CN111334712A - Environment-friendly free-cutting ferritic stainless steel and manufacturing method thereof - Google Patents
Environment-friendly free-cutting ferritic stainless steel and manufacturing method thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
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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
- C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
- C22C33/06—Making ferrous alloys by melting using master alloys
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- 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
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
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- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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- Y02P10/20—Recycling
Abstract
The invention provides an environment-friendly free-cutting ferritic stainless steel, which comprises the following components in percentage by weight: 0.006-0.020% of C, 0.3-0.6% of Si, 1.0-1.2% of Mn, 18.5-22.0% of Cr, 0.02-0.04% of P, 0.30-0.45% of S and Te, wherein the content of Te satisfies the condition that Te/S is less than 0.07, 1.5-2.0% of Mo, 0.08-0.18% of V, 0.15-0.25% of Ni, 0.10-0.20% of Bi, 0.012-0.020% of O, 0.015-0.040% of Nb and the balance of Fe and inevitable impurities. The invention also provides a manufacturing method of the environment-friendly free-cutting ferritic stainless steel, which has the characteristics of high efficiency, short flow and low cost.
Description
Technical Field
The invention belongs to the field of metallurgy, and particularly relates to environment-friendly free-cutting ferritic stainless steel and a manufacturing method thereof.
Background
Small-size precision mechanical parts or electronic parts (such as ball-point pen heads, clock bearings, printer parts and the like) machined by a full-automatic machine tool are mainly made of free-cutting stainless steel materials added with sulfur-lead (S-Pb) in a composite mode for many years, due to the fact that the structure is complex, the cutting speed is high, and the requirements on machining and assembling precision are high, machining materials need to meet the requirements on corrosion resistance, free-cutting and stable machining performance. The Pb is distributed in the stainless steel matrix in the form of tiny elementary particles, and is easily melted into liquid in the high-speed processing process due to the low melting point of the Pb, so that the aims of easy cutting and reduction of tool abrasion are fulfilled.
However, lead (Pb) is a toxic and harmful element, and causes pollution to the environment during smelting production, and causes harm to human bodies during processing and using of products.
The environment-friendly free-cutting ferritic stainless steel has been studied at home and abroad, and mainly uses other free-cutting elements to reduce the content of lead (Pb) elements or completely replace the lead (Pb) elements. For example, Japanese patent "ferrite type free-cutting stainless steel Japanese patent" (JP2005060812A) provides a sulfur-selenium (S-Se) composite addition scheme, but studies have shown that the sulfur-selenium composite addition alone does not achieve the free-cutting property of the sulfur-lead (S-Pb) composite addition, and that excessive selenium (Se) uptake is also harmful to the human body; the domestic patent "a free-cutting stainless steel and its preparation method" (CN108315643B) provides a scheme of sulfur-lead-bismuth-tellurium (S-Pb-Bi-Te) composite addition, although the content of lead (Pb) is reduced, 0.001-0.1% of lead is remained, and the problem of lead pollution still exists.
The free-cutting stainless steel material processed by the full-automatic machine tool is high-end special steel, and the demand of market subdivision is limited, for example, the demand of the free-cutting stainless steel for national ballpoint pen manufacture is only 2000-3000 tons, and large-scale steel enterprises can not pay attention to the free-cutting stainless steel material. The patent "a free-cutting stainless steel and its preparation method" (CN108315643B) provides the preparation method as follows: the method has the advantages of long process, high cost and unsuitability for medium and small special steel mills.
Disclosure of Invention
The invention aims to provide an environment-friendly free-cutting ferritic stainless steel and a manufacturing method thereof, which solve the pollution problem in the prior art. The free-cutting performance of the environment-friendly stainless steel is better improved by successfully alloying the tellurium and bismuth to replace lead elements, and the preparation method has the characteristics of high efficiency, short flow and low cost.
In one aspect, the present invention provides an environment-friendly free-cutting ferritic stainless steel, comprising, in weight percent:
C：0.006～0.020％，
Si：0.3～0.6％，
Mn：1.0～1.2％，
Cr：18.5～22.5％，
P：0.02～0.04％，
S：0.30～0.45％，
te, and the content of the Te satisfies Te/S <0.07,
Mo：1.5～2.0％，
V：0.08～0.18％，
Ni：0.15～0.25％，
Bi：0.10～0.20％，
O：0.012～0.020％，
Nb：0.015～0.040％，
the balance being Fe and unavoidable impurities, the sum of the percentages by weight of the individual components being 100%.
Preferably, the environment-friendly free-cutting ferritic stainless steel comprises, by weight:
C：0.008～0.018％，
Si：0.4～0.6％，
Mn：1.05～1.18％，
Cr：19.0～21.0％，
P：0.02～0.03％，
S：0.35～0.45％，
te, and the content of the Te satisfies Te/S <0.07,
Mo：1.7～2.0％，
V：0.10～0.15％，
Ni：0.18～0.22％，
Bi：0.12～0.18％，
O：0.013～0.018％，
Nb：0.025～0.035％，
the balance being Fe and unavoidable impurities, the sum of the percentages by weight of the individual components being 100%.
Most preferably, the environmentally friendly free-cutting ferritic stainless steel comprises, in weight percent:
C：0.011％，
Si：0.43％，
Mn：1.17％，
Cr：20.5％，
P：0.024％，
S：0.38％，
te, and the content of Te satisfies that Te/S is 0.068,
Mo：1.93％，
V：0.12％，
Ni：0.21％，
Bi：0.15％，
O：0.018％，
Nb：0.025％，
the balance being Fe and unavoidable impurities, the sum of the percentages by weight of the individual components being 100%.
Meanwhile, the invention also provides an environment-friendly free-cutting ferritic stainless steel which comprises the following components in percentage by weight:
C：0.006～0.020％，
Si：0.3～0.6％，
Mn：1.0～1.2％，
Cr：18.5～22.5％，
P：0.02～0.04％，
S：0.30～0.45％，
te, and the content of the Te satisfies Te/S <0.07,
Mo：1.5～2.0％，
V：0.08～0.18％，
Ni：0.15～0.25％，
Bi：0.10～0.20％，
O：0.012～0.020％，
Nb：0.015～0.040％，
the balance being Fe and unavoidable impurities, the sum of the percentages by weight of the individual components being 100%.
Preferably, the environment-friendly free-cutting ferritic stainless steel comprises the following components in percentage by weight:
C：0.008～0.018％，
Si：0.4～0.6％，
Mn：1.05～1.18％，
Cr：19.0～21.0％，
P：0.02～0.03％，
S：0.35～0.45％，
te, and the content of the Te satisfies Te/S <0.07,
Mo：1.7～2.0％，
V：0.10～0.15％，
Ni：0.18～0.22％，
Bi：0.12～0.18％，
O：0.013～0.018％，
Nb：0.025～0.035％，
the balance being Fe and unavoidable impurities, the sum of the percentages by weight of the individual components being 100%.
Most preferably, the environment-friendly free-cutting ferritic stainless steel comprises the following components in percentage by weight:
C：0.011％，
Si：0.43％，
Mn：1.17％，
Cr：20.5％，
P：0.024％，
S：0.38％，
te, and the content of Te satisfies that Te/S is 0.068,
Mo：1.93％，
V：0.12％，
Ni：0.21％，
Bi：0.15％，
O：0.018％，
Nb：0.025％，
the balance being Fe and unavoidable impurities, the sum of the percentages by weight of the individual components being 100%.
The microstructure of the environment-friendly free-cutting ferritic stainless steel is ferrite, and the grain size is more than or equal to 10 grade.
The area percentage of the A-type coarse inclusions in the environment-friendly free-cutting ferritic stainless steel is more than or equal to 50%.
The hardness of the environment-friendly free-cutting ferritic stainless steel is HV260-300, and the fluctuation range of the hardness on the same cross section is less than or equal to HV 15.
In another aspect, the present invention provides a method for manufacturing an environment-friendly free-cutting ferritic stainless steel, comprising:
(1) scrap steel, pure iron and alloy are taken as raw materials, and are sequentially added into an electric furnace to be smelted according to a proportion, and the raw materials are pretreated;
(2) casting the pretreated molten steel into a steel ingot of 2-3 tons;
(3) when the steel ingot is cooled to 700 ℃ or more, preferably 800 ℃ or more, the steel ingot is sent to a billet rolling workshop and is heated and rolled into small billets.
(4) Directly sending the billet into a bar continuous rolling unit, rolling at the temperature of 1050-.
In the preparation method, the pretreatment in the step (1) is to blow pure argon at 1450-1600 ℃, preferably 1500-1580 ℃ and stir for not less than 10 minutes.
In the manufacturing method, the Bi-containing and Te-containing materials in the raw materials in the step (1) are finely crushed alloys with the diameter of less than 20mm, and are added in two minutes before casting.
In the manufacturing method, the oxygen is precisely controlled in the pretreatment process in the step (1), and the molten steel casting in the step (2) can be carried out until the weight percentage of the components of the molten steel reaches the following ratio:
0.006-0.020% of C, 0.3-0.6% of Si, 1.0-1.2% of Mn, 18.5-22.0% of Cr, 0.02-0.04% of P, 0.30-0.45% of S and Te, wherein the content of Te satisfies the condition that Te/S is less than 0.07, 1.5-2.0% of Mo, 0.08-0.18% of V, 0.15-0.25% of Ni, 0.10-0.20% of Bi, 0.012-0.020% of O and 0.015-0.040% of Nb, and the sum of the weight percentages of all the components is 100%.
Preferably, 0.008-0.018% of C, 0.4-0.6% of Si, 1.05-1.18% of Mn, 19.0-21.0% of Cr, 0.02-0.03% of P, 0.35-0.45% of S and Te, wherein the content of Te satisfies the condition that Te/S is less than 0.07, 1.7-2.0% of Mo, 0.10-0.15% of V, 0.18-0.22% of Ni, 0.12-0.18% of Bi, 0.013-0.018% of O and 0.025-0.035% of Nb0.6%, and the sum of the weight percentages of all the components is 100%.
In the manufacturing method, when the billet is rolled in the step (4), the billet is cooled to room temperature and directly sent to the next step for rolling, so that short-process continuous casting and rolling are realized.
In the above-mentioned manufacturing method, in the step (4), the cooling water of the roughing mill, the intermediate mill and the finishing mill of the bar continuous rolling mill set is set to 900 to 1000m3Preferably 920 to 1000 m/hour3And in one hour, the length of the head and the tail cut by the third flying shear is increased to be 1.5-2.5 times, preferably 1.8-2.3 times, of the length of the head and the tail cut by the carbon alloy structural steel, so that the head of the steel is ensured to be higher in temperature and does not split when entering a finishing mill.
The environment-friendly free-cutting ferritic stainless steel solves the pollution problem in the prior art, and better improves the free-cutting performance of the environment-friendly stainless steel by the composite addition of free-cutting elements of sulfur-bismuth-tellurium (S-Bi-Te). The environment-friendly free-cutting stainless steel is suitable for machining small-size precision parts of various automatic machine tools. The manufacturing method adopts scrap steel, pure iron and alloy electric furnace smelting and continuous casting and rolling short-flow technology, has the characteristics of high efficiency and low cost, and is suitable for production of small and medium-sized special steel enterprises.
Detailed Description
The present invention will be described in detail with reference to specific embodiments in order to further clarify the objects, features and effects of the present invention. It will be understood by those skilled in the art that these specific embodiments and examples are for the purpose of illustrating the invention and are not to be construed as limiting the invention.
Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. The process of the present invention employs conventional methods or apparatus in the art, except as described below.
Aiming at the problem that the traditional free-cutting stainless steel material contains lead and is easy to cause harm to the environment and human bodies, the invention adopts the compound addition of the free-cutting element sulfur-bismuth-tellurium (S-Bi-Te) without adding lead (Pb), thereby avoiding the harm to the environment and human bodies in the smelting production and use processes of the stainless steel and being the environment-friendly free-cutting stainless steel material. The stainless steel manufacturing method adopts scrap steel, pure iron and alloy electric furnace smelting and continuous casting and rolling short-flow technology, has the characteristics of high production efficiency and low cost, and is suitable for production of small and medium-sized special steel enterprises.
In one aspect, the present invention provides an environment-friendly free-cutting ferritic stainless steel, comprising, in weight percent: 0.006-0.020% of C, 0.3-0.6% of Si, 1.0-1.2% of Mn, 18.5-22.0% of Cr, 0.02-0.04% of P, 0.30-0.45% of S and Te, wherein the content of Te satisfies the condition that Te/S is less than 0.07, 1.5-2.0% of Mo, 0.08-0.18% of V, 0.15-0.25% of Ni, 0.10-0.20% of Bi, 0.012-0.020% of O, 0.015-0.040% of Nb, and Fe and inevitable impurities, and the sum of the weight percentages of all the components is 100%. Preferably, the alloy comprises 0.008-0.018% of C, 0.4-0.6% of Si, 1.05-1.18% of Mn, 19.0-21.0% of Cr, 0.02-0.03% of P, 0.35-0.45% of S and Te, wherein the content of Te satisfies the condition that Te/S is less than 0.07, 1.7-2.0% of Mo, 0.10-0.15% of V, 0.18-0.22% of Ni, 0.12-0.18% of Bi, 0.013-0.018% of O and 0.025-0.035% of Nb, and the sum of the weight percentages of all the components is 100%.
Meanwhile, the invention also provides environment-friendly free-cutting ferritic stainless steel which comprises the following components in percentage by weight: 0.006-0.020% of C, 0.3-0.6% of Si, 1.0-1.2% of Mn, 18.5-22.0% of Cr, 0.02-0.04% of P, 0.30-0.45% of S and Te, wherein the content of Te satisfies the condition that Te/S is less than 0.07, 1.5-2.0% of Mo, 0.08-0.18% of V, 0.15-0.25% of Ni, 0.10-0.20% of Bi, 0.012-0.020% of O, 0.015-0.040% of Nb, and Fe and inevitable impurities, and the sum of the weight percentages of all the components is 100%. Preferably, the alloy comprises 0.008-0.018% of C, 0.4-0.6% of Si, 1.05-1.18% of Mn, 19.0-21.0% of Cr, 0.02-0.03% of P, 0.35-0.45% of S and Te, wherein the content of Te satisfies the condition that Te/S is less than 0.07, 1.7-2.0% of Mo, 0.10-0.15% of V, 0.18-0.22% of Ni, 0.12-0.18% of Bi, 0.013-0.018% of O and 0.025-0.035% of Nb, and the sum of the weight percentages of all the components is 100%.
The following is a description of the role and limitations of the main chemical components involved in the present invention:
carbon: the C element can form carbide in steel and also can play a role in solid solution strengthening, the content of C in ferrite is very low, the excessive content of C can reduce the corrosion resistance of the steel and the toughness of the ferrite, and the content of C in the invention is not higher than 0.02%.
Silicon: si element is soluble in ferrite and acts as solid solution strengthening, but too high Si content deteriorates corrosion resistance and lowers cold workability. The invention controls the content of Si to be 0.3-0.6%.
Chromium: the Cr element mainly plays a role in improving the corrosion resistance of the alloy, the higher the content of the Cr element is, the higher the corrosion resistance of the stainless steel is, but the Cr element is soluble in ferrite, and the high content of the Cr element can increase the hardness and the brittleness of the steel. The invention controls the Cr content to be 18.5-22.0%.
Nickel: ni is soluble in ferrite and improves the corrosion resistance of steel, but Ni has a very strong austenite stabilizing effect and is relatively expensive. The invention controls the Ni content to be 0.15-0.25%.
Manganese and sulfur: mn and S elements can be combined to form MnS, and the MnS is a plastic inclusion and can be used as a crack source of cutting chips, thereby being beneficial to improving the free-cutting property of the stainless steel. The Mn content is generally more than 2 times of the S content, the Mn content is controlled to be 1.0-1.2%, and the S content is controlled to be 0.3-0.45%.
Molybdenum: the Mo element can obviously improve the corrosion resistance of the stainless steel, is also a ferrite element and can play a role in solid solution strengthening, and is also a rare precious element, and the content of the Mo is controlled to be 1.5-2.0%.
Phosphorus: p can improve the free-cutting performance of the steel, but the P obviously increases the cold brittleness of the stainless steel, and the content of P is controlled to be 0.01-0.04 percent.
Bismuth: bi and Pb have lower melting points, and Bi is lower than Pb, so that the cutting tool can be lubricated during processing, the same performance can be achieved only by half of the Pb content, and the free-cutting performance of the stainless steel is greatly improved. Moreover, Bi has no toxic action, and the harm to the production and use process caused by the existence of Pb element is eliminated. The Bi content is designed to be 0.10-0.20%.
Tellurium: te is an element with extremely high surface activity, the shear resistance in the deformation process can be effectively reduced, when the content of Te meets the condition that Te/S is less than 0.07, MnTe appears in the stainless steel structure, and part of telluride exists at the edge of MnS to form a soft wrapping layer, so that the compression deformation of MnS can be reduced, the length-width ratio of MnS inclusions is reduced, and the cutting performance is favorably improved.
Oxygen: the O content can adjust the solubility of S in molten steel, influences the quantity and the form of formed sulfides, and the proper oxygen content is favorable for converting the form of MnS inclusions from B to A, so that the average diameter and the area fraction of the MnS inclusions are increased, the quantity is reduced, the length-width ratio is reduced, and the free-cutting performance is improved, therefore, the invention requires accurate oxygen control in steel, and the O content is controlled to be 0.012-0.020%.
Vanadium and niobium: both V and Nb form inclusions with C, N in the steel, refining the austenite grains. However, too much V and Nb form coarse inclusions, and deteriorate the properties of the structure. The content of V is controlled to be 0.08-0.18%, and the content of Nb is controlled to be 0.015-0.040%.
The A-type inclusion in the environment-friendly free-cutting ferritic stainless steel material is a plastic inclusion, the content of the A-type inclusion is high, the form of the A-type inclusion is mostly elliptical, the A-type inclusion is distributed uniformly, turning chips are easy to break and fall off in the machining process, tool sticking is avoided, and the service life of a tool is prolonged.
The hardness of the environment-friendly free-cutting ferritic stainless steel material is determined by the following specific method: and cutting a section of the prepared stainless steel round rod, wherein the height of the stainless steel round rod is 10-20 mm, polishing the section smoothly by using No. 1000 abrasive paper, and placing the section on a Vickers hardness tester objective table. The load of the hardness tester is set to be 0.3 (or 0.5/1.0) kg, hardness values of 5 different positions are respectively measured on the surface to be measured, and the hardness values are respectively a central point and the central points are from the upper direction, the lower direction, the left direction and the right direction to the middle position of the edge.
The result shows that the hardness of the stainless steel material is HV260-300, the hardness fluctuation range on the same cross section is less than or equal to HV20, the processing stability of the stainless steel material on an automatic machine tool is ensured, and the processing quality of the stainless steel material is greatly improved.
On the other hand, the invention provides a preparation method of the environment-friendly free-cutting ferritic stainless steel, which comprises the following steps:
(1) scrap steel, pure iron and alloy are taken as raw materials, and are sequentially added into an electric furnace to be smelted according to a proportion, and the raw materials are pretreated;
(2) casting the pretreated molten steel into a steel ingot of 2-3 tons;
(3) when the steel ingot is cooled to above 700 ℃, the steel ingot is sent to a square billet rolling workshop and is heated and rolled into a small square billet;
(4) directly sending the small square billet into a bar continuous rolling unit, rolling at the temperature of 1100-1180 ℃ and rolling into a stainless steel round bar.
In the preparation method, the pretreatment in the step (1) is to blow pure argon at the temperature of 1550-1600 ℃ and stir the mixture for not less than 10 minutes in a weak way.
In the manufacturing method, in the step (1), because the melting points of Bi and Te are lower and the yield of the added early alloy is low, the Bi-containing material and the Te-containing material are added two minutes before casting, and the material is a fine alloy with the diameter less than 20mm, so that the material is convenient to melt in time.
In the manufacturing method, in the step (1), oxygen is precisely controlled in the molten steel pretreatment process, and the molten steel casting in the step (2) is carried out when the weight percentage of the molten steel components reaches the following ratio:
0.006-0.020% of C, 0.3-0.6% of Si, 1.0-1.2% of Mn, 18.5-22.0% of Cr, 0.02-0.04% of P, 0.30-0.45% of S and Te, wherein the content of Te satisfies the condition that Te/S is less than 0.07, 1.5-2.0% of Mo, 0.08-0.18% of V, 0.15-0.25% of Ni, 0.10-0.20% of Bi, 0.012-0.020% of O and 0.015-0.040% of Nb, and the sum of the weight percentages of all the components is 100%.
In the manufacturing method, in the step (4), the unequal steel ingots and the small square billets are cooled to room temperature and directly sent to the next step for rolling, so that short-process continuous casting and rolling are realized.
In the manufacturing method, in the step (4), the cooling water of the roughing mill, the intermediate mill and the finishing mill of the bar continuous rolling mill set is set to be 900-1000 m 3/h, and the length of the head and the tail cut by the third flying shear is increased to be 1.5-2.5 times of the length of the head and the tail cut under the condition of the carbon alloy structural steel, so that the head of the steel is ensured to be high in temperature and does not split when entering the finishing mill.
Example one
The environment-friendly free-cutting ferritic stainless steel comprises the following chemical components:
melting the scrap steel, the pure iron and the alloy raw materials in an electric furnace according to the proportion, blowing pure argon gas at the temperature of 1560 ℃ for smelting for 12 minutes, crushing Bi-containing and Te-containing materials into fine crushed alloy with the diameter of less than 20mm, and adding the alloy for two minutes before casting. Monitoring and adjusting chemical components in the smelting process, and casting the molten steel into 2-ton steel ingots.
And (3) conveying the steel ingot to a square billet rolling workshop at 700 ℃, and heating and rolling the steel ingot into a small square billet.
Directly feeding the small square billet into a bar continuous rolling unit, and rolling at 1160 ℃. In the bar rolling process, cooling water of a roughing mill, a middle mill and a finishing mill of a continuous rolling mill group is set to 930m3And in one hour, the length of the head and the tail cut by the third flying shear is increased to be 1.8 times of the length of the head and the tail cut under the condition of carbon alloy structural steel, the temperature of the head of the steel is ensured to be higher, and the steel enters a finishing mill under the condition of no head splitting to prepare round steel with the diameter of 40 mm.
The A-type inclusion in the environment-friendly free-cutting ferritic stainless steel material is plastic inclusion MnS, the weight percentage content of the A-type inclusion is more than 50 percent of the total content of MnS, the A-type inclusion is mostly elliptical, and the A-type inclusion is distributed uniformly. A section of the prepared stainless steel round rod is cut, the cross section is polished to be smooth by using No. 1000 abrasive paper, and the stainless steel round rod is placed on a Vickers hardness tester objective table. The load of the hardness tester is set to be 0.5kg, hardness values of 5 different positions are respectively measured on the surface to be measured and are respectively taken as a central point, and the central positions from the upper direction, the lower direction, the left direction and the right direction of the central point to the edge, the hardness measurement values of the same section are respectively HV283, HV269, HV287, HV278 and HV288, and the processing performance is stable.
Example two
The environment-friendly free-cutting ferritic stainless steel comprises the following chemical components:
melting the scrap steel, the pure iron and the alloy raw materials in an electric furnace according to the proportion, blowing pure argon at the temperature of 1580 ℃ for 15 minutes for smelting, crushing the Bi-containing material and the Te-containing material into fine crushed alloy with the diameter of less than 20mm, and adding the alloy for two minutes before casting. Monitoring and adjusting chemical components in the smelting process, and casting the molten steel into a 2.5-ton steel ingot.
And (3) conveying the steel ingot to a square billet rolling workshop at 750 ℃, and heating and rolling the steel ingot into a small square billet.
Directly sending the small square billets into a bar continuous rolling unit, and rolling at the temperature of 1110 ℃. In the bar rolling process, the cooling water of the roughing mill, the intermediate mill and the finishing mill of the continuous rolling mill group is set to be 960m3And in one hour, the length of the head and the tail cut by the third flying shear is increased to be 2.3 times of the length of the head and the tail cut under the condition of carbon alloy structural steel, the temperature of the head of the steel is ensured to be higher, and the steel enters a finishing mill under the condition of no head splitting to prepare round steel with the diameter of 60 mm.
The A-type inclusion in the environment-friendly free-cutting ferritic stainless steel material is plastic inclusion MnS, the weight percentage content of the A-type inclusion is more than 50 percent of the total content of MnS, the A-type inclusion is mostly elliptical, and the A-type inclusion is distributed uniformly. A section of the prepared stainless steel round rod is cut, the cross section is polished to be smooth by using No. 1000 abrasive paper, and the stainless steel round rod is placed on a Vickers hardness tester objective table. The load of the hardness tester is set to be 0.5kg, hardness values of 5 different positions are measured on the surface to be measured respectively and are respectively taken as a central point, and the hardness values of the same section are respectively HV286, HV275, HV282, HV287 and HV267 from the central point to the middle position of the edge in four different directions, and the processing performance is stable.
EXAMPLE III
The environment-friendly free-cutting ferritic stainless steel comprises the following chemical components:
melting the scrap steel, the pure iron and the alloy raw materials in an electric furnace according to the proportion, blowing pure argon at the temperature of 1600 ℃ for 11 minutes for smelting, crushing Bi-containing and Te-containing materials into fine crushed alloy with the diameter of less than 20mm, and adding the alloy for two minutes before casting. Monitoring and adjusting chemical components in the smelting process, and casting the molten steel into 2.8-ton steel ingots.
And (3) conveying the steel ingot to a square billet rolling workshop at 780 ℃, and heating and rolling the steel ingot into a small square billet.
Directly sending the small square billets into a bar continuous rolling unit, and rolling at the temperature of 1150 ℃. In the process of rolling the bar, the cooling water of the roughing mill, the intermediate mill and the finishing mill of the continuous rolling mill set is set to 1000m3And in one hour, the length of the head and the tail cut by the third flying shear is increased to be 2.5 times of the length of the head and the tail cut under the condition of carbon alloy structural steel, the temperature of the head of the steel is ensured to be higher, and the steel enters a finishing mill under the condition of no head splitting to prepare round steel with the diameter of 80 mm.
The A-type inclusion in the environment-friendly free-cutting ferritic stainless steel material is plastic inclusion MnS, the weight percentage content of the A-type inclusion is more than 50 percent of the total content of MnS, the A-type inclusion is mostly elliptical, and the A-type inclusion is distributed uniformly. A section of the prepared stainless steel round rod is cut, the cross section is polished to be smooth by using No. 1000 abrasive paper, and the stainless steel round rod is placed on a Vickers hardness tester objective table. The load of the hardness tester is set to be 0.5kg, hardness values of 5 different positions are measured on the surface to be measured respectively and are respectively a central point, and the hardness values of the same section are HV283, HV289, HV292, HV278 and HV295 respectively from the upper direction, the lower direction, the left direction and the right direction of the central point to the middle position of the edge, and the processing performance is stable.
Example four
The environment-friendly free-cutting ferritic stainless steel comprises the following chemical components:
melting the scrap steel, the pure iron and the alloy raw materials in an electric furnace according to the proportion, blowing pure argon at the temperature of 1590 ℃ for 13 minutes for smelting, crushing the Bi-containing and Te-containing materials into fine crushed alloy with the diameter of less than 20mm, and adding the alloy for two minutes before casting. Monitoring and adjusting chemical components in the smelting process, and casting the molten steel into a steel ingot of 3.0 tons.
And (3) conveying the steel ingot to a square billet rolling workshop at 800 ℃, and heating and rolling the steel ingot into a small square billet.
Directly sending the small square billet into a bar continuous rolling unit, and rolling at 1170 ℃. In the bar rolling process, the cooling water of a roughing mill, a middle rolling mill and a finishing mill of a continuous rolling mill set is set to 990m3And in one hour, the length of the head and the tail cut by the third flying shear is increased to be 2.0 times of the length of the head and the tail cut under the condition of carbon alloy structural steel, the temperature of the head of the steel is ensured to be higher, and the steel enters a finishing mill under the condition of no head splitting to prepare round steel with the diameter of 70 mm.
The A-type inclusion in the environment-friendly free-cutting ferritic stainless steel material is plastic inclusion MnS, the weight percentage content of the A-type inclusion is more than 50 percent of the total content of MnS, the A-type inclusion is mostly elliptical, and the A-type inclusion is distributed uniformly. A section of the prepared stainless steel round rod is cut, the cross section is polished to be smooth by using No. 1000 abrasive paper, and the stainless steel round rod is placed on a Vickers hardness tester objective table. The load of the hardness tester is set to be 0.5kg, hardness values of 5 different positions are respectively measured on the surface to be measured and are respectively taken as a central point, and the central points are respectively taken as the middle positions from the upper direction, the lower direction, the left direction and the right direction of the central point to the edge, the hardness measurement values of the same section are respectively HV280, HV290, HV294, HV279 and HV297, and the processing performance is stable.
The preferred embodiments of the present invention disclosed above are those skilled in the art, and it should be understood that these embodiments are merely illustrative of the present invention and should not be construed as limiting the scope of the present invention, and therefore, all changes and substitutions that are equivalent to these embodiments should be considered as being included in the scope of the claims of the present invention. The protection scope of the present invention should be subject to the scope defined in the claims.
Claims (11)
1. An environment-friendly free-cutting ferritic stainless steel, characterized by comprising, in weight percent:
C：0.006～0.020％，
Si：0.3～0.6％，
Mn：1.0～1.2％，
Cr：18.5～22.0％，
P：0.02～0.04％，
S：0.30～0.45％，
te, and the content of the Te satisfies Te/S <0.07,
Mo：1.5～2.0％，
V：0.08～0.18％，
Ni：0.15～0.25％，
Bi：0.10～0.20％，
O：0.012～0.020％，
Nb：0.015～0.040％，
the balance being Fe and unavoidable impurities, wherein the sum of the percentages by weight of the individual components amounts to 100%.
2. The environment-friendly free-cutting ferritic stainless steel according to claim 1, characterized by comprising, in weight percent:
C：0.011％，
Si：0.43％，
Mn：1.17％，
Cr：20.5％，
P：0.024％，
S：0.38％，
te, and the content of the Te satisfies Te/S <0.07,
Mo：1.93％，
V：0.12％，
Ni：0.21％，
Bi：0.15％，
O：0.018％，
Nb：0.025％，
the balance being Fe and unavoidable impurities, wherein the sum of the percentages by weight of the individual components amounts to 100%.
3. The environment-friendly free-cutting ferritic stainless steel according to claim 1 or 2, characterized in that the microstructure of the stainless steel is ferrite with a grain size of not less than 10 grade.
4. The environment-friendly free-cutting ferritic stainless steel as set forth in claim 1 or 2, characterized in that the area ratio of a-type coarse inclusions of the stainless steel is not less than 50%.
5. The environment-friendly free-cutting ferritic stainless steel as set forth in claim 1 or 2, characterized in that the hardness of the stainless steel is HV260-300 and the fluctuation range of the hardness on the same cross section is not more than HV 20.
6. The method for manufacturing an environment-friendly free-cutting ferritic stainless steel set forth in any one of claims 1 to 5, characterized by comprising:
(1) scrap steel, pure iron and alloy are taken as raw materials, and are sequentially added into an electric furnace to be smelted according to a proportion, and the raw materials are pretreated;
(2) casting the pretreated molten steel into a steel ingot of 2-3 tons of steel;
(3) when the steel ingot is cooled to above 700 ℃, the steel ingot is sent to a square billet rolling workshop and is heated and rolled into a small square billet;
(4) directly sending the small square billet into a bar continuous rolling unit, rolling at 1050-1200 ℃ and rolling into a stainless steel round bar.
7. The method according to claim 6, wherein the pretreatment in the step (1) is blowing pure argon gas at 1450 to 1600 ℃ for less than 10 minutes with weak stirring.
8. The method according to claim 6, wherein the Bi-containing and Te-containing materials in the raw materials in the step (1) are finely divided alloys having a diameter of less than 20mm, and are added two minutes before the casting in the step (2).
9. The manufacturing method according to claim 6, wherein the pre-treatment in the step (1) is performed by controlling oxygen precisely, and the molten steel is cast in the step (2) until the molten steel has the following composition weight percentage:
0.006-0.020% of C, 0.3-0.6% of Si, 1.0-1.2% of Mn, 18.5-22.0% of Cr, 0.02-0.04% of P, 0.30-0.45% of S and Te, wherein the content of Te satisfies the condition that Te/S is less than 0.07, 1.5-2.0% of Mo, 0.08-0.18% of V, 0.15-0.25% of Ni, 0.10-0.20% of Bi, 0.012-0.020% of O and 0.015-0.040% of Nb, and the sum of the weight percentages of all the components is 100%.
10. The method according to claim 6, wherein the billet is rolled in the step (4) while being cooled to room temperature, and is directly fed to the next rolling step.
11. The method according to claim 6, wherein in the step (4), the cooling water of the roughing mill, the intermediate mill and the finishing mill of the bar continuous rolling mill train is set to 900 to 1000m3And in the hour, the length of the head and the tail cut by the third flying shear is increased to be 1.5-2.5 times of the length of the head and the tail cut under the condition of the carbon alloy structural steel.
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| CN107723597A (en) * | 2017-10-18 | 2018-02-23 | 启东市荣盛铜业有限公司 | A kind of ball pen head leadless environment-friendly free cutting stainless steel material and its smelting process |
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