JPH0361748B2 - - Google Patents
Info
- Publication number
- JPH0361748B2 JPH0361748B2 JP889986A JP889986A JPH0361748B2 JP H0361748 B2 JPH0361748 B2 JP H0361748B2 JP 889986 A JP889986 A JP 889986A JP 889986 A JP889986 A JP 889986A JP H0361748 B2 JPH0361748 B2 JP H0361748B2
- Authority
- JP
- Japan
- Prior art keywords
- fatigue resistance
- tin
- steel
- less
- fatigue
- 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 24
- 239000010959 steel Substances 0.000 claims description 24
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims description 19
- 238000005242 forging Methods 0.000 claims description 7
- 239000012535 impurity Substances 0.000 claims description 2
- 229910001566 austenite Inorganic materials 0.000 description 6
- 238000010438 heat treatment Methods 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 238000007792 addition Methods 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 238000010791 quenching Methods 0.000 description 2
- 230000000171 quenching effect Effects 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000005496 tempering Methods 0.000 description 2
- 238000005452 bending Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000009661 fatigue test Methods 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000004881 precipitation hardening Methods 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 238000009864 tensile test Methods 0.000 description 1
Description
「発明の目的」
本発明は耐疲労特性の優れた熱間鍛造用非調質
鋼の創案に係り、熱間鍛造後の焼入れ焼戻しのよ
うな熱処理を省略せしめ、しかも耐疲労特性に優
れると共に被削性についても良好で自動車部品な
どの素材として好適な非調質鋼を提供しようとす
るものである。
産業上の利用分野
熱間鍛造用の耐疲労特性に優れた非調質鋼。
従来の技術
熱間鍛造品は従来において熱間鍛造してから焼
入れ焼戻しの調質を行つていたが、近年省エネル
ギー的観点からこの調質を省略した、即ち熱間鍛
造ままで調質鋼と同等の特性を有する非調質鋼が
開発され、本発明者等も特開昭59−1002556号の
如きを提案している。即ちこのような従来のもの
は特に非調質鋼の短所である靭性の改善を目的と
したものが多く、Ｖ単独添加鋼と、Ｖ−Ti複合
添加鋼から成つている。
発明が解決しようとする問題点
ところが上記したような従来のものにおいて
は、それが実際に使用されることの多い自動車等
の部品として用いられた場合において要求される
耐疲労特性の如きにおいて必ずしも好ましいもの
でない。即ち前記したＶ単独添加鋼はオーステナ
イト粒径が大きく、耐疲労特性も調質鋼に比較す
ると劣つている。又Ｖ−Ti複合添加鋼ではオー
ステナイト粒は細かくなるが硬質のTiN介在物
が生成し、やはり耐疲労特性が劣化する。
「発明の構成」
問題点を解決するための手段
１ Ｃ：0.20〜0.45wt％、Si：0.01〜1.5wt％、
Mn：0.8〜2.0wt％、 Ｖ：0.01〜0.20wt％
Ti：0.003〜0.010wt％、
を含有すると共にＮを下式の関係を満足するよう
に含有し、残部がFeおよび不可避的不純物から
成り、且つTiN介在物の最大サイズが7.5μm以下
であることを特徴とする耐疲労特性の優れた熱間
鍛造用非調質鋼。
0.2＜Ti／Ｎ＜2.5
作 用
Ｃが0.20wt％以上、Siが0.01wt％以上、Mnが
0.8wt％以上、Ｖが0.01wt％以上含有されること
によつて強度を確保し、又Ｃを0.45wt％以下とす
ることにより所要強度を大きく超えることなく、
Siが1.5wt％以下、Mnが2.0wt％以下とされるこ
とによつて靭性上好ましくない組織の顕われるこ
とを回避する。Ｖを0.20wt％以下とすることによ
り、経済性と有効性を確保する。Tiが0.003wt％
以上含有させることでオーステナイト粒の微細化
を図つて耐疲労特性を向上し、又0.010％以下と
することでTiNのサイズ、量が共に小さくなり
耐疲労特性劣化を回避する。
Ｎを0.2＜Ti／Ｎ＜2.5とすることで必要強度を
確保する。
実施例
上記したような本発明について更に説明する
と、本発明者等は上述したような従来のものにお
ける問題点を解決することについて研究を重ねた
結果、Tiを前記したような範囲内とし、TiN量、
サイズを適当なものとすることにより耐疲労特性
が適切な改善されることを見出した。
即ち前記したような本発明によるものの成分組
成限定理由についてwt％（以下単に％という）
により説明すると以下の如くである。
Ｃ：0.20〜0.45％
Ｃが0.45％を超えると所要の強度を大きく超え
てしまうので、0.45％を上限とした。またこのＣ
が0.20％未満では必要強度確保のためのMn等の
添加量が多くならざるを得ず、経済的に不利とな
るので、0.20％を下限とした。
Si：0.01〜1.5％
Siは、脱酸剤として、あるいは強度上昇を図る
ために必要な元素であるが、1.5％を超えると靭
性上好ましくない組織が顕われることがあり、ま
た0.01％未満では前記したような効果が不充分で
あるので、0.01〜1.5％とした。
Mn：0.8〜2.0％
強度の確保からはMnが0.8％以上とすることが
必要であり、これを下限とした。また2.0％を超
えると靭性上好ましくない組織が顕われることが
あるので上限を2.0％とする。
Ｖ：0.01〜0.20％
Ｖは析出硬化により強度増加をもたらすのに必
要な元素であつて、このためには0.01％以上とす
ることが必要である。一方0.20％を超えることは
経済性および有効性からそれぞれ不利となるので
これを上限とした。
Ti：0.003〜0.010％。
Tiは本発明において最も重要な元素であつて、
耐疲労特性の向上のためには0.003％以上で、し
かも0.010％を上限とすべきである。即ち0.003％
未満ではオーステナイト粒の微細化をなし得ない
ため耐疲労特性が劣化し、又0.010％を超えると
TiNのサイズ、量とも大きなものとなり耐疲労
特性が劣化する。
Ｎ：0.2＜Ti／Ｎ＜2.5
ＮはＶと窒化物を形成し析出強化に必要な元素
であるが、Ti／Ｎ＞2.5ではTiN生成によりＶと
結びつくＮが少くなり過ぎて必要強度が得られな
い。またTi／Ｎ＜0.2ではTiNの生成が少なすぎ
て必要な特性が得られない。これらの関係から、
0.2＜Ti／Ｎ＜2.5にＮの範囲を規定することが必
要である。
TiN介在物の最大サイズ：7.5μm以下
TiN介在物について最大サイズを7.5μm以下に
抑えたのは、疲労の起点となると考えられる5μm
超えのTiNの数（mm2当り）を大きく抑えて、耐
疲労特性を向上させるためである。即ちこの関係
については第２図に示す通りであつて、TiNの
最大サイズを7.5μm以下とすることにより5μm超
えTiN数を１〜２個／mm2以下とすることができ
て耐疲労特性を充分に向上することができる。
本発明によるものの具体的な製造例について、
比較例と共に示すと以下の如くである。
製造例 １
次の第１表に示す化学成分を有する本発明鋼No.
３、４および比較鋼No.１、２と５、６を150Kg大
気溶解炉で溶製し、60mm厚の板に圧延した。
``Object of the Invention'' The present invention relates to the creation of a non-temperature steel for hot forging with excellent fatigue resistance, which eliminates heat treatment such as quenching and tempering after hot forging, and which has excellent fatigue resistance and is resistant to heat treatment. The aim is to provide a non-tempered steel that has good machinability and is suitable as a material for automobile parts. Industrial Applications Non-thermal steel with excellent fatigue resistance for hot forging. Conventional technology In the past, hot forged products were hot-forged and then subjected to quenching and tempering, but in recent years, this refining has been omitted from the viewpoint of energy conservation. A non-tempered steel having similar properties has been developed, and the present inventors have also proposed a steel as disclosed in Japanese Patent Application Laid-open No. 1002556/1983. That is, many of these conventional steels are aimed at improving toughness, which is a disadvantage of non-thermal treated steels, and are made of steels with single V addition and steels with V-Ti composite additions. Problems to be Solved by the Invention However, the above-mentioned conventional products are not necessarily desirable in terms of fatigue resistance, which is required when they are used as parts of automobiles, etc., which are often actually used. It's not something. That is, the above-mentioned steel containing only V has a large austenite grain size and its fatigue resistance is inferior to that of tempered steel. In addition, in V-Ti composite steel, the austenite grains become finer, but hard TiN inclusions are formed, which also deteriorates the fatigue resistance. "Structure of the invention" Means for solving the problem 1 C: 0.20-0.45wt%, Si: 0.01-1.5wt%, Mn: 0.8-2.0wt%, V: 0.01-0.20wt% Ti: 0.003-0.010 wt%, N is contained so as to satisfy the relationship of the following formula, the balance is Fe and unavoidable impurities, and the maximum size of TiN inclusions is 7.5 μm or less. Non-thermal steel for hot forging with excellent fatigue properties. 0.2<Ti/N<2.5 Effect C is 0.20wt% or more, Si is 0.01wt% or more, Mn is
Strength is ensured by containing 0.8 wt% or more and V 0.01 wt% or more, and by keeping C at 0.45 wt% or less, the required strength is not greatly exceeded.
By setting Si to 1.5 wt% or less and Mn to 2.0 wt% or less, the appearance of a structure that is unfavorable in terms of toughness is avoided. Economic efficiency and effectiveness are ensured by keeping V below 0.20wt%. Ti 0.003wt%
By containing TiN in this amount, the austenite grains are refined and the fatigue resistance properties are improved, and by containing TiN at 0.010% or less, both the size and amount of TiN are reduced, thereby avoiding deterioration of the fatigue resistance properties. The required strength is ensured by setting N to 0.2<Ti/N<2.5. EXAMPLES To further explain the present invention as described above, as a result of repeated research into solving the problems in the conventional products as described above, the present inventors set Ti within the range described above, and TiN amount,
It has been found that by making the size appropriate, the fatigue resistance properties can be appropriately improved. That is, the reason for limiting the composition of the product according to the present invention as described above is wt% (hereinafter simply referred to as %).
The explanation is as follows. C: 0.20-0.45% If C exceeds 0.45%, the required strength will be greatly exceeded, so 0.45% was set as the upper limit. Also this C
If it is less than 0.20%, the amount of Mn, etc. added must be large to ensure the required strength, which is economically disadvantageous, so 0.20% is set as the lower limit. Si: 0.01-1.5% Si is an element necessary as a deoxidizing agent or to increase strength, but if it exceeds 1.5%, a structure that is unfavorable in terms of toughness may appear, and if it is less than 0.01%, Since the above-mentioned effects were insufficient, the content was set at 0.01 to 1.5%. Mn: 0.8 to 2.0% To ensure strength, it is necessary that Mn be 0.8% or more, and this was set as the lower limit. Moreover, if it exceeds 2.0%, a structure that is unfavorable in terms of toughness may appear, so the upper limit is set at 2.0%. V: 0.01 to 0.20% V is an element necessary to increase strength through precipitation hardening, and for this purpose, it must be at least 0.01%. On the other hand, exceeding 0.20% is disadvantageous in terms of economy and effectiveness, so this was set as the upper limit. Ti: 0.003~0.010%. Ti is the most important element in the present invention,
In order to improve fatigue resistance properties, the content should be 0.003% or more, and the upper limit should be 0.010%. i.e. 0.003%
If it is less than 0.010%, the austenite grains cannot be refined and the fatigue resistance deteriorates, and if it exceeds 0.010%, the austenite grains cannot be refined.
Both the size and amount of TiN become large, and the fatigue resistance deteriorates. N: 0.2<Ti/N<2.5 N forms a nitride with V and is an element necessary for precipitation strengthening, but when Ti/N>2.5, the amount of N that combines with V becomes too small due to the formation of TiN, making it difficult to obtain the required strength. I can't do it. Further, when Ti/N<0.2, the formation of TiN is too small and the necessary characteristics cannot be obtained. From these relationships,
It is necessary to specify the range of N as 0.2<Ti/N<2.5. Maximum size of TiN inclusions: 7.5 μm or less The reason for keeping the maximum size of TiN inclusions to 7.5 μm or less is 5 μm, which is considered to be the starting point of fatigue.
This is to greatly suppress the number of excess TiN (per mm2 ) and improve fatigue resistance. In other words, this relationship is as shown in Figure 2, and by setting the maximum size of TiN to 7.5 μm or less, the number of TiNs exceeding 5 μm can be reduced to 1 to 2 pieces/mm 2 or less, improving fatigue resistance. can be improved sufficiently. Regarding specific manufacturing examples of products according to the present invention,
The results are shown below along with comparative examples. Production Example 1 Invention steel No. 1 having the chemical composition shown in Table 1 below.
3, 4 and comparative steels No. 1, 2, 5, and 6 were melted in a 150 kg atmospheric melting furnace and rolled into a 60 mm thick plate.
【表】【table】
【表】
これらの鋼板は1200℃に加熱し、３バスで30mm
厚まで圧延する熱間鍛造をシミユレーシヨンした
圧延を行つたものを供試材とした。
圧延ままで、圧延方向の板厚中心から引張、疲
労試験片を採取し、引張はJIS4号（平行部14mm
φ、標点距離50mm）、疲労は小野式回転曲げ試片
（平行部10mmφ）を用いた。
これらの試験結果は次の第２表に示す通りであ
る。[Table] These steel plates were heated to 1200℃ and heated to 30mm in 3 baths.
The test material was rolled to simulate hot forging to a thickness. Tensile and fatigue test specimens were taken from the center of the sheet thickness in the rolling direction while still being rolled.
φ, gauge length 50 mm), and an Ono type rotary bending specimen (parallel part 10 mm φ) was used for fatigue. The results of these tests are shown in Table 2 below.
【表】
然して疲労については疲労限度比（疲労限／引
張強さ）で整理し、Ti量との関係を示すと第１
図の如くである。即ちこの第１図から理解される
ようにTiが0.003〜0.010％で耐疲労特性が大きく
改善されている。これは前記した第２図のように
Ti＞0.010％ではTiNの最大サイズが7.5μmを超
えてしまい、結果として5μm超えのTiNの数が増
加し耐疲労特性が劣化すること、および第３図に
示すようにTi＜0.003％ではオーステナイト粒の
微細化が達成できないため、耐疲労特性が劣化す
ることからTiが0.003〜0.010％が最適であること
を示している。
製造例 ２
次の第３表に示す化学成分をもつた本発明鋼Ａ
および比較鋼Ｂを５トン真空溶解炉で溶製した。[Table] However, regarding fatigue, if we organize it by the fatigue limit ratio (fatigue limit/tensile strength) and show the relationship with Ti content, the first
As shown in the figure. That is, as understood from FIG. 1, fatigue resistance is greatly improved when Ti is 0.003 to 0.010%. This is as shown in Figure 2 above.
When Ti > 0.010%, the maximum size of TiN exceeds 7.5 μm, and as a result, the number of TiN larger than 5 μm increases, deteriorating the fatigue resistance. This shows that the optimal Ti content is 0.003 to 0.010% because fatigue resistance deteriorates because grain refinement cannot be achieved. Production Example 2 Invention steel A having the chemical composition shown in Table 3 below
and Comparative Steel B were melted in a 5-ton vacuum melting furnace.
【表】
鋼Ａは連続鋳造で、又鋼Ｂは鋼塊として造塊
し、その後前記した製造例１と同様の方法で試験
片を作成し、試験を行つた結果は次の第４表に示
す如くであるが、TiN介在物の最大サイズが
7.5μm以下である本発明鋼Ａのものが耐疲労特性
において優れていることが明かである。[Table] Steel A was continuously cast, and Steel B was ingot-formed as a steel ingot. Test pieces were then prepared in the same manner as in Production Example 1 above, and the results of the tests are shown in Table 4 below. As shown, the maximum size of TiN inclusions is
It is clear that the steel A of the present invention, which has a diameter of 7.5 μm or less, has excellent fatigue resistance.
【表】
「発明の効果」
以上説明したような本発明によるときは、熱間
鍛造後の熱処理を省略できることは勿論、耐疲労
特性において優れ、更には被削性についてもTi
が上記のような範囲内では問題がないことになり
自動車部品等の素材として好適な鋼を提供し得る
ものであつて、工業的にその効果の大きい発明で
ある。[Table] "Effects of the Invention" According to the present invention as explained above, heat treatment after hot forging can be omitted, and fatigue resistance is excellent, and machinability is also improved compared to Ti.
However, within the above range, there is no problem, and it is possible to provide steel suitable as a material for automobile parts, etc., and this invention is industrially highly effective.
図面は本発明の技術的内容を示すものであつ
て、第１図はTi量と疲労限度比との関係を示し
た図表、第２図はTi量とTiN最大サイズおよび
5μm超TiNの数の関係を示した図表、第３図は加
熱温度とオーステナイト粒径との関係を示した図
表である。
The drawings show the technical contents of the present invention, and Figure 1 is a chart showing the relationship between Ti content and fatigue limit ratio, and Figure 2 is a chart showing the relationship between Ti content and TiN maximum size and
Figure 3 is a diagram showing the relationship between the number of TiN particles larger than 5 μm, and Figure 3 is a diagram showing the relationship between heating temperature and austenite grain size.
Claims (1)
Mn：0.8〜2.0wt％、Ｖ：0.01〜0.20wt％、Ti：
0.003〜0.010wt％を含有すると共にＮを下式の関
係を満足するように含有し、残部がFeおよび不
可避的不純物から成り、且つTiN介在物の最大
サイズが7.5μm以下であることを特徴とする耐疲
労特性の優れた熱間鍛造用非調質鋼。 0.2＜Ti／Ｎ＜2.5[Claims] 1 C: 0.20 to 0.45 wt%, Si: 0.01 to 1.5 wt%,
Mn: 0.8-2.0wt%, V: 0.01-0.20wt%, Ti:
It contains 0.003 to 0.010 wt% and N in a manner that satisfies the relationship of the following formula, the remainder consists of Fe and unavoidable impurities, and the maximum size of TiN inclusions is 7.5 μm or less. Non-thermal steel for hot forging with excellent fatigue resistance. 0.2<Ti/N<2.5
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP889986A JPS62167855A (en) | 1986-01-21 | 1986-01-21 | Unrefined steel for hot forging having superior fatigue resistance |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP889986A JPS62167855A (en) | 1986-01-21 | 1986-01-21 | Unrefined steel for hot forging having superior fatigue resistance |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS62167855A JPS62167855A (en) | 1987-07-24 |
| JPH0361748B2 true JPH0361748B2 (en) | 1991-09-20 |
Family
ID=11705525
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP889986A Granted JPS62167855A (en) | 1986-01-21 | 1986-01-21 | Unrefined steel for hot forging having superior fatigue resistance |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS62167855A (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0649945B2 (en) * | 1987-10-14 | 1994-06-29 | 住友電気工業株式会社 | Diamond-coated hydrogen-brittle metal and method for producing the same |
| JP3241897B2 (en) * | 1993-10-12 | 2001-12-25 | 新日本製鐵株式会社 | Non-heat treated steel for hot forging with excellent tensile strength, fatigue strength and machinability |
-
1986
- 1986-01-21 JP JP889986A patent/JPS62167855A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS62167855A (en) | 1987-07-24 |
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