JPH0355539B2 - - Google Patents
Info
- Publication number
- JPH0355539B2 JPH0355539B2 JP58096947A JP9694783A JPH0355539B2 JP H0355539 B2 JPH0355539 B2 JP H0355539B2 JP 58096947 A JP58096947 A JP 58096947A JP 9694783 A JP9694783 A JP 9694783A JP H0355539 B2 JPH0355539 B2 JP H0355539B2
- Authority
- JP
- Japan
- Prior art keywords
- product
- cast steel
- strength
- cooling
- products
- 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 - Lifetime
Links
- 229910001208 Crucible steel Inorganic materials 0.000 claims description 45
- 238000001816 cooling Methods 0.000 claims description 26
- 229910045601 alloy Inorganic materials 0.000 claims description 12
- 239000000956 alloy Substances 0.000 claims description 12
- 238000004519 manufacturing process Methods 0.000 claims description 7
- 238000000034 method Methods 0.000 claims description 7
- 239000000126 substance Substances 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 5
- 229910052720 vanadium Inorganic materials 0.000 claims description 4
- 229910052782 aluminium Inorganic materials 0.000 claims description 3
- 229910052748 manganese Inorganic materials 0.000 claims description 2
- 229910052750 molybdenum Inorganic materials 0.000 claims description 2
- 229910052759 nickel Inorganic materials 0.000 claims description 2
- 239000000047 product Substances 0.000 description 67
- 238000010438 heat treatment Methods 0.000 description 14
- 238000010791 quenching Methods 0.000 description 12
- 230000000694 effects Effects 0.000 description 11
- 230000000171 quenching effect Effects 0.000 description 11
- 238000005496 tempering Methods 0.000 description 11
- 238000005266 casting Methods 0.000 description 8
- 230000007423 decrease Effects 0.000 description 7
- 229910000831 Steel Inorganic materials 0.000 description 6
- 238000005242 forging Methods 0.000 description 6
- 239000010959 steel Substances 0.000 description 6
- 238000010586 diagram Methods 0.000 description 5
- 238000011282 treatment Methods 0.000 description 5
- 238000009826 distribution Methods 0.000 description 4
- 238000001556 precipitation Methods 0.000 description 4
- 238000004881 precipitation hardening Methods 0.000 description 4
- 229910001566 austenite Inorganic materials 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 3
- 238000010276 construction Methods 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 229910000859 α-Fe Inorganic materials 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229920002165 CarbonCast Polymers 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000003610 charcoal Substances 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 230000003009 desulfurizing effect Effects 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 238000010606 normalization Methods 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 230000003014 reinforcing effect Effects 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 239000002436 steel type Substances 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 238000009864 tensile test Methods 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/02—Hardening by precipitation
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Articles (AREA)
- Heat Treatment Of Steel (AREA)
Description
〈産業上の利用分野〉
この発明は、機械建設をはじめ機械構造用とし
て用いられる高強度鋳鋼品の製造方法に関する。
〈従来の技術〉
建設機械をはじめ機械構造用として用いられる
鋳鋼は、一般に“低合金鋳鋼”あるいは“炭素鋳
鋼品”と呼ばれる鋼種が主体となつている。
この種の鋳鋼品に要求される引張強さが60〜70
Kgｆ／mm2以下であれば、鋳造後焼きならしを施す
ことにより、これを満足することが可能である
が、それを越える引張強さ、例えば75Kgｆ／mm2以
上の引張強さを必要とする場合は、更に焼入れ、
焼戻しが必要となり、それだけ製品は高コストに
なる。
更に焼入れ、焼戻しにかかるコストに加え、鋳
鋼品のサイズ（肉厚）が大きくなるに従つてより
高い焼入れ性が要求されるため、これを満足させ
る成分を鋳鋼に添加する必要があり、材料のコス
トも高くなる。
従来、熱間鍛造用棒鋼の処理方法として、錬鋼
にＶを含ませ、熱間鍛造した製品の冷却を放冷よ
りも早目にコントロールし、Ｖによる折出硬化を
利用して焼きならし、或は焼入れ、焼戻しの必要
なく製品の強度を80Kgｆ／mm2に高め得ることは特
開昭56−169723号公報により公知である。
〈発明が解決しようとする課題〉
しかし、合金鋳鋼にＶを含ませて製品を鋳造し
ても、それだけでは強度をＶ入り熱間鍛造製品と
同程度にまで高めることはできない。
即ち、熱間鍛造の場合は、1100〜1200℃、或は
それ以上の温度に加熱して鍛造した製品を、その
鍛造温度から常温に冷却する際、その冷却速度は
自由にコントロールすることができる。しかし、
鋳造では合金鋳鋼の溶湯を鋳型に注入し、冷却し
て凝固するまで製品は鋳型の中にある。従つて、
鋳型の中の製品の冷却速度をコントロールするこ
とは実際上、不可能である。そして、假に放冷よ
りも早い冷却速度で冷却を行なうと、Ｖの析出効
果により高強度が得られるにしても製品の組織は
早い冷却速度によつて同一方向に揃い、脆くなつ
て所望の製品にはならない。
〈課題を解決するための手段〉
そこで本発明は、合金鋳鋼中に同様にＶを含ま
せ、Ｖの析出硬化を利用して焼きならし、或は焼
入れ、焼戻しを行なうことなく引張強さが60〜70
Kgｆ／mm2を越える、例えば75Kgｆ／mm2以上の高強
度鋳鋼品を安価に製造することを課題として研究
の結果、化学成分に適切に定め、一連の独特な処
理手順を踏むことで鋳造によつても上記高強度の
製品が得られることを見出したもので、機械構造
用高強度鋳鋼品の製造方法として、
Ｃ：0.30〜0.55％、Si：0.40〜0.80％、Mn：
1.00〜1.60％、Ｖ：0.07〜0.25％、Al：0.02〜0.08
％、Ｐ：0.04％以下、Ｓ：0.10％以下であつて、
CE＝Ｃ＋Mn／６＋Cr＋Mo＋Ｖ／５＋Ni＋Cu／＋15
としてCE値0.6以上の化学成分を持つ合金鋳鋼に
依り製品を鋳造し、その製品を常温に冷却し鋳仕
上げ加工後、870〜1000℃の温度範囲で加熱処理
した後、冷却速度５〜100℃／分で冷却すること
を特徴とする。
尚、上記合金鋳鋼は0.30％以下のCr、0.20％以
下のMo、0.30％以下のNi、0.40％以下のCuのう
ち少なくとも一種、又は二種以上を更に含有して
もよい。
〈実施例〉
合金鋳鋼中のＣは鋳鋼品の引張強さを高め、更
にＶ、Cr等との炭化分を形成することによりマ
トリツクスの強化を図る上で、必要な元素である
が、0.30％未満では強度が不足し、0.55％を越え
ると炭化物の過剰な析出により必要以上に硬度が
増し、靭性が低下するとともに溶接上好ましくな
い。又、Siは強力な脱酸剤としての効果ととも
に、空冷後のマトリツクスのフエライトを強化す
る上でも有効であるが、0.40％未満では脱酸、強
度確保の上で懸念があり、また0.80％を越える
と、靭性が低下するとともに被切削性の上でも好
ましくない。Mnは脱硫剤、脱酸剤としての効果
を有するとともに、フエライト強化による強度ア
ツプの面でも有効な元素であるが、1.00％未満で
は強度が不足し、又1.60％を越えると、被切削性
が著しく損なわれるとともに、冷却時に質量効果
による内外の硬さの不均一を生ずる原因となる。
Ｖはこの発明による鋳鋼品の加熱、冷却処理にお
いて、炭．窒化物を形成し、これにより強度の増
加を図る上で極めて有効な元素であるが、0.07％
未満では強度が不足し、0.25％を越えると強度上
昇に伴う靭性低下が生ずるとともに、材料コスト
も高くなる。
一方、Alは脱酸効果と、結晶粒を微細化させ
る効果を有するが、0.02％未満ではその効果が乏
しく、0.08％を越えると増量効果がないばかり
か、AlN形成によりVNの析出を阻害する。
又、Ｐは有害不純物であり、0.04％越えると鋳
鋼に好ましくない影響が表われる。Ｓは一般には
有害不純物として扱われているが、被切削性の改
善を目的として添加する場合を考慮してその上限
を0.10％とした。
更にCrは一般に機械的性質の広汎な改善に有
効な元素として知られているが、この発明では特
に添加しなくてもよく、強度レベルの調整用とし
て加える場合を考え、上限を0.30％とした。又、
以上の化学成分以外にNi、Moはフエライトを強
化する元素と知られて居り、これらを加えること
もできるが、本発明にとつては必須の元素ではな
いと共に、過剰の添加は製造コストを引き上げる
ことになる。更にCuも特に添加しなくてもよい
が、鋼屑を循環的に使用する結果として0.4％以
下含まれる可能性がある。
尚、
CE＝Ｃ＋Mn／６＋Cr＋Mo＋Ｖ／５＋Ni＋Cu／＋15
とした場合、CE値を0.6以上としたのは、CE値が
0.6未満であると、所定の機械的性質を有する鋳
鋼品が得られないためである。
又、以上のような化学成分の合金鋳鋼を870〜
1000℃又はA3変態点以上1000℃以下の温度範囲
で加熱処理を行なうのは、Ｖがオーステナイトに
固溶し、析出効果を生むためと、結晶の微粒化と
組織の改善のためであり、加熱温度は、普通鋳鋼
品の焼きならし温度（約850℃）よりも高く、Ｃ
量に応じて完全にオーステナイト領域となるよう
にその下限を定め、又上限の1000℃は鋳鋼品の熱
衝撃性と、それ以上の温度に加熱すると結晶粒の
粗大化による靭性の低下が懸念されること、及び
通常の加熱装置の能力を考慮して定める。
この加熱処理は十分にオーステナイトに固溶す
るのに必要な時間、行なうが、この時間は製品の
質量により大きく変動するため、実際の加熱時間
は個々の製品により定めなければならない。
又、加熱後の冷却は５〜100℃／分の冷却速度
で行なう。これは充分にＶの炭窒化物を析出させ
るためであるが、通常の機械構造部品では上記の
冷却速度は空冷により充分に達成することができ
る。
別表及び図面第１図はCE値と加熱処理を施し
た鋳鋼品の機械的性質との関係を示すもので、別
表においてサンプルNo.１〜No.３はＶ添加のCE値
0.6未満の比較製品、サンプルNo.１〜No.14はＶ無
添加のJIS SCMn 3A、サンプルNo.４〜No.９は本
発明による製品であり、又表中、機械的性質の下
段（ ）内は加熱処理をしない鋳放し（as cast）
でのデータを示す。
そして別表及び第１図によれば、Ｖ添加、CE
値0.6以上、加熱、冷却処理の三条件のうちいず
れの条件を欠いても所定の機械的性質のものを得
ることができないのに対し、以上の条件のすべて
満足する本発明による製品は引張強さ、耐力、伸
び、硬さ等の機械的性質において満足すべきもの
を得ることができた。
<Industrial Application Field> The present invention relates to a method for producing high-strength cast steel products used for machine construction and other machine structures. <Prior Art> Cast steel used for machine structures such as construction machinery is generally made up of steel types called "low alloy cast steel" or "carbon cast steel products." The tensile strength required for this type of cast steel product is 60 to 70.
If it is less than Kgf/ mm2 , it is possible to satisfy this by normalizing after casting, but it is necessary to have a tensile strength exceeding that, for example, 75Kgf/ mm2 or more. If necessary, further quenching,
Tempering is required, which increases the cost of the product. Furthermore, in addition to the cost of quenching and tempering, higher hardenability is required as the size (thickness) of the cast steel increases, so it is necessary to add ingredients to the cast steel that satisfy this requirement. The cost will also be higher. Conventionally, as a treatment method for hot-forged steel bars, V is added to the wrought steel, cooling of the hot-forged product is controlled to be faster than cooling, and normalization is performed using precipitation hardening caused by V. Alternatively, it is known from JP-A-56-169723 that the strength of the product can be increased to 80 Kgf/mm 2 without the need for quenching or tempering. <Problems to be Solved by the Invention> However, even if a product is cast by incorporating V into alloy cast steel, the strength cannot be increased to the same level as a V-containing hot forged product. In other words, in the case of hot forging, when a product that has been heated and forged to a temperature of 1100 to 1200°C or higher is cooled from the forging temperature to room temperature, the cooling rate can be freely controlled. . but,
In casting, molten alloy cast steel is poured into a mold, and the product remains in the mold until it cools and solidifies. Therefore,
It is virtually impossible to control the cooling rate of the product in the mold. Furthermore, if cooling is performed at a faster cooling rate than when left to cool, even though high strength can be obtained due to the precipitation effect of V, the structure of the product will be aligned in the same direction due to the fast cooling rate, and the product will become brittle and not as desired. It will not become a product. <Means for Solving the Problems> Therefore, the present invention similarly includes V in alloy cast steel and utilizes precipitation hardening of V to increase tensile strength without normalizing, quenching, or tempering. 60-70
As a result of research aimed at producing high-strength cast steel products with a strength exceeding Kgf/mm 2 , for example 75 Kgf/mm 2 or more, we found that by appropriately determining the chemical composition and following a series of unique processing steps, We have found that the above-mentioned high-strength products can be obtained even if the above-mentioned methods are used, and as a manufacturing method for high-strength cast steel products for machine structures, we use C: 0.30 to 0.55%, Si: 0.40 to 0.80%, Mn:
1.00~1.60%, V: 0.07~0.25%, Al: 0.02~0.08
%, P: 0.04% or less, S: 0.10% or less, and a product is cast using alloy cast steel having a chemical composition of CE = C + Mn / 6 + Cr + Mo + V / 5 + Ni + Cu / + 15 and a CE value of 0.6 or more, and the product is heated to room temperature. After cooling and casting finishing, heat treatment is performed at a temperature range of 870 to 1000°C, and then cooling is performed at a cooling rate of 5 to 100°C/min. The alloy cast steel may further contain at least one or more of 0.30% or less Cr, 0.20% or less Mo, 0.30% or less Ni, and 0.40% or less Cu. <Example> C in alloy cast steel is a necessary element to increase the tensile strength of cast steel products and further strengthen the matrix by forming carbonized components with V, Cr, etc., but at 0.30%. If it is less than 0.55%, the strength will be insufficient, and if it exceeds 0.55%, the hardness will increase more than necessary due to excessive precipitation of carbides, the toughness will decrease, and this is not desirable for welding. In addition, Si is effective as a strong deoxidizing agent and is also effective in strengthening the ferrite in the matrix after air cooling, but if it is less than 0.40%, there are concerns about deoxidizing and ensuring strength. If it exceeds this, the toughness decreases and it is also unfavorable in terms of machinability. Mn is effective as a desulfurizing agent and a deoxidizing agent, and is also effective in increasing strength by reinforcing ferrite, but if it is less than 1.00%, the strength will be insufficient, and if it exceeds 1.60%, machinability will decrease. This results in significant damage and causes non-uniform hardness between the inside and outside due to the mass effect during cooling.
V is charcoal in the heating and cooling treatment of cast steel products according to the present invention. It is an extremely effective element in forming nitrides and thereby increasing strength, but at 0.07%
If it is less than 0.25%, the strength will be insufficient, and if it exceeds 0.25%, the toughness will decrease as the strength increases, and the material cost will also increase. On the other hand, Al has a deoxidizing effect and an effect of refining crystal grains, but if it is less than 0.02%, the effect is poor, and if it exceeds 0.08%, it not only has no effect of increasing the amount of aluminum, but also inhibits the precipitation of VN by forming AlN. . Furthermore, P is a harmful impurity, and if it exceeds 0.04%, it will have an unfavorable effect on cast steel. Although S is generally treated as a harmful impurity, the upper limit was set at 0.10% in consideration of the case where S is added for the purpose of improving machinability. Furthermore, although Cr is generally known as an element effective in widely improving mechanical properties, in this invention it does not need to be added, and the upper limit was set at 0.30% considering the case where it is added to adjust the strength level. . or,
In addition to the above chemical components, Ni and Mo are known to be elements that strengthen ferrite, and they can be added, but they are not essential elements for the present invention, and excessive addition increases manufacturing costs. It turns out. Further, Cu does not need to be particularly added, but as a result of cyclical use of steel scraps, it may be contained at 0.4% or less. In addition, when CE=C+Mn/6+Cr+Mo+V/5+Ni+Cu/+15, the CE value is set to 0.6 or more because the CE value is
This is because if it is less than 0.6, a cast steel product having predetermined mechanical properties cannot be obtained. In addition, alloy cast steel with the above chemical composition is made from 870~
The reason for heat treatment at 1000℃ or above the A3 transformation point and below 1000℃ is to dissolve V into austenite and produce a precipitation effect, and to refine the crystal grains and improve the structure. The heating temperature is higher than the normalizing temperature of ordinary cast steel products (approximately 850℃), and C
The lower limit is set so that it becomes completely austenite depending on the amount of steel, and the upper limit of 1000℃ is concerned about the thermal shock resistance of the cast steel product, and heating to a higher temperature may cause a decrease in toughness due to coarsening of crystal grains. It is determined by taking into account the actual heating conditions and the capacity of ordinary heating equipment. This heat treatment is carried out for a period of time necessary to sufficiently form a solid solution in austenite, but since this time varies greatly depending on the mass of the product, the actual heating time must be determined for each individual product. Further, cooling after heating is performed at a cooling rate of 5 to 100°C/min. This is to sufficiently precipitate V carbonitride, but for ordinary mechanical structural parts, the above cooling rate can be sufficiently achieved by air cooling. The attached table and Figure 1 of the drawing show the relationship between the CE value and the mechanical properties of heat-treated cast steel products.
Comparative products with less than 0.6, Samples No. 1 to No. 14 are JIS SCMn 3A without V additive, Samples No. 4 to No. 9 are products according to the present invention, and in the table, the lower row of mechanical properties ( ) Inside is as cast without heat treatment
Showing the data. According to the attached table and Figure 1, V addition, CE
While it is not possible to obtain the desired mechanical properties without any one of the three conditions of a value of 0.6 or higher, heating, and cooling treatment, the product according to the present invention that satisfies all of the above conditions has tensile strength. Satisfactory mechanical properties such as strength, yield strength, elongation, and hardness were obtained.
【表】【table】
【表】
第２図は本発明による製品及びそれ以外の方法
による製品の引張り強度を80Kgｆ／mm2程度にまで
向上させる手段の相違をわかり易く示した比較図
である。
図中、含Ｖ熱間鍛造製品とは従来例に挙げた特
開昭56−169723号公報による製品のことで、熱間
鍛造により成形した製品を、鍛造温度から常温に
冷却する冷却速度をコントロールすることにより
Ｖの析出硬化により冷却時点で約80Kgｆ／mm2の引
張り強度を有する。
又、Ｖを含有しない普通鋼の熱間鍛造製品は、
鍛造して冷却することにより引張り強度は高々60
Kgｆ／mm2であるが、焼入れ、焼戻しを行なうと80
Kgｆ／mm2程度にまで増加させることができる。
Ｖを含有しない普通鋳鋼は鋳造製品の引張り強
度は鋳造後の冷却状態で約50Kgｆ／mm2、これに通
常の焼きならし処理を行なうと若干の強度増加は
期待できるものの例えば60Kgｆ／mm2程度であり、
約80Kgｆ／mm2以上にするには更に焼入れ、焼戻し
を行なう必要がある。
これに対し、本発明による含Ｖ鋳造製品の引張
り強度は鋳造後の冷却状態で約50Kgｆ／mm2である
が、約900℃の加熱処理を行ない、冷却すると80
Kgｆ／mm2に向上し、この場合は焼入れ、焼戻しは
必要としない。
トラクターの覆帯駆動用フロント・アイドラ支
持体である第３図に示すリコイルヨークを本発明
の製造方法と、一般鋳鋼（JIS SCMo ３）を焼
入れ、焼戻しする方法とで製造し、表面硬さ、及
び断面硬さ分布、引張り特性、疲労特性を比較し
た所、次のような結果が得られた。
表面硬さ、及び断面硬さ分布
第４図は本発明製品と、焼入れ、焼戻した一
般鋳鋼製品の第３図のハツチング部分から採取
したテストピースの断面硬さ分布図であつて、
この図から明らかなように表面硬さは本発明製
品と一般鋳鋼製品は同レベルであるが、一般鋳
鋼製品では芯部程、硬さが低下している。これ
は材料の焼入れ性と、製品の質量効果の制約に
基因する。これに対して、本発明製品ではバナ
ジウム炭窒化物の析出硬化が５〜100℃／分と
いう比較的広範囲の冷却条件下で起きるため製
品の芯部まで、つまり製品の断面のどの位置で
も表面硬さと同程度の高い硬さが均一に得られ
ている。
この事実は、一般鋳鋼製で、焼入れ、焼戻し
を行なつても芯部まで充分に焼きが入らず、強
度不足が懸念される製品は、本発明によつて製
造した方が質量効果が余り受けず、芯部まで強
化することができるので好ましいことを強く示
唆するものであり、後述する引張り特性及び疲
労特性のデータもこれを裏付けている。
引張り特性[Table] Fig. 2 is a comparative diagram that clearly shows the difference in the means for improving the tensile strength of products according to the present invention and products produced by other methods to about 80 Kgf/mm 2 . In the figure, the V-containing hot forged product is the product according to Japanese Patent Application Laid-Open No. 169723, which is cited as a conventional example, and the cooling rate of the product formed by hot forging is controlled from the forging temperature to room temperature. As a result, it has a tensile strength of about 80 Kgf/mm 2 at the time of cooling due to precipitation hardening of V. In addition, hot forged products of ordinary steel that do not contain V,
By forging and cooling, the tensile strength is at most 60
Kgf/ mm2 , but if quenched and tempered, it will be 80
It can be increased to about Kgf/ mm2 . The tensile strength of ordinary cast steel that does not contain V is approximately 50 Kgf/mm 2 in the cooled state after casting, and although a slight increase in strength can be expected by normalizing it, for example, about 60 Kgf/mm 2 and
In order to achieve a value of about 80 kgf/mm 2 or more, it is necessary to further quench and temper. On the other hand, the tensile strength of the V-containing cast product according to the present invention is approximately 50 Kgf/mm 2 in the cooled state after casting, but it is 80 kgf/mm 2 when heat treated at approximately 900°C and cooled.
Kgf/mm 2 , and in this case, quenching and tempering are not required. The recoil yoke shown in Fig. 3, which is a front idler support for a tractor's belt drive, was manufactured by the manufacturing method of the present invention and a method of quenching and tempering general cast steel (JIS SCM o 3), and the surface hardness was improved. , cross-sectional hardness distribution, tensile properties, and fatigue properties, the following results were obtained. Surface hardness and cross-sectional hardness distribution Figure 4 is a cross-sectional hardness distribution diagram of test pieces taken from the hatched area in Figure 3 of the product of the present invention and a general cast steel product that has been quenched and tempered.
As is clear from this figure, the product of the present invention and the general cast steel product have the same surface hardness, but the hardness of the general cast steel product decreases toward the core. This is due to the hardenability of the material and the constraints on the mass effect of the product. In contrast, in the product of the present invention, precipitation hardening of vanadium carbonitride occurs under a relatively wide range of cooling conditions of 5 to 100°C/min, so surface hardness can occur up to the core of the product, that is, at any position on the cross section of the product. A high level of hardness comparable to that of This fact indicates that products made of general cast steel that are not sufficiently hardened to the core even after quenching and tempering, and where there are concerns about insufficient strength, are better manufactured using the present invention because of the mass effect. This strongly suggests that it is preferable because it can be strengthened to the core, and the data on tensile properties and fatigue properties described below also support this. tensile properties
【表】
上記で述べた通り、両製品の表面硬さは同
レベルであつても、一般鋳鋼製品は芯部へ行く
程硬さは低下する傾向があるので表面から少し
内部に入つた部分から採取した引張り試験片で
は本発明製品の方がはるかに高い引張り強さを
示した。
又、伸び、絞りといつた延性面からの評価に
おいても本発明製品は一般鋳鋼製品に対し遜色
はない。これはＶが含有の非調質鍛造鋼製品の
鍛造温度に較べると低い900℃という比較的低
温の加熱温度により組織が微細化しているため
である。
疲労特性
実際の負荷状態よりも更に苛酷な条件として
前記第３図で矢印の位置に４トンの荷重を30
回／分、繰返して加え、疲労破壊起点から破断
するまでのサイクル数を夫々５個宛、測定し、
その測定値と、それを基にワイブル解析して算
出したB10ライフ、B50ライフ（10％、50％が
破断に至るまでのサイクル数）を下表に示す。[Table] As mentioned above, even though the surface hardness of both products is at the same level, the hardness of general cast steel products tends to decrease as you go towards the core. The tensile test specimens taken showed that the product of the present invention had much higher tensile strength. Furthermore, the products of the present invention are comparable to general cast steel products in terms of ductility such as elongation and reduction of area. This is because the structure is refined due to the relatively low heating temperature of 900°C, which is lower than the forging temperature of non-thermal forged steel products containing V. Fatigue characteristics As a condition even more severe than the actual load condition, a load of 4 tons is applied at the position of the arrow in Figure 3 above.
Repeat the application times/minute, and measure the number of cycles from the fatigue fracture origin to rupture for each of 5 pieces,
The table below shows the measured values and the B10 life and B50 life (number of cycles until 10% and 50% breakage) calculated by Weibull analysis based on them.
【表】
破壊サイクル数を比較して明らかなように本
発明製品は一般鋳鋼製品に比し疲労特性は格段
と優れ、B10ライフ、B50ライフにおいても本
発明製品は一般鋳鋼製品の1.3倍、1.7倍も優れ
た強度を示した。
本発明による合金鋳鋼はＶを含ませる事と、
鋳仕上げ後の加熱冷却処理をすることのため、
普通鋳鋼よりもコスト高になるが、普通鋳鋼の
製品の引張り強度を80Kgｆ／mm2に向上するには
焼きならし処理、焼入れ、焼戻し処理を要する
コストを考慮すると、本発明による方法は材料
コストが僅かに高くても、焼きならし処理、焼
入れ、焼戻し処理を行なう必要がない分、現状
で1/3程度のコスト低減が計れる製品を提供す
ることができる。
〈発明の効果〉
以上要するに、この発明によれば前述のような
化学成分の合金鋳鋼で製品を鋳造し、鋳造後、そ
の製品を特殊に加熱した後冷却することによつ
て、
引張り強さ……735MPa（75Kgｆ／mm2）以上
耐力（0.2％永久歪）……490MPa（50Kgｆ／mm2）
以上
伸び……８％以上
硬さ（前断面）……BHN220以上
の機械的性質を有する鋳鋼品を得ることができ
る。
そして、この機械的性質は建設機械等の機械構
造用の高強度鋳鋼品として充分に満足できるもの
であり、しかもこの発明では通常の焼入れ、焼戻
しは不要なため、廉価に製造して提供することが
できる。[Table] As is clear from the comparison of the number of fracture cycles, the fatigue properties of the products of the present invention are significantly superior to those of general cast steel products, and the fatigue properties of the products of the present invention are 1.3 times and 1.7 times higher than those of general cast steel products in terms of B10 life and B50 life. It showed double the strength. The alloy cast steel according to the present invention contains V,
Due to heating and cooling treatment after casting finish,
Although the cost is higher than that of ordinary cast steel, considering the cost of normalizing, quenching, and tempering treatments to improve the tensile strength of ordinary cast steel products to 80 kgf/ mm2 , the method according to the present invention reduces the material cost. Even if the value is slightly higher, since there is no need to perform normalizing, quenching, and tempering, it is possible to provide a product that can reduce the cost by about 1/3 of the current cost. <Effects of the Invention> In summary, according to the present invention, by casting a product with alloy cast steel having the above-mentioned chemical composition, and after casting, the product is specially heated and then cooled, the tensile strength... ...735MPa (75Kgf/mm 2 ) or more proof stress (0.2% permanent set)...490MPa (50Kgf/mm 2 )
It is possible to obtain a cast steel product having mechanical properties of elongation of 8% or more and hardness (front section) of BHN220 or more. This mechanical property is sufficiently satisfactory as a high-strength cast steel product for machine structures such as construction machinery, and since the present invention does not require normal quenching and tempering, it can be manufactured and provided at a low cost. I can do it.
第１図は本発明による製品と比較製品のCE値
（炭素当量）と引張り強度（T.S）、耐力（Y.S）、
伸び（El）等の機械的性質の関係曲線図表、第２
図は本発明による製品、及びそれ以外の方法によ
る製品の強度向上手段を示す比較図、第３図は本
発明による製品と、一般鋳鋼を焼入れ、焼戻しし
て製造した製品の機械的強度を比較するために製
造したリコイルヨークの立面図、第４図は第３図
のリコイルヨークのハツチング部分から採取した
テストピースの断面の硬さ分布図である。
Figure 1 shows the CE value (carbon equivalent), tensile strength (TS), yield strength (YS), and
Relationship curve diagram of mechanical properties such as elongation (El), 2nd
The figure is a comparison diagram showing the strength improvement means of the product according to the present invention and the product by other methods. Figure 3 is a comparison of the mechanical strength of the product according to the present invention and a product manufactured by quenching and tempering general cast steel. FIG. 4 is an elevational view of a recoil yoke manufactured for the purpose of the present invention, and FIG. 4 is a hardness distribution diagram of a cross section of a test piece taken from the hatched portion of the recoil yoke shown in FIG.
Claims (1)
1.00〜1.60％、Ｖ：0.07〜0.25％、Al：0.02〜0.08
％、Ｐ：0.04％以下、Ｓ：0.10％以下であつて、 CE＝Ｃ＋Mn／６＋Cr＋Mo＋Ｖ／５＋Ni＋Cu／＋15 としてCE値0.6以上の化学成分を持つ合金鋳鋼に
依り製品を鋳造し、その製品を常温に冷却し鋳仕
上げ加工後、870〜1000℃の温度範囲で加熱処理
した後、冷却速度５〜100℃／分で冷却すること
を特徴とする機械構造用高強度鋳鋼品の製造方
法。 ２ 特許請求の範囲第１項に記載の機械構造用高
強度鋳鋼品の製造方法において、合金鋳鋼は0.30
％以下のCr、0.20％以下のMo、0.30％以下のNi、
0.40％以下のCuのうち少なくとも一種、又は二種
以上を更に含有する機械構造用高強度鋳鋼品の製
造方法。[Claims] 1 C: 0.30-0.55%, Si: 0.40-0.80%, Mn:
1.00~1.60%, V: 0.07~0.25%, Al: 0.02~0.08
%, P: 0.04% or less, S: 0.10% or less, and a product is cast using alloy cast steel having a chemical composition of CE = C + Mn / 6 + Cr + Mo + V / 5 + Ni + Cu / + 15 and a CE value of 0.6 or more, and the product is heated to room temperature. A method for producing a high-strength cast steel product for machine structures, which comprises cooling and finishing, heat-treating at a temperature range of 870 to 1000°C, and cooling at a cooling rate of 5 to 100°C/min. 2. In the method for manufacturing high-strength cast steel products for machine structures as set forth in claim 1, the alloy cast steel has a 0.30
Cr below %, Mo below 0.20%, Ni below 0.30%,
A method for producing a high-strength cast steel product for machine structures that further contains at least one or more of Cu at 0.40% or less.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9694783A JPS59226114A (en) | 1983-06-02 | 1983-06-02 | Production of high strength cast steel product used for mechine structure |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9694783A JPS59226114A (en) | 1983-06-02 | 1983-06-02 | Production of high strength cast steel product used for mechine structure |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS59226114A JPS59226114A (en) | 1984-12-19 |
| JPH0355539B2 true JPH0355539B2 (en) | 1991-08-23 |
Family
ID=14178493
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP9694783A Granted JPS59226114A (en) | 1983-06-02 | 1983-06-02 | Production of high strength cast steel product used for mechine structure |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS59226114A (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2625572B2 (en) * | 1990-10-24 | 1997-07-02 | 株式会社クボタ | Heat treatment method for cast steel products |
| CN103469116B (en) * | 2013-08-07 | 2016-03-02 | 安徽蓝博旺机械集团合诚机械有限公司 | A kind of fork-truck steering saves cast steel material |
| CN104120364B (en) * | 2014-08-16 | 2016-02-24 | 西安煤矿机械有限公司 | Modified cast steel of a kind of rocker arm of coal mining machine alloy and preparation method thereof |
| EA201891069A1 (en) * | 2018-05-30 | 2019-12-30 | РЕЙЛ 1520 АйПи ЛТД. | ALLOY CASTING STEEL AND PRODUCTS FROM IT |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS56156717A (en) * | 1980-05-08 | 1981-12-03 | Daido Steel Co Ltd | Manufacture of nonrefined forged parts for automobile |
| JPS56169723A (en) * | 1980-05-28 | 1981-12-26 | Nippon Steel Corp | Treatment of reheating-omit type hot forging bar steel |
-
1983
- 1983-06-02 JP JP9694783A patent/JPS59226114A/en active Granted
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS56156717A (en) * | 1980-05-08 | 1981-12-03 | Daido Steel Co Ltd | Manufacture of nonrefined forged parts for automobile |
| JPS56169723A (en) * | 1980-05-28 | 1981-12-26 | Nippon Steel Corp | Treatment of reheating-omit type hot forging bar steel |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS59226114A (en) | 1984-12-19 |
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