CN112921230A - Improved method of screw carburized part - Google Patents
Improved method of screw carburized part Download PDFInfo
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- CN112921230A CN112921230A CN202110056881.9A CN202110056881A CN112921230A CN 112921230 A CN112921230 A CN 112921230A CN 202110056881 A CN202110056881 A CN 202110056881A CN 112921230 A CN112921230 A CN 112921230A
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- molten iron
- screw
- spheroidizing
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/08—Making cast-iron alloys
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C1/00—Refining of pig-iron; Cast iron
- C21C1/10—Making spheroidal graphite cast-iron
- C21C1/105—Nodularising additive agents
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/0006—Adding metallic additives
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C37/00—Cast-iron alloys
- C22C37/04—Cast-iron alloys containing spheroidal graphite
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C37/00—Cast-iron alloys
- C22C37/10—Cast-iron alloys containing aluminium or silicon
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Mechanical Engineering (AREA)
- Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
Abstract
The application discloses an improvement method of a carburized part of a screw, relates to the technical field of fastener preparation, and solves the problems that in the prior art, a carburized part in the screw is eliminated in a heat treatment mode, so that the production process period is prolonged, the production cost is increased, and the production benefit is greatly reduced. The embodiment of the invention provides an improvement method of a screw carburized part, which comprises the following steps: melting the raw materials into molten iron at 1500-1570 ℃, and pouring the molten iron into a spheroidizing bag; adding bismuth into the spheroidizing ladle, and uniformly fusing the spheroidizing ladle and the molten iron; pouring the fused molten iron into a cavity for smelting and pouring; and processing the cast product. The method of the embodiment of the invention effectively reduces carburized parts in the screw, realizes high-efficiency production of the screw and reduces the production cost of the screw.
Description
Technical Field
The application relates to the technical field of fastener preparation, in particular to an improvement method of a screw carburized part.
Background
A screw is a common fastener on the market, and is a fastener composed of a head and a screw rod.
Most of the existing screws are of an integral metal structure, and in the production and manufacturing process of the screws, when liquid molten iron is converted into a solid state, because the cooling speed is high, cementite is easy to appear at the edge surface, the edge angle and the thin wall of a casting, so that the hardness and the brittleness of a workpiece are high, and the processing and the forming are not facilitated.
At present, the elimination of carburized parts in cast iron or steel is mainly realized by the process modes of normalizing, spheroidizing annealing, drawing and high-temperature recrystallization annealing, but for small fasteners such as screws, the production process period is prolonged, the production cost is increased and the production benefit is greatly reduced by adopting a heat treatment process mode.
Disclosure of Invention
The embodiment of the application provides an improved method for a carburized part of a screw, and solves the problems that in the prior art, a carburized part in the screw is eliminated in a heat treatment mode, so that the production process period is prolonged, the production cost is increased, and the production benefit is greatly reduced, so that the efficient production of the screw is realized, and the production cost of the screw is reduced.
The embodiment of the invention provides an improved method for a screw carburized part, which comprises the following process steps:
melting the raw materials into molten iron at 1500-1570 ℃, and pouring the molten iron into a spheroidizing bag;
adding bismuth into the spheroidizing ladle, and uniformly fusing the spheroidizing ladle and the molten iron, wherein the percentage content of chemical components in the fused molten iron is as follows:
C：3.46%~3.76%；
Si：2.75%~2.93%；
Mn：0.22%~0.29%；
P：0.025%~0.031%；
S：0.012%~0.014%；
Mg：0.055%~0.072%；
Re：0.003%~0.004%；
Bi：0.01%~0.015%；
the balance of Fe;
pouring the fused molten iron into a cavity for smelting and pouring;
and processing the cast product.
Further, the adding bismuth into the spheroidizing bag comprises:
in the spheroidizing bag, when the molten iron is poured into 1/3, bismuth is added into the spheroidizing bag.
Furthermore, the ratio of Fe to Bi in the fused molten iron is 62500: 1.
Furthermore, in the molten iron after the fusion, 3.7% of C, 2.93% of Si, 0.25% of Mn, 0.031% of P, 0.012% of S, 0.072% of Mg, 0.004% of Re, 0.015% of Bi and the balance of Fe.
Furthermore, when the fused molten iron is poured into a cavity for smelting and pouring, the pouring temperature is controlled to be 1400-1460 ℃.
One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages:
in the method for improving the screw carburization part, provided by the embodiment of the invention, scrap iron or scrap steel is smelted, the smelted molten iron is poured into a spheroidizing ladle, bismuth is added into the spheroidizing ladle for spheroidizing and inoculation, in addition, the addition amount of C and Si in the molten iron is properly increased, so that fine and more graphite crystal nuclei can be formed in a liquidus line, the increase of the graphite number and the refinement of graphite are facilitated, the formation of ferrite is stably and intensively promoted, and the precipitation of cementite is hindered. By adopting the method provided by the embodiment of the invention, the problems that the production process period is prolonged, the production cost is increased and the production benefit is greatly reduced because the carburized part in the screw is eliminated by adopting a heat treatment mode in the prior art are solved, so that the high-efficiency production of the screw is realized and the production cost of the screw is reduced.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments of the present invention will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a flow chart of an improved method for forming a screw carburized part according to an exemplary embodiment of the present disclosure.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the embodiments of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience in describing the embodiments of the present invention and simplifying the description, but do not indicate or imply that the referred devices or elements must have specific orientations, be configured in specific orientations, and operate, and thus, should not be construed as limiting the present invention. The terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. Furthermore, the terms "mounted," "connected," and "connected" are to be construed broadly and may, for example, be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. Specific meanings of the above terms in the embodiments of the present invention can be understood by those of ordinary skill in the art according to specific situations.
As shown in fig. 1, an embodiment of the present invention provides an improved method for a screw carburized part, which includes the following process steps:
s101: melting the raw materials into molten iron at 1500-1570 ℃, and pouring the molten iron into a spheroidizing bag.
The method comprises the steps of putting scrap steel or scrap iron as a raw material into a smelting furnace for smelting, ensuring that the temperature is raised to 1500-1570 ℃, and if the temperature is lower than the temperature range, causing insufficient melting of molten metal, and causing various influences on the appearance, internal organization structure, performance and the like of a formed casting, wherein part of alloy cannot be sufficiently melted into the molten metal; if the temperature is higher than the temperature range, the molten metal is oxidized, and part of the alloy elements are burnt greatly. Therefore, the proper temperature is ensured during smelting, and the temperature during tapping is ensured to reach 1570 ℃.
S102: adding bismuth into the spheroidizing ladle, and uniformly fusing the spheroidizing ladle and molten iron, wherein the percentage content of chemical components in the fused molten iron is as follows:
c: 3.46% -3.76%; si: 2.75% -2.93%; mn: 0.22% -0.29%; p: 0.025% -0.031%; s: 0.012% -0.014%; mg: 0.055% -0.072%; re: 0.003% -0.004%; bi: 0.01% -0.015%; the balance being Fe.
In the step, before the molten iron is poured into the spheroidizing ladle, pure bismuth particles are added at the bottom of the ladle, and bismuth and the molten iron are fully fused, and a large amount of experimental data prove that when the added Bi is less than 0.01 percent, the content of ferrite in the internal tissue is reduced, and free strip-shaped and block-shaped cementite is generated; when the Bi content is more than 0.015%, precipitation of free cementite is inhibited, but the ferrite content is rapidly decreased and pearlite is increased; when the Bi is between 0.01 and 0.015 percent, cementite does not exist in the structure, and the content of ferrite can reach 80 to 90 percent, so that the proper amount of Bi can effectively promote the formation of fine graphite crystal nuclei and can stably and intensively promote the formation of the ferrite. Besides, a rare earth element Re is properly added in addition to Bi, and is combined with Bi to form heterogeneous crystal nuclei of graphite, increase the amount of graphite and refine graphite, and can widen the eutectic temperature range, hinder the precipitation of cementite structure, strengthen and stabilize ferrite.
S103: pouring the fused molten iron into a cavity for smelting and pouring.
S104: and processing the cast to produce the screw meeting the specification requirement.
The casting prepared in the embodiment of the invention can be used for producing 50167 screws, the blocking platform at the head of the casting is very thin, the thickness of the blocking platform is less than 2mm, the casting is cooled quickly during solidification, chilling cementite is easy to form, and the processed part has high hardness and high brittleness due to the cementite and is not beneficial to processing. Therefore, according to the method for improving the screw carburized part, the scrap iron or the scrap steel is smelted, the smelted molten iron is poured into the spheroidizing ladle, bismuth is added into the spheroidizing ladle for spheroidizing and inoculation, in addition, the addition amount of C and Si in the molten iron is properly increased, the formation of fine and more graphite crystal nuclei can be ensured at the liquidus line, the increase of the graphite amount and the refinement of the graphite are facilitated, the formation of ferrite is stably and intensively promoted, and the precipitation of cementite is hindered. The method solves the problems that the production process period is prolonged, the production cost is increased and the production benefit is greatly reduced because the carburized part in the screw is eliminated by adopting a heat treatment mode in the prior art, further realizes the high-efficiency production of the screw and reduces the production cost of the screw.
Specifically, the inventors conducted the following analysis of cementite produced in the cast structure by the following representative test data:
| serial number | C | Si | Mn | P | S | Mg | Re | Bi | Content of cementite% |
| 1 | 3.46 | 2.75 | 0.23 | 0.025 | 0.012 | 0.055 | 0.004 | 0 | 3.5 |
| 2 | 3.65 | 2.85 | 0.23 | 0.031 | 0.013 | 0.062 | 0.003 | 0.010 | 2.5 |
| 3 | 3.66 | 2.88 | 0.24 | 0.027 | 0.013 | 0.059 | 0.003 | 0.012 | 1.5 |
| 4 | 3.76 | 2.9 | 0.29 | 0.026 | 0.014 | 0.069 | 0.004 | 0.012 | 0.5 |
| 5 | 3.7 | 2.93 | 0.25 | 0.031 | 0.012 | 0.072 | 0.004 | 0.015 | 0 |
| 6 | 3.65 | 2.89 | 0.22 | 0.03 | 0.012 | 0.068 | 0.003 | 0.015 | 0 |
TABLE 1
As can be seen from the data analysis in table 1: when metal bismuth is not added, the content of cementite generated in the structure is up to 3.5 percent, and the separated cementite is gradually reduced along with the increase of the content of bismuth until the content of the cementite is 0; in addition, appropriate increases in the contents of C, Si, P, Mg and Re contribute to the reduction in cementite precipitation.
As a further improvement of this example, bismuth was added to the spheroidizing ladle, including: in the spheroidizing ladle, when molten iron is poured into 1/3, bismuth is added into the spheroidizing ladle.
In this embodiment, the melting point of bismuth is low, and the bismuth is oxidized due to too early addition, and the bismuth and the molten iron are not uniformly fused and even evaporated due to too late addition, so that the addition time node needs to be well controlled, and the bismuth is added in a corresponding proportion when 1/3 of the total amount of the molten iron is poured into the spheroidizing bag, so as to avoid affecting the absorption of the bismuth.
In this embodiment, the ratio of Fe to Bi in the molten iron after the fusion is 62500: 1.
Specifically, when 1t of Fe is contained in the molten iron to be smelted, 16g of bismuth is added into the spheroidizing bag, so that the bismuth and the Fe are fully fused, and according to the proportion, the formation of ferrite can be promoted, and the effects of moving reinforcement and stability are achieved.
In this example, in the molten iron after the melting, 3.7% of C, 2.93% of Si, 0.25% of Mn, 0.031% of P, 0.012% of S, 0.072% of Mg, 0.004% of Re, 0.015% of Bi, and the balance Fe.
When the component proportion in the molten iron is the above proportion, on one hand, the content of precipitated cementite is effectively reduced, on the other hand, through a plurality of tests, the tensile strength, yield strength and elongation of a casting cast by the molten iron with the above proportion are all obviously enhanced, the nodularity is increased, the content of pearlite is reduced, the hardness HB is reduced, and the number of graphite balls is increased, and the specific data parameters are as follows:
| serial number | Tensile strength | Yield strength | Elongation percentage% | Hardness HB | The spheroidization rate% | Pearlite amount% | Number of graphite balls |
| 1 | 467 | 340 | 18 | 165 | 85 | 12 | 150 |
| 2 | 501 | 350 | 18 | 162 | 85 | 10 | 150 |
| 3 | 490 | 348 | 18 | 162 | 85 | 12 | 150 |
| 4 | 505 | 352 | 18 | 163 | 85 | 11 | 150 |
| 5 | 464 | 337 | 19 | 160 | 90 | 9 | 200 |
| 6 | 517 | 366 | 20 | 161 | 90 | 7 | 200 |
Watch two
The second table corresponds to the data in the first table, and the analysis of the first table and the second table shows that when metal bismuth is not added, the strength, the nodularity and the number of graphite spheres of a casting are all lower, the contents of the hardness HB and the pearlite are relatively higher, the tensile strength of the casting is increased, the yield strength is also enhanced, the elongation is improved, the nodularity is increased, the number of graphite spheres is also increased, meanwhile, the amount of the pearlite is reduced, the hardness is reduced, and the processing of the casting is more facilitated.
In the embodiment, when the fused molten iron is poured into the cavity for smelting and pouring, the pouring temperature is controlled to be 1400-1460 ℃.
The pouring temperature is controlled to be 1400-1460 ℃, the molten iron can be guaranteed to fully pour the cavity in the pouring process, in addition, the liquid shrinkage is effectively reduced, shrinkage cavities and shrinkage porosity are reduced, and further the appearance, the internal organization structure and the performance of the formed casting are guaranteed to be the best.
The embodiments in the present specification are described in a progressive manner, and the same or similar parts among the embodiments may be referred to each other, and each embodiment focuses on the differences from the other embodiments.
The above embodiments are only used to illustrate the technical solutions of the present application, and not to limit the present application; although the present application has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications or substitutions do not depart from the spirit and scope of the present disclosure.
Claims (5)
1. An improved method for a screw carburized part is characterized by comprising the following process steps:
melting the raw materials into molten iron at 1500-1570 ℃, and pouring the molten iron into a spheroidizing bag;
adding bismuth into the spheroidizing ladle, and uniformly fusing the spheroidizing ladle and the molten iron, wherein the percentage content of chemical components in the fused molten iron is as follows:
C：3.46%~3.76%；
Si：2.75%~2.93%；
Mn：0.22%~0.29%；
P：0.025%~0.031%；
S：0.012%~0.014%；
Mg：0.055%~0.072%；
Re：0.003%~0.004%；
Bi：0.01%~0.015%；
the balance of Fe;
pouring the fused molten iron into a cavity for smelting and pouring;
and processing the cast product.
2. The improved method of screw carburization of claim 1, where said adding bismuth to said spheroidizing coating comprises:
in the spheroidizing bag, when the molten iron is poured into 1/3, bismuth is added into the spheroidizing bag.
3. The improved method of the screw carburized part according to claim 1, characterized in that the ratio of Fe to Bi in the molten iron after fusion is 62500: 1.
4. The improved method of a screw carburized part according to claim 1, characterized in that in the molten iron after fusion, C is 3.7%, Si is 2.93%, Mn is 0.25%, P is 0.031%, S is 0.012%, Mg is 0.072%, Re is 0.004%, Bi is 0.015%, and the balance is Fe.
5. The improved method of the screw carburized part according to claim 1, characterized in that when the molten iron after the melting is poured into a cavity for melt casting, the casting temperature is controlled to 1400 to 1460 ℃.
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