JPH01165721A - Production of wire rod for non-tempered steel bolt - Google Patents
Production of wire rod for non-tempered steel boltInfo
- Publication number
- JPH01165721A JPH01165721A JP32331587A JP32331587A JPH01165721A JP H01165721 A JPH01165721 A JP H01165721A JP 32331587 A JP32331587 A JP 32331587A JP 32331587 A JP32331587 A JP 32331587A JP H01165721 A JPH01165721 A JP H01165721A
- Authority
- JP
- Japan
- Prior art keywords
- wire rod
- rolling
- steel
- under
- strength
- 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.)
- Granted
Links
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 20
- 239000010959 steel Substances 0.000 title claims abstract description 20
- 238000004519 manufacturing process Methods 0.000 title claims description 10
- 238000005096 rolling process Methods 0.000 claims abstract description 24
- 238000001816 cooling Methods 0.000 claims abstract description 14
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 7
- 238000010438 heat treatment Methods 0.000 claims abstract description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 4
- 238000000034 method Methods 0.000 claims description 6
- 238000005482 strain hardening Methods 0.000 abstract description 2
- 229910045601 alloy Inorganic materials 0.000 description 7
- 239000000956 alloy Substances 0.000 description 7
- 239000000463 material Substances 0.000 description 7
- 239000000203 mixture Substances 0.000 description 6
- 238000005491 wire drawing Methods 0.000 description 4
- 239000013078 crystal Substances 0.000 description 3
- 238000000137 annealing Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000009864 tensile test Methods 0.000 description 2
- 238000004804 winding Methods 0.000 description 2
- 229910000746 Structural steel Inorganic materials 0.000 description 1
- 229910001563 bainite Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 150000001721 carbon Chemical class 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
- 230000023556 desulfurization Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 229910001562 pearlite Inorganic materials 0.000 description 1
- 238000004881 precipitation hardening Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
Landscapes
- Heat Treatment Of Steel (AREA)
Abstract
Description
及皿ム■カ It's too late
本発明は非調質鋼ボルト用線材の製造方法に関し、とく
に８Ｔ級のボルトを与えることのできる線材の製造方法
に関する。The present invention relates to a method for manufacturing a wire rod for non-tempered steel bolts, and in particular to a method for manufacturing a wire rod that can provide an 8T class bolt.
一般に鋼ボルトの製造は、３４５Ｇに代表される機械構
造用鋼を線材圧延し、焼鈍により軟化させて伸線しくそ
の間に必要により球状化焼鈍を行なう）、冷間でヘッダ
ー加工および転造を行なったのち、焼入れ焼もどしをす
るという工程に従っで行なわれている。
上記の工程をできるだけ簡略にし、大量のボルトを廉価
に供給するため、熱処理を省略した非調質鋼ボルトの製
造が、種々試みられている。
出願人は、さきに、合金成分のバランスを検討して定め
た特定の組成の鋼を選択された条件下に線材圧延するこ
とにより、７Ｔ級（７０〜８０Ｋｇｆ／ｍ ）から８
Ｔ級（８０〜１００Ｋｇｆ／Ｉｎ！ｒＩ２）のボルトを
非調質で製造する技術を確立し、すでに開示した（特開
昭５９−１０７０６３号）。
この線材からつくったボルトは、ボルトの実用試験であ
る楔引張試験において首下破断がないという利点がある
。
ボルトの強度は、いうまでもなく伸線後の材料の引張強
度により決定される。 ７Ｔ級から８Ｔ級へと、より高
い強度を求める場合は伸線材の強度が高くなるようにす
ればよい。 しかし、伸線した材料の強度が高すぎると
、ボルトへの冷間加工の加工性が低下し、ヘッダー工具
の寿命が短くなって、ボルトのコスト低下という要請に
は、かえって反することになる。
伸線後の材料の強度は、線材圧延後の強度に伸線加工に
よる硬化がプラスされたものである。
従って、非調質鋼ボルトの製造に当っては、線材圧延後
の強度と、伸線後の強度とを、それぞれ適切なレベルに
すべきことになる。Generally, steel bolts are manufactured by rolling a wire rod of mechanical structural steel, such as 345G, softening it through annealing, drawing the wire (with spheroidizing annealing if necessary), and then cold header processing and rolling. The process is then quenched and tempered. In order to simplify the above-mentioned process as much as possible and to supply large quantities of bolts at low cost, various attempts have been made to manufacture non-tempered steel bolts that omit heat treatment. The applicant first studied the balance of alloy components and rolled steel with a specific composition under selected conditions, thereby converting it from 7T class (70 to 80 kgf/m2) to 8.
We have established a technology for manufacturing T-class (80-100 Kgf/In!rI2) bolts without heat refining and have already disclosed it (Japanese Patent Application Laid-open No. 107063/1983). Bolts made from this wire have the advantage of not breaking under the neck in wedge tension tests, which are practical tests for bolts. Needless to say, the strength of the bolt is determined by the tensile strength of the material after wire drawing. If higher strength is desired from 7T class to 8T class, the strength of the drawn wire material should be increased. However, if the strength of the drawn wire material is too high, the workability of cold working into bolts will be reduced, the life of the header tool will be shortened, and this will go against the desire to reduce the cost of bolts. The strength of the material after wire drawing is the strength after wire rolling plus the hardening due to wire drawing. Therefore, in manufacturing non-tempered steel bolts, the strength after wire rod rolling and the strength after wire drawing should be at appropriate levels.
本発明の目的は、上記のような観点から、適切な線材圧
延後の引張強度を有し、かつボルト加工したものは楔引
張試験で首下破断が生じることがないような、非調質鋼
ボルト用線材を提供することにある。
及服五璽メ
（問題点を解決するための手段］
本発明の非調質鋼ボルト用線材の製造方法は、Ｃ：０．
１２〜０．１７％、ｓｒ ：０．１５〜０゜３５％、
Ｍｎ ：１．３〜１．６％、Ｃｒ ：０．２５％以下お
よびＶ：０．０８〜０．１３％を含有し、Ｐ：０．０２
０％以下、Ｓ：０．０１０％以下であって、残部が実質
的にＦｅからなり、次式であらわされる炭素当量
ＣｅＱ＝Ｃ＋Ｓｉ ／７＋Ｍｎ １５＋Ｃｒ ／９十Ｖ
／２
が０．５３〜０．５５の範囲にある鋼を、加熱温度１０
００〜１０５０℃、圧延仕上段階において温度７５０〜
８５０℃、減面率５０％以上の条件で線材圧延し、４．
５〜６．５℃／ ＳｅＣの冷却速度で冷却することから
なる。
冷却速度は、５．０〜６．０℃／ＳｅＣ（７）範囲が好
ましい。 それによって、線材圧延後の引張強度が最適
範囲６５〜７５ Ｋｌ ｆ ／ｍｕ２に入る線材を得る
ことが容易になる。From the above-mentioned viewpoints, the object of the present invention is to create a non-tempered steel that has an appropriate tensile strength after wire rod rolling and that does not cause below-neck fracture in a wedge tension test when bolted. Our objective is to provide wire rods for bolts. (Means for solving the problem) The method for producing a wire rod for non-tempered steel bolts of the present invention is characterized in that C: 0.
12~0.17%, sr: 0.15~0°35%,
Contains Mn: 1.3-1.6%, Cr: 0.25% or less, V: 0.08-0.13%, P: 0.02
0% or less, S: 0.010% or less, the balance substantially consisting of Fe, and the carbon equivalent represented by the following formula: CeQ=C+Si/7+Mn 15+Cr/90V
/2 is in the range of 0.53 to 0.55 at a heating temperature of 10
00~1050℃, temperature 750~ at rolling finishing stage
4. Wire rod rolling at 850°C and area reduction rate of 50% or more.
It consists of cooling at a cooling rate of 5-6.5°C/SeC. The cooling rate is preferably in the range of 5.0 to 6.0°C/SeC(7). Thereby, it becomes easy to obtain a wire rod whose tensile strength after wire rod rolling falls within the optimum range of 65 to 75 Kl f /mu2.
上記した鋼の合金組成は、さきに開示した非調質のボル
ト用線材の合金組成を基礎にして、前記の目的を達成で
きる狭い範囲を選択したものである。 各合金成分につ
いて、組成の限定理由を以下に記す。
Ｃ：０．１２〜０．１７％
ボルトに所要の強度を与えるとともに、加工性と靭性を
高いレベルに保つため、上記の下限および上限を設けた
。
ｓｒ ：０．１５〜０．３５％
脱酸剤としての必要に加えて、基地の固溶強化に役立つ
が、加工性と冷間成形性を考慮して、この範囲にえらん
だ。
Ｍｎ ：１．３〜１．６％
脱酸および脱硫に寄与し、焼入性を高めて適切な強度を
与える。 靭性にとっても有用であるが、過大になると
かえって有害になるので、上記の限定をおいた。
Ｃｒ ：０．２５％以下
焼入性を高めて、鋼に強度を与える。 その効果を適切
なレベルにするためには、上記の限度内で他の合金成分
の与える焼入性との間に調整をはかる必要がある。
ｖ：ｏ、ｏａ〜０．１３％
結晶組織を微細化して靭性を高く保ち、一方、炭窒化物
の析出硬化により強度を高める。
下限は効果の認められる限界であり、上限は強度を適切
なレベルにおくという観点から定めたものである。
Ｐ ：０．０２０％以下、Ｓ：０．０１０％以下これ
らの不純物は、加工性および靭性にとって有害であるか
ら、含有量は少ないほどよく、許容限界としてそれぞれ
上記の値を定めた。
炭素当ＬｉＣｅＱ＝Ｃ＋Ｓｉ ／７＋Ｍｒｌ １５＋Ｃ
ｒ ／９＋Ｖ／２＝０．５３〜０．５５
圧延後の線材に適切な範囲の引張強度を与えるために、
加工条件とともに、この炭素当量条件をみたすことが必
要である。
線材圧延条件：加熱温度１０００〜１０５０℃、圧延仕
上段階において温度７５０〜８５０℃、減面率５０％以
上
圧延に先立つ加熱温度は、■を、その炭窒化物を析出さ
せるためいったん固溶させるという見地からは高くした
いが、結晶粒を微細にするという目的にとっては低い方
がよく、両者の調和点として上記の範囲に定めた。 仕
上段階の温度は、低すぎると加工性や圧延の寸法精度が
低下したり巻取り困難になったりするので、一応のめや
すとして７５０°Ｃの下限を定めた。 上限の８５０℃
は、結晶粒の粗大化を避ける意図で設けたものである。
通常の圧延では下限を下回る仕上温度は考えられず、む
しろ上限を超えないよう冷却する必要がある。 いずれ
にせよ、この種の材料の製造に従来行なわれてきた加工
条件にくらべて、一般に低い温度を採用することがひと
つの特徴である。 減面率５０％以上は、結晶粒の微細
化を所望の程度まで実現するのに必要な条件である。
冷却速度：４．５〜６．５℃／ｓｅｃ 、好ましくは５
．０〜６．０℃／ ＳｅＣ
冷却の過程でフェライト＋パーライト域を通過する時間
を適切にえらぶことによって、所定の強度をもたせる狙
いがある。 ベイナイトの生成を防止するためには上限
を超えない速度の冷却をすべきであり、一方で、ある程
度の焼入れ効果を得るためには下限を下回らない速度で
の冷却が必要である。 このような冷却は、圧延の仕上
温度つまり巻取温度のコントロールと、衝用冷却の風量
調節により実現できる。
［実施例］
第１表に示す合金組成の鋼を溶製し、第２表に示す条件
で圧延および冷却して、直径６．５Ｍの線材とした。
第２表中の仕上前温度とは、圧延の中途で直径１７Ｉｎ
Ｉｒ１の段階における温度である。
直径１７ｍ−＋６．５ｍの圧延の減面率は、８５％であ
る。
各線材の引張強度を測定し、その結果を第２表に併記し
た。
これらの線材から、ヘッダー加工および転造によりボル
トを製造した。 ボルトの引張試験を行なって得た数値
を、やはり第２表に掲げる。 楔形引張試験において、
ボルト首下破断は皆無であった。
及更Ω四男
本発明の製造方法は、注意深く選択された合金組成の鋼
を、従来と異なる低温域で加熱および線材圧延し、コン
トロールされた速度で冷却するという要件の組み合わせ
により、ボルトの材料として有用な非調質鋼ボルト用線
材を得ることに可能にした。
この線材は、ヘッダー加工および転造によりボルトに加
工するのに最適なレベルの引張強度を有し、それから得
られたボルトは、加工硬化を加えて８Ｔ級の強度を確保
し、首下破断を生じることのない、すぐれた製品である
。
このようにして本発明は、高品質のボルトを低いコスト
で提供できる。
特許出願人 大同特殊鋼株式会社
代理人 弁理士 須 賀 総 夫The alloy composition of the steel described above is based on the alloy composition of the non-tempered wire for bolts disclosed above, and is selected within a narrow range that can achieve the above object. The reasons for limiting the composition of each alloy component are described below. C: 0.12 to 0.17% In order to provide the bolt with the required strength and maintain workability and toughness at a high level, the above lower and upper limits were set. sr: 0.15 to 0.35% In addition to being necessary as a deoxidizing agent, it is useful for solid solution strengthening of the matrix, and was selected within this range in consideration of workability and cold formability. Mn: 1.3-1.6% Contributes to deoxidation and desulfurization, improves hardenability and provides appropriate strength. Although it is useful for improving toughness, it can be harmful if it becomes too large, so the above limitations were set. Cr: 0.25% or less Improves hardenability and gives strength to steel. In order to bring the effect to an appropriate level, it is necessary to adjust the hardenability provided by other alloy components within the above limits. v: o, oa ~ 0.13% The crystal structure is refined to maintain high toughness, while the strength is increased by precipitation hardening of carbonitrides. The lower limit is the limit at which the effect is recognized, and the upper limit is determined from the viewpoint of keeping the strength at an appropriate level. P: 0.020% or less, S: 0.010% or less These impurities are harmful to workability and toughness, so the lower the content, the better, and the above values were determined as the allowable limits. Carbon per LiCeQ=C+Si/7+Mrl 15+C
r/9+V/2=0.53-0.55 In order to give the wire after rolling an appropriate range of tensile strength,
It is necessary to satisfy this carbon equivalent condition as well as processing conditions. Wire rolling conditions: heating temperature 1000 to 1050°C, temperature 750 to 850°C in the rolling finishing stage, area reduction rate of 50% or more. From a viewpoint, it is desirable to have a high value, but for the purpose of making crystal grains finer, a lower value is better, and the above range is set as a point of harmony between the two. If the temperature in the finishing step is too low, the workability and dimensional accuracy of rolling will deteriorate, and winding will become difficult, so a lower limit of 750°C was set as a guideline. Upper limit of 850℃
is provided with the intention of avoiding coarsening of crystal grains. In normal rolling, a finishing temperature below the lower limit is unthinkable; rather, it is necessary to cool the material so as not to exceed the upper limit. In any case, one feature is that generally lower temperatures are employed compared to the processing conditions conventionally used to produce this type of material. A reduction in area of 50% or more is a necessary condition to achieve grain refinement to a desired degree. Cooling rate: 4.5-6.5°C/sec, preferably 5
．． 0 to 6.0°C/SeC The aim is to provide a predetermined strength by appropriately selecting the time for passing through the ferrite + pearlite region during the cooling process. In order to prevent the formation of bainite, cooling should be performed at a rate that does not exceed the upper limit, while in order to obtain a certain degree of quenching effect, cooling should be performed at a rate that does not fall below the lower limit. Such cooling can be achieved by controlling the finishing temperature of rolling, that is, the winding temperature, and adjusting the air volume of impulse cooling. [Example] Steel having the alloy composition shown in Table 1 was melted and rolled and cooled under the conditions shown in Table 2 to obtain a wire rod with a diameter of 6.5M.
The pre-finishing temperature in Table 2 refers to the diameter of 17 In in the middle of rolling.
This is the temperature at the Ir1 stage. The area reduction rate for rolling a diameter of 17 m-+6.5 m is 85%. The tensile strength of each wire rod was measured, and the results are also listed in Table 2. Bolts were manufactured from these wire rods by header processing and rolling. The values obtained from the bolt tensile test are also listed in Table 2. In the wedge tensile test,
There were no fractures below the bolt neck. The manufacturing method of the present invention uses a combination of requirements to heat and wire-roll steel with a carefully selected alloy composition at an unconventional low temperature range and cool it at a controlled rate. This made it possible to obtain a wire rod for non-tempered steel bolts that is useful as a material. This wire has an optimal level of tensile strength for processing into bolts through header processing and rolling, and the bolts obtained from it are work-hardened to ensure 8T class strength and prevent below-neck fractures. This is an excellent product that never occurs. In this way, the present invention can provide high quality bolts at low cost. Patent applicant Daido Steel Co., Ltd. Agent Patent attorney Souo Suga
Claims (2)
．３５％、Ｍｎ：１．３〜１．６％、Ｃｒ：０．２５％
以下およびＶ：０．０８〜０．１３％を含有し、Ｐ：０
．０２０％以下、Ｓ：０．０１０％以下であって、残部
が実質的にＦｅからなり、次式であらわされる炭素当量
Ｃｅｑ＝Ｃ＋Ｓｉ／７＋Ｍｎ／５＋Ｃｒ／９＋Ｖ／２ が０．５３〜０．５５の範囲にある鋼を、加熱温度１０
００〜１０５０℃、圧延仕上段階において温度７５０〜
８５０℃、減面率５０％以上の条件で線材圧延し、４．
５〜６．５℃／ｓｅｃの冷却速度で冷却することを特徴
とする非調質鋼ボルト用線材の製造方法。(1) C: 0.12-0.17%, Si: 0.15-0
．． 35%, Mn: 1.3-1.6%, Cr: 0.25%
Contains the following and V: 0.08-0.13%, P: 0
．． 020% or less, S: 0.010% or less, the remainder substantially consists of Fe, and the carbon equivalent Ceq = C + Si / 7 + Mn / 5 + Cr / 9 + V / 2 expressed by the following formula is 0.53 to 0.55 Steel in the range of heating temperature 10
00~1050℃, temperature 750~ at rolling finishing stage
4. Wire rod rolling at 850°C and area reduction rate of 50% or more.
A method for manufacturing a wire rod for non-thermal steel bolts, characterized by cooling at a cooling rate of 5 to 6.5° C./sec.
圧延後の引張強度を６５〜７５Ｋｇｆ／ｍｍ＾２の範囲
とする特許請求の範囲第１項の製造方法。(2) Select a cooling rate of 5.0 to 6.0°C/sec,
The manufacturing method according to claim 1, wherein the tensile strength after rolling is in the range of 65 to 75 Kgf/mm^2.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62323315A JP2658101B2 (en) | 1987-12-21 | 1987-12-21 | Manufacturing method of wire rod for non-heat treated steel bolt |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62323315A JP2658101B2 (en) | 1987-12-21 | 1987-12-21 | Manufacturing method of wire rod for non-heat treated steel bolt |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH01165721A true JPH01165721A (en) | 1989-06-29 |
| JP2658101B2 JP2658101B2 (en) | 1997-09-30 |
Family
ID=18153415
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP62323315A Expired - Lifetime JP2658101B2 (en) | 1987-12-21 | 1987-12-21 | Manufacturing method of wire rod for non-heat treated steel bolt |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2658101B2 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2017170756A1 (en) * | 2016-03-31 | 2017-10-05 | 株式会社神戸製鋼所 | Non-heat-treated wire rod for bolt, non-heat-treated steel wire for bolt, and method for manufacturing same, and non-heat-treated bolt |
| CN109797339A (en) * | 2019-02-28 | 2019-05-24 | 本钢板材股份有限公司 | A kind of tensile strength >=960MP martensite Micro Alloying high-strength steel and its manufacturing method |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5356120A (en) * | 1976-11-02 | 1978-05-22 | Nippon Steel Corp | Production of high tensile bolt for low temperature service |
| JPS59107063A (en) * | 1982-12-10 | 1984-06-21 | Daido Steel Co Ltd | Wire rod for bolt and its production |
| JPS61284554A (en) * | 1985-06-12 | 1986-12-15 | Kobe Steel Ltd | Alloy steel for unrefined bolt or the like having superior toughness and steel material for unrefined bolt or the like using same |
-
1987
- 1987-12-21 JP JP62323315A patent/JP2658101B2/en not_active Expired - Lifetime
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5356120A (en) * | 1976-11-02 | 1978-05-22 | Nippon Steel Corp | Production of high tensile bolt for low temperature service |
| JPS59107063A (en) * | 1982-12-10 | 1984-06-21 | Daido Steel Co Ltd | Wire rod for bolt and its production |
| JPS61284554A (en) * | 1985-06-12 | 1986-12-15 | Kobe Steel Ltd | Alloy steel for unrefined bolt or the like having superior toughness and steel material for unrefined bolt or the like using same |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2017170756A1 (en) * | 2016-03-31 | 2017-10-05 | 株式会社神戸製鋼所 | Non-heat-treated wire rod for bolt, non-heat-treated steel wire for bolt, and method for manufacturing same, and non-heat-treated bolt |
| CN109797339A (en) * | 2019-02-28 | 2019-05-24 | 本钢板材股份有限公司 | A kind of tensile strength >=960MP martensite Micro Alloying high-strength steel and its manufacturing method |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2658101B2 (en) | 1997-09-30 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN103882330B (en) | A kind of low yield strength ratio superhigh intensity non-quenched and tempered steel plate and production method thereof | |
| EP0429094A1 (en) | High strength low carbon steels, steel articles thereof and method for manufacturing the steels | |
| JP2004137542A (en) | Method for manufacturing hot-forged member of microalloyed steel | |
| CN106399840A (en) | Low-cost and low-yield-ratio hardening and tempering type Q690E steel plate and production method | |
| US5156692A (en) | Process for manufacturing steel wires for use in wire drawing | |
| CN105695882A (en) | J55-grade low-yield-ratio steel for electric resistance welding casing pipe and manufacturing method of J55-grade low-yield-ratio steel | |
| CN112410671A (en) | Production method for producing steel for rim by adopting complex phase structure | |
| CN107354376A (en) | Roll-forming yield strength 550MPa levels cold-rolled steel sheet and production method | |
| JPS58107416A (en) | Method of directly softening steel wire or rod steel useful for mechanical construction | |
| JPH11199926A (en) | Production of bar steel for high strength bolt, excellent in cold workability and delayed fracture resistance | |
| JPS6156235A (en) | Manufacture of high toughness nontemper steel | |
| JPH01165721A (en) | Production of wire rod for non-tempered steel bolt | |
| JPS62199750A (en) | Unrefined steel bar having superior toughness and its manufacture | |
| JPH01116032A (en) | Production of high-strength-high-toughness un-tempered steel | |
| JPH0213004B2 (en) | ||
| JPH02274810A (en) | Production of high tensile untempered bolt | |
| JP2000219915A (en) | Production of seamless steel pipe having high strength and high toughness | |
| JPH03260010A (en) | Production of non-heattreated steel bar for hot forging and production of hot forged non-heattreated parts | |
| JPH0445227A (en) | Production of steel product with low yield ratio | |
| JPH0617122A (en) | Production of non-heattreated steel excellent in durability ratio | |
| JPH06136452A (en) | Production of hard steel wire | |
| JPH0366383B2 (en) | ||
| JPH10280036A (en) | Wire rod for high strength bolt excellent in strength and ductility and its production | |
| JPH0995733A (en) | Production of high strength non-heat treated wire rod for bolt | |
| CN118109756A (en) | Spring flat steel with high performance and production method thereof |