JPH0480965B2 - - Google Patents
Info
- Publication number
- JPH0480965B2 JPH0480965B2 JP27377185A JP27377185A JPH0480965B2 JP H0480965 B2 JPH0480965 B2 JP H0480965B2 JP 27377185 A JP27377185 A JP 27377185A JP 27377185 A JP27377185 A JP 27377185A JP H0480965 B2 JPH0480965 B2 JP H0480965B2
- Authority
- JP
- Japan
- Prior art keywords
- tensile strength
- bolt
- bolts
- wire
- carbon
- 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
- 238000000034 method Methods 0.000 claims description 16
- 229910052799 carbon Inorganic materials 0.000 claims description 13
- 229910000655 Killed steel Inorganic materials 0.000 claims description 10
- 238000004519 manufacturing process Methods 0.000 claims description 10
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 9
- 239000000463 material Substances 0.000 claims description 9
- 238000005096 rolling process Methods 0.000 claims description 9
- 238000005491 wire drawing Methods 0.000 claims description 9
- 229910000831 Steel Inorganic materials 0.000 claims description 5
- 239000010959 steel Substances 0.000 claims description 5
- 238000001816 cooling Methods 0.000 claims description 4
- 229910001562 pearlite Inorganic materials 0.000 claims description 4
- 238000000137 annealing Methods 0.000 description 7
- RQMIWLMVTCKXAQ-UHFFFAOYSA-N [AlH3].[C] Chemical compound [AlH3].[C] RQMIWLMVTCKXAQ-UHFFFAOYSA-N 0.000 description 5
- 229910052782 aluminium Inorganic materials 0.000 description 4
- 238000003754 machining Methods 0.000 description 4
- 238000007796 conventional method Methods 0.000 description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 229910000975 Carbon steel Inorganic materials 0.000 description 1
- 238000003483 aging Methods 0.000 description 1
- 239000010962 carbon steel Substances 0.000 description 1
- 229910001567 cementite Inorganic materials 0.000 description 1
- 238000010273 cold forging Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical group C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 238000004881 precipitation hardening Methods 0.000 description 1
- 238000005482 strain hardening Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Landscapes
- Heat Treatment Of Steel (AREA)
- Heat Treatment Of Articles (AREA)
Description
（産業上の利用分野）
本発明はJISのボルトナツト規格により引張強
さ60Kg／mm2以上、降伏点36Kg／mm2以上のものと規
定されている6Tボルトを低コストで製造するこ
とができる低炭素アルミキルド鋼製の6Tボルト
の製造方法に関するものである。
（従来の技術）
従来、6TボルトはSWRCH45K等の冷間圧造
用炭素鋼線材に加工時におけるボルト頭部の加工
割れ等を防止するために球状化焼鈍処理を施して
冷間鍛造性を向上させたうえで伸線、圧造、ねじ
転造を行い、この加工によるボルト首部の硬化を
頭飛びが発生しないレベルまで緩和するために
400〜600℃の応力除去焼鈍を施す方法により製造
されている。ところがこのような従来法において
は、球状化焼鈍により材料費が20〜40円／Kgもア
ツプするため、ボルトのコストが高いものとなる
欠点があつた。
（発明が解決しようとする問題点）
本発明は上記のような従来の6Tボルトの製造
方法の問題点を解決して、球状化焼鈍工程を省略
した簡単な工程によりボルト頭部の加工割れや加
工型命数の低下を防止しつつJISに規定される強
度を十分に満足することのできる低炭素アルミキ
ルド鋼性の6Tボルトの製造方法を目的として完
成されたものである。
（問題点を解決するための手段）
本発明はＣ％＋１／6Mn％として定義される
炭素当量が0.32±0.03％である低炭素アルミキル
ド鋼線材を寸法公差±0.15mmに精密圧延し、強制
空冷により安定したパーライト組織とするととも
に、その抗張力を50±３Kg／mm2、昇抗張力を0.7
〜0.8Kg／mm2／％に調整し、この材料を伸線、圧
造、ねじ転造の工程によりボルトの形状に加工し
たうえ、青熱脆性域温度でブルーイング処理する
ことを特徴とするものである。
本発明においては前記のようにコストアツプの
原因となつている球状化焼鈍工程を省いても
SWRCH45Kのような冷間圧造用炭素鋼線材に球
状化焼鈍処理を施した素材と同程度の延性を持た
せることのできる素材として、SWRCH15A〜
20Aのような低炭素アルミキルド鋼の線材が用い
られる。この素材にボルト加工時において加工割
れや加工型命数の低下を生じさせない安定した加
工性を維持させるために、本発明においては素材
の特性に最も大きい影響を及ぼす化学成分をＣ％
＋１／6Mn％として定義される炭素当量に換算
して、0.32±0.03％の範囲に納めるように厳しく
コントロールする。炭素当量が0.35％を越えると
抗張力が高くなるため加工割れや型命数が低下す
ることとなり、逆に炭素当量が0.29％未満である
と6Tボルトに必要とされる抗張力が得られない
こととなる。また本発明においては上記の素材に
製鋼段階において強制空冷を行うことにより低炭
素アルミキルド鋼を安定したパーライト組織と
し、これらの手段によつてボルト形状に加工する
前の線材の抗張力を50±３Kg／mm2、昇抗張力を
0.7〜0.8Kg／mm2／％に調整する。この段階におい
て線材の抗張力が53Kg／mm2を越えると後の伸線工
程を経たときの抗張力が高くなり過ぎて加工によ
る頭部割れ、加工型命数の低下等の問題を生ず
る。逆にこの段階における線材の抗張力が47Kg／
mm2未満であると6Tボルトに必要とされる抗張力
を達成することが困難となる。また昇降力は図面
に示されるように伸線加工による減面率（断面積
の減少割合）１％当りの抗張力の上昇量として定
義される物性値であつて、材料によつてほぼ決定
される値であるが、上記のような本発明に用いら
れる低炭素アルミキルド鋼線材においては一般的
に0.6〜0.9Kg／mm2／％となるので、焼ならし方法
を調節することにより0.7〜0.8Kg／mm2／％に調節
するものとする。次にこの線材を伸線加工するの
であるが、図面からも分かるように、抗張力が50
±３Kg／mm2、昇抗張力を0.7〜0.8Kg／mm2、％とな
るように管理された線材を伸線加工して6Tボル
トに要求される60Kg／mm2の抗張力を得るには減面
率が19〜23％となるよう圧延を管理する必要があ
る。また逆に言えば、減面率が20％程度の一定値
となるよう設定された工程においては素材となる
線材の昇抗張力を0.7〜0.8Kg／mm2／％に調整しな
ければ6Tボルトに要求される抗張力に達しなか
つたり、あるいは抗張力が大きくなり過ぎて加工
性の悪化を招く等の問題を生ずることになる。こ
のようにして伸線したのち、常法に従つてボルト
頭部の圧造及び転造を行い、ボルト形状への加工
が行われる。
上記の加工の結果、ボルト頭部は加工硬化によ
つて強度が上昇するが、ボルト軸部は圧縮応力を
受けるために降伏点及び弾性限が著しく低下しこ
のままでは6Tボルトに必要な強度が保証できな
い。そこで本発明においては得られたボルトを
250〜400℃の青熱脆性域温度でブルーイング処理
することにより降伏点及び弾性限を回復させる。
一般にキルド鋼ではAl又はSiが鋼中のＮを脱酸
により十分に固定するので歪時効硬化が少いとさ
れているが、本発明の低炭素アルミキルド鋼を上
記のように青熱脆性域温度でブルーイング処理す
ると伸線及び圧造時に鋼中のセメンタイトが分解
して生じたＣが固定され、炭化物の析出硬化によ
つて降伏点、弾性限等が著しく回復する現象が認
められる。しかもこのブルーイング処理を行うと
ボルト頭部の加工歪も固定されるので頭飛びの防
止にも効果的である。このようにして得られたボ
ルトは後の実施例にも示されるように60Kg／mm2を
はるかに越える引張強さを備え、6Tボルトとし
ての規格を十分に満足できるものである。
（実施例）
次に本発明の実施例を示す。
JISにSWRCH18Aとして規定される0.18％Ｃ、
0.03％Si、0.74％Mn、0.02％Ｐ、0.01％Ｓ、0.05
％Al、残部Feの組成の低炭素アルミキルド鋼線
材（炭素当量0.30）を製鋼段階において850℃〜
880℃の温度域から200℃〜400℃の温度域まで強
制空冷してパーライト組成とするとともに、その
抗張力を50Kg／mm2、昇抗張力を0.7Kg／mm2／％に
調整した。この線材を減面率が19％となるように
精密に管理しつつ伸線加工したうえ常法に従つて
圧造、ねじ転造を行い引張強さ61.1Kg／mm2、0.2
％耐力49.0Kg／mm2、破断延び8.0％、降伏比（0.2
％耐力／引張強さ）79.5％のボルトを得た。次に
これを200℃、300℃、400℃、550℃でそれぞれ熱
処理したところ、次表のとおり300〜400℃の青熱
脆性域においてブルーイング処理されたものは
6Tボルトの規格を十分に越える強度を示した。
なお圧造、ねじ転造の際にボルト頭部の加工割れ
は全く発生せず、加工型命数も従来の
SWRCH45Kを球状化焼鈍処理した素材を用いる
場合と変らなかつた。
(Field of Industrial Application) The present invention is a low-cost bolt that can manufacture 6T bolts at low cost, which are specified by the JIS bolt and nut standards as having a tensile strength of 60 kg/mm 2 or more and a yield point of 36 kg/mm 2 or more. This invention relates to a method for manufacturing 6T bolts made of carbon-aluminum killed steel. (Conventional technology) Conventionally, 6T bolts are made of carbon steel wire rods for cold heading such as SWRCH45K, which are subjected to spheroidizing annealing treatment to improve cold forging properties in order to prevent cracks in the bolt head during processing. After that, wire drawing, heading, and thread rolling are performed to reduce the hardening of the bolt neck caused by this process to a level that prevents head popping.
Manufactured by stress relief annealing at 400-600°C. However, in this conventional method, the material cost increases by 20 to 40 yen/Kg due to spheroidizing annealing, resulting in a disadvantage that the cost of the bolt becomes high. (Problems to be Solved by the Invention) The present invention solves the problems of the conventional 6T bolt manufacturing method as described above, and eliminates machining cracks in the bolt head through a simple process that eliminates the spheroidizing annealing process. This was completed with the aim of creating a method for manufacturing 6T bolts made of low-carbon aluminum killed steel that can sufficiently satisfy the strength specified by JIS while preventing a decrease in processing die life. (Means for Solving the Problems) The present invention involves precision rolling a low carbon aluminum killed steel wire rod with a carbon equivalent of 0.32±0.03%, defined as C%+1/6Mn%, to a dimensional tolerance of ±0.15mm, and forced air cooling. In addition to creating a more stable pearlite structure, the tensile strength is 50±3Kg/mm 2 and the elevated tensile strength is 0.7.
The material is adjusted to ~0.8Kg/mm 2 /%, processed into the shape of a bolt through the processes of wire drawing, heading, and thread rolling, and then subjected to bluing treatment at a temperature in the blue brittle range. It is. In the present invention, even if the spheroidizing annealing process, which causes cost increase as mentioned above, is omitted,
SWRCH15A~
Low carbon aluminum killed steel wire such as 20A is used. In order to maintain stable workability of this material without causing processing cracks or reduction in processing die life during bolt processing, in the present invention, the chemical component that has the greatest effect on the properties of the material is reduced to C%.
Converted to carbon equivalent defined as +1/6Mn%, it is strictly controlled to be within the range of 0.32±0.03%. If the carbon equivalent exceeds 0.35%, the tensile strength will increase, leading to processing cracks and reduced mold life. Conversely, if the carbon equivalent is less than 0.29%, the tensile strength required for 6T bolts will not be obtained. . In addition, in the present invention, the above-mentioned material is subjected to forced air cooling during the steel manufacturing stage to form a stable pearlite structure in the low carbon aluminum killed steel, and by these means, the tensile strength of the wire rod before being processed into a bolt shape is increased to 50 ± 3 kg/ mm 2 , increasing tensile strength
Adjust to 0.7-0.8Kg/mm 2 /%. If the tensile strength of the wire exceeds 53 Kg/mm 2 at this stage, the tensile strength during the subsequent wire drawing process will be too high, leading to problems such as cracking of the head during processing and a reduction in the lifespan of the processing die. Conversely, the tensile strength of the wire at this stage is 47Kg/
If it is less than mm 2 , it will be difficult to achieve the tensile strength required for 6T bolts. In addition, as shown in the drawing, the lifting force is a physical property value defined as the amount of increase in tensile strength per 1% area reduction (reduction rate of cross-sectional area) due to wire drawing, and is almost determined by the material. The value is generally 0.6 to 0.9 Kg/mm 2 /% for the above-mentioned low carbon aluminium-killed steel wire used in the present invention, so by adjusting the normalizing method, it can be reduced to 0.7 to 0.8 Kg. /mm 2 /% shall be adjusted. Next, this wire is drawn, but as you can see from the drawing, the tensile strength is 50
±3Kg/mm 2 , increased tensile strength of 0.7-0.8Kg/mm 2 , wire drawing process to obtain the tensile strength of 60Kg/mm 2 required for 6T bolts. It is necessary to manage rolling so that the rolling ratio is between 19 and 23%. Conversely, in a process where the area reduction rate is set to a constant value of about 20%, unless the tensile strength of the wire material is adjusted to 0.7 to 0.8 Kg/mm 2 /%, it will be 6T bolt. This results in problems such as failure to reach the required tensile strength or excessive tensile strength resulting in deterioration of workability. After the wire is drawn in this manner, the bolt head is pressed and rolled according to conventional methods, and processed into a bolt shape. As a result of the above processing, the strength of the bolt head increases due to work hardening, but the yield point and elastic limit of the bolt shaft are significantly lowered due to compressive stress, and the strength required for a 6T bolt is guaranteed if this continues. Can not. Therefore, in the present invention, the obtained bolt is
The yield point and elastic limit are restored by bluing treatment at a temperature in the blue brittle region of 250 to 400°C.
Generally, in killed steel, strain age hardening is said to be low because Al or Si sufficiently fixes N in the steel through deoxidation. When subjected to bluing treatment, carbon generated by decomposition of cementite in the steel during wire drawing and heading is fixed, and a phenomenon is observed in which the yield point, elastic limit, etc. are significantly recovered by precipitation hardening of carbides. Furthermore, this bluing process also fixes machining distortions in the bolt head, which is effective in preventing the bolt head from flying off. The bolt thus obtained has a tensile strength far exceeding 60 kg/mm 2 as shown in the later examples, and can fully satisfy the standards for a 6T bolt. (Example) Next, an example of the present invention will be shown. 0.18%C specified in JIS as SWRCH18A,
0.03%Si, 0.74%Mn, 0.02%P, 0.01%S, 0.05
Low carbon aluminum killed steel wire rod (carbon equivalent 0.30) with a composition of %Al and the balance Fe is heated at 850℃~ during the steel manufacturing stage.
It was forced air-cooled from a temperature range of 880°C to a temperature range of 200°C to 400°C to obtain a pearlite composition, and its tensile strength was adjusted to 50Kg/mm 2 and elevated tensile strength to 0.7Kg/mm 2 /%. This wire was drawn with precision control so that the area reduction rate was 19%, then heading and thread rolling were performed according to conventional methods, resulting in a tensile strength of 61.1 Kg/mm 2 and 0.2
% proof stress 49.0Kg/mm 2 , elongation at break 8.0%, yield ratio (0.2
A bolt with a yield strength/tensile strength of 79.5% was obtained. Next, this was heat treated at 200℃, 300℃, 400℃, and 550℃, and as shown in the following table, the blueing treatment in the blue brittle region of 300 to 400℃ was
It showed strength that sufficiently exceeded the standard for 6T bolts.
Furthermore, no machining cracks occur on the bolt head during heading and thread rolling, and the machining die life is also the same as before.
The results were the same as when using SWRCH45K which had been annealed to form a spheroid.
【表】
（発明の効果）
本発明は以上の説明からも明らかなように、炭
素当量を厳しく管理された特殊な素材に強制空冷
を施し抗張力、昇抗張力を所定範囲内に調整し、
これを伸線、圧造、ねじ転造によりボルトの形状
に加工したうえで更に特殊な熱処理を施すことに
より球状化焼鈍工程を省略してJIS規格を満足す
ることのできる6Tボルトを製造できるようにし
たものである。従つて本発明によればコストアツ
プの原因となつている球状化焼鈍工程を必要とし
ないので6Tボルトの製造コストを大幅に引下げ
ることができるものであるから、従来の問題点を
解決した低炭素アルミキルド鋼製の6Tボルトの
製造方法として、業界に寄与するところは大であ
る。[Table] (Effects of the Invention) As is clear from the above description, the present invention applies forced air cooling to a special material whose carbon equivalent is strictly controlled, and adjusts the tensile strength and elevated tensile strength within a predetermined range.
By processing this into a bolt shape through wire drawing, heading, and thread rolling, and then applying special heat treatment, we were able to omit the spheroidizing annealing process and manufacture 6T bolts that meet JIS standards. This is what I did. Therefore, according to the present invention, the manufacturing cost of 6T bolts can be significantly reduced because the spheroidizing annealing process, which causes cost increases, is not required. As a manufacturing method for 6T bolts made of aluminum killed steel, this method will greatly contribute to the industry.
図面は伸線加工時の減面率と抗張力との関係を
示すグラフである。
The drawing is a graph showing the relationship between area reduction rate and tensile strength during wire drawing.
Claims (1)
量が0.32±0.03％である低炭素アルミキルド鋼線
材を寸法公差±0.15mmに精密圧延し、強制空冷に
より安定したパーライト組織とするとともに、そ
の抗張力を50±３Kg／mm2、昇抗張力を0.7〜0.8
Kg／mm2／％に調整し、この材料を伸線、圧造、ね
じ転造の工程によりボルトの形状に加工したう
え、青熱脆性域温度でブルーイング処理すること
を特徴とする低炭素アルミキルド鋼製の6Tボル
トの製造方法。A low-carbon aluminum-killed steel wire rod with a carbon equivalent of 0.32±0.03%, defined as 1C%+1/6Mn%, is precision rolled to a dimensional tolerance of ±0.15mm, and forced air cooling is used to create a stable pearlite structure, and its tensile strength is 50±3Kg/mm 2 , increasing tensile strength from 0.7 to 0.8
Kg/mm 2 /%, this material is processed into the shape of a bolt through the processes of wire drawing, heading, and thread rolling, and is then subjected to bluing treatment at a temperature in the blue brittle range. Manufacturing method for steel 6T bolts.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP27377185A JPS62133020A (en) | 1985-12-05 | 1985-12-05 | Production of 6t bolt made of low carbon aluminum killed steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP27377185A JPS62133020A (en) | 1985-12-05 | 1985-12-05 | Production of 6t bolt made of low carbon aluminum killed steel |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS62133020A JPS62133020A (en) | 1987-06-16 |
| JPH0480965B2 true JPH0480965B2 (en) | 1992-12-21 |
Family
ID=17532350
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP27377185A Granted JPS62133020A (en) | 1985-12-05 | 1985-12-05 | Production of 6t bolt made of low carbon aluminum killed steel |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS62133020A (en) |
-
1985
- 1985-12-05 JP JP27377185A patent/JPS62133020A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS62133020A (en) | 1987-06-16 |
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