable as valve steel that requires wear resistance because it collides with the valve seat. Next, using the product of the present invention and the comparative example,
The degree of oxidation was investigated after holding for a certain period of time. The test method was to place a sample with a diameter of 8 mm x 15 mm into a magnetic crucible that had been air-fired at 1000°C for 1 hour, and after heating in the air in an electric furnace for a predetermined time, it was taken out and weighed, and the oxidation weight gain of the sample was calculated. The test results are shown in Table 5. In the case of No. 1 to No. 3, which are products of the present invention, the oxidation weight gain is 2.20 to 3.22.
mg/ cm2 . On the other hand, in the case of No. 8
It was large at 3.73mg/ cm2 . Next, the limit processing rate was investigated using the products of the present invention and comparative examples (No. 8 and No. 9). In this case, diameter 10
A round rod-shaped sample with a diameter of 10 mm and a height of 10 mm was produced, and the sample was compressed by hitting it with a 32 kg hammer from both sides. The lifting angle of the hammer was then changed sequentially, and the compression processing rate at which cracks occurred in the sample was taken as the limit processing rate. This test was conducted at various temperatures within the range of 950°C to 1200°C, which is the processing temperature of the valve. The test results are shown in the figure. As shown in the figure,
In the case of No. 1, which is the product of the present invention, the test temperature was 1050
If the temperature is above ℃, the limit processing rate showed a value of 70% or more. As is clear from the figure, this value is JIS-SUH35
This value is considerably larger than that of No. 8, which is a series alloy. On the other hand, in the case of No. 9, which is Inconel 751, the limit processing rate is quite low at about 48 to 64%. In particular, the limit machining rate of No. 9, which is Inconel 751, is even at its highest value.
It was only 64%.
【表】【table】
【表】【table】
【表】【table】
【表】【table】
【表】【table】
図は、加工温度と限界加工率との関係を示すグ
ラフである。
The figure is a graph showing the relationship between processing temperature and limit processing rate.
Claims (1)
1.0％、マンガンが5.0〜15.0％、ニツケルが5.0〜
10.0％、クロムが18.0〜25.0％、銅が0.2〜1.0
％、モリブデンが1.0〜3.0％、ニオブが0.5〜1.5
％、窒素が0.35〜0.55％、ボロンが0.0005〜0.01
％、および不可避の不純物が含まれ、残部鉄の組
成の合金からなることを特徴とする熱間疲労強度
の大きな弁用鋼。 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、22Kgｆ／mm2以
上である特許請求の範囲第１項記載の弁用鋼。 ４ 900℃で300時間保持したときの酸化増量は、
2.2mg／cm2以上である特許請求の範囲第１項記載
の弁用鋼。[Claims] 1% by weight: 0.25 to 0.35% carbon, 0.1 to 0.1% silicon
1.0%, manganese 5.0~15.0%, nickel 5.0~
10.0%, chromium 18.0-25.0%, copper 0.2-1.0
%, molybdenum 1.0-3.0%, niobium 0.5-1.5
%, nitrogen 0.35-0.55%, boron 0.0005-0.01
%, and unavoidable impurities, and the balance is iron, and the valve steel has a high hot fatigue strength. 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 22 Kgf/mm 2 or more. 4 The oxidation weight gain when held at 900℃ for 300 hours is
The valve steel according to claim 1, which has a content of 2.2 mg/cm 2 or more.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP18565083A JPS6077964A (en) | 1983-10-04 | 1983-10-04 | Steel used for valve |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP18565083A JPS6077964A (en) | 1983-10-04 | 1983-10-04 | Steel used for valve |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS6077964A JPS6077964A (en) | 1985-05-02 |
| JPS6213428B2 true JPS6213428B2 (en) | 1987-03-26 |
Family
ID=16174475
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP18565083A Granted JPS6077964A (en) | 1983-10-04 | 1983-10-04 | Steel used for valve |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS6077964A (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6389645A (en) * | 1986-10-01 | 1988-04-20 | Toyota Motor Corp | Valve steel |
| JP2543417B2 (en) * | 1989-12-05 | 1996-10-16 | トヨタ自動車株式会社 | Valve steel |
| US5257453A (en) * | 1991-07-31 | 1993-11-02 | Trw Inc. | Process for making exhaust valves |
| CN111041386B (en) * | 2018-10-12 | 2022-07-29 | 博格华纳公司 | Austenitic alloys for turbochargers |
-
1983
- 1983-10-04 JP JP18565083A patent/JPS6077964A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6077964A (en) | 1985-05-02 |
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