CN109680216A - The excellent middle carbon easy-cutting steel of hot rolling and its manufacturing method - Google Patents

The excellent middle carbon easy-cutting steel of hot rolling and its manufacturing method Download PDF

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CN109680216A
CN109680216A CN201811187652.5A CN201811187652A CN109680216A CN 109680216 A CN109680216 A CN 109680216A CN 201811187652 A CN201811187652 A CN 201811187652A CN 109680216 A CN109680216 A CN 109680216A
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steel
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林男锡
朴仁圭
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Posco Holdings Inc
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Posco Co Ltd
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    • 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
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/0081—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for slabs; for billets
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Heat Treatment Of Steel (AREA)

Abstract

Preferred embodiment of the invention provides a kind of excellent middle carbon easy-cutting steel of hot rolling and its manufacturing method, the steel includes C:0.40%~0.50% in terms of weight %, Si: less than be equal to 0.3% (except 0%), Mn:1.0%~1.5%, P: less than be equal to 0.015% (except 0%), S: less than be equal to 0.008% (except 0%), B:0.005%~0.015%, N:0.010%~0.020%, Al: less than be equal to 0.05% (except 0%), the Fe of surplus and other inevitable impurity, the weight ratio of N/B is 1.3~2.8, in the rolling direction section of wire rod, the area fraction of MnS is less than or equal to 0.1%, diameter is less than or equal to 5 μm of the fine every 1m of BN field trash M2More than or equal to 100, the average aspect ratio of BN is less than or equal to 2.0.

Description

The excellent middle carbon easy-cutting steel of hot rolling and its manufacturing method
Technical field
The present invention relates to fastener, the office automation devices as Hydraulic Elements, household appliances for automobile Automatic steel used in the material of shaft member (Shaft), conventional cutting product and mechanical structure etc..More specifically, the present invention relates to And a kind of middle carbon easy-cutting steel and its manufacturing method of hot rolling and excellent in machinability.
Background technique
In general, automatic steel is widely used as the Hydraulic Elements of automobile, household appliances fastening as the steel with high machinability The material of part, the shaft member of office automation devices, conventional cutting product etc., purposes and demand are gradually increasing.
The automatic steel conduct of similar strength with excellent machinability and dimensional accuracy and common medium-carbon steel level Steel for mechanical structure is also widely used.
In order to produce the automatic steel of excellent in machinability, a small amount of low melting point element lead (Pb) etc. is added or make MnS Field trash crystallization, so as to improve cutter life and chip breaking, can also improve the surface quality and dimensional accuracy of product.So And recently as the reinforcing of environmental legislation, the Element Lead being harmful to the human body gradually is abandoned, when manufacturing automatic steel, instead of Pb Relatively environment-friendly bismuth (Bi) or tin (Sn) is added, to improve the quality of automatic steel.
However, the low melting point element being added to improve machinability, it will usually the hot rolling of automatic steel be caused to decline. In addition, for the resulfurizing series free cutting steel that a large amount of sulphur (S) is added to guide MnS to be formed, also because a large amount of formed stretches along hot rolling direction Long MnS and the anisotropy for causing mechanical performance, the problems such as so as to cause toughness decline.Therefore, end meeting when wire rod rolling It splits, in order to make up this problem, carries out operation bidirectional before wire rod rolling, by blank end sharpening such as tip of a pencil shape, thus Productivity is caused to substantially reduce.
In order to solve these problems, graphite (graphite) automatic steel etc. is being studied, but is making initial pearlite group The problems such as heat treatment time needed for knitting graphitization is long, therefore there are still productivity and expenses.
Citation
Patent document 1: Japanese Laid-Open Patent Publication the 2011-052299th
Summary of the invention
Technical problem
One aspect of the present invention is intended to provide the middle carbon easy-cutting steel of a kind of hot rolling and excellent in machinability.
Another aspect of the present invention is intended to provide a kind of manufacturing method of the middle carbon easy-cutting steel of hot rolling and excellent in machinability.
Technical solution
A preferred embodiment of the invention provides a kind of hot rolling excellent middle carbon easy-cutting steel, and the steel is in terms of weight % Include C:0.40%~0.50%, Si: less than being equal to 0.3% (except 0%), Mn:1.0%~1.5%, P: less than to be equal to 0.015% (except 0%), S: less than be equal to 0.008% (except 0%), B:0.005%~0.015%, N:0.010%~ 0.020%, Al: less than be equal to 0.05% (except 0%), the Fe of surplus and other inevitable impurity, the weight ratio of N/B are 1.3~2.8, in the rolling direction section of wire rod, the area fraction of MnS is less than or equal to 0.1%, and diameter is less than or equal to 5 μm The fine every 1mm of BN field trash2More than or equal to 100, the average aspect ratio (aspect ratio) of BN is less than or equal to 2.0.
The content of the Si of the steel can be able to be the content of 0.001%~0.015%, S for the content of 0.01%~0.3%, P It can be able to be 0.01%~0.05% for the content of 0.001%~0.008% and Al.
The diameter is less than or equal to 5 μm of for example every 1mm of fine BN field trash2It can be 100~200.
Another preferred embodiment of the invention provides a kind of manufacturing method of the excellent middle carbon easy-cutting steel of hot rolling, described Method includes: molten steel cast to the continuous casting step of steel bloom (bloom), the molten steel in terms of weight % comprising C:0.40%~ 0.50%, Si: less than being equal to 0.3% (except 0%), Mn:1.0%~1.5%, P: less than be equal to 0.015% (except 0%), S: less than being equal to 0.008% (except 0%), B:0.005%~0.015%, N:0.010%~0.020%, Al: less than is equal to The weight ratio of the Fe and other inevitable impurity of 0.05% (except 0%), surplus, N/B are 1.3~2.8；
The step of billet rolling obtains billet (billet) is carried out to the steel bloom；And
The wire rod rolling step of wire rod is rolled into after the billet is heated in heating furnace.
The content of the Si of the molten steel can be able to be containing for 0.001%~0.015%, S for the content of 0.01%~0.3%, P Amount can be able to be 0.01%~0.05% for the content of 0.001%~0.008% and Al.
In the continuous casting step, electromagnetic stirring device for crystallizer (EMS) and slighter compress device can be driven to institute simultaneously It states molten steel and carries out continuous casting.
When the billet rolling, steel bloom can be placed in heating furnace more than or equal to 1100 DEG C at a temperature of keep 3 Hour~5 hours.When the wire rod rolling, billet can be placed in heating furnace and be protected under 1100 DEG C~1200 DEG C of range It holds 2 hours~5 hours.
Invention effect
Preferred embodiment according to the present invention can provide the automatic steel with environmental protection characteristic and excellent hot rolling, easily Suitable B, N are added in Cutting Steel to guide BN to be precipitated, to have excellent hot rolling and machinability, while without containing lead etc. Low melting point element.
Various interesting advantages of the invention and effect are not limited to above-mentioned content, are illustrating specific embodiment party of the invention It may be more readily understood during formula.
Detailed description of the invention
Fig. 1 is the schematic diagram of the machinability evaluation method of automatic steel according to an embodiment of the invention.
The explanation of appended drawing reference
100: cold-drawn bar (Cold-Drawn)
200: tool for cutting machining
Specific embodiment
Illustrate the preferred embodiment of the present invention below.
Embodiments of the present invention can be deformed into various other forms or can be combined into various embodiments, this hair Bright range is not limited to following embodiments.In addition, in order to which the those of ordinary skill into technical field more completely says It is bright the present invention and a specific embodiment of the invention is provided.Therefore, in order to more clearly be illustrated, can amplify in attached drawing Shape and size of component etc. with the component that the same symbol indicates are identical components in attached drawing.
Automatic steel is widely used in automobile, office equipment, household appliances etc., especially has machinability and dimensional accuracy excellent Different characteristic.In order to improve the machinability of automatic steel, low melting point element, but low melting point element can be added in manufacturing process Additional amount when increasing, the surface defect of the automatic steel generated in wire-making processes will increase.That is, in order to improve Machinability, when low melting point element being added in automatic steel, additional amount is bigger, and hot rolling can be reduced more.
The present invention provides a kind of middle carbon easy-cutting steel and its manufacturing method, although in improving carbon easy-cutting steel machinability, But without using the low melting point element or MnS of hot rolling may be reduced, but guide there is equally distributed fine BN to generate with Ensure machinability, so as to ensure hot rolling and machinability simultaneously.
The middle carbon easy-cutting steel excellent to the hot rolling of a preferred embodiment according to the present invention is illustrated below.
The excellent middle carbon easy-cutting steel of the hot rolling of a preferred embodiment according to the present invention, the steel are wrapped in terms of weight % : less than it is equal to 0.3% (except 0%), Mn:1.0%~1.5%, P: less than containing C:0.40%~0.50%, Si to be equal to 0.015% (except 0%), S: less than be equal to 0.008% (except 0%), B:0.005%~0.015%, N:0.010%~ 0.020%, Al: less than be equal to 0.05% (except 0%), the Fe of surplus and other inevitable impurity, the weight ratio of N/B are 1.3~2.8, in the rolling direction section of wire rod, the area fraction of MnS is less than or equal to 0.1%, and diameter is less than or equal to 5 μm The fine every 1mm of BN field trash2More than or equal to 100, the average aspect ratio of BN is less than or equal to 2.0.
The ingredient of steel and composition range are illustrated below.
Carbon (C): 0.40 weight of weight %~0.50 %
Carbon is to form carbide to make the intensity of material and the increased element of hardness, largely with pearly-lustre in middle carbon easy-cutting steel Body (pearlite) form exists, such as can play the role of assigning appropriate intensity, makes it possible to for middle carbon mechanical structure etc.. If the content of carbon may be reduced less than 0.40 weight %, intensity and harden ability.On the contrary, if the content of carbon is greater than 0.50 weight %, then the hardness of material can excessively increase, cutter life when may shorten cutting.Therefore, the content of the carbon It is preferably limited to 0.40 weight of weight %~0.50 %.
Silicon (Si): less than be equal to 0.3% (except 0%)
If silicone content is greater than 0.30 weight %, the SiO system non-metallic inclusion of hard can be generated largely, in Cutting free Cutter life may be reduced in the cutting technology of steel.Therefore, the Si content is preferably limited to less than or equal to 0.30 weight Measure %.Preferred Si content is Si:0.01%~0.3%.
Manganese (Mn): 1.0 weight of weight %~1.5 %
In order to improve the intensity of steel and prevent the harmfulness of S present in steel, Mn is added and forms MnS, to prevent red heat Brittleness.When Mn content is more than or equal to 1.0 weight %, required harden ability and intensity can be obtained, austenite region broadens, can To postpone to generate pro-eutectoid ferrite in the operation of rolling, and when can inhibit hot rolling steel billet surface defect.But if Mn Content be greater than 1.5 weight %, then toughness can decline, and may will form thicker pearlite band in material cooling procedure (pearlite band), to may result in surface roughness variation in the cutting process.Therefore, the content of the manganese is excellent Choosing is limited in 1.0 weight of weight %~1.5 %.
Phosphorus (P): less than be equal to 0.015% (except 0%)
Phosphorus is the element being added to improve machinability, is existed to the cyrystal boundary segregation of material or with compound form, because This built-up edge (Build-Up Edge) that can inhibit easy to form in cutting tool front end.But when phosphorus is excessively added, The mechanical performance of automatic steel and hot rolling can decline.Therefore, the phosphorus content is preferably limited to less than or equal to 0.015 weight Measure %.Preferred phosphorus content is 0.001%~0.015%.
Sulphur (S): less than be equal to 0.008% (except 0%)
S forms MnS in conjunction with Mn in steel.Due to forming MnS, machinability can be improved.But in the present invention, even if The machinability for being not based on MnS promotes effect and also ensures that machinability, when excessive S is added, crystal boundary may be promoted to be precipitated Netted FeS.This FeS is very fragile and fusing point is low, may will be greatly reduced hot rolling.Moreover, due to a large amount of S is added When generating MnS, also such as FeS reduction hot rolling, and it is unevenly distributed over and rolls using MnS coarse as karyogenesis BN or BN Around the MnS extended in system, uniformity decline may result in.Therefore, the content of the S, which is preferably limited to, is less than or equal to 0.008 weight %.Preferred S content is 0.001 weight of weight %~0.008 %.
Boron (B): 0.005 weight of weight %~0.015 %
B forms BN field trash when steel is solidified in conjunction with N, thus helps to improve machinability.If the content of B is less than 0.0050 weight %, then the amount for being formed by BN is very few, can not show above-mentioned effect, and if it is greater than 0.0150 weight % is measured, then since BN is excessive, will cause hot rolling decline instead.Therefore, the content of the B is preferably limited to 0.005 weight % ~0.015 weight %.
Nitrogen (N): 0.010 weight of weight %~0.020 %
Nitrogen (N) forms BN field trash when steel is solidified in conjunction with B, thus helps to improve machinability.But if N Content is then difficult to expect above-mentioned effect less than 0.010 weight %, and if it is greater than 0.020 weight %, then it is difficult to make steel, and And pin hole (pin hole) and crackle etc. are generated when due to continuous casting, it is likely to result in surface quality decline.Therefore, the N contains Amount is preferably limited to 0.010 weight of weight %~0.020 %.
Aluminium (Al): less than be equal to 0.05% (except 0%)
As previously mentioned, the automatic steel of embodiment according to the present invention, such as can be by molten steel with Al-Si complex deoxidization State is tapped to ladle.If aluminium content is greater than 0.05 weight %, due to the Al of hard2O3It is that non-metallic inclusion can be big Amount generates, and may result in cutter life in the cutting technology of automatic steel and is decreased obviously.Therefore, the Al content is excellent Choosing is limited to less than equal to 0.05 weight %.Preferred Al content is 0.01 weight of weight %~0.05 %.
The weight ratio of N/B: 1.3~2.8
BN is formed and the solid solution capacity of remnants N, the weight ratio of N/B are very important parameter.If the weight ratio of N/B Less than 1.3, then since N is very few, sufficient BN field trash can not be formed.On the contrary, if the weight ratio of N/B is greater than 2.8, After BN is formed, the drawing hardening effect excessive when increasing and deforming of the hardness as caused by remaining N, to machinability and processability Generate adverse effect.Therefore, the N/B weight ratio is preferably limited to 1.3~2.8.
In addition, iron Fe and inevitable impurity of the ladle containing surplus.But it can not be kept away in conventional manufacturing process It is mixed into the unexpected impurity from raw material or ambient enviroment with exempting from, therefore cannot exclude and be mixed into impurity.These impurity are these Anyone impurity for both knowing about of the those of ordinary skill of technical field, thus it is no longer superfluous in relevant all the elements this specification It states.Meanwhile other than above-mentioned component, it is not excluded that other effective components are added.
The excellent middle carbon easy-cutting steel of the hot rolling of a preferred embodiment according to the present invention, in the rolling direction of wire rod In section, for the area fraction of MnS less than 0.1%, diameter is less than or equal to 5 μm of the fine every 1mm of BN field trash2More than or equal to 100 A, the average aspect ratio of BN is less than or equal to 2.0.
In the rolling direction section of wire rod, if the area fraction of MnS is more than or equal to 0.1%, hot rolling decline can Surface defect can be will lead to.
Non-metallic inclusion, that is, boron nitride (BN) have almost with play the role of in graphite automatic steel improving machinability Crystal structure as graphite-like and physical property, therefore also referred to as white graphite.
In the present invention, by generating BN in right amount, BN is made to become stress raiser in cutting, so that crackle is easy to produce And extension, so that machinability can be improved in the case where hot rolling will not decline to a great extent, and BN is played during the cutting process Solid lubricant effect reduces the frictional force between material and cutting tool, so as to reduce cutting force.
As described herein, it is appropriate be added form BN needed for B, N, keep it fine when being uniformly distributed in steel, in hot rolling Property can also improve machinability in the case where will not declining.
When diameter is less than or equal to 5 μm of the fine every 1mm of BN field trash2When less than 100, it is difficult to ensure sufficient machinability Promote effect.
The diameter is less than or equal to 5 μm of fine BN field trash, such as every 1mm2It can be 100~200.
If the average aspect ratio of BN is greater than 2.0, the anisotropy of mechanical properties is generated, it is thick to be likely to result in cutting face Rugosity decline.
The manufacturing method of the middle carbon easy-cutting steel excellent to the hot rolling of another preferred embodiment according to the present invention below It is illustrated.
The manufacturing method of the excellent middle carbon easy-cutting steel of the hot rolling of another preferred embodiment according to the present invention includes: will Molten steel casts the continuous casting step of steel bloom, and the molten steel includes C:0.40%~0.50%, Si: less than be equal in terms of weight % 0.3% (except 0%), Mn:1.0%~1.5%, P: less than being equal to 0.015% (except 0%), S: less than are equal to 0.008% (except 0%), B:0.005%~0.015%, N:0.010%~0.020%, Al: less than be equal to 0.05% (except 0%), remaining The Fe of amount and other inevitable impurity, the weight ratio of N/B are 1.3~2.8；
The step of billet rolling obtains billet is carried out to the steel bloom；And
The wire rod rolling step of wire rod is rolled into after the billet is heated in heating furnace.
In the continuous casting step, such as electromagnetic stirring device for crystallizer (EMS) and slighter compress device can be driven simultaneously Continuous casting is carried out to the molten steel.
During manufacturing when carbon easy-cutting steel, filled in continuous casting process using electromagnetic stirring device for crystallizer (EMS) and slighter compress It sets and continuous casting is carried out to molten steel, it is hereby achieved that excellent slab.By utilizing electromagnetic stirring device for crystallizer, it can have and obtain The advantages of obtaining equally distributed non-metallic inclusion, and by utilizing slighter compress device, it is possible to reduce the center segregation of slab And the surface defects such as pin hole, stomata can be reduced in casting billet surface.
When the billet rolling, steel bloom can be placed in heating furnace more than or equal to 1100 DEG C at a temperature of keep 3 Hour~5 hours.When the wire rod rolling, billet can be placed in heating furnace and be protected under 1100 DEG C~1200 DEG C of range It holds 2 hours~5 hours.
If the temperature of the steel bloom is lower than 1100 DEG C or the retention time was less than 3 hours, rolling may be generated Defect, and if the retention time is greater than 5 hours, manufacture efficiency can decline.
In addition, corner ruptures or generates surface defect if the temperature of the billet is lower than 1100 DEG C, it can not Obtain good wire surface quality.
The automatic steel manufactured by above-mentioned manufacturing method can have excellent hot rolling and machinability.
Below by embodiment, present invention be described in more detail.But following embodiments are only intended to further in detail Illustrate that example of the invention, interest field of the invention are not limited to following embodiments.
Using the molten steel of the component with the following table 1 by utilizing electromagnetic stirring device for crystallizer (EMS) and slighter compress device Continuous casting process produce section be 500mm × 600mm steel bloom.Then, steel bloom is heated to 1200 DEG C and keeps 3 small When, then the billet that section is 160mm × 160mm is made by rolling mill practice.The billet so manufactured is again heated to 1150 DEG C are kept for 2 hours, are then rolled into the wire rod that diameter is 27mm, are finally made the cold-drawn bar (Cold- that diameter is 25mm Drawn Bar)。
In table 1 below, the material for meeting chemical constituent proposed by the present invention is used as " invention material ", in order to compare The test material of manufacture is used as " contrast material ".
BN density (a/mm is carried out to the cold-drawn bar (invention material and contrast material) so manufactured2), MnS Line Integral Number (%), aspect ratio, BN average diameter (μm), tool wear depth (μm), hot rolling and cutting sex investigation, the results are shown under In table 2.
In the following table 2, hot rolling and machinability measure by the following method.
In order to understand chemical component and BN forms influence to hot rolling, live hot rolling evaluation, which uses, to be implemented wire rod and rolls System is visually inspected the method for surface state on the way or after implementing wire rod rolling, and judges to mark according to the product quality qualification of regulation Standard is evaluated.Pass through the observation in the operation of rolling based on thermal imaging camera and the observation to final wire rod finished surface Carry out the final judgement of hot rolling.
In the following table 2, O indicates rolling property well without the material of rolling defect more than 100 μm of discovery (micron), X table Show the material of the bad surface defect for generating Local Cracking or 100 μm of discovery (micron) or more of rolling property.
Machinability is evaluated, using being evaluated after CNC lathe process, machining sample at this time and cutter One example is shown in Figure 1.Machining uses turning (turning) mode, the cold-drawn bar for being 25mm by initial diameter d1 (100) the diameter d2 after being processed into machining is 23mm, and the moving distance T of each sample is 20mm.Each sample Machining amount is 11.9 grams, carries out machining to 300 components and eliminates total 5950 grams.Tool for cutting machining 200 has water chestnut Shape, wedge angle are 55 degree, and relief angle is 7 degree, and nose radius (R) is 0.4mm, and cutter material has used cermet (cermet).It cuts It is 200m/min, feed speed 0.075mm/rev, cutting depth 0.5mm, final 300 that cut processing conditions, which be cutting speed, The depth capacity of the flank wear (flankwear) of cutter is determined after a component processing is complete.
It is mark with 200 μm of maximum side wearing depth (micron) of cutter of 300 component processings after complete in the following table 2 Standard, when wearing depth is less than 200 μm, machinability is expressed as " O ", and when wearing depth is greater than 200 μm, machinability is expressed as " X ".
[table 1]
[table 2]
Shown in Tables 1 and 2 as above, its carbon content of contrast material 1 is that 0.75 weight % has exceeded the carbon provided in the present invention 0.5 weight % of content standard upper limit value.Therefore, although hot rolling meets standard value, hardness excessively rises, therefore after cutting Tool wear increases, and machinability is not able to satisfy standard value.
Its Si content of contrast material 2 is 0.61 weight %, SiO2The excessive generation and solution strengthening of oxide lead to hardness Rise, therefore tool wear depth greatly increases compared with invention material.
Its sulphur (S) content of contrast material 3 is more than the range provided in the present invention, and due to the generation of MnS, machinability is mentioned Height, but hot rolling can decline.
Its boron (B) content of contrast material 4 is less than the standard provided in the present invention, therefore the BN quantity of each unit area is 78/mm2Less than the 100/mm of lower limit standard provided in the present invention2.Since N/B ratio increases, it is not bound with into the solid solution of BN N also will increase, therefore hardness also will increase, so as to cause machinability decline.Moreover, due to superfluous solid solution N, in continuous casting When can also generate surface defect caused by pin hole etc. etc..
On the contrary, N the and N/B ratio that contrast material 5 contains the standard of being less than is lower than standard value, the surplus not in conjunction with N Solid solution B cutting when cause adherency caused by viscosity, thus cause reduce machinability adverse effect.Further, since the amount of N Less, BN quantity generated also only has 67/mm less2, do not contribute machinability is improved.
The excessive S that is added of contrast material 6 has exceeded the S content standard provided in the present invention, therefore the MnS score extended increases Add, the coarse BN uneven distribution generated using MnS as core, so that hot rolling and machinability be caused all to be substantially reduced.
In addition, meeting invention material 1-5 of the invention, tool wear depth (cutter life), hot rolling and machinability It is all excellent.
The present invention is not limited to above-mentioned embodiment and attached drawing, the scope of the present invention is subject to claims.Therefore, exist In the range of the technical concept of the invention recorded in claims, those of ordinary skill in the art can be into The various forms of replacements of row, deformation and change, these replacements, deformation and change should fall into the scope of the present invention.

Claims (8)

1. a kind of excellent middle carbon easy-cutting steel of hot rolling, it is characterised in that:
The steel in terms of weight % comprising C:0.40%~0.50%, Si: less than be equal to 0.3% (except 0%), Mn:1.0%~ 1.5%, P: less than being equal to 0.015% (except 0%), S: less than be equal to 0.008% (except 0%), B:0.005%~ 0.015%, 0.05% (except 0%) of N:0.010%~0.020%, Al: less than be equal to, surplus Fe and other are inevitable Impurity, the weight ratio of N/B is 1.3~2.8, and in the rolling direction section of wire rod, the area fraction of MnS is less than or equal to 0.1%, diameter is less than or equal to 5 μm of the fine every 1mm of BN field trash2More than or equal to 100, the average aspect ratio of BN is less than or equal to 2.0。
2. the excellent middle carbon easy-cutting steel of hot rolling according to claim 1, it is characterised in that:
The content of the Si of the steel is 0.01%~0.3%, the content of P is 0.001%~0.015%, the content of S is The content of 0.001%~0.008% and Al is 0.01%~0.05%.
3. the excellent middle carbon easy-cutting steel of hot rolling according to claim 1, it is characterised in that:
The diameter is less than or equal to 5 μm of the fine every 1mm of BN field trash2It is 100~200.
4. a kind of manufacturing method of the excellent middle carbon easy-cutting steel of hot rolling, it includes:
Molten steel cast to the continuous casting step of steel bloom, the molten steel in terms of weight % comprising C:0.40%~0.50%, Si: less than : less than it is equal to 0.015% (except 0%), S: less than equal to 0.3% (except 0%), Mn:1.0%~1.5%, P to be equal to 0.008% (except 0%), B:0.005%~0.015%, N:0.010%~0.020%, Al: less than it is equal to 0.05% (0% Except), the Fe and other inevitable impurity of surplus, the weight ratio of N/B is 1.3~2.8；
The step of billet rolling obtains billet is carried out to the steel bloom；And
The wire rod rolling step of wire rod is rolled into after the billet is heated in heating furnace.
5. the manufacturing method of the excellent middle carbon easy-cutting steel of hot rolling according to claim 4, it is characterised in that:
The content of the Si of the molten steel is 0.01%~0.3%, the content of P is 0.001%~0.015%, the content of S is The content of 0.001%~0.008% and Al is 0.01%~0.05%.
6. the manufacturing method of the excellent middle carbon easy-cutting steel of hot rolling according to claim 4, it is characterised in that:
In the continuous casting step, while electromagnetic stirring device for crystallizer and slighter compress device being driven to connect the molten steel Casting.
7. the manufacturing method of the excellent middle carbon easy-cutting steel of hot rolling according to claim 4, it is characterised in that:
When the billet rolling, steel bloom is placed in heating furnace small in the at a temperature of holding 3 hours~5 more than or equal to 1100 DEG C When.
8. the manufacturing method of the excellent middle carbon easy-cutting steel of hot rolling according to claim 4, it is characterised in that:
When the wire rod rolling, billet is placed in heating furnace and is kept for 2 hours under 1100 DEG C~1200 DEG C of temperature range ~5 hours.
CN201811187652.5A 2017-10-19 2018-10-12 The excellent middle carbon easy-cutting steel of hot rolling and its manufacturing method Pending CN109680216A (en)

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