TW200300799A - Free cutting steel - Google Patents

Abstract

A low carbon free cutting steel can be obtained by allowing the steel to contain 0.02 to 0.15 mass % of C, 0.05 to 1.8 mass % of Mn, 0.20 to 0.49 mass % of S, more than 0.01 mass % and not more than 0.03 mass % of O, 0.3 to 2.3% of Cr, and the balance consisting of Fe and inevitable impurities, the Cr /S ratio falling within a range of between 2 and 6.

Description

200300799 发明 Description of the invention [Technical field to which the invention belongs] The present invention relates to free-cutting steel, and is particularly suitable as a substitute steel for the previous low-carbon sulfur composite free-cutting steel. 0.15 to 0.35% low-carbon free-cutting steel with greatly reduced mass, and machinab 11 ity with better low-carbon sulfur composite free-cutting steel than before, and lower oxygen content and surface than before Sulfur or sulfur composite free-cutting steel with excellent flawability and few machinability. [Prior art] In the past, low-carbon free-cutting steels have been known as low-carbon and sulfur-free composite free-cutting steels which are added with lead (Pb) and sulfur (S) as free-cutting elements. However, with regard to Pb among these elements, there have been attempts to curb its use due to global environmental problems. In response to this situation, Japanese Unexamined Patent Publication No. 9-2 5 5 3 9 (hereinafter, referred to as the prior art 1) discloses a non-additive type of Pb non-additive that promotes finely dispersed precipitation of M n S by adding N d. Non-refined steel. Also, Japanese Patent Application Laid-Open No. 2000-1 602 84 (hereinafter referred to as "the prior art 2") discloses that the addition of a large amount of S increases the amount of sulfide and suppresses the sulfide form of P b non-additive type by oxygen. Cut steel. Furthermore, in Japanese Patent Publication No. 2-6 8 2 4 (hereinafter referred to as "prior art 3"), it is disclosed that the addition of Cr, which is more likely to form a compound with S than Mn, can replace MnS to form CrS, which improves the machinability. steel. However, the ‘preceding technology 1’ is a non-refined steel containing C: 0.2 to 0.6% of the target steel type, and because it uses a special element N d, it cannot fully meet the requirements for cost reduction. In addition, since the prior art 2 adds a large amount of S, it may cause thermal delay 7 312 / Invention Specification / 92-02 / 9113475 6 200300799 to deteriorate. In addition, the prior art 3 is an expensive Cr addition amount of 3.5 to 5.9%, which cannot fully meet the requirements for cost reduction, and if a large amount of Cr S is generated like this technology, material melting is increased. The difficulty is therefore disadvantageous. Therefore, for the low-carbon-sulfur composite free-cutting steel, from the viewpoint of saving processing costs, it is strongly desired to further improve the machinability. JP-A No. 1-3 2 3 02 (hereinafter referred to as "prior art 4") that meets such expectations "exposes that the sulfide is not increased by adding more S and the sulfide form is controlled by T e, and Limiting the amount of oxygen to 0.0030% or less reduces the number of alumina clusters and improves free-cutting steel. Also, in Japanese Unexamined Patent Publication No. 3 09 94 6 (hereinafter, referred to as the prior art 5), it is disclosed that the sulfide is increased by adding more S and the free-cutting element Pb is added to improve machinability. Oxide defects are free-cutting steels that limit the amount of oxygen to less than 0.08%. However, since the prior arts 4 and 5 are both low in oxygen, they cannot be said to be machinable to sufficiently control the form of effective sulfides, become prolonged sulfides, and the effect of improving machinability is insufficient. Further, the above-mentioned prior art 2 also controls the form of a large amount of sulfides through oxygen, and therefore has excellent machinability. However, as described above, since a large amount of S is added, the hot ductility may be lowered. On the other hand, in sulfur and sulfur composite free-cutting steels, in order to control machinability in the form of effective sulfides, a large amount of oxygen is generally contained. However, since all of the oxygen is not solid-solved in the sulfide, it is impossible to avoid the formation of giant oxides at the same time, which is the cause of defects and causes major defects in processed products. In this case, in order to avoid such defects, the above-mentioned prior art 5 allows 8 312 / Invention Specification / 92-02 / 911347 to allow 200300799 to have an oxygen weight of 0.008% or less. In addition, the above-mentioned prior art 2 is to add incremental s and reduce the necessary amount of oxygen. Furthermore, the foregoing prior art 1 uses N d as a sharp element and reduces the necessary amount of oxygen. However, although the "advanced technology 5 limits the oxygen content to less than 0.008%, but because the oxygen content is only reduced," the sulfide form cannot be fully controlled as described above, and there is an extended sulfide. Not enough from a point of view. In addition, the "prior art 2" is concerned with the fear that S will reduce the heat ductility as described above. Furthermore, the prior art 1 has the problem of reducing costs as described above. [Summary of the Invention] The first object of the present invention is to provide no added lead, or the lead addition amount is significantly reduced compared to the previous low carbon sulfur composite free-cutting steel, which will not hinder the reduction of costs and will not cause the reduction of hot ductility. Low-carbon free-cutting steel with the same machinability as the previous low-carbon-sulfur composite free-cutting steel. A second object of the present invention is to provide a low-carbon and sulfur-free composite free-cutting steel that has lead and sulfur that are not increased as compared with the previous ones, and has better machinability than the previous ones. A third object of the present invention is to provide a machinable material that does not prevent cost reduction, does not cause reduction in hot ductility, has less oxygen content than before, and is comparable to previous steels containing the same amount of sulfur and lead. Sulfur or sulfur-composite free-cutting steel with excellent surface properties and low surface defects due to the delay of the pressure of bubbles that occurs during casting by achieving low oxidation. According to the first aspect of the present invention, it is provided to contain mass% C: 0.02 to 0.15%, Mn: 0.05 to 1.8%, S: 0.20 to 0.49%, 0: more than 0.01 to 0.03%, and Cr: 0.2 to 2.3. % ', And the remaining portion is made of Fe and unavoidable impurities, and the low-carbon free-cutting steel with a Cr / S ratio of 2 to 6 mm. 9 312 / Invention specification / 92-02 / 91134756 200300799 According to the second aspect of the present invention, it is provided that the mass% C: 〇, 〇2 ~ 0.15%, 1 ^ 11: 0.05 ~ 1.0%, 3: 0.20 to 0.49%, 〇: more than 0.08 to 0.030%, Pb: 0.04 to 0.35%, Cr: 0.3 to 2.3%, and the remainder is composed of Fe and unavoidable impurities, and the Cr / S ratio is 2 Low carbon and sulfur composite free-cutting steel with a range of ~ 6 and excellent machinability. According to the third aspect of the present invention, a sulfide-based intermediary substance having a mass% s of 0: 16 to 0.49%, 0: 0.002 to 0.0 10%, and a long diameter having a particle diameter of 10 # m or more is provided. In the aspect ratio of 5 or less, 80% or more, sulfur or sulfur composite free-cutting steel with few surface defects and excellent machinability ° According to the fourth aspect of the present invention, the mass content C is provided: 0.02 to 0.15 %, Μη: 0.05 to 1.8%, S: 0.16 to 0.49%, 0: 0.002 to 0 · 0 1 0%, C r: 0.3 to 2.3 · 3%, and the remaining portion is Fe and inevitable impurities Sulfur or sulfur-composite free-cutting steel composed of sulphur or sulfur-composite free-cutting steel with a small Cr / S ratio in the range of 2 to 6 and excellent machinability. [Embodiment] Hereinafter, the present invention will be described in detail. 1. The first free-cutting steel The first free-cutting steel is the low-carbon free-cutting steel of the first aspect described above, and contains mass% C: 0.02 to 0.15%, Mn: 0.05 to 1.8%, S: 0.20 to 0.49%, 0: more than 0.01 to 0.03%, Cr: 0.3 to 2.3%, and the remainder is composed of Fe and unavoidable impurities, and the Cr / S ratio is in the range of 2 to 6. Further, it may further contain Si by mass: 0.1% or less, P: 0.001 to 0.12%, and A: 0.01% or less. Furthermore, in the above-mentioned basic composition or substances that further contain Si, P, and A1, 10 312 / Invention Specification / 92-02 / 9113475 6 200300799 may further contain mass% 0: 0.0001 to 0.0005%,? Heart 0.0: Se: 0.02 to 0.30%, Te: 0.1 to 0.15%, Bi: 0.02 to 0.20% to 0.02%, B: 0.04 to 0.010%, N: 0.005 to 0.015%, 0.50 %, Ti: 〇〇〇〇〇3 ~ 0.090%, V: 0.005 ~ 0.200%, 2 0.090%, minus 2: 〇〇〇〇〇〜0.0080% are selected from the group consisting of: In steel, the long diameter is 90% of the total sulfide media with sulfide-based intermediaries, and the long diameter is the ratio of sulfide media with a particle size of 1 // m or more. Those below 5 account for more than 80%. In addition, it is preferable to have a fatty and granular body and a boletic structure in this type, and the austenite field particle size is more than 7 is preferred. In order to achieve the above first object, the inventors of the present invention repeatedly found the following findings. (i) Through proper addition of Cr, Mn, and S and appropriate adaptation of Cr, an appropriate amount of S-Cr-Mn composite sulfide can be obtained. The sulfide-based intermediary composition of this composite system is long in thermal processing. Therefore, when the sulfide-based intermediary is made to be large and spun-like (η) is compared with the same S amount, if the previously known sulfur media is considered to be larger, or closer to the spun-like shape, the machinability is improved If the above-mentioned Cr, Mn, and S are added in an appropriate amount and the Cr / S ratio & is formed into a large and spun-like sulfide-based intermediary, the handleability and surface machinability can be improved.

(i 1 i) It has been known in the past that the machinability is improved by the anisotropy of hot workability or mechanical properties as the amount of S increases. S 312 / Invention Specification / 92-02 / 91134756 -0.03% ^, Sn: 0.003 C u: 0 · 0 5 to: r: 0.005 to one less. The upper particle size is preferred. In medium and vertical cutting steel, the excessive grain size is studied, and the / S ratio of the intermediary system inhibits elongation. In the chemical system: the opinion, 5 is appropriate, including high chip content, but limited by the amount of 11 200300799. In this case, if the Cr, Mn, and S amounts and the Cr / S ratio are adjusted as described above to form a large-sized and spun-like sulfide-based compound, the upper limit of the amount of S can be increased. As a result, Even if it is not Pb, or even if it is significantly reduced compared with the past, the machinability including the roughness of the chip-handling surface can be significantly improved. The above-mentioned first free-cutting steel was obtained based on the findings, whereby the amount of lead or lead added is significantly reduced compared to the previous low-carbon and sulfur-free composite free-cutting steel, which will not hinder the reduction of costs and will not cause the reduction of hot ductility. , And can be selected from the previous low-carbon sulfur composite free-cutting steel more than the same machinability. Next, the reason for making the first free-cutting steel as described above will be explained. (a) C: 0.02 to 0.15 mass% C is a heavy element because it has a large effect on the strength and machinability of steel. However, if the content is less than 0.02 mass%, sufficient strength cannot be obtained. On the other hand, when the content exceeds 0.15 mass%, the strength is too high, and the machinability is deteriorated. Therefore, the C content is set in the range of 0.0 2 to 0.1 5%. The range of 0.02 to 0.10 mass% is preferred. (b) Mn: 0.05 to 1.8% by mass Mn is an element that forms a sulfide important for machinability. However, if the amount is less than 0.05% by mass, the machinability cannot be obtained because the amount of sulfide is too small. On the other hand, when the content exceeds 1.8% by mass, the compound is elongated and machinability is reduced. Therefore, the Mη content is set to a range of 0.1 to 1.8% by mass. Preferably it is 0.22 mass% or more and less than 0.60%. (c) S: 0.20 ~ 0.49% by mass 312 / Invention Specification / 92-02 / 91134756 Adding agent addition, table addition is low, and the content of the required content becomes mass, and its content is sufficient. Sulfur 05 ~ mass 12 200300799 s to form Sulfide-forming elements of sulfides effective for machinability. However, if its content is less than 0.20% by mass, the amount of sulfide is small, so the effect on machinability is small. On the other hand, if the content exceeds 0.49% by mass, the hot workability and ductility are significantly reduced. Therefore, the S content is set to a range of 0.20 to 0.49% by mass. (d) 〇: More than 0.01 to 0.03% by mass 〇 is an effective element that suppresses sulfide elongation during hot working such as compression and drawing, and is an important element that improves machinability by its action. However, if the content is 0.01% by mass or less, the effect of suppressing the elongation of the sulfide is insufficient, and the effect of the remaining elongated sulfide cannot be fully exhibited. On the other hand, even if it is added more than 0.03% by mass, the elongation suppressing effect of the sulfide is saturated, and if it is added in an excessive amount, it is not economical, and casting defects such as blow holes occur. Therefore, the content is set to a range exceeding 0.01 to 0.03% by mass. (e) Cr: 0.3 to 2.3% by mass

Cr is an effective element that suppresses sulfide elongation during hot working such as compression and drawing, and is an important element that improves machinability by its action. Therefore, if the content is less than 0.3% by mass, the effect of suppressing the elongation of the sulfide is insufficient, and the elongated sulfide remains, so that the sufficient effect is not obtained. On the other hand, even if it is added more than 2.3% by mass, the elongation suppressing effect of the sulfide is saturated, and excessive addition is not economical. Therefore, the Cr content is set to the range of 0.3 to 2.3% by mass. It is preferably from 0.3 to 1.5 mass%. (f) C1 " S ratio: 2 to 6

The Cr / S ratio is an important index of the degree of sulfide elongation during hot working such as left and right compression. By specifying the ratio, the desired elongation can be obtained to improve machinability. 13 312 / Invention Specification / 92-02 / 91134756 200300799 Length of sulfide. However, if the ratio is less than 2, the elongation of sulfide is remarkably caused by the generation of M η -S single-system sulfide, so that the machinability is deteriorated. On the other hand, when the ratio exceeds 6, the effect of suppressing elongation of the sulfide is saturated. Therefore, let Cr / S be in the range of 2 to 6. The range of 2 to 4 is preferable. The first free-cutting steel requires the above-mentioned requirements, and the other requirements are as follows. (g) S 1: 0 · 1% by mass or less S: is a deacidifying element, and the oxide of S 1 acts as a nucleus for generating sulfides, promotes the generation of sulfides and makes the sulfides fine, and deteriorates the life of the cutting tool Therefore, in the case where the tool life is to be prolonged, the S 1 content is specified to be 0.1% by mass or less. More preferably, it is not more than 0.03% by mass. (h) P: 0 · 01 to 0.12% by mass. P is an effective element for reducing the thickness of the machined surface by suppressing the formation of a tool tip structure during cutting. However, if the content is less than 0.001% by mass, a sufficient effect cannot be obtained. On the other hand, when the content exceeds 0.12% by mass, the above effects are saturated and the hot workability and ductility are significantly reduced. Therefore, 'the ρ content is set in the range of 0.01 to 0.12 mass%. The range of 0,01 to 0.09 mass% is preferred. (1) Α1: 0 · 01% by mass or less. A1 is the same as Si, which is a deacidifying element. 'The oxide of A1 acts as a nucleus for generating sulfides, promotes the generation of sulfides and makes sulfides fine.' The life is deteriorated. Therefore, in the case where the life of the tool is to be prolonged, it is preferable to set the A1 content to 0.01% by mass or less. It is more preferably 0.0003% by mass or less. (j) Ca: 0.000 1 to 0.0005 mass%

Pb: 0.01 to 0.03 mass% 14 312 / Invention specification / 92-02 / 91134756 200300799

Se: 0.02 to 0.30 mass%

Te: 0.1 to (M5 mass%

Bi: 0.02 to 0.20% by mass

Sn: 0.003 to 0.020 mass% Β: 0.004 to 0.010 mass% Ν: 0.005 to 0.015 mass%

CikO.05 〜〇.5〇 Mass%

Ti: 0.003 to 0.090 mass% V: 0.005 to 0.200 mass%

Zr: 0.005 to 0.090% by mass

Mg: 0.0005 to 0.0080% by mass

Ca, Pb, Se, Te, Bi, Sn, B, N, Cu, butadiene 1, v, Zr, Mg are added in cases where machinability is important. However, if their added amounts are less than the above-mentioned lower limit, a sufficient machinability improvement effect cannot be obtained. On the other hand, even if it exceeds the above-mentioned upper limit, the machinability improvement effect is saturated, and it is economically disadvantageous. Therefore, in the case where they are added, Ca: 0.0000i to 0.0005 mass%, PbiO.O1 to 0.03 mass%, Se: 0.02 to 0.30 mass%, and Te: 0.1 to 0.15 mass. %, Bi: 0.02 to 0.20% by mass, Sn: 0.003 to 0.020% by mass, B: 〇〇〇〇4 to 0.010% by mass, meaning 0.005 to 0.015% by mass, cu: 0.05 to 0.50% by mass , Ti: 0.003 to 0.090% by mass, V: 0.005 to 0.200% by mass, Zr: 0.005 to 0.090% by mass, and Mg: 0.0005 to 0.0080% by mass. (k) Microstructure 15 312 / Invention Specification / 92-02 / 91134756 200300799 The microstructure of the first free-cutting steel is preferably the structure of the main body of fat and granules. The larger austenite particle size is advantageous for machinability, but it can maintain good machinability even with fine particles. From the viewpoint of the mechanical properties of the product, it is better to make fine particles with a particle size exceeding No. 7 (the particle size according to the Austenitic body measurement method of Π S G 0 5 51). (l) Particle size of sulfide-based intermediaries It is advantageous for machinability to greatly generate sulfide-based intermediaries. Therefore, it is preferable that the long diameter is 10 0 m or more, and the amount thereof is preferably 90% or more in the sulfide-based intermediary. (m) Aspect ratio of sulfide-based intermediary The aspect ratio of sulfide-based intermediary is as shown in Figure 1. When the major axis of the sulfide-based intermediary particle is L and the short diameter is d, the ratio is L / d. Means. For machinability, it is advantageous for the sulfide-based intermediary to be produced in the form of a spinning reed. Therefore, the aspect ratio is preferably 5 or less, and the proportion of sulfide intermediary in such aspect ratio is preferably 80% or more in the sulfide-based intermediary having a major diameter of 10 / m or more. 1Second free-cutting steel The second free-cutting steel is a low-carbon free-cutting steel according to the above-mentioned second viewpoint. It contains mass% C: 0.02 to 0.15%, Mn: 0.05 to 1.00%, and S: 0.20 to 0.49. %, 〇: more than 0.008 to 0.030%, Pb: 0.04 to 0.35%, Cr: 0.3 to 2.3%, and the remainder is composed of Fe and unavoidable impurities, and the Cr / S ratio is in the range of 2 to 6. In addition, it may further contain Si by mass: 0.1% or less, P: 01 to 12%, and A1: 0.01% or less. 16 312 / Invention specification / 92-02 / 91134756 200300799 Furthermore, in the above-mentioned basic composition or substances containing Si, P, and A1 ', they may further contain mass% c: 0.0001 to 0.0005%, Se: 0.02 to 0.30% Te: 0.1 to 0.15%, Beta: 0.02 to 0.20%, Sn: 0.003 to 0.02%, B: 0.004 to 0.010%, N: 0.005 to 0.015%, Cu: 0.05 to 0.50%, Ti: 0.003 At least one selected from the group consisting of ~ 0.090%, V: 0.005 to 0.200%, Zr: 0.005 to 0.090%, and Mg: 0.0005 to 0.00 0%. In order to achieve the above-mentioned second object, the present inventors and the like repeatedly made investigations, and as a result, found the following. (1) As described above, by adding an appropriate amount of Ci ·, Mn, and S and by adjusting the Cr / S ratio, an appropriate amount of S-Cr-Mn composite sulfide-based intermediary can be obtained. The sulfide-based intermediary composed of this composite system suppresses elongation during hot working. Therefore, by making the sulfide-based intermediary large and spun-like, the machinability including chip handling and surface roughness can be improved. (ii) As described above, if a large amount of sulfide intermediary is formed through the appropriate addition of Cr, Mn, and S and the Cr / S ratio, the upper limit of the amount of S can be increased. As a result, , Can improve the machinability including chip handling and surface roughness. (in) As described above, the effect of the quick-cutting element Pb is complementary, which significantly improves the machinability including chip handling and surface roughness. The above-mentioned second free-cutting steel was obtained based on such findings, whereby 'lead and sulfur have not increased more than before, and can exhibit better machinability than before. Next, the reasons for the second free-cutting steel as described above will be explained. (a) C: 0.02 to 0.15% by mass Same as the first free-cutting steel, but the content of c is less than 0.0 2% by mass, '17 312 / Invention Specification / 92-02 / 91134756 200300799 cannot be obtained sufficiently, if it exceeds 0, .1 5 mass%, the strength becomes too high, and machinability deteriorates. Therefore, the C content is set to a range of 0.2 to 0.15% by mass. The range of 0.02 to 0.10 mass% is preferred. (b) Mn: 0.05 to 1.00% by mass Mn is an element that forms a sulfide important for machinability. However, if the content is less than 0.05% by mass, the machinability cannot be obtained because the sulfide content is too small. On the other hand, when the content exceeds 1.0% by mass, the sulfide is elongated and machinability is reduced. Therefore, the M η content is set to a range of 0.05 to 1.00% by mass. Preferably it is 0.22 mass% or more and less than 0.60 mass%. (c) S: 0.20 to 0.49 mass% Same as the first free-cutting steel. If the S content is less than 0.20 mass%, the amount of sulfide is small, so the effect on machinability is small. If it exceeds 0.4 9 mass%, hot workability And significant reduction in ductility. Therefore, the S content is set to 0.20 to 0.49 mass%. (d) 〇: More than 0.008 to 0.030% by mass 〇 It is an effective element that suppresses sulfide elongation during hot working such as compression and drawing, and is an important element that can improve machinability by its action. However, if the content is 0.008 mass% or less, the effect of suppressing the elongation of the sulfide is insufficient, and the effect of the remaining elongated sulfide cannot be fully exhibited. On the other hand, even if it exceeds 0.030% by mass, the elongation suppressing effect of the sulfide is saturated, and if it is added in an excessive amount, it is unfavorable to economy, and casting defects such as porosity occur. Therefore, the content is set to a range exceeding 0.008 to 0.030% by mass. (e) Pb: 0.04 to 0.35 mass% 18 312 / Invention specification / 92-02 / 9113475 6 200300799

Pb is an important element for improving machinability. When the content is less than 0.04 mass%, the effect on machinability is small because the content is small. On the other hand, even if it exceeds 0.35% by mass, the improvement of machinability is saturated, and the hot workability is significantly reduced. Therefore, the Pb content is set in the range of 0.04 to 0.35 mass%. (f) Ci \ 0.3 to 2.3% by mass Same as the first free-cutting steel, if the content of Cr is less than 0.3% by mass, the effect of suppressing the elongation of sulfide is insufficient, and the remaining elongated sulfide cannot obtain sufficient effect, even if added. If it exceeds 2.3% by mass, the effect of suppressing the elongation of the sulfide is saturated, and excessive addition is not economical. Therefore, the Cr content is set to a range of 0.3 to 2.3% by mass. It is preferably 0.3 to 1.4% by mass. (g) Cr / S ratio: 2 ~ 6 The second free-cutting steel is also the same as the first free-cutting steel. The Cr / S ratio is important. If the ratio is less than 2, it passes through the η-S single system sulfide. The generated sulfide is remarkably deteriorated in machinability, and if the ratio exceeds 6, the effect of suppressing sulfide elongation is saturated. Therefore, let Cr / S be in the range of 2 to 6. The range of 2 to 4 is preferable. The second free-cutting steel requires the above-mentioned requirements, and the other requirements are as follows. (h) SkO.1% by mass or less As described above, S! is intended to prolong the life of cutting tools. Therefore, in the case of extending the tool life, the content of S1 is set to 0. 1% by mass or less as in the first free-cutting steel. Better. More preferably, it is 0.03 mass% or less. (i) P: 0 · 01 ~ 0.12 mass% Same as the first free-cutting steel, if the P content is less than 0.001 mass%, it cannot be charged at 19 312 / Invention Specification / 92-02 / 91134756 200300799 points to reduce the processing As for the effect of the surface roughness, if the content exceeds 0.12% by mass, the above effects are saturated and the hot workability and ductility are significantly reduced. Therefore, 'let the P content be in the range of 0.01 to 0.12 mass%. The range of 0.001 to 0.09 mass% is preferred. (j) Α1: 0 · 01% by mass or less As described above, A1 is to degrade the life of the cutting tool '. Therefore, in the case where the tool life is to be prolonged', it is preferable to set the content of A1 to 0.001% by mass or less. It is preferably 0.003 mass% or less. (k) Ca: 0.0001 to 0.0005 mass%

Se: 0.02 to 0.30 mass%

Te: 0.1 to 0.15 mass%

Bi: 0.02 to 0.20% by mass

Sn: 0.003 to 0.020 mass% B: 0.004 to 0.010 mass% N: 0.005 to 0.015 mass%

Cu: 0.05 to 0.50 mass%

Ti: 0.003 to 0.090 mass% V: 0.005 to 0.200 mass%

Zr: 0.005 to 0.090% by mass

Mg: 0.0005 to 0.0080% by mass

Ca, Se, Te, Bi, Sn, B, N, Cu, butadiene, V, Zr, and Mg are added when the machinability is important. However, if their added amounts are less than the aforementioned lower limit, sufficient machinability improvement effects cannot be obtained. In another aspect of 20 312 / Invention Specification / 92-02 / 91134756 200300799, even if it exceeds the above upper limit, the machinability improvement is saturated, and it is also economically disadvantageous. Therefore, in the additive form, Ca: 0.0001 to 0.0005 mass%, Se: 0.02 to 0.30: Te: 0.1 to 0.15 mass%, Beta: 0.02 to 0.20 mass%, Sn: 0.003 mass%, and B: 0.004. ~ 0.010 mass%, N: 0.005 to 0.015 | Cu: 0.05 to 0.50 mass%, Ti: 0.003 to 0.090 mass%, V: 0.200 mass%, Zr: 0.005 to 0.090 mass%, Mg: 0.0005, mass% range. (k) Microstructure The microstructure of the second free-cutting steel is preferably the same as that of the first free-cutting steel. The larger austenite size is good for cutting, but it can maintain good machinability even with fine particles. From the viewpoint of mechanical properties, it is preferable that the grain size exceeds the same as that of the first free-cutting steel and is made fine. Third free-cutting steel The third free-cutting steel is sulfur or sulfur-combined free-cutting steel with the above-mentioned third viewpoint. Mass%: 8: 0.16 ~ 0.49%, 0: 0.002 ~ 0.010%, and vulcanization with a particle diameter of more than 10m. In the intermediary of the system, the aspect ratio is 5 which accounts for more than 80%. The specific composition of C that realizes such sulfide-based intermediaries and stipulates the machinability is as shown in the sulfur or sulfur compound of the fourth aspect described above, containing mass% C: 0.02 to 0.15%, Mn: 0.05 to 1.8% to 0.49%, 0: 0.002 to 0.010%, CrO.3 to 2.3%, and composed of residual Fe and unavoidable impurities, and the Cr / S ratio is 2 to 6 of 312 / Invention Specification / 92- 02/91134756 The effect is equal to mass%, ~ 0.020 I% by weight, 0.005 to -0.0080 For the range. 21 200300799 It may further contain mass% S 1: 0.1% or less, P: ο. 〇 4, A1: 〇. 〇 1% or less. In addition, the above basic composition or Si, P, and A1 may further include mass% Ca: 0.0001 to 0.0090%, Pb: 0.01 Se: 0.02 to 0.30%, Te: 0.03 to 0.15%, and Bi: 〇. 〇2 to 0.20% to 0.02%, Beta: 0.004 to 0.010%, N: 0.005 to 0.015%, 0.50%, Ti: 0.003 to 0.090%, V: 0.005 to 0.200%, 2 0.090%, ^^: selected from the group consisting of 0.0005 to 0.0080%. In order to achieve the third object described above, the inventors repeatedly found the following findings. (1) For sulfide systems with a major diameter of 1 0 // m or more, the aspect ratio of 5 or less is 80% or more. By making the sulfide into a large and spun reed, even if it is larger than the previous steel The addition and decrease of oxygen make the chip handleability and surface roughness machinability more than before. (i 1) As described above, through appropriate addition and adaptation of C r, M η, and S, appropriate amounts of sulfur mediators of the S-C r-M η composite system can be obtained, and the sulfide system composed of this composite system Since the intermediary substance suppresses thermal elongation, a large-sized and spun-like sulfur intermediary substance can be obtained as shown in (i). (in) Since the oxygen content can be reduced more than the previous steel, the air bubbles generated during casting are reduced more than before. Reducing air bubbles can suppress surface flaws that occur as a starting point of pressing and pulling, so the surface flaws of the pressing and pulling materials (iv) have been known from the past to increase as the amount of S increases and can be cut 312 / Invention Specification / 92-02 / 91134756, 〇 · 12%, ~ 0.40% of the substance, Sn: 0.〇〇3 Cu: 0.05 ~: r: 0 · 0 0 5 ~ less—species. According to research, the amount of intermediaries in 1 medium can also be the same as the Cr / S ratio of the steel in the chemical system during processing, which can sometimes be used to reduce defects. Machinability, but 22 200300799 Due to the problem of hot workability or mechanical anisotropy, the upper limit of s is set. In this case, if the large and spun-like intermediary is formed as described above, the upper limit of the s content can be increased, and as a result, the machinability including chip handling properties and surface roughness can be significantly improved. The above-mentioned third free-cutting steel was obtained based on such findings, thereby reducing costs and not causing a reduction in hot ductility, which is less prevalent than before and compared with previous steels containing sulfur and lead in equal amounts , The machinability is more excellent, and by achieving low oxidation, the surface defects when the pores are pulled during the cause can be reduced. Next, the reason why the third free-cutting steel is specified as described above (a) S: 0.16 to 0.49 mass% S is a sulfide formation that forms a sulfide effective for machinability, but the content is less than 0.16 mass%. Since the amount of sulfide is small, the effect on machinability is small. On the other hand, if the content exceeds 0.4 9 mass, hot workability and ductility are significantly reduced. Therefore, the S content is set to a range of 0.1 <% by mass. (b) 〇: 0.002 to 0.010% by mass 〇 is an effective element that suppresses sulfide elongation during hot working such as compression and drawing, and is an important element that improves machinability by its action. However, when the content is 0.002 mass%, the effect of suppressing the elongation of the sulfide is insufficient, and the effect of the long sulfide cannot be fully exhibited. On the other hand, air bubbles are generated at the time of manufacture, and from this point on, the surface occurs during compression. Therefore, excessive content is harmful. If the content of Ο exceeds 0.010% by mass, there are many such bubbles, and the surface defects at the time of compression tend to increase. 312 / Invention Specification / 92-02 / 91134756 Sulfur is present in the amount, so that the package does not hinder the amount of oxygen, and can Available in casting elements. If it can be cut by%, then the content is 0.49, and if the content is the residual extension, the defect occurs, and the effect of 23 200300799 to suppress the elongation of sulfide is small. Therefore, the content of 0 is set to the range of 0.002 to 0.010% by mass. (c) In a sulfide-based intermediary having a particle diameter of 10 mm or more, the aspect ratio of 5 or less is 80% or more. For machinability, the sulfide-based intermediary is large and spinning. State generators are more advantageous. Therefore, the large-scale sulfide-based intermediary with a long diameter of more than 10 // m must have an aspect ratio of 5 or less, which must account for more than 80%. In order to obtain such sulfide-based intermediaries, in addition to S and 0, the C, Mn, Cr, and Cr / S ratios are defined as described above. (d) C: 0.02 to 0.15 mass% Same as the first free-cutting steel, if the C content is less than 0.02 mass%, sufficient strength cannot be obtained. If it exceeds 0.15 mass%, the strength becomes too high. , Machinability deteriorates. Therefore, the C content is set to a range of 0.2 to 0.15% by mass. The range of 0.02 to 0.10 mass% is preferred. (e) Mn: 0. 05 to 1.8% by mass As with the first free-cutting steel, if the content of Mn is less than 0.05% by mass, the amount of sulfide is too small, and sufficient machinability cannot be obtained. When the content exceeds 1.8% by mass, the sulfide has a long elongation and the machinability is reduced. Therefore, the Mη content is set to a range of 0.05 to 1.8% by mass. It is preferably 0.22 mass% or more and less than 0.60 mass%. (f) Cr: 0.3 to 2.3% by mass Same as the first free-cutting steel, with an S content of less than 0.3% by mass, the effect of suppressing the elongation of the sulfide is insufficient, and the remaining elongated sulfide cannot achieve a sufficient effect. Even if it is added more than 2.3% by mass, the effect of suppressing sulfide elongation 24 312 / Invention Specification / 92-02 / 91134756 200300799 is saturated, and excessive addition is not economical. Therefore, the Cr content is set to the range of 0.3 to 2.3% by mass. It is preferably 0.3 to 1.5% by mass. (g) Cr / S ratio: 2 ~ 6 In the third free-cutting steel, it is also the same as the first and second free-cutting steels. The Cr / S ratio is important. If the ratio is less than 2, it is passed through Μ η-S. Since the sulfide produced by the sulfide is significantly elongated, the machinability is deteriorated, and if the ratio exceeds 6, the effect of suppressing the sulfide elongation is saturated. Therefore, let Cr / S be in the range of 2 to 6. The range of 2 to 4 is preferable. The other requirements of the third free-cutting steel are as follows. (h) S i: 0 · 1% by mass or less As described above, S 1 is to deteriorate the life of the cutting tool. Therefore, in the case where the tool life is to be prolonged, the Si content is set to 0.1 as in the first and second free-cutting steels. It is preferably at most% by mass. More preferably, it is 0.03 mass% or less. (i) P: 0 · 04 to 0.12% by mass If the content of P is less than 0.04% by mass, the effect of inhibiting the generation of built-up edges at the cutting edge cannot be effectively exerted, and the machining surface cannot be fully exerted. As for the effect of the coarseness, if the content exceeds 0.12% by mass, the above effects are saturated and the hot workability and ductility are significantly reduced. Therefore, the P content is set to a range of 0.04 to 0.12% by mass. (j) A 1: 0.0 1% by mass or less As described above, A1 deteriorates the life of the cutting tool. Therefore, if the tool life is to be prolonged, the A1 content is preferably 0.01% by mass or less. It is preferably 0.003 mass% or less. (k) Ca: 0.0001 to 0.0090% by mass 25 312 / Invention specification / 92-02 / 9113 彳 75 6 200300799

Pb: 0.01 to 0.40% by mass S e: 0.0 2 to 0 · 30% by mass

Te: 0.03 to 0.15 mass% Beta: 0.02 to 0.20 mass%

Sn: 0.003 to 0.020 mass% B: 0.004 to 0.010 mass% N: 0.005 to 0.015 mass%

Cu: 0.05 to 0.50 mass%

Ti: 0.003 to 0.090 mass% V: 0.005 to 0.200 mass%

Zr: 0.005 to 0.090% by mass

Mg: 0.0005 to 0.0080% by mass

Ca, Pb, Se, Te, Bi, Sn, B, N, Cu, Ti, V, Zr, and Mg are all added when the machinability is important. However, if their added amounts are less than the above-mentioned lower limit, a sufficient machinability improvement effect cannot be obtained. On the other hand, even if it exceeds the above-mentioned upper limit, the machinability improvement effect is saturated, and it is economically disadvantageous. Therefore, when they are added, Ca: 0.0001 to 0.0090% by mass, Pb: 0.01 to 0.40% by mass, Se: 0.02 to 0.30% by mass, Te: 0.03 to 0.15% by mass, and Beta: 0.02 to 0.20% by mass. , Sn: 0.003 to 0.020 mass%, B: 0.004 to 0.010 mass%, N: 0.005 to 0.015 mass%, Cu: 0.05 to 0.50 mass%, Ti: 0.003 to 0.090 mass%, V: 0.005 to 0.200 mass%, Zr : 0.005 to 0.090% by mass, and Mg: 0.0005 to 0.0080% by mass. 26 312 / Invention Specification / 92-02 / 91134756 200300799 (k) Microstructure The microstructure of the third free-cutting steel is the same as that of the first and second free-cutting steels. The larger Austenite particle size is advantageous for machinability, but it can maintain good machinability even for fine particles. From the viewpoint of the mechanical properties of the product, it is preferable that the same size as that of the first free-cutting steel exceeds No. 7 and is made into fine particles. In addition, the manufacturing methods of the first to third free-cutting steels are not particularly limited. Casting and hot-pressing can be performed under normal conditions, and the subsequent heat treatment is also not particularly limited. For example, ordinary normalization can be used. (Η 〇rma 1 izing). (Examples) Examples of the present invention will be described below. First Embodiment Here, an embodiment regarding a first free-cutting steel is shown. Steels having a chemical composition composition within the range of the first free-cutting steel shown in Table 1 (hereinafter, referred to as examples of the present invention) N. 1 to 6, respectively, having a chemical composition composition outside the range of the first free-cutting steel are melted. Steel (hereinafter, referred to as Comparative Example) No. 7 ~ 1 1 and No. 1 2 low-carbon sulfur composite free-cutting steel as a reference example, which were cast into a cast ingot having a cross section of 400 mmx300 mm and then hot-pressed to 80 mm Bar steel of diameter. Furthermore, after heating at 9 25 ° C for 1 hour, it was normalized by air cooling to room temperature. The sulphide-based intermediary morphology was measured on the thus produced steel bars with various component compositions, and the machinability test was performed. The morphology of the sulfide-based intermediary was determined as all the sulfide-based intermediaries present in the area of 5.5 mm X 1 1 mm in the middle part of the bar steel. The image analysis apparatus 27 312 / Invention specification / 92-02 / 91134756 200300799 was used to determine the long diameter L. (Length in the direction of compression) and short diameter d (thickness, length in the direction of tension in the direction of compression), and determine the proportion of sulfide-based intermediaries with a length of 10 # or more, and a length of 10 β In sulfide-based intermediaries above m, the ratio of aspect ratio L / d is 5 or less. The machinability test was performed under the conditions shown in Table 2. 28 312 / Invention specification / 92-02 / 91134756 200300799 6 (n

Cr / S 〇 〇cn Γ- inch C < 1 cn m r- (NI ON inch ON ο co oo r- csi r- ο inch m υη ο 〇〇ΓΟ CN! Ι Η ν〇τ—Η Ο _ Λ Φ Φ Chain _ _ Μ _ CNl oo iW _ Μ _ _ τ—Η tribulus quinoa m. Quinoa quinoa m. Quinoa CNl ®! 圏 图 ffil 圏 图 图 圈 W ο P = 1 _ _ _ υο o _ raraW _ M quinoa quinoa quinoa quinoa m 圏 圏 H 圏 ϋ 圏 ϋ m 〇0044 0.0028 0.005 5 0.005 1 0198 0044 006 1 00 5 3 0.0045 00 14 0.005 2 0152 〇ο o ο 〇〇ο • 005 5 0.006 8 0.0095 τ—Η CO! «Ο ο • 0 198 • 00 5 4 • 00 8 1.007 3 0.005 5 0.0104 .0 122 0.0102 〇ο 〇ο 〇ο < _ Quinoa • 001 Quinoa_ Quinoa Μ m • 008 _ quinoa_ quinoa_ quinoa 1—H 〇〇 • 00 1 _ heliosphere 〇m diagram o diagram diagram 〇ο diagram Vh u cn CNJ un 1〇CO 1 1 < Csl f 'i 1 < ON Ο CN cn vo COCO r- ^ r—Η 〇〇〇〇cn CN r—Η wn r—Η CS1 ο r—4 〇〇〇ο oo 402 0.304 0.403 404 455 301 403 0.177 0.43 1 399 402 〇 τ—Η m ο 〇〇ο 〇ο ο Ou 077 075 0.077 inch τ—H o 078 074 077 0.074 078 077 079 07 1 〇〇o ο 〇ο 〇ο ο ο c S r ...... iv〇C0 CN 1 < 〇CN1 WO CO mr— < cn wn 1 «CNl Ό cn inch 〇〇Ν inch CO CS1 < N τ i 〇〇 C ^ l 〇ο fflW _ r—Η oo o > < _ _ Tune M _ Chenopodium quinoa ο Tribulus m 'quinoa 〇 Figure 〇ο Figure 圏 u VO o 〇〇CNJ 〇cn τ—H r- 〇oo 〇ο 〇〇〇〇ο Ό 〇 〇 〇 0 〇〇o 〇ο 〇〇ο 〇 distinguish Inventive Example Inventive Example Inventive Example Inventive Example Introducing Inventive Example Comparative Example Comparative Example Comparative Example Comparative Example Reference Example ο 1 < CN CO Inch wn VO 〇〇〇 \ ο r-Η r-Η csi r — 4 9 U es-rsl6 / _ ^^^ total / < Nl e 200300799 csl «[1! i Evaluation method BB c < \ o II PQ > _ Surface: Record Se» Evaluation of cutting shape (total 1 5 Cutting conditions) 1 chip length is less than 30mm: 1 point 1 chip length is more than 30mm: 3 points maximum surface roughness Rmax life: until cutting is not possible © DD 槪 ε Β ο ο ο Ε § < | π Ε Cutting conditions Lubricants, soil condensate, water solubility, cutting oil use, cutting time min-cutting speed m / min 150 ί_ 30,50, 100,150 200 150 100 〇〇〇〇CSJ cutting depth mm ο CN 〇CN 〇C &1; Feed 2.0 mm / rev 〇 οί 〇 0.10 0.20 0.30 〇CS) 〇0.20 〇Tool material P20 SKH4 SKH51! (0 10) nn Peripheral rotary drill hole 1 oe 9P inchelI6 / s-CN6 / s ^? iK ^ / (NIe 200300799) The test results are shown in Table 3. Fig. 2 shows the relationship between the service life of the external cutting tool (SKH4) and the service life of the drill tool as a representative characteristic 値. As clarified in Table 3, the present invention examples No. 1 to No. 6 were compared with the low carbon sulfur composite free-cutting steel of the reference example No. 1.2, and confirmed to have better characteristics. In contrast, Comparative Example No. 7 indicates that the amount of Mη exceeds the upper limit, Comparative Example No. 9 indicates that the amount of Cr is less than the lower limit, Comparative Example No. 10 indicates that the amount is less than 0, and Comparative Example No. 11 indicates that the Cr / S is less than the lower limit. Alas, the aspect ratio of any of the sulfides becomes larger, and the machinability is inferior to the examples of the present invention. In Comparative Example No. 8, the amount of S is less than the lower limit 値, so the total amount of sulfide-based intermediaries effective for machinability is insufficient, and the machinability is still inferior to the examples of the present invention. 31 312 / Invention Specification / 92-02 / 91134756 200300799

Old 7 Granularity 00 00 Bu 00 00 Bu 00 00 00 00 i Micro-organism 1 1 Fat and body · Bolai body and fat body · Bolai body and fat body · Bolai body and fat body · Bolai body and fat body · Bolai body fat body, Bolai body fat body, Bolai body fat body, Bolai body fat body, Bolai body fat body, Bolai body fat body, Bolai body fat body, wave Source 1 Surface Roughness 1 [-Rmax L πί] Inch 1-1 LO τ-Η Inch rH (XI (XI CD rH LO 1-1 LO 00 bu C0 CD 00 LO CO CD 00 bu τ-1 Chip evaluation points (points) LO 1 ~ 1 LO Τ—Η LO τ-Η LO 1 ~ 1 LO rH LO τ-Η 00 C0 Bu 00 CD CO oo CO r—H CO rH (XI cutting tool life drill life ( m / min) CD CD CO LO r—1 Bu ① LO (XI CD 〇CD 00 Bu CO CO CO oo 00 rH 00 inch life outside cut SKH4 life (min) CD inch CO CD LO CD inch 00 00 LD 00 rH CO o 00 ① CXI ο Inch cut P20 life (min) 00 Inch inch 〇LO CD Inch inch OLO 00 CO Inch CXI Inch CXI CXI 03 r-1 (XI τ-Η Inch sulfide morphology aspect ratio S 5 ratio ( %) 00 00 CD 00 LO 00 CO 00 00 CX1 00 τ—Η inch 00 C0 CD inch τ * ⑦ CO CM Proportion (%) above 10 // m 00 CD CD LO CX) 00 CD LO CO CO CD LO LO rH CD CO 0- 1 Division 1 1 Inventive Example 1 f Inventive Example 1 Inventive Example 1 Inventive Example 1 Inventive Example 1 Inventive Example 1 Comparative Example Comparative Example Comparative Example Comparative Example Comparative Example Reference Example 6 r—N (N m inch \ 〇 卜 〇〇ON o τ—H CN (Ne 9ς Buinch e 116 / s-z6 / _s ^ K ^ / ne 200300799 Second Example Here, an example of the second free-cutting steel is shown. Let the chemical composition in the range of the second free-cutting steel shown in Table 4 Steel (hereinafter, referred to as the present invention example) N 0.2 1 to 2 6. Steel having a chemical composition composition outside the range of the second free-cutting steel (hereinafter, referred to as a comparative example) N 0.27 to 31, and a reference example The low carbon sulfur composite free-cutting steel of N 0.32 was cast and hot-pressed under the same conditions as in the first embodiment, and then normalized under the same conditions as in the first embodiment. With respect to the thus-produced bar steel of each component composition, the morphology measurement and machinability test of the sulfide-based intermediary were performed in the same manner as in the first embodiment. 33 312 / Invention Specification / 92-02 / 9113475 6 200300799 inch ec ο -Η J csi o cn inch CNl m cn 卜 CN CN Ό un inch t T— ^ CNl inch 〇〇ro o oo inch cn 〇 Csl m OO cn cn r—Η c CN Γ " < inch 〇 X) cx csi cn csi O inch csl Csl Csi 〇v〇CNl 〇 inch CNl IT) Csl cn CNl inch CN ο inch CNl o ON 〇 csi csi O oo o o o ο o Μ _ _ _ _ _〇〇_ _ _ 1_ oo ο fflW quinoa meaning quinoa quinoa map H 圏 圏 圏 circle 圏 〇1-* 〇〇oo 1- 0.00 8 8, 0 105, 0 152 ON cn r < i O 0.0145 \ 〇〇 \ 〇〇.00 8 6 r-< 〇 f 1 * Ο ο, 丨 丨 ν〇Τ—Η Ο .0019 .0152 丨 1 o O ο o 〇O ο ο, 007 1! 0.0 0 6 8 0.0107 CN t—Η 1—Ί 〇 〇 〇 01 39, 00 5 5 0.0086 0.0076 Γ i! 1 < r1 i Ο Ο ........ i inch ι11 4 Ο, 0099 .0 102 _! »o OO Ο ο ο < r- * H oo 0.001 _ _ _ oo oo _ _ τ—Η Ο 0.001 _ _ quinoa quinoa quinoa o 圏 圏 o 圏 圏Figure ο 圏 Figure < RU r— ^ CN inch r- ON cn 1 < ι— (o CN inch o υη r—Η r— * OO cn C < l cn Inch 〇r— (ο 1 i τ i ο ο ι—Η 〇 Pan LTj • 401 .303 r_H o Inch. 402 • 458 • 303 un o Inch. 175 .434 0.403 .345 T 1 < cn o ο 〇ο O oo ο ο ο 〇0 »,, 075 0.07 4 0.077 cn r ·· " i 〇! 0 · 0 7 6 1_ 0.073, 076 0.072, 075, 077 .074, 072 O Ο O ο ο ο 〇Μη mi〇r-i CN) Ο 1 < o csl un CO ti UT) cn wn cn m ο CS1 CSI wn cn τ—Η r—Η m CNl r ·· — O Ο 1 * τ —1 CNJ ο Ο M Μ oo 〇Γ " i _ _ r < m _ Ο Μ mm 〇 tribulus quinoa 〇m quinoa m _ 圏 o 〇 Figure 〇ο 1! Ο u VO o Ο Ο CO oo cn % < o ON oov〇〇〇 卜 ο oo Ο Ο CN) τ—Η 〇 v〇〇o 〇 o ο 〇 ο 〇m Comparative Example Comparative Example Comparative Example Comparative Example Reference Example JR i Distillation Distillation (D t—Η (N CN CO m CN inch CN1 v〇csi CN r- CN οο CS1 ON csi ο cn r—_ — m CNl m inch e u5s-z6 / _ ^^^ micro / zie 200300799 The test results are shown in Table 5, as explained in this table. Ν ο. 2 1~2 Example 6 of the present invention are of square and v. Lower sulfur compound of Reference Example 32 as compared to more cutting steel, was confirmed to have more excellent characteristics. In contrast, Comparative Example No. 27 indicates that the amount of Mη exceeds the upper limit, Comparative Example No. 29 indicates the lower limit of Cr content, Comparative Example No. 30 indicates the lower limit of Cr / S, and Comparative Example N 0.31 is 〇The amount is small ', so the aspect ratio of any sulfide becomes large, and the machinability is inferior to the examples of the present invention. In Comparative Example No. 28, the amount of S is less than the lower limit. Therefore, the total amount of sulfide-based intermediaries effective for machinability is insufficient, and machinability is still inferior to that of the present invention. 35 312 / Invention specification / 92-〇2 / 91134756 200300799

Vo fefe ([[θ R ma X (^ m) inch 1 '< r—tmr—ί r < < NI CN1 i 1 1 m OO cn cn 卜 \ D cn F · 1 < ± Η mil Persuade m ©] ^ 1 s ft ^ © un r—Η un 1 t un r— < υη r— < υη υη τ—Η υο m \ D mv〇rsl cn r〇mr— < ro earn nnl ( Η © in ^ Miscellaneous 51¾ | m ν〇Ό οα \ 〇f " i r- 〇 \ wn Ο oo Ο Ι > · CO vo m CNI cn 1 1 ro 1 '< cn inch size outside cut SKH4 life (min ) un inch inch inch oo inch inch υη σ \ inch 1 < cn to m cn m 〇m σ \ < NI 〇 inch outside cut P 2 0 life (min) inch y < n inch inch v〇 inch 0 \ ο inch CN CO m CN inch CN CN cs i · Ι Oi inch SS 惺 惺 値 (-) vn v〇rH Vm '" < ν〇1 < m inch v〇f 1 inch 1 "' < BU inch inch I 1 Inch average 値 (-) ν / Ί m ν〇m COCO m ΟΝ CS1 r- cn m \ o VO VO \\ 〇04 \ 〇Differential distillate distillate, distillate, distillate, distillate, m, 誃 m, compare Example Comparative Example Comparative Example Comparative Example Comparative Example Reference Example CS CS CN m CN inch CS to \ 〇csi r- CN oo CN 〇 \ CN) 〇 mr —H m CN1 200300799 Third Example Here, an example of the third free-cutting steel is shown. Let a steel having a chemical composition composition within the range of the third free-cutting steel shown in Table 6 (hereinafter referred to as the present invention) Example) N 0.4. 1 to 4 6. Steels with chemical composition outside the range of the third free-cutting steel (hereinafter, referred to as Comparative Examples) N 0.47 to 51, and Reference Example No. 52. IS SUM23L to Casting and hot-pressing are performed under the same conditions as in the first embodiment, and then normalized under the same conditions as in the first embodiment. The sulfide-based intermediary similar to that in the first embodiment is performed on the bar steel of each component composition thus manufactured. Determination of material morphology and machinability test. 37 312 / Invention Specification / 92-02 / 91134756 200300799 ooe oo ν-ί U cn o cn oo oo CNl inch ON ο CO oo inch csl OO inch OQ τ—Η OO c〇 ο ί Ή οο r— < wn ο ΌΟ cn r- Csl τ—Η vc r—H 〇_ »Chain It cu Very small amount Very small amount Very small amount Very small amount Very small amount Very small amount Very small amount Very small amount f < CN 〇0.0084 L 0.0075 0.007 8 1 i CN f ....... 4 oo 0.0082 0. 0080 0.007 1 0.0065 0.008 2 0.009 1 0.006 1 0.0082 〇0.003 8 0.005 1 0.0098 0.003 5 0.0075 0.00 8 9 0.006 1 0.0066 0.005 2 0.0009 0.0069 0.0152 ψ -__ i Extreme amount 0.008 Extreme amount 0.00 1 Extreme amount 0.00 1 Extreme amount 0.00 1 Trace 0.001 0.00 1 Trace CN u CNl CN t—ί cn r < 1 < 〇〇〇CS1 cn O ON Ο oo ο cn τ—Η r—Ή οο ο CNl Cs] 〇T—Η 1 tr— * 〇 〇o CO 0.403 0.404 0.457 0.301 oo Ο Ο m ψ * cn o 0.402 0.105 0.433 0.399 0.402 σ \ 1 i CO o cu 0.076 inch 1 '' < 〇 〇 0.07 8 | 0.074 0.072 0.07 1 0.077 0.073 0.076 0.077 0.079 0.07 0.07 1 Mn csi om CN 〇 inch cn 1—Η cn cn r—H r— ^ un 〇CNl WO o inch csi inch ο inch 〇ON inch 1 " < r--H 〇CNl csi T ~ < 〇〇1 " < 〇o very small amount of r-i 〇 〇 〇〇〇〇〇 very small amount of very small amount of very small amount of the very small amount of < 〇〇 extremely small amount of very small amount of the very small amount oo cn r-Η 〇 〇 〇 ο ο CNl oo VO oo \ D 〇〇oo ο ο ο ο 〇〇vo ο ο r- oo VO oo Inventive Examples Inventive Examples Inventive Examples Inventive Examples Comparative Examples Comparative Examples Comparative Examples Comparative Examples ο r—Η Inch OC cn Inch Inch Inch VO Inch οο Inch ON Inch ο r— < in Γ0 v〇9ln KI I6 / ss / _ ^ i ^^ still / π e 200300799 The test results are shown in Table 7. As illustrated in this table, Nos. 41 to 44 in the examples of the present invention are compared with ΠSSUM23L of the No. 52 reference example. To confirm that it has better characteristics. In addition, No. 45 is an example of a case where the amount of S is the same as that of Reference Example N 0.52 of JIS SUM 23L, and the amount of 0 is 1/2, which is approximately equivalent to JIS SUM23L of Reference Example No. 52. The machinability, combined with surface imperfections, is almost unpredictable. ^ .46 is the same as the reference example of No. 113311 "231 ^ N 0.52, and the amount of 0 is less than N 0.52, but more than N 0.45, and N Compared with 0.2, the machinability is relatively good. In contrast, Comparative Example N 0.47 has an amount of M η exceeding the upper limit 値, and Comparative Example N 0.49 has a lower limit of the amount of Cr Cr, Comparative Example No. 5 1 is the lower limit of Cr / S ', so the aspect ratio of any sulfide becomes larger, and the machinability is worse than that of the examples of the present invention. Moreover, Comparative Example No. 48 is the lower limit of S amount 値, so it is possible The total amount of sulfide-based intermediaries effective for machinability is insufficient, and the machinability is still worse than that of the examples of the present invention. Comparative Example No. 0.5 is less than the lower limit of the amount 故, so the machinability is still worse than the examples of the present invention. 312 / Invention specification / 92-02 / 91134756 39 200300799 0 inch surface defect total length (cm) 〇ο wn O VO υη Ο oo o o 42.5 surface roughness Rmax (β m) inch 1 1 t ΓνΙ CN r · ' · &Quot; 1 1 " 1 < \ D υη r — tm oo cn VsO un cn m r- 1 < Cutting processability chip evaluation point (β m) vn > 1 mi _ 1 1 ·· 1 un i 1 σ \ τ—Η v〇1—4 inch cn m \ o cn rsi m 11 t cn 1 '" < csi cutting tool life drill life (m / min) \ 〇VsO 〇 \ m \ D o un inch r—iv〇mm C < im CO r " H cn inch inch cut SKH4 life (min) to ON 1 1,11 '< CN m υη m CN m 沄 CN ο outside cut P20 life (min) 卜 rH inch ON inch csi CN) cn CN) inch CO csi CNJ CNl r—Η Inch sulfide with a diameter of 10 // m or more and an aspect ratio of $ 5 (1) v〇oo oo wn oo oo \ 〇〇〇OO cn m VO IO 10 inch \ D m 1 distinguish 1 Example 1 I Example of the present invention II Example of the present invention II Example of the present invention [J 1 Example of the present invention 1 1 Example of the present invention 1 Comparative example Comparative example 1 Comparative example 1 Comparative example Comparative example Reference example 〇〇ϊ cn Inch v〇r- Inch oo Inch Oi U 6? 592: 6 / _helmet shrink ^ Total / 2 £ 200300799 [Brief description of the diagram] Figure 1 is a diagram for explaining the aspect ratio. Fig. 2 is a graph showing the relationship between the life of a cutting tool and the life of a drill tool.

41 312 / Invention Specification / 92-02 / 91134756

Claims (1)

200300799 Scope of patent application 1. A low-carbon free-cutting steel characterized by containing 鼍% c 〇 02 ～ 0.15%, 1 ^ 11: 0. 05 ~ 1.8%, 3: 0.20 ~ 0.49%, 〇 : More than 0.001 to 0.03%, Cr: 0.3 to 2.3%, the remainder is composed of Fe and inevitable impurities, and the Cr / S ratio is in the range of 2 to 6. 2 · If the low-carbon free-cutting steel in item 1 of the patent application scope, it further contains mass% S i: 0 · 1% or less, p: 〇 · 〇1 ～ 〇 · 丨 2%, A1: 0 · 0 1 % the following. 3. If the low-carbon free-cutting steel according to item 丨 of the patent application scope, it contains mass% Ca: 0.0001 to 0.0005%, Pb: 0.01 to 0.03%, Se. 〇2 to 0.30%, Te: 0.1 to 0.15 %, Βκ0 ~ 02 ~ 0.20%, Sn.〇00〇3 ~ 0.020%, B: 0 · 004 ~ 0.010%, N: 0.005 ~ 0.015%, Cu: 0.005 ~ 0.50%, Ti: 0.003 ~ At least one species is selected from the group consisting of 0.090%, V: 0.005 to 0.200%, Zr: 0 005 to 0.090%, and Mg: 0.0005 to 0.0080%. 4. If the low-carbon free-cutting steel in item 2 of the patent application scope, which contains the mass% 0 &: 0.0001 to 0.0005%,? 13: 0.01 ~ 0.03%, 36: 0'02 ~ 0.30% 'Te: 0.1 ~ 〇15%, Bi: 0.02 ~ 0.20%, Sn: 0.003 ~ 0.020%, B: 0 · 004 ~ 0.010%, Ν: At least one selected from the group consisting of 0 · 005 to 0.015%, Cu · 0.05 to 0.50%, Ti: 0.003 to 0.090%, V: 0.005 to 0.200%, Zr: 0.005 to 0.090%, and Mg: 0.0005 to 0.0080%. 5 · The low-carbon free-cutting steel according to any one of claims 1 to 4 in which the long diameter is a sulfide-based intermediary having a particle size of 10 μm or more is 9 of the total sulfide-based intermediary. 0% or more. 6. The low-carbon free-cutting steel according to any one of claims 1 to 4, wherein the long diameter is in a sulfide-based intermediary with a particle size of 1 0 // m or more, 42 312 / Invention Specification / 92-02 / 91134756 200300799 If the aspect ratio is 5 or less, it will occupy more than 80%. 7 _If the low-carbon free-cutting steel in item 5 of the patent application scope, in which the long diameter is in the sulfide-based intermediary with a particle diameter of more than 10 // m, the aspect ratio is 5 or less, occupying more than 80% . 8 · The low-carbon free-cutting steel according to any one of the items 1 to 4 of the scope of application for a patent, which has a fertilized body and a boletite structure, and the particle size number in the Austenite particle size determination method exceeds 7. 9 · A low carbon and sulfur composite free-cutting steel with excellent machinability, which is characterized by mass% C: 0.02 to 0.15%, Mn: 0.05 to 1.00%, S: 0.20 to 0.49%, and 〇: more than 0.008 to 0.030% , Pb: 0.04 to 0.35%, Cr: 0.3 to 2.3%, the remainder is composed of Fe and unavoidable impurities, and the Cr / s ratio is in the range of 2 to 6. 10. The low carbon and sulfur composite free-cutting steel according to item 9 of the scope of patent application, which further contains mass% Si: 0.1% or less, p: 0.01 to 0.12%, and A1: 0 · 01% or less. . Π, such as low-carbon-sulfur composite free-cutting steel in the scope of application patent No. 9 or 10, which further contains mass% Ca: 0.0001 to 0.0005%, Se: 0.02 to 0.30%, Te: 0.1 to 0.15%, Beta: 0.002 to 0.20%, Sn: 0.003 to 0.020%, Bi: 0.004 to 0.010%, N: 0.005 to 0.015%, Cu: 0.05 to 0.50%, Tκ0 to 0.003 to 0.090%, V :. At least one selected from the group consisting of 0.005 to 0.200%, Zr: 0.005 to 0.090%, and Mg: 0.0005 to 0.0080%. 1 2. —Sulfur or sulfur composite free-cutting steel with excellent surface machinability with few surface flaws, which is characterized by containing mass% S: 0.16 to 0.49%, 0: 0.002 to 0 · 0 1 0%, and the long diameter is In a sulfide-based intermediary having a particle size of 10 mm or more, an aspect ratio of 5 or less is occupied by 80% or more. 43 312 / Invention specification / 92-02 / 91134756 200300799 1 3. —Sulfur or sulfur steel with low surface defects and excellent machinability, which is characterized by containing mass% (:: 0.02 ~ 0.15%, 1411: 0.05 S : 0.16 to 0.49%, 0: 0.002 to 0.010%, Cr: 0.3 to 2.3% Divided into Fe and unavoidable impurities, and the Cr / S ratio is around 2. 1 4. If the scope of patent application is No. 12 or The sulfur or sulfur compound of item 13 is further containing mass% SkO.1% or less, P: 0.04 ~ 0.12% or less. 1 5. If the sulfur or sulfur compound of item 12 or 13 of the scope of patent application is, it is It further contains mass% 03: 0.0001 to 0.0090%,? 1 0.01 to Se: 0.02 to 0.30%, Te: 0.03 to 0.15%, Bi: 0.02 to 0.20%, to 0.020%, and Beta: 0.004 to 0.010% , N: 0 · 005 ~ 0.015%, ~ 0.50%, Ti: 0.003 ~ 0.090%, V: 0.005 ~ 0.200%, ~ 0.090%, 乂 £: 0.0005 ~ 0.0080% are selected to the group of 16. The scope of patent No. 14 is sulfur or sulfur compound which is easy to attack and then contains mass% Ca: 0.0001 to 0.0090%, Pb: 0.01 to Se: 0.02 to 0.30%, Te: 0.03 to 0.15%, Bi: 0.02 to 0.20%, ~ 0.020%, B: 0 · 004 ~ 0.010%, N: 0 · 005 ~ 0.015%, ~ 0.50%, Ti: 0.003 ~ 0.090%, V: 0.005 ~ 0.200%, ~ .0.090%, Mg: 0.0005 ~ 0.0080% selected from the group consisting of 312 / Invention Specification / 92-02 / 91134756 Compound Free-cutting steel ~ 1.8%, free residue steel ~ 6, free-cutting steel, A 1: 0.0 1% free-cutting steel, 0.40% 'S η: 0 · 00 3 Cu: 0.05 Zr: 0.005 One less. Turn, it is 0.40% 'S η: 0.0 0 3 Cu: 0.05 Zr: 0.005 one less ° 44