JPS6364495B2 - - Google Patents
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- Publication number
- JPS6364495B2 JPS6364495B2 JP194882A JP194882A JPS6364495B2 JP S6364495 B2 JPS6364495 B2 JP S6364495B2 JP 194882 A JP194882 A JP 194882A JP 194882 A JP194882 A JP 194882A JP S6364495 B2 JPS6364495 B2 JP S6364495B2
- Authority
- JP
- Japan
- Prior art keywords
- steel
- crystal grains
- less
- temperature
- content
- 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
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- 229910000831 Steel Inorganic materials 0.000 claims description 21
- 239000010959 steel Substances 0.000 claims description 21
- 238000010438 heat treatment Methods 0.000 claims description 16
- 229910001566 austenite Inorganic materials 0.000 claims description 14
- 239000013078 crystal Substances 0.000 claims description 14
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 6
- 239000000463 material Substances 0.000 claims description 6
- 238000003303 reheating Methods 0.000 claims description 6
- 229910000760 Hardened steel Inorganic materials 0.000 claims description 5
- 238000005098 hot rolling Methods 0.000 claims description 4
- 238000004519 manufacturing process Methods 0.000 claims description 4
- 239000012535 impurity Substances 0.000 claims description 3
- 229910052742 iron Inorganic materials 0.000 claims description 3
- 238000000034 method Methods 0.000 description 7
- 238000010586 diagram Methods 0.000 description 6
- 238000005255 carburizing Methods 0.000 description 4
- 238000005096 rolling process Methods 0.000 description 4
- 229910052796 boron Inorganic materials 0.000 description 3
- 230000003749 cleanliness Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 230000003009 desulfurizing effect Effects 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000005204 segregation 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
- C21D7/00—Modifying the physical properties of iron or steel by deformation
- C21D7/13—Modifying the physical properties of iron or steel by deformation by hot working
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Crystallography & Structural Chemistry (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
Description
本発明は、低温加熱法で製造される含Ｂ肌焼鋼
について浸炭処理時等再加熱時のオーステナイト
結晶粒の粗大化を抑制できる含Ｂ肌焼鋼の製造法
に関するものである。
含Ｂ鋼は微量のＢ添加により焼入性を改善でき
るため安価な鋼材とする特長を有しているが、Ｂ
を有効に作用せしめるためには、オーステナイト
化時にボロンをフリーな状態（析出物BNになつ
ていない状態）で存在することが必要である。こ
のため従来から含Ｂ鋼にTiを添加し、ＮをTiで
固定することが行なわれている。そしてそのTi
添加はまた結晶粒の微細化にも寄与することとな
つている。
ところで近時省エネルギー対策等として圧延時
の鋼材（ビレツト）の加熱温度を1150℃以下（従
来は1200〜1250℃）とする低温加熱が行なわれて
来つつある。
この方法をTi添加含Ｂ鋼に適用することを検
討すると、低温加熱法の場合にはTiN等のTi析
出物が鋼中に溶け込まず凝集することとなるた
め、再加熱時にオーステナイト結晶粒が粗大化し
やすいことが判明した。
本発明は、Ti添加含Ｂ鋼の低温加熱法におけ
る上述の問題を解決し、浸炭処理等の再加熱時に
オーステナイト結晶粒の粗大化を抑制した含Ｂ肌
焼鋼を得ることを目的としてなされたものであ
る。
すなわち本発明は、C0.13〜0.27％、Si0.1〜0.5
％、Mn0.3〜2.0％、B0.0005〜0.003％、N0.0035
％以下、SolAl0.005〜0.1％、Ti（５×Ｎ％＋
0.02）〜0.05％を含み、更に必要に応じてCr2％
以下、Mo0.5％以下の１種又は２種を含み、残部
鉄及び不純物からなる鋼材を1150℃〜A3点の温
度に加熱した後、熱間圧延すること特徴とする再
加熱時のオーステナイト結晶粒の粗大化を抑制し
た含Ｂ肌焼鋼の製造法、である。
本発明において、Ti及びＮの含有量及び両者
の関係は重要な意味を有する。
すなわちTiはＢの焼入性効果を減ずるBNに析
出を抑制すべくＮの固定のために必要な元素であ
る。理論的には3.4倍（重量）のTiが存在すれば
Ｎを固定できるが、酸化物等となるTiを考える
と、TiはＮの５倍必要となる。
ところでTiのＮの５倍又はそれ以上添加した
２種の含Ｂ鋼（第１表）について、圧延前加熱温
度を種々変えて熱間圧延し、得られた棒鋼を925
℃×６時間で浸炭処理し、オーステナイト結晶粒
の粗大化挙動を調べた。その結果を第１図に示
す。第１図から知られるように、Ti含有量がＮ
の約５倍である供試材No.１では低温加熱の場合に
は結晶粒の粗大化率（結晶粒度No.が４以下の粗大
結晶粒の占める面積比率）が大きくなり、一方
Ti含有量が（Ｎ％×５＋0.03）％程度と過剰であ
る供試材No.２の場合には低温加熱においても結晶
粒粗大化率がほとぼど０であり、微細結晶粒状態
が維持されている。
この１図から知られるように、低温加熱法にお
いて結晶粒の微細化を図るためにはTiをＮの５
倍を越えて過剰に含有せしめる必要があり、第１
図の例からみて、Ti含有量の下限は（0.02＋５×
Ｎ％）％が適当である。一方後述の第３図からも
知られるように、介在物型のTi析出物が多くな
り過ぎ、延性、冷間加工性を劣化せしめることに
なるので、Ti含有量の上限は0.05％に抑えるべき
である。
The present invention relates to a method for producing B-containing case-hardened steel that can suppress coarsening of austenite crystal grains during reheating such as carburizing treatment of B-containing case-hardened steel produced by a low-temperature heating method. B-containing steel has the advantage of being an inexpensive steel material because its hardenability can be improved by adding a small amount of B.
In order for this to work effectively, it is necessary for boron to exist in a free state (not in the form of precipitates, BN) during austenitization. For this reason, it has been conventional practice to add Ti to B-containing steel and fix N with Ti. And that Ti
The addition is also supposed to contribute to grain refinement. Nowadays, as an energy saving measure, low-temperature heating of steel materials (billets) during rolling is being carried out to lower the heating temperature to 1150° C. or lower (conventionally 1200 to 1250° C.). When considering applying this method to Ti-added B-containing steel, it is found that in the case of low-temperature heating, Ti precipitates such as TiN do not dissolve into the steel and agglomerate, resulting in coarse austenite crystal grains during reheating. It turned out that it is easy to change. The present invention was made with the aim of solving the above-mentioned problems in the low-temperature heating method of Ti-added B-containing steel, and obtaining a B-containing case hardening steel that suppresses coarsening of austenite crystal grains during reheating such as carburizing treatment. It is something. That is, in the present invention, C0.13~0.27%, Si0.1~0.5%
%, Mn0.3~2.0%, B0.0005~0.003%, N0.0035
% or less, SolAl0.005~0.1%, Ti (5 x N% +
Contains 0.02) ~ 0.05%, and further Cr2% if necessary
Hereinafter, the austenite during reheating is characterized by hot rolling a steel material containing one or two types of Mo0.5% or less, the balance being iron and impurities, after heating to a temperature of 3 points from 1150℃ to A. This is a method for producing B-containing case hardened steel that suppresses coarsening of crystal grains. In the present invention, the content of Ti and N and the relationship between the two have important meaning. That is, Ti is an element necessary for fixing N in order to suppress precipitation into BN, which reduces the hardenability effect of B. Theoretically, N can be fixed if Ti is present in an amount 3.4 times (by weight), but when considering Ti as an oxide, 5 times as much Ti as N is required. By the way, two types of B-containing steels (Table 1) containing 5 times or more of Ti and N are hot-rolled at various pre-rolling heating temperatures, and the resulting steel bars are 925
Carburizing treatment was carried out at ℃×6 hours, and the coarsening behavior of austenite crystal grains was investigated. The results are shown in FIG. As is known from Figure 1, the Ti content is N
In sample No. 1, which is about five times as large as
In the case of sample No. 2, which has an excessive Ti content of about (N% x 5 + 0.03)%, the coarsening rate of crystal grains is almost 0 even when heated at low temperature, and the state of fine crystal grains is maintained. is maintained. As is known from Figure 1, in order to refine the crystal grains in the low-temperature heating method, it is necessary to add Ti to 50% of N.
It is necessary to contain an excessive amount of
From the example in the figure, the lower limit of Ti content is (0.02+5×
N%)% is appropriate. On the other hand, as shown in Figure 3 below, the amount of inclusion-type Ti precipitates becomes too large and deteriorates ductility and cold workability, so the upper limit of the Ti content should be kept at 0.05%. It is.
【表】
次にＮについて述べると、ＮはＢの効果を減ず
るという点では有害な元素であるが、一方TiN
の生成による結晶粒微細化効果が期待できる。第
２図は0.2％Ｃ―0.25％Si―0.9％Mn―0.03％Al―
0.02％、又は0.04％Ti―0.0015％Ｂ肌焼鋼につい
てＮ含有量を変えて低温加熱法で熱間圧延して製
造した棒鋼についてオーステナイト域に再加熱し
た場合の、オーステナイト結晶粒の粗大化温度
（結晶粒度No.４以下の粗大粒が面積比率で10％と
なる温度）とＮ含有量との関係を示す図である。
第２図から知られるように、Ti含有量が上述の
（Ｎ％×５＋0.02）％以上であつて、しかもＮ含
有量が0.003％以下の場合にオーステナイト結晶
粒の粗大化が相当の高温まで抑えられる。また第
３図は第２図と同様の含Ｂ肌焼鋼についてTi，
Ｎの含有量を変えた場合のTi系介在物について
の清浄度を示す図であり、Ｎを0.0035％以下で
0.002％程度まで低減させた場合にはTi系介在物
が極めて少なくなることが知られる。
次に他の化学成分について述べる。Ｃは強度付
与元素であり、0.1％以下では必要な強度が得ら
れず、また0.3％以上では延靭性が劣化するので、
C0.1〜0.3％である。肌焼鋼としてはC0.13〜0.27
％が好適である。Siは脱酸剤ととして使用され
0.05％以上必要であるが、一方多すぎると延性、
冷間加工性が悪くなるので、上限を0.5％とする。
Mnは脱酸・脱硫剤ならびに焼入性向上元素とし
て含有され、0.3％以上必要であるが、多すぎる
と偏析による組織の不均一が生じ、冷間加工性を
悪くなるので上限を2.0％とする。Ｂは微量の添
加で焼入性を向上させる元素であり、0.0005〜
0.003％が適量である。Alは脱硫剤として使用さ
れ、また結晶粒微細化にも有効であり、酸可溶性
Al（SolAl）として0.005〜0.1％が適量である。
本発明では上述の元素の他に必要に応じて強度
付与元素としてCr，Moの１種又は２種を含有せ
しめるこができる。Cr2％以上、Mo0.5％以上で
はいずれも延性、冷間加工性が悪くなる。
上述の化学成分を有する鋼材（ビレツト）は低
温加熱法により熱間圧延される。加熱温度は省エ
ネルギーの観点、及び圧延後の組織を微細にする
ために1150℃以下にする必要がある。なお加熱温
度の下限は完全オーステナイト化の必要からA3
点となる。
次に本発明の実施例を比較例と共に示す。
第２表に示す化学成分を有する鋼材（ビレツ
ト）を1150〜900℃の温度に加熱し熱間圧延によ
り棒鋼を製造した。これらの棒鋼のTi系介在物
の清浄度及び925℃での浸炭処理後のオーステナ
イト結晶粒の粗大化率を第３表に示す。第２表、
第３表から知られるように、本発明である記号Ｄ
〜Ｊはいずれも本発明に規定するTi，Ｎの含有
量の条件を満足したものについて低温加熱法によ
る熱間圧延を行なつたものであり、浸炭処理時に
オーステナイト結晶粒の粗大化が起つていない。[Table] Next, referring to N, N is a harmful element in that it reduces the effect of B, but on the other hand, TiN
A grain refinement effect can be expected due to the formation of . Figure 2 shows 0.2%C-0.25%Si-0.9%Mn-0.03%Al-
Coarsening temperature of austenite crystal grains when steel bars manufactured by hot rolling 0.02% or 0.04% Ti - 0.0015% B case hardening steel with varying N content using low temperature heating method are reheated to the austenite region. FIG. 3 is a diagram showing the relationship between (temperature at which the area ratio of coarse grains with a grain size of No. 4 or less is 10%) and N content.
As can be seen from Figure 2, when the Ti content is above (N% x 5 + 0.02)% and the N content is below 0.003%, the austenite grains become coarser at a considerably high temperature. It can be suppressed to Figure 3 also shows Ti, B-containing case hardening steel similar to Figure 2.
This is a diagram showing the cleanliness of Ti-based inclusions when the N content is changed, and when N is 0.0035% or less.
It is known that when the content is reduced to about 0.002%, the amount of Ti-based inclusions becomes extremely small. Next, we will discuss other chemical components. C is a strength-imparting element, and if it is less than 0.1%, the necessary strength cannot be obtained, and if it is more than 0.3%, the ductility deteriorates.
C0.1-0.3%. C0.13~0.27 for case hardening steel
% is preferred. Si is used as a deoxidizer and
0.05% or more is necessary, but if it is too much, it will cause ductility and
Since cold workability deteriorates, the upper limit is set at 0.5%.
Mn is contained as a deoxidizing/desulfurizing agent and a hardenability improving element, and is required to be at least 0.3%, but if it is too large, the structure will become uneven due to segregation and cold workability will deteriorate, so the upper limit should be 2.0%. do. B is an element that improves hardenability when added in a small amount, from 0.0005 to
0.003% is an appropriate amount. Al is used as a desulfurizing agent, is also effective in grain refinement, and is acid-soluble.
A suitable amount of Al (SolAl) is 0.005 to 0.1%. In the present invention, in addition to the above-mentioned elements, one or both of Cr and Mo can be contained as strength-imparting elements, if necessary. When Cr is 2% or more and Mo is 0.5% or more, ductility and cold workability deteriorate. A steel material (billet) having the above-mentioned chemical composition is hot rolled by a low temperature heating method. The heating temperature needs to be 1150°C or less from the viewpoint of energy saving and to make the structure fine after rolling. The lower limit of the heating temperature is A 3 due to the need for complete austenitization.
It becomes a point. Next, examples of the present invention will be shown together with comparative examples. A steel bar (billet) having the chemical composition shown in Table 2 was heated to a temperature of 1150 to 900°C and hot rolled to produce a steel bar. Table 3 shows the cleanliness of Ti-based inclusions in these steel bars and the coarsening rate of austenite crystal grains after carburizing at 925°C. Table 2,
As is known from Table 3, the symbol D, which is the invention
- J are all hot-rolled by low-temperature heating method on products that satisfy the Ti and N content conditions specified in the present invention, and coarsening of austenite crystal grains occurs during carburization. Not yet.
【表】
＊ ppm
[Table] *ppm
第１図は圧延前加熱温度とオーステナイト結晶
粒の粗大化率の関係を示す図、第２図はＮ含有量
とオーステナイト結晶粒の粗大化温度との関係を
示す図、第３図はTi，Ｎ含有量とTi系介在物の
清浄度との関係を示す図である。
Figure 1 is a diagram showing the relationship between pre-rolling heating temperature and coarsening rate of austenite crystal grains, Figure 2 is a diagram showing the relationship between N content and coarsening temperature of austenite grains, and Figure 3 is a diagram showing the relationship between Ti, FIG. 3 is a diagram showing the relationship between N content and cleanliness of Ti-based inclusions.
Claims (1)
B0.0005〜0.003％、N0.0035％以下、SolAl0.005
〜0.1％、Ti（５×Ｎ％＋0.02）〜0.05％を含み、
残部鉄及び不純物からなる鋼材を1150℃〜A3点
の温度に加熱した後熱間圧延することを特徴とす
る再加熱時のオーステナイト結晶粒、の粗大化を
抑制した含Ｂ肌焼鋼の製造法。 ２ C0.1〜0.3％、Si0.1〜0.5％、Mn0.3〜2.0％、
B0.0005〜0.003％、N0.0035％以下、SolAl0.005
〜0.1％、Ti（５×Ｎ％＋0.02）〜0.05％を含み、
更にCr2％以下、Mo0.5％以下の１種又は２種を
含み、残部鉄及び不純物からなる鋼材を1150℃〜
A3点の温度に加熱した後、熱間圧延することを
特徴とする再加熱時のオーステナイト結晶粒の粗
大化を抑制した含Ｂ肌焼鋼の製造法。[Claims] 1 C0.1-0.3%, Si0.1-0.5%, Mn0.3-2.0%,
B0.0005~0.003%, N0.0035% or less, SolAl0.005
Contains ~0.1%, Ti (5 x N% + 0.02) ~0.05%,
Production of B-containing case-hardened steel that suppresses coarsening of austenite crystal grains during reheating, which is characterized by heating a steel material consisting of the balance iron and impurities to a temperature of 1150°C to 3 points A and then hot rolling it. Law. 2 C0.1~0.3%, Si0.1~0.5%, Mn0.3~2.0%,
B0.0005~0.003%, N0.0035% or less, SolAl0.005
Contains ~0.1%, Ti (5 x N% + 0.02) ~0.05%,
In addition, steel materials containing one or two types of Cr2% or less and Mo0.5% or less, with the balance consisting of iron and impurities, are heated to 1150℃~
A method for producing B-containing case hardened steel that suppresses coarsening of austenite crystal grains during reheating, which is characterized by heating to three temperatures and then hot rolling.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP194882A JPS58120719A (en) | 1982-01-08 | 1982-01-08 | Manufacture of case hardening b steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP194882A JPS58120719A (en) | 1982-01-08 | 1982-01-08 | Manufacture of case hardening b steel |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS58120719A JPS58120719A (en) | 1983-07-18 |
| JPS6364495B2 true JPS6364495B2 (en) | 1988-12-12 |
Family
ID=11515824
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP194882A Granted JPS58120719A (en) | 1982-01-08 | 1982-01-08 | Manufacture of case hardening b steel |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS58120719A (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61253347A (en) * | 1985-04-30 | 1986-11-11 | Kobe Steel Ltd | Low carbon steel having superior cold workability |
| JPH0765140B2 (en) * | 1986-10-20 | 1995-07-12 | 大同特殊鋼株式会社 | Case hardening steel for cold forging |
| JPH02197546A (en) * | 1989-01-26 | 1990-08-06 | Kobe Steel Ltd | Steel for surface quenching having excellent workability |
| JPH0756046B2 (en) * | 1989-04-08 | 1995-06-14 | 株式会社神戸製鋼所 | Method for producing B-containing steel |
| JP2823052B2 (en) * | 1990-01-23 | 1998-11-11 | トピー工業 株式会社 | Low carbon manganese-boron steel footwear and method for producing the same |
| US5853502A (en) * | 1995-08-11 | 1998-12-29 | Sumitomo Metal Industries, Ltd. | Carburizing steel and steel products manufactured making use of the carburizing steel |
| JP3477030B2 (en) * | 1997-06-12 | 2003-12-10 | ダイハツ工業株式会社 | Carburized members |
| CN107532252B (en) | 2015-01-27 | 2019-12-31 | 杰富意钢铁株式会社 | Case hardening steel |
-
1982
- 1982-01-08 JP JP194882A patent/JPS58120719A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS58120719A (en) | 1983-07-18 |
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