A method for forging free-cutting steel, free-cutting steel and applications thereof

Abstract

The application discloses a forging method of free-cutting steel, the free-cutting steel and application thereof, and the method comprises the following steps: homogenizing treatment of a free-cutting steel ingot; upsetting and drawing of the free-cutting steel ingot after the homogenizing treatment to obtain a free-cutting steel billet; multi-pass forging of the free-cutting steel billet, wherein each pass is performed at different rotary feeding angles, and the free-cutting steel is obtained after the forging is completed. Through the homogenizing heat treatment and the upsetting and drawing process, the macrosegregation and microsegregation of the free-cutting steel ingot are improved, the composition uniformity is greatly improved, and the porosity and shrinkage hole defects in the core of the ingot are welded. Through the three-pass forging process, the feeding speed, the rotation angle, the forging temperature and other parameters of each pass are strictly controlled, the microstructure uniformity of the forged ingot is improved, and the material can have good grain size and quality. The smelting and forging process of the application is simple, the raw material sources are wide, and the application prospect of the application in the manufacturing of automobile, high-speed rail, household appliance and office equipment parts is good.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of forging processing technology of metal materials, in particular to a kind of free-cutting steel forging method, free-cutting steel and its application. BACKGROUND

[0002] Free-cutting steel refers to the alloy steel that a certain amount of one or more than one of sulfur, phosphorus, lead, calcium, selenium, tellurium and other free-cutting elements are added to improve its machinability. According to the different free-cutting elements contained, free-cutting steel can be divided into sulfur-based free-cutting steel, lead free-cutting steel, titanium free-cutting steel and composite free-cutting steel. Sulfur-based free-cutting steel is the earliest in time, so far the largest and the most widely used free-cutting steel, accounting for 70% and more than 90% of the total output of free-cutting steel in the world and China. Sulfur-based free-cutting steel is mainly used in bolts, nuts, pipe fittings and spring seats and other complex mechanical parts. These complex parts need to be machined on a numerical control machine tool. In order to prolong the service life of the tool, reduce the processing cost and improve the production efficiency, the steel must have good machinability. The sulfur in sulfur-based free-cutting steel mainly exists in the form of manganese sulfide. The notch effect of manganese sulfide can cut off the continuity of the matrix, so that the stress in the cutting process can be released. Manganese sulfide has good plasticity in steel, which plays a lubricating role as a soft phase, can reduce the wear of the tool, and effectively improve the cutting performance of the steel.

[0003] It has been found that free-cutting steel is prone to generate elongated manganese sulfide after forging or rolling deformation, causing anisotropy of the steel and reducing the overall performance of the steel. Therefore, it is of great significance to control the morphology, size and aspect ratio of manganese sulfide in sulfur-containing free-cutting steel to improve the cutting performance of the steel. SUMMARY

[0004] The purpose of the present application is to effectively control the morphology, size and distribution state of manganese sulfide during forging deformation, so as to improve the key parameters such as size, aspect ratio and maximum chord length of manganese sulfide inclusions, and improve the cutting performance of Y12Cr18Ni9Cu2 type free-cutting steel.

[0005] In order to achieve the above purpose, the present application provides a kind of free-cutting steel forging method, comprising.

[0006] homogenizing treatment of free-cutting steel ingot;

[0007] upsetting and drawing the free-cutting steel ingot after homogenization treatment to obtain free-cutting steel billet;

[0008] multi-pass forging of the free-cutting steel billet, each pass being carried out at a different rotation feed angle, to obtain the free-cutting steel.

[0009] Further, the free-cutting steel casting billet is forged in multiple passes, each pass is performed at a different rotation feeding angle, and the free-cutting steel is obtained after the forging,

[0010] The free-cutting steel casting billet is forged in three passes:

[0011] The rotation feeding angle of the first pass is 90° / hammer, and a square billet with a side length of 100-120 mm is obtained;

[0012] The rotation feeding angle of the second pass is 45° / hammer, and a regular octagonal billet with an inscribed circle of 80-90 mm is obtained;

[0013] The rotation feeding angle of the third pass is 15° / hammer, and a rod-shaped billet with a diameter of 50-80 mm, i.e., the free-cutting steel, is obtained;

[0014] In the three passes, the feeding speed, the forging hammering frequency, and the time interval of each forging are also controlled.

[0015] Further, the feeding speed is 0.3-0.5 m / s;

[0016] The forging hammering frequency is 80-100 times / min.

[0017] Further, the upsetting and drawing of the homogenized free-cutting steel casting ingot to obtain the free-cutting steel casting billet comprises,

[0018] The homogenized free-cutting steel casting ingot is upset, drawn, and rounded at a temperature of ≥1120℃ to obtain a forging ingot with a diameter of 180-200 mm, the reduction of the upsetting is 20-50%, and the reduction of the drawing is 10-20%;

[0019] The forging ingot is kept at a temperature of 1100-1200℃ for 3-5 h, the surface temperature and the core temperature of the forging ingot are controlled within ±10℃ during the keeping process, and the free-cutting steel casting billet is obtained after the keeping.

[0020] Further, the homogenization treatment of the free-cutting steel casting ingot comprises,

[0021] The free-cutting steel casting ingot is kept at a temperature of 30-50℃ below the melting point for 5-10 h.

[0022] Further, the preparation method of the free-cutting steel casting ingot comprises,

[0023] The raw materials are prepared according to the composition of the free-cutting steel casting ingot;

[0024] The raw materials are vacuum smelted and cast to obtain a preliminary casting ingot, the composition of the preliminary casting ingot comprises, by weight percentage,

[0025] C is 0.03-0.04%; Si is 0.2-0.3%; Mn is 1.5-2.5%; P is 0.01-0.02%; S is 0.2-0.3%; Ni is 7.0-8.0%; Cr is 15.0-18.0%; Mo is 0.15-0.25%; H is 0.0001-0.0009%; O is 0.01-0.02%; N is 0.01-0.02%, Cu is 1.5-3.5%, and the rest is Fe and inevitable impurity elements;

[0026] The preliminary ingot is refined to obtain the free-cutting steel ingot.

[0027] Further, the content of Mn in the preliminary ingot is 7-10 times of the content of S.

[0028] The content of Cu is 1.5-2.0%.

[0029] Further, the free-cutting steel ingot is a column with a diameter of 200-205 mm.

[0030] The application further provides a free-cutting steel prepared by the forging method of the free-cutting steel.

[0031] The application also provides the application of the free-cutting steel, which is applied to the manufacture of parts of automobiles, high-speed rails, household appliances and office equipment.

[0032] Compared with the prior art, the application has the following beneficial effects:

[0033] (1) The 210-230 mm preliminary ingot smelted by the vacuum smelting furnace is used as the raw material, the size of the ingot is small, the processing difficulty of the material is reduced, the preparation period is shortened, and the material quality is improved.

[0034] (2) The macroscopic segregation and microscopic segregation of the free-cutting steel ingot are improved by one-time homogenization heat treatment and one-time upsetting and drawing process, the composition uniformity is greatly improved, and the shrinkage cavity defects in the core of the ingot are welded.

[0035] (3) The organization uniformity of the forged ingot is improved by one-time heating and three-time forging process, and the parameters such as the feeding speed, the rotation angle and the forging temperature of each time are strictly controlled, so that the material has good grain size and quality.

[0036] (4) The smelting and forging process of the application is simple and the raw material source is wide, does not contain lead element, does not pollute the environment and meets the development strategy of national energy saving and emission reduction, and has good application prospect in the direction of manufacturing parts of automobiles, high-speed rails, household appliances and office equipment.

[0037] Additional features and advantages of the present application will be set forth in the description that follows, and in part will be apparent from the description, or can be learned by practice of the present application. The objectives and other advantages of the present application will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative effort.

[0039] Figure 1 The strength-ductility curve of Y12Cr18Ni9Cu2 type free-cutting steel is shown;

[0040] Figure 2 The electron microscope graph showing the sulfide distribution state in the free-cutting steel ingot in the embodiment is shown;

[0041] Figure 3 The electron microscope graph showing the sulfide distribution state in the free-cutting steel in the embodiment is shown;

[0042] Figure 4 The length-width ratio distribution graph of the sulfides in the free-cutting steel in the embodiment is shown;

[0043] Figure 5 The size distribution graph of the sulfides in the free-cutting steel in the embodiment is shown;

[0044] Figure 6 The maximum chord length distribution graph of the sulfides in the free-cutting steel in the embodiment is shown;

[0045] Figure 7 The cutting chip graph of the free-cutting steel in the embodiment is shown. DETAILED DESCRIPTION

[0046] The endpoints of the ranges and any values described herein are not limited to the precise values stated. The ranges and values should be construed to be approximations that allow for significant variation. It is noted that various ranges and values are stated herein as being "between" two endpoints. It is to be understood that such a range is inclusive of the endpoints. It is further noted that the endpoints of the ranges can be combined with one another to form further ranges, which are also within the scope of the present application. It is to be understood that the endpoints of the ranges are not significant and are intended to be merely illustrative and are merely intended to indicate one example of the scope of the present application.

[0047] Y12Cr18Ni9Cu2 is an austenitic type stainless steel, which is a kind of improved cutting performance steel, and is suitable for making rollers, shafts, bolts and nuts by rapid cutting (such as automatic lathe).

[0048] The establishment concept of the present application comprises improving the macrosegregation and microsegregation of the free-cutting steel ingot by improving the forging method, improving the composition uniformity, welding the ingot core porosity and shrinkage hole defects by homogenization heat treatment and upsetting and drawing process; the organization uniformity of the forged ingot is improved by strictly controlling the feeding speed, rotation angle, forging temperature and other parameters of each pass of the forging process, and the material has good grain size and quality, thereby improving the cutting performance of Y12Cr18Ni9Cu2 free-cutting steel.

[0049] Therefore, the present application provides a forging method of free-cutting steel, comprising,

[0050] S101, homogenizing treatment of the free-cutting steel ingot.

[0051] In step S101, the free-cutting steel ingot is homogenized at a temperature below the melting point of 30-50℃ for 5-10h.

[0052] The preparation method of the free-cutting steel ingot comprises,

[0053] According to the composition of the free-cutting steel ingot, the raw materials are prepared; the raw materials are vacuum smelted and tapped to obtain a preliminary ingot, and the composition of the preliminary ingot comprises, by weight percentage, C 0.03-0.04%; Si 0.2-0.3%; Mn 1.5-2.5%; P 0.01-0.02%; S 0.2-0.3%; Ni 7.0-8.0%; Cr 15.0-18.0%; Mo 0.15-0.25%; H 0.0001-0.0009%; O 0.01-0.02%; N 0.01-0.02%, Cu 1.5-3.5%, and the rest is Fe and inevitable impurity elements; and the preliminary ingot is finished to obtain the free-cutting steel ingot.

[0054] Preferably, the vacuum smelting is to load the components except Fe and S in the alloy raw materials into the crucible according to the raw material ratio and the carbon additive, melt the alloy liquid under the vacuum condition of 50-500Pa, add Fe, S and the carbon additive to the alloy liquid in the steel liquid refining stage, and adjust the composition according to the composition of the free-cutting steel ingot before tapping, so that the composition is qualified before tapping. It should be noted that the carbon additive is not added as a raw material according to the demand, and the carbon additive is a commonly used carbon additive in the art, which can be graphite, coke, etc.

[0055] More preferably, the vacuum degree of the vacuum condition is 50Pa.

[0056] Preferably, the temperature of the tapping and casting is 1500-1580℃, and the preliminary ingot with a diameter of 210-230mm is obtained by tapping and casting.

[0057] More preferably, the temperature of the tapping and casting is 1550℃, and the tapping and casting is into a preliminary ingot with a diameter of 210mm.

[0058] Preferably, the preliminary ingot is air-cooled, and after cooling to room temperature, the easy-to-cut steel ingot is obtained by finishing.

[0059] Preferably, the easy-to-cut steel ingot is a columnar shape with a diameter of 200-205mm.

[0060] More preferably, the diameter of the easy-to-cut steel ingot is 200mm.

[0061] Preferably, the content of Mn in the preliminary ingot is 7-10 times the weight of S.

[0062] More preferably, the content of Mn in the preliminary ingot is 9-10 times the weight of S.

[0063] Preferably, the weight percentage of Cu is 1.5-2.0%.

[0064] It should be noted that the easy-to-cut steel ingot in the present application is not limited to preparation, as long as the composition of the easy-to-cut steel ingot meets the requirements, including preparation by the proposed method and direct acquisition, the method of the present application can be used for forging.

[0065] S102, the homogenized easy-to-cut steel ingot is upset and drawn to obtain an easy-to-cut steel billet.

[0066] In step S102, the homogenized easy-to-cut steel ingot is upset, drawn and rounded at a temperature ≥1120℃ to obtain a forging ingot with a diameter of 180-200mm, the reduction rate of the upsetting is 20-50%, and the reduction rate of the drawing is 10-20%; the forging ingot is kept at 1100-1200℃ for 3-5h, and the surface temperature and core temperature of the forging ingot are controlled within ±10℃ during the keeping process, and the easy-to-cut steel billet is obtained after the keeping process.

[0067] Preferably, the upsetting is performed using a 10t press.

[0068] Preferably, the forging ingot is heated and kept in a regenerative step heating furnace, and the temperature of the regenerative step heating furnace is well controlled with small temperature error.

[0069] Preferably, the forging ingot is kept at 1180℃ for 5h.

[0070] S103, the easy-to-cut steel billet is forged in multiple passes, each pass is performed at a different rotary feed angle, and the easy-to-cut steel is obtained after the forging.

[0071] In step S103, the free-cutting steel casting blank is forged for three times: the rotation feed angle of the first forging is 90° / hammer, and a square blank with a side length of 100-120 mm is obtained; the rotation feed angle of the second forging is 45° / hammer, and an octagonal blank with an inscribed circle of 80-90 mm is obtained; the rotation feed angle of the third forging is 15° / hammer, and a rod-shaped blank with a diameter of 50-80 mm, i.e., the free-cutting steel, is obtained; wherein the sample feeding speed, the forging hammer frequency and the time interval of each forging are controlled in the three times of forging.

[0072] Preferably, the first forging obtains a square blank with a side length of 100 mm; the second forging obtains an octagonal blank with an inscribed circle of 85 mm; and the third forging obtains a rod-shaped blank with a diameter of 65 mm.

[0073] Preferably, the sample feeding speed is 0.3-0.5 m / s.

[0074] More preferably, the sample feeding speed is 0.5 m / s.

[0075] Preferably, the forging hammer frequency is 80-100 times / min.

[0076] More preferably, the forging hammer frequency is 100 times / min.

[0077] By controlling the hammer frequency, the surface temperature of the forging ingot is controlled to be 0-20℃, and the core temperature is controlled to be below 15℃.

[0078] Preferably, the time interval from the end of the first forging to the start of the second forging is 1-15 s; and the time interval from the end of the second forging to the start of the third forging is 1-15 s.

[0079] The present application also provides a free-cutting steel prepared by the above-mentioned forging method of free-cutting steel.

[0080] The present application also provides the application of the free-cutting steel, which is applied to the manufacture of automobile, high-speed rail, household appliance and office equipment parts.

[0081] The technical solutions in the embodiments of the present application will be clearly and completely described with reference to the specific embodiments of the present application and the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0082] Embodiments

[0083] A forging method of free-cutting steel, comprising the following steps,

[0084] a. Preparation of Y12Cr18Ni9Cu2 free-cutting steel ingot:

[0085] a1. According to the composition of Y12Cr18Ni9Cu2 free-cutting steel, ingredients are prepared in mass percentage, C 0.03-0.04%; Si 0.2-0.3%; Mn 1.5-2.5%; P 0.01-0.02%; S 0.2-0.3%; Ni 7.0-8.0%; Cr 15.0-18.0%; Mo 0.15-0.25%; H 0.0001-0.0009%; O 0.01-0.02%; N 0.01-0.02%, Cu 1.5-3.5%, the rest is Fe and inevitable impurities, and a carbon additive is also prepared.

[0086] a2. The ingredients except Fe and S in the ingredients prepared in step a1 are loaded into a crucible according to the raw material ratio and the carbon additive, the vacuum degree of the vacuum induction furnace is adjusted to 50 Pa, then the crucible is transferred to the vacuum induction furnace, and then power is supplied to melt to obtain an alloy liquid, Fe, S and the carbon additive are added to the alloy liquid in the steel liquid refining stage, and the composition is adjusted according to the composition of the free-cutting steel ingot before tapping, and the composition is qualified before tapping.

[0087] a3. The steel is tapped and cast at 1550℃ to obtain a preliminary ingot with a diameter of 210mm, the preliminary ingot is air-cooled, and the diameter of the preliminary ingot is finished after cooling to room temperature to obtain a free-cutting steel ingot, the free-cutting steel ingot is a column with a diameter of 200mm. The composition of the free-cutting steel ingot is shown in Table 1, and Fe and inevitable impurities are not shown.

[0088] Table 1 Composition of free-cutting steel ingot (wt. %)

[0089]

[0090] b. Homogenization treatment: the free-cutting steel ingot obtained in step a is subjected to homogenization treatment at 1350℃ for 10h to obtain a free-cutting steel ingot after homogenization treatment.

[0091] c. One-fire quick forging upsetting and drawing: the free-cutting steel ingot after homogenization treatment is upset by using a 10t press at a temperature ≥1120℃, the drawing is immediately performed after the upsetting is completed, and then the roundness is rolled to a diameter of 200mm to obtain a forged ingot, wherein the upsetting reduction is 30%, and the drawing reduction is 15%.

[0092] d. Reheating: the forged ingot obtained in step c is placed in a regenerative step-heating furnace with good temperature control and small temperature error, and the temperature is determined as 1180℃ according to the strength-plasticity curve of Figure 1 and is kept for 5h to obtain a free-cutting steel billet.

[0093] e. Multi-pass forging:

[0094] e1. The first forging begins 60 seconds after the free-cutting steel billet exits the regenerative walking beam furnace. The feeding speed for the first forging pass is 0.5 m / s; the rotational feeding angle is 90° / hammer; the forging hammer frequency is controlled at 100 times / min. By controlling the hammer frequency, the surface temperature rise of the forged ingot is controlled at 0-20℃, and the core temperature rise is controlled below 15℃. The first forging pass yields a square billet with a side length of 100 mm.

[0095] e2. After the first forging pass is completed, the second forging pass is performed after a 10-second interval. The feeding speed of the second forging pass is controlled at 0.5 m / s; the rotational feeding angle is 45° / hammer; the forging hammer frequency is 100 times / min. By controlling the hammer frequency, the surface temperature rise of the forged ingot is controlled at 0-20℃, and the core temperature rise is controlled below 15℃. The second forging pass yields a regular octagonal billet with an outer circle of 85 mm.

[0096] e3. After the second forging pass, a third forging pass is performed after a 10-second interval. The feeding speed during the third forging pass is controlled at 0.5 m / s; the rotational feeding angle is 15° / hammer; and the forging hammer frequency is 100 times / min. By controlling the hammer frequency, the surface temperature rise of the forged ingot is controlled at 0-20℃, and the core temperature rise is controlled below 15℃. The third forging pass yields a bar-shaped billet with a diameter of 65 mm, i.e., free-cutting steel.

[0097] Test case

[0098] The Phenom Partical X-ray benchtop scanning electron microscope-energy dispersive spectroscopy (EDS-MS) offers high accuracy and efficiency in sulfide detection, enabling quantitative analysis of sulfides in free-cutting steel ingots and steels. The results allow for statistical analysis of important information such as sulfide dimensions, aspect ratio, and maximum chord length. The Phenom Partical X-ray benchtop scanning electron microscope-EDS-MS was used to quantitatively analyze sulfides in free-cutting steel ingots and steels in the example, with a sample scanning area of ​​8.991093 mm². 2 .

[0099] from Figure 2 It can be seen that the sulfides in the free-cutting steel ingot are mostly precipitated along the grain boundaries and are distributed in clusters, which is not conducive to the cutting performance of the steel.

[0100] from Figure 3 As can be seen from the example, the free-cutting steel ingot obtained by the forging method of the example has a relatively uniform sulfide distribution and fine sulfides, which is beneficial to improving the cutting performance of the steel.

[0101] from Figure 4 It can be seen that the proportion of sulfides with an aspect ratio ≤3 in free-cutting steel reaches 43.59%.

[0102] From Figure 5 It can be seen from the table that the proportion of sulfides with a size of ≤3 of the free-cutting steel reaches 48.33%.

[0103] From Figure 6 It can be seen from the table that the proportion of sulfides with a maximum chord length of ≤3 of the free-cutting steel reaches 43.79%.

[0104] From Figures 4-6 It can be seen from the table that the proportion of sulfides with a size of ≤3 of the free-cutting steel reaches 48.33%.

[0105] The free-cutting steel obtained in the example is also subjected to cutting at a feed amount of 0.06 mm and 500 revolutions / min, Figure 7 It is shown that the cutting chips are uniformly and finely distributed. According to the Phenom Partical X sulfide characterization results and the actual cutting performance, it can be concluded that the free-cutting steel forged by the forging method of the example has good cutting performance.

[0106] In summary, the forging method of the present application uses a 210-230 mm initial ingot smelted by a vacuum smelting furnace as a raw material, and the ingot size is small, which reduces the processing difficulty of the material, shortens the preparation period, and improves the material quality. By one homogenization heat treatment and one upsetting and drawing process, the macrosegregation and microsegregation of the free-cutting steel ingot are improved, the composition uniformity is greatly improved, and the ingot core porosity and shrinkage hole defects are welded. By one heating and three forging processes, the parameters such as the feed speed, the rotation angle, and the forging temperature of each pass are strictly controlled, the microstructure uniformity of the forged ingot is improved, and the material has good grain size and quality. The melting and forging process of the present application is simple and the raw material source is wide, and has good application prospect in the manufacture of automobile, high-speed rail, household appliance and office equipment parts.

[0107] Finally, it should be noted that: the above only describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent replacements to some technical features, as long as they are within the spirit and principles of the present application. Any modification, equivalent replacement, improvement, etc. made shall be included in the protection scope of the present application.

Claims

1. A forging method for free-cutting steel, characterized in that, include, Homogenize the free-cutting steel ingots; The free-cutting steel ingot after homogenization treatment is upset to obtain a free-cutting steel billet. Free-cutting steel billets are forged in multiple passes, each pass performed at a different rotary feed angle. The resulting free-cutting steel includes... The free-cutting steel billet is forged in three passes: The first forging cycle has a rotary feed angle of 90° per hammer, resulting in a square billet with a side length of 100-120mm. The second forging cycle has a rotary feed angle of 45° per hammer, resulting in a regular octagonal billet with a circumscribed circle of 80-90mm. The rotary feed angle of the third forging is 15° / hammer, which yields a bar-shaped billet with a diameter of 50-80mm, i.e., free-cutting steel. In the three forging passes, the feed rate, forging hammer frequency, and time interval between each forging pass are also controlled. The feed rate is 0.3-0.5 m / s, and the forging hammer frequency is 80-100 times / min.

2. The forging method for free-cutting steel according to claim 1, characterized in that, The process of upsetting and drawing a homogenized free-machining steel ingot to obtain a free-machining steel billet includes... At a temperature ≥1120℃, the homogenized free-machining steel ingot is upset, drawn, and rounded to obtain a forging ingot with a diameter of 180-200mm. The upsetting reduction rate is 20-50%, and the drawing reduction rate is 10-20%. The forged ingot is held at 1100-1200℃ for 3-5 hours. During the holding process, the surface temperature and core temperature of the forged ingot are controlled within ±10℃. After the holding is completed, a free-cutting steel billet is obtained.

3. The forging method for free-cutting steel according to claim 1, characterized in that, The homogenization treatment of the free-cutting steel ingot includes... Hold the free-cutting steel ingot at a temperature below its melting point of 30-50℃ for 5-10 hours.

4. The forging method for free-cutting steel according to any one of claims 1-3, characterized in that, The method for preparing the free-cutting steel ingot includes, Raw materials are obtained by batching according to the composition of free-cutting steel ingots; The raw materials are vacuum smelted and then cast to obtain a preliminary ingot. The composition of the preliminary ingot, by weight percentage, includes... C is 0.03-0.04%; Si is 0.2-0.3%; Mn is 1.5-2.5%; P is 0.01-0.02%; S is 0.2-0.3%; Ni is 7.0-8.0%; Cr is 15.0-18.0%; Mo is 0.15-0.25%; H is 0.0001-0.0009%; O is 0.01-0.02%; N is 0.01-0.02%; Cu is 1.5-3.5%, and the remainder is Fe and unavoidable impurity elements; The preliminary ingot is then refined to obtain a free-cutting steel ingot.

5. The forging method for free-cutting steel according to claim 4, characterized in that, In the composition of the preliminary ingot, Mn is 7-10 times the weight of S; The weight percentage of Cu is 1.5-2.0%.

6. The forging method for free-cutting steel according to claim 5, characterized in that, The free-cutting steel ingot is cylindrical with a diameter of 200-205 mm.

7. A free-cutting steel, characterized in that, It is prepared by the forging method according to any one of claims 1-5.

8. An application of the free-cutting steel according to claim 7, characterized in that, Used in the manufacture of parts for automobiles, high-speed trains, home appliances, and office equipment.

Images