JP2791832B2 - Manufacturing method of mild steel wire rod with excellent workability during cold forging - Google Patents
Manufacturing method of mild steel wire rod with excellent workability during cold forgingInfo
- Publication number
- JP2791832B2 JP2791832B2 JP31628990A JP31628990A JP2791832B2 JP 2791832 B2 JP2791832 B2 JP 2791832B2 JP 31628990 A JP31628990 A JP 31628990A JP 31628990 A JP31628990 A JP 31628990A JP 2791832 B2 JP2791832 B2 JP 2791832B2
- Authority
- JP
- Japan
- Prior art keywords
- wire rod
- cold forging
- rolling
- steel wire
- mild steel
- 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
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- Heat Treatment Of Steel (AREA)
Description
【発明の詳細な説明】 (産業上の利用分野) 本発明は冷間鍛造加工に供せられるところの強度が低
く、かつ冷間鍛造時の加工性に優れた軟鋼線材の製造法
に関するものである。Description: TECHNICAL FIELD The present invention relates to a method for producing a mild steel wire rod having low strength for cold forging and excellent workability during cold forging. is there.
(従来の技術) ねじ類や各種部品を冷間鍛造にて製造する場合、熱間
圧延された軟鋼線材を用いるときは、例えば軟化焼鈍、
脱スケールおよび潤滑処理等の前処理を経て、冷間伸線
加工によって鋼線とした後、ダブルヘッダ或いは多段フ
ォーマによる冷間鍛造加工によって、ボルト、部品等、
その最終用途に応じた形状に成形加工される。(Conventional technology) When manufacturing screws and various parts by cold forging, when using a hot-rolled mild steel wire rod, for example, softening annealing,
After pre-treatments such as descaling and lubrication, the steel wire is formed by cold drawing, and then bolts, parts, etc. are formed by cold forging with a double header or multi-stage former.
It is formed into a shape according to its final use.
しかし、近年、生産能率の向上やコストの低減を目的
として、鍛造機が高速化されるとともに、製品によって
は軟化焼鈍も省略されるに至り、鍛造工具の短命化が重
要な問題となっている。However, in recent years, for the purpose of improving production efficiency and reducing costs, forging machines have been accelerated, and depending on the product, soft annealing has been omitted, and shortening the life of forging tools has become an important problem. .
このような工具の短命化の要因は種々想定されるが、
被加工材の面からはその変形抵抗が大きく影響し、特に
高速化された冷間鍛造加工においては、加工熱によって
被加工材が著しく昇温し、被加工材は動的歪時効によっ
て変形抵抗が著しく増大して工具寿命を短命化する。There are various possible factors for shortening the life of such tools,
The deformation resistance has a great effect on the surface of the workpiece, especially in high-speed cold forging, where the temperature of the workpiece rises significantly due to the processing heat, and the deformation resistance of the workpiece decreases due to dynamic strain aging. And the tool life is shortened.
このように工具が短命化すると、鍛造機の稼働率、ひ
いては生産能力が低下することとなるので、冷間鍛造時
の加工性が良い軟鋼線材が求められている。If the life of the tool is shortened in this way, the operating rate of the forging machine and, consequently, the production capacity will be reduced. Therefore, a mild steel wire rod having good workability during cold forging is required.
上記のような軟鋼線の軟質化については従来より線材
圧延後のフェライト結晶粒径を大きくすることにより、
直接、降伏強度が低い線材を製造することが試みられて
きた。For the softening of mild steel wire as described above, by increasing the ferrite crystal grain size after wire rod rolling than before,
Direct production of wires with low yield strength has been attempted.
特公昭55−29126号公報においては加熱温度を1100℃
以上の高温にし、熱間加工を1000℃以上で終了させるこ
とにより粗粒のオーステナイト結晶を出現させ、その後
緩冷却することにより塊状フェライト組織を得ることが
できると述べられている。In Japanese Patent Publication No. 55-29126, the heating temperature is 1100 ° C.
It is stated that coarse ferritic austenite crystals appear by setting the temperature to the above high temperature and finishing the hot working at 1000 ° C. or more, and then a massive ferrite structure can be obtained by slow cooling.
しかし加熱温度を上昇させることはスケール量および
脱炭量の増加を招き、品質が低下するばかりでなく、在
炉時間も長くなり作業効率が低減する。また使用ガス量
も増加し、環境に及ぼす影響も大きくなる。However, increasing the heating temperature causes an increase in the amount of scale and the amount of decarburization, not only deteriorating the quality but also increasing the furnace time and reducing the working efficiency. Also, the amount of gas used increases, and the effect on the environment also increases.
(発明が解決しようとする課題) 本発明は、線材圧延後のフェライト結晶粒を粗大化さ
せるため、線材圧延加熱温度を低く抑え、仕上圧延速度
を高速化することにより圧延仕上温度を上昇させて降伏
強度の低い軟鋼線を得る製造法を提供することを目的と
する。(Problems to be Solved by the Invention) In the present invention, in order to coarsen ferrite crystal grains after wire rod rolling, the wire rod heating temperature is kept low, and the finishing rolling speed is increased by increasing the finishing rolling speed. An object of the present invention is to provide a manufacturing method for obtaining a mild steel wire having a low yield strength.
(課題を解決するための手段) 本発明の要旨とするところは、C:0.15wt%以下、Mn:
0.5wt%以下、Al:0.03wt%以下を含有し、残部がFeおよ
び不可避的不純物からなる組成の鋼片を用いて、加熱温
度を900〜1000℃の範囲で加熱し、線材の仕上圧延速度
を100m/sec以上、仕上温度を1200〜1250℃の範囲内で圧
延し、その後の冷却速度を0.5〜2℃/secの範囲で冷却
することを特徴とする冷間鍛造時の加工性に優れた軟鋼
線材の製造法にある。(Means for Solving the Problems) The gist of the present invention is that C: 0.15 wt% or less, Mn:
Using a steel slab containing 0.5 wt% or less and Al: 0.03 wt% or less, with the balance being Fe and unavoidable impurities, heating at a heating temperature in the range of 900 to 1000 ° C, and finishing rolling speed of the wire rod Excellent workability during cold forging characterized by rolling at a finishing temperature of 1200 to 1250 ° C and cooling at a subsequent cooling rate of 0.5 to 2 ° C / sec. Manufacturing method of mild steel wire rod.
(作用) 本発明における軟鋼線材の化学組成範囲および製造条
件の限定理由について述べる。(Operation) The reasons for limiting the chemical composition range of the mild steel wire rod and the manufacturing conditions in the present invention will be described.
Cは鋼の強度を支配する元素であり、低炭素化するほ
ど軟質化する。上限は加工性を劣化させない限度である
0.15wt%とした。C is an element that controls the strength of steel, and softens as the carbon becomes lower. The upper limit is the limit that does not deteriorate workability
0.15wt%.
Mnは脱酸元素であるとともに鋼に固溶して強化する元
素であり、加工硬化を低くするためには低い方が望まし
い。上限は加工性を劣化させない限界として0.5wt%と
した。Mn is a deoxidizing element and an element that forms a solid solution in steel and strengthens the steel. It is desirable that Mn be low in order to reduce work hardening. The upper limit is set at 0.5 wt% as a limit that does not deteriorate workability.
Alは鋼の脱酸元素として知られている他、鋼中のNと
結合してオーステナイト結晶粒の粗大化を阻止する元素
であるが、0.03wt%を越えて含有させると硬質介在物起
因による切削性の劣化および疲労強度の低下を招くので
上限を0.03wt%とした。Al is known as a deoxidizing element of steel, and is an element that combines with N in steel to prevent the austenite crystal grains from coarsening. However, if it exceeds 0.03 wt%, it is caused by hard inclusions. The upper limit was set to 0.03 wt%, since this would lead to deterioration in machinability and decrease in fatigue strength.
線材圧延における加熱温度は鋼片の成分を均一に固溶
させるとともに圧延中の鋼材の温度に影響を与える。加
熱温度の下限は、オーステナイト化温度以上で鋼片の成
分が均一に固溶し、かつ圧延中の鋼材温度をA1変態点以
上に確保するために900℃とした。上限はスケールおよ
び脱炭層の量を低く抑えるために1000℃とした。The heating temperature in wire rod rolling causes the components of the slab to be uniformly dissolved and affects the temperature of the steel material during rolling. The lower limit of the heating temperature, the components of the steel pieces are uniformly dissolved in the austenitizing temperature or higher, and the steel material temperature during rolling was 900 ° C. in order to secure more than the A 1 transformation point. The upper limit was set to 1000 ° C. in order to keep the amount of scale and decarburized layer low.
線材圧延の仕上速度は加工発熱による温度上昇の大き
な要因となる。このことを本発明者等は実験的に求め
た。その内容は第1図に示すように、線材圧延仕上速度
の上昇に伴い加工発熱により鋼材の温度が上昇している
ことがわかる。線材圧延の仕上温度は組織のオーステナ
イト結晶粒度に大きな影響を与え、圧延仕上温度の上昇
により粗粒のオーステナイト結晶粒が得られる。The finishing speed of wire rolling is a major factor in temperature rise due to heat generated during processing. The present inventors have experimentally determined this. As shown in FIG. 1, it can be seen that the temperature of the steel material has increased due to the heat generated during the processing as the wire rod finishing speed has increased. The finishing temperature of wire rolling has a great effect on the austenite grain size of the structure, and coarse austenite grains can be obtained by raising the rolling finishing temperature.
圧延仕上温度を1200℃以上にするため圧延速度の下限
は100m/secとした。一方、設備の制約から上限は120m/s
ecとなる。The lower limit of the rolling speed was set to 100 m / sec in order to make the rolling finish temperature 1200 ° C. or higher. On the other hand, the upper limit is 120m / s due to equipment restrictions.
ec.
線材圧延の仕上温度は組織のオーステナイト結晶粒度
に大きな影響を与える。従来60m/sec程度であった仕上
圧延速度を高速化すると加工発熱により鋼材温度が上昇
する。これにより粗粒のオーステナイト結晶粒が得られ
る。よってオーステナイト結晶粒を粒度番号8番以下の
粗粒にするための仕上圧延温度の下限を1200℃とした。
一方、上限は線材圧延設備の維持補修のため1250℃とし
た。The finishing temperature of wire rolling greatly affects the austenite grain size of the structure. When the finish rolling speed, which was about 60 m / sec in the past, was increased, the temperature of the steel material increased due to the heat generated during processing. As a result, coarse austenite crystal grains are obtained. Accordingly, the lower limit of the finish rolling temperature for making the austenite crystal grains coarser than grain size number 8 was set to 1200 ° C.
On the other hand, the upper limit was set to 1250 ° C for maintenance and repair of wire rod rolling equipment.
冷却速度はフェライト変態時の粒径を決めるもので、
粗粒化させるためにはできる限り徐冷する必要がある。
上限は加工性を得るフェライト粒組織とするために2℃
/secとし、下限は圧延設備の制約から0.5℃/secとし
た。The cooling rate determines the grain size during ferrite transformation,
In order to make the grains coarse, it is necessary to cool as slowly as possible.
The upper limit is 2 ° C in order to obtain a ferrite grain structure for obtaining workability.
/ sec, and the lower limit was set to 0.5 ° C./sec due to restrictions on rolling equipment.
(実施例) 低炭素鋼を250トン転炉で溶製し、脱ガス処理設備を
用いて脱炭ならびに成分調整を行なった。(Example) Low carbon steel was melted in a 250-ton converter, and decarburization and component adjustment were performed using degassing equipment.
第1表に供試鋼の化学成分を示す。 Table 1 shows the chemical components of the test steel.
第1表のA〜Dは本発明鋼の例、E〜Gは比較鋼の例
である。E鋼はC量が上限を越え、F鋼はMn量が上限を
越え、G鋼はAl量が上限を越えている。In Table 1, A to D are examples of the steel of the present invention, and E to G are examples of comparative steels. Steel E has a C content exceeding the upper limit, steel F has a Mn content exceeding the upper limit, and steel G has an Al content exceeding the upper limit.
これらの供試鋼を連続鋳造設備により300×500mm鋳片
とし、さらに分塊圧延により122mm角断面の鋼片を製造
した。These test steels were cast into 300 × 500 mm slabs by a continuous casting facility, and further subjected to slab rolling to produce slabs having a cross section of 122 mm square.
これらの鋼片を第2表に示す線材圧延条件で加熱後、
高速線材圧延シミュレーターにより直径5.5mmの線材に
圧延し、ステルモア冷却を行なった。そして、一部、こ
の5.5mmφ圧延材を用いて冷間鍛造時における加工性を
冷間据え込み性試験により求めた。After heating these billets under the wire rolling conditions shown in Table 2,
The wire was rolled into a wire having a diameter of 5.5 mm by a high-speed wire rod simulator, and was subjected to steermore cooling. Then, a part of the 5.5 mmφ rolled material was used to determine the workability during cold forging by a cold upsetting test.
試験ダイスは第2図に示すように、工具面に溝の深さ
は0.4mm、ピッチは0.7mmの同心円溝を刻んだものであ
る。これは試料上下面の組成流動を完全に拘束すること
を目的としたものである。また、この接触面は超硬合金
で作成した。As shown in FIG. 2, the test dies were formed by forming concentric grooves having a groove depth of 0.4 mm and a pitch of 0.7 mm on the tool surface. This is intended to completely restrain the composition flow on the upper and lower surfaces of the sample. This contact surface was made of a cemented carbide.
試験片の高さ直径比h0/D0を1.5で一定とした線材切
断片に、その表面に沿って深さ0.4mmの上仕上V字溝を
溝底の丸み半径0.15mm、開先角度120度に形成して試験
片とし、これを軸線方向に圧縮する試験用ダイスとし
て、外径60mm、長さ60mmの円筒台よりなり、その試験片
に接する端面直径40mmの領域内に、半径方向ピッチ0.7m
mの同心多重環状配列で谷の開き角度120度のV字溝を刻
んだ上下一対を用いて、試験片に圧縮歪速度:3.3×10-3
sec-1で圧縮荷重を加えて割れ発生を目視判定し、限界
圧縮率(%)として、 εhc=(h0−hc)/h0×100 εhc:限界据え込み率 h0 :試験片の元の高さ hc :割れ発生時の試験片の高さ の値を計算することによって求めた。A cut piece of wire rod with the height / diameter ratio h 0 / D 0 constant at 1.5 was placed along the surface with an upper finish V-shaped groove with a depth of 0.4 mm, a round bottom radius of the groove of 0.15 mm, and a groove angle. A test die formed at 120 degrees to form a test specimen, which is a test die for compressing the test piece in the axial direction, consisting of a cylindrical table having an outer diameter of 60 mm and a length of 60 mm. Pitch 0.7m
Compressive strain rate: 3.3 × 10 -3 on the test piece using a pair of upper and lower carved with a V-shaped groove with a valley opening angle of 120 degrees in a concentric multiple annular array of m
A compressive load is applied in sec- 1 to visually determine the occurrence of cracks, and the limit compression ratio (%) is ε hc = (h 0 −h c ) / h 0 × 100 ε hc : Limit upsetting ratio h 0 : Test original height h c of the pieces: was determined by calculating the height values of cracking when the test piece.
引張試験はJISZ2201の2号試験片を用い、JISZ2241記
載の方法で行なった。The tensile test was performed using the JISZ2201 No. 2 test piece according to the method described in JISZ2241.
フェライト粒径は光学顕微鏡観察により求めた。 The ferrite grain size was determined by observation with an optical microscope.
このようにして得られた特性値を第2表に併せて示
す。The characteristic values thus obtained are also shown in Table 2.
No.5〜No.11は比較鋼である。 No. 5 to No. 11 are comparative steels.
No.5は加熱温度が低すぎたため、仕上圧延温度が低下
し、フェライト結晶粒が微細となり、このため加工性が
低下した。In No. 5, since the heating temperature was too low, the finish rolling temperature was lowered, and the ferrite crystal grains became finer, so that the workability was lowered.
No.6は加熱温度が高すぎたため、スケール量が増加
し、加工性が低下した。In No. 6, since the heating temperature was too high, the scale amount increased and the workability decreased.
No.7は仕上圧延出側速度が遅すぎたため、仕上圧延温
度が低下し、フェライト結晶粒が微細となり、加工性が
低下した。In No. 7, the finish-rolling exit speed was too slow, so that the finish-rolling temperature was lowered, the ferrite grains became finer, and the workability was reduced.
No.8は冷却速度が速すぎたため、フェライト変態速度
が上昇し、微細な結晶が生じた。これにより加工性が低
下した。In No. 8, the cooling rate was too high, so the ferrite transformation rate increased, and fine crystals were formed. Thereby, the workability was reduced.
No.9はC量が高すぎたため、加工性が劣化した。 In No. 9, the workability deteriorated because the C content was too high.
No.10はMn量が高すぎたため、加工性が劣化した。 In No. 10, the workability was deteriorated because the Mn content was too high.
No.11はAl量が高すぎたため、硬質介在物起因による
加工性の劣化が生じた。In No. 11, the workability was degraded due to hard inclusions because the Al content was too high.
(発明の効果) 以上述べた如く、本発明法に従って製造された軟鋼線
材は、従来法による線材に比べて、より一段と軟質化さ
れており、これにより冷間鍛造時の加工性に優れた線材
を製造することができる。従って、本発明によれば、冷
間鍛造時の工具寿命を長くでき、生産能力を上昇させる
ことが可能になるので、産業上貢献するところが極めて
大である。 (Effects of the Invention) As described above, the mild steel wire manufactured according to the method of the present invention is more softened as compared with the wire manufactured by the conventional method, and thus has excellent workability during cold forging. Can be manufactured. Therefore, according to the present invention, the tool life during cold forging can be lengthened, and the production capacity can be increased, so that the industrial contribution is extremely large.
第1図は線材仕上圧延における圧延速度と鋼材の温度の
関係を示す図である。 第2図は冷間鍛造時における加工性を判断するための冷
間据え込み性試験における圧縮工具の側断面図である。FIG. 1 is a diagram showing a relationship between a rolling speed and a temperature of a steel material in wire rod finish rolling. FIG. 2 is a side sectional view of a compression tool in a cold upsetting test for judging workability during cold forging.
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 昭60−121220(JP,A) 特開 昭62−47429(JP,A) 特開 昭64−31390(JP,A) (58)調査した分野(Int.Cl.6,DB名) C21D 8/06──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-121220 (JP, A) JP-A-62-47429 (JP, A) JP-A-64-31390 (JP, A) (58) Field (Int.Cl. 6 , DB name) C21D 8/06
Claims (1)
3wt%以下を含有し、残部がFeおよび不可避的不純物か
らなる組成の鋼片を用いて、加熱温度を900〜1000℃の
範囲で加熱し、線材の仕上圧延速度を100m/sec以上、仕
上温度を1200〜1250℃の範囲内で圧延し、その後の冷却
速度を0.5〜2℃/secの範囲で冷却することを特徴とす
る冷間鍛造時の加工性に優れた軟鋼線材の製造法。C: 0.15 wt% or less, Mn: 0.5 wt% or less, Al: 0.0
Using a steel slab containing 3 wt% or less and the balance being Fe and unavoidable impurities, the heating temperature is heated in the range of 900 to 1000 ° C, the finish rolling speed of the wire is 100 m / sec or more, and the finishing temperature is A method for producing a mild steel wire excellent in workability at the time of cold forging, characterized in that is rolled in the range of 1200 to 1250 ° C, and then cooled at a cooling rate of 0.5 to 2 ° C / sec.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP31628990A JP2791832B2 (en) | 1990-11-21 | 1990-11-21 | Manufacturing method of mild steel wire rod with excellent workability during cold forging |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP31628990A JP2791832B2 (en) | 1990-11-21 | 1990-11-21 | Manufacturing method of mild steel wire rod with excellent workability during cold forging |
Publications (2)
Publication Number | Publication Date |
---|---|
JPH04187717A JPH04187717A (en) | 1992-07-06 |
JP2791832B2 true JP2791832B2 (en) | 1998-08-27 |
Family
ID=18075453
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP31628990A Expired - Lifetime JP2791832B2 (en) | 1990-11-21 | 1990-11-21 | Manufacturing method of mild steel wire rod with excellent workability during cold forging |
Country Status (1)
Country | Link |
---|---|
JP (1) | JP2791832B2 (en) |
-
1990
- 1990-11-21 JP JP31628990A patent/JP2791832B2/en not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
JPH04187717A (en) | 1992-07-06 |
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