Cold-pressed pellets, method for their production and use

Abstract

The present application belongs to the technical field of steelmaking waste treatment, and particularly relates to a cold-pressed pellet and a preparation method and application thereof. The cold-pressed pellet is composed of the following raw material components in mass fraction: 46% to 54% of ladle slag, 39% to 45% of iron oxide scale, 6% to 8% of lime and 0.8% to 1.2% of binder. The cold-pressed pellet provided by the present application can be directly used for converter smelting in the steelmaking process due to low melting point and high oxide content, so as to realize the purposes of resource saving and environment friendliness.

Description

Technical Field

[0001] This invention belongs to the field of steelmaking waste treatment technology, specifically relating to a cold-pressed pellet, its preparation method, and its application. Background Technology

[0002] Sulfur-based free-cutting steel 1215 is a green and environmentally friendly material that replaces the original lead-containing free-cutting steel 1214. With the rapid development of my country's automotive and machinery manufacturing industries in recent years, the demand is increasing.

[0003] However, the disposal of waste materials generated during the smelting process, such as ladle slag, continuous casting cut-off scrap, rolling mill scale, and downstream wire drawing scale, is quite difficult. Continuous casting cut-off scrap can be categorized and stored, and then added to the steelmaking furnace for disposal when smelting similar steel grades. The remaining ladle slag, rolling mill scale, and wire drawing scale are much harder to handle. Scrap materials with high sulfur content are harmful to the smelting of most steel grades, hindering cost reduction and quality improvement. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a cold-pressed pellet and its preparation method, primarily used to treat steelmaking waste such as ladle casting residue, steel rolling oxide scale, and wire drawing oxide scale, thereby achieving resource conservation and environmental friendliness.

[0005] This invention is achieved through the following technical solution:

[0006] In a first aspect, the present invention provides a cold-pressed pellet composed of the following raw material components by mass fraction:

[0007] 46%–54% of large-batch casting residue, 39%–45% of iron oxide scale, 6%–8% of lime, and 0.8%–1.2% of binder.

[0008] The cold-pressed pellets provided by this invention have a low melting point and high oxide content, and can be directly used in converter smelting during the steelmaking process, achieving the goals of resource conservation and environmental friendliness.

[0009] In some possible implementations, the source of the iron oxide scale includes at least one of rolled steel iron oxide scale and iron oxide scale generated from wire drawing.

[0010] In some possible implementations, the adhesive includes at least one of sodium silicate, bentonite, and carboxymethyl cellulose.

[0011] In some possible implementations, the moisture content in the cold-pressed pellets is less than 0.5%.

[0012] In some possible implementations, the size of the cold-pressed pellets is 33mm~37mm×28mm~32mm×16mm~20mm.

[0013] In some possible implementations, the average particle size of the slag residue from the large-batch casting is below 250 μm.

[0014] In some possible implementations, the average particle size of the iron oxide scale is below 250 μm.

[0015] In some possible implementations, the average particle size of the lime is below 250 μm.

[0016] In some possible implementations, the average particle size of the adhesive is below 250 μm.

[0017] Secondly, the present invention provides a method for preparing the above-mentioned cold-pressed pellets, comprising the following steps:

[0018] The mixture is cold-pressed to obtain cold-pressed pellets;

[0019] The mixture includes slag from large-batch casting, iron oxide scale, lime, and binder.

[0020] The method for preparing cold-pressed pellets provided by this invention is simple and easy to implement.

[0021] In some possible implementations, preparing the mixture includes the following steps:

[0022] Mix the slag, iron oxide scale, and lime from the large batch of casting, then add the binder and stir. The stirring speed is 30 rpm to 50 rpm, and the stirring time is 3 min to 5 min.

[0023] In some possible implementations, the cold pressing process includes the following steps:

[0024] The mixture is pressed using a briquetting machine to obtain primary pellets, which are then left to stand to obtain cold-pressed pellets.

[0025] In some possible implementations, the linear pressure of the briquetting machine is 20kN / cm to 30kN / cm, and the rotational speed is 16rpm to 20rpm.

[0026] In some possible implementations, the settling time is 24 hours or more, preferably 24 hours to 48 hours.

[0027] Thirdly, the present invention provides an application of the cold-pressed pellets provided by the present invention in the field of iron and steel smelting. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described and illustrated below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. All other embodiments obtained by those skilled in the art based on the embodiments provided by this invention without inventive effort are within the scope of protection of this invention.

[0029] Obviously, the following description is merely some examples or embodiments of the present invention. Those skilled in the art can apply the present invention to other similar scenarios without any inventive effort. Furthermore, it is understood that although the effort involved in such development may be complex and lengthy, for those skilled in the art related to the content disclosed in this invention, modifications to design, manufacturing, or production based on the technical content disclosed in this invention are merely conventional technical means and should not be construed as insufficient disclosure of the present invention.

[0030] However, there may be instances where unnecessary detailed descriptions are omitted. For example, detailed descriptions of well-known matters or repetitive descriptions of essentially the same structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the following description is provided to enable those skilled in the art to fully understand the invention and is not intended to limit the subject matter of the claims.

[0031] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions, and all technical features and optional technical features of the present invention can be combined with each other to form new technical solutions.

[0032] The term "content" refers to the mass fraction.

[0033] The following is a detailed description of a cold-pressed pellet, its preparation method, and its application according to an embodiment of the present invention.

[0034] Cold-pressed pellets

[0035] A first aspect of this invention provides a cold-pressed pellet, composed of the following raw material components by mass fraction:

[0036] 46%–54% of slag from large-batch casting, 39%–45% of iron oxide scale, 6%–8% of lime, and 0.8%–1.2% of binder;

[0037] The melting point of cold-pressed pellets is 1150℃~1250℃, and the oxygen content is 15%~25%.

[0038] The cold-pressed pellets provided in this invention use ladle slag and iron oxide scale as raw materials. The resulting cold-pressed pellets have a low melting point and high oxide content, allowing them to be directly used in converter smelting during steelmaking, achieving resource conservation and environmental friendliness. Furthermore, after being used in converter smelting, the sulfur content of the molten steel increases by 0.002% to 0.004% upon tapping, thus reducing costs without affecting steel quality. In addition, the cold-pressed pellets provided in this invention stabilize the converter smelting process, improve slag formation, and result in lower phosphorus content at the final stage.

[0039] Ladle slag refers to the slag formed after deoxidation in a converter during the production of free-cutting steel or plain carbon steel.

[0040] In some embodiments, the source of iron oxide scale includes at least one of rolled steel iron oxide scale and iron oxide scale generated from wire drawing.

[0041] In some embodiments, the adhesive includes at least one of sodium silicate, bentonite, and carboxymethyl cellulose.

[0042] In some embodiments, the moisture content in the cold-pressed pellets is less than 0.5%.

[0043] In some embodiments, the size of the cold-pressed pellets is (33mm~37mm)×(28mm~32mm)×(16mm~20mm).

[0044] In some embodiments, the average particle size of the residue from the bulk casting is below 250 μm.

[0045] In some specific embodiments, the average particle size of the residue from the bulk casting is 200μm to 250μm.

[0046] In some embodiments, the average particle size of the iron oxide scale is less than 250 μm.

[0047] In some specific embodiments, the average particle size of the iron oxide scale is 200 μm to 250 μm.

[0048] In some embodiments, the average particle size of lime is less than 250 μm.

[0049] In some specific embodiments, the average particle size of the lime is 200 μm to 250 μm.

[0050] In some embodiments, the average particle size of the adhesive is less than 250 μm.

[0051] In some specific embodiments, the average particle size of the adhesive is 200 μm to 250 μm.

[0052] Preparation method of cold-pressed pellets

[0053] A second aspect of this invention provides a method for preparing the above-mentioned cold-pressed pellets, comprising the following steps:

[0054] S1. The mixture is cold-pressed to obtain cold-pressed pellets;

[0055] The mixture includes bulk casting residue, iron oxide scale, lime, and binder.

[0056] The method for preparing cold-pressed pellets provided in this embodiment of the invention is simple and easy to implement.

[0057] In some embodiments, in step S1 above, preparing the mixture includes the following steps:

[0058] S101. Mix the slag, iron oxide scale, and lime from the large batch of casting, then add the binder and stir. The stirring speed is 30 rpm to 50 rpm, and the stirring time is 3 min to 5 min.

[0059] In some embodiments, in step S1 above, the cold pressing process includes the following steps:

[0060] S102. The mixture is pressed using a briquetting machine to obtain primary pellets, which are then left to stand to obtain cold-pressed pellets.

[0061] In some embodiments, in step S102 above, the linear pressure of the briquetting machine is 20kN / cm to 30kN / cm, and the rotation speed is 16rpm to 20rpm.

[0062] In some embodiments, in step S102 above, the settling time is 24 hours or more.

[0063] In some specific embodiments, the settling time in step S102 above is 24h to 48h.

[0064] The following description, in conjunction with specific embodiments, provides further details.

[0065] For simplicity, in the comparative examples below, the size of the cold-pressed pellets is 35mm × 30mm × 18mm.

[0066] Example 1

[0067] Example 1 provides a cold-pressed pellet, composed of the following raw material components by mass fraction:

[0068] 50% slag from large-batch casting, 42% iron oxide scale from steel rolling, 7% lime and 1% bentonite.

[0069] The average particle size of the residue from the large-batch casting is 250 μm.

[0070] The average particle size of the iron oxide scale in rolled steel is 250 μm;

[0071] The average particle size of lime is 250 μm;

[0072] The average particle size of bentonite is 250 μm;

[0073] The moisture content of the cold-pressed pellets is 0.1%;

[0074] The cold-pressed pellets have a melting point of 1200℃ and an oxygen content of 20%.

[0075] This embodiment also proposes a method for preparing cold-pressed pellets, the steps of which are as follows:

[0076] S10. Mix the slag from the large ladle, the iron oxide scale from the rolled steel, and the lime, then add bentonite and stir. The stirring speed is 40 rpm and the stirring time is 3 minutes to obtain the mixture.

[0077] S20. The mixture is pressed using a briquetting machine to obtain primary pellets; wherein the linear pressure of the briquetting machine is 25 kN / cm and the rotation speed is 18 rpm.

[0078] S30. Let the primary pellets stand for 24 hours to obtain cold-pressed pellets.

[0079] Example 2

[0080] Example 2 provides a cold-pressed pellet composed of the following raw material components by mass fraction:

[0081] 46% slag from large-batch casting, 45% iron oxide scale from steel rolling, 8% lime and 1% bentonite.

[0082] The average particle size of the residue from the large-batch casting is 180μm.

[0083] The average particle size of the iron oxide scale in rolled steel is 150 μm;

[0084] The average particle size of lime is 200 μm;

[0085] The average particle size of bentonite is 200 μm;

[0086] The moisture content of the cold-pressed pellets is 0.4%;

[0087] The cold-pressed pellets have a melting point of 1150℃ and an oxygen content of 25%.

[0088] This embodiment also proposes a method for preparing cold-pressed pellets, with the same steps as in Example 1.

[0089] Example 3

[0090] Example 3 provides a cold-pressed pellet composed of the following raw material components by mass fraction:

[0091] 54% slag from large-batch casting, 39.2% iron oxide scale from steel rolling, 6% lime and 0.8% bentonite.

[0092] The average particle size of the residue from the large-batch casting is 180μm.

[0093] The average particle size of the iron oxide scale in rolled steel is 150 μm;

[0094] The average particle size of lime is 200 μm;

[0095] The average particle size of bentonite is 200 μm;

[0096] The moisture content of the cold-pressed pellets is 0.4%;

[0097] The cold-pressed pellets have a melting point of 1250℃ and an oxygen content of 15%.

[0098] Comparative Example 1

[0099] Comparative Example 1 provides a cold-pressed pellet composed of the following raw material components by mass fraction:

[0100] 60% of large-batch casting residue, 30% of rolled iron oxide scale, 5% lime and 5% bentonite.

[0101] The cold-pressed pellets have a melting point of 1400℃ and an oxygen content of 10%.

[0102] To verify the advancement of the cold-pressed pellets and their preparation method provided in the embodiments of the present invention, the cold-pressed pellets provided in the embodiments and comparative examples were applied to the converter smelting of sulfur-containing free-cutting steel 1215 (or 1215MS) and other steel grades. The change in sulfur content of the molten steel after the addition of cold-pressed pellets was detected. The results of the change in sulfur content are shown in Table 1 below.

[0103] in:

[0104] (1) The conditions for using cold-pressed pellets in converter smelting are as follows:

[0105] ① When charging scrap steel into the converter, add it to the scrap steel hopper, accounting for 10±2% of the total scrap steel added. After the converter starts blowing oxygen, the oxygen lance position is 10mm lower than usual.

[0106] ② During the converter smelting process, add the slag at the 7-10 minute mark, just before the "re-drying" phase begins. It can be added from the high-level silo of the converter as a slag-reducing agent to adjust the slag condition during the smelting process. Add 500 kg per batch, with a maximum of 3 batches.

[0107] ③ The carbon content of the tapped steel should not exceed 0.06%, and slag discharge is strictly prohibited during the tapping process.

[0108] ④ After tapping is completed, the molten steel is transferred to the argon station and 20 kg of aluminum granules are added to the slag surface for deoxidation (no aluminum granules are added if the final C ≥ 0.04%). Soft blow for 3 min to 5 min and then turn off the argon gas. Then take a sample using an Al-containing sampler.

[0109] Table 1

[0110]

[0111] From Table 1 above, at least the following conclusions can be drawn: When smelting sulfur-containing free-cutting steel in a converter, adding the cold-pressed pellets provided in this embodiment of the invention increases the sulfur content of the molten steel at the time of tapping by 0.002% to 0.004%, which is beneficial for cost reduction and does not affect quality. Analysis based on observations of the smelting process and a comparison of the final phosphorus content of the molten steel shows that adding the cold-pressed pellets provided in this embodiment of the invention results in a stable smelting process, good slag formation, and a lower final phosphorus content compared to the comparative example.

[0112] It should be noted that the present invention is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments that have the same structure and perform the same effects as the technical concept within the scope of the present invention are included within the scope of the present invention. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of the present invention, are also included within the scope of the present invention.

Claims

1. A cold-pressed pellet, characterized in that, It consists of the following raw material components by mass fraction: 46%~54% of slag from large-batch casting, 39%~45% of iron oxide scale, 6%~8% of lime, and 0.8%~1.2% of binder; The ladle slag is the slag formed after deoxidation in a converter during the production of free-cutting steel or ordinary carbon steel. The cold-pressed pellets are used in the converter smelting of sulfur-containing free-cutting steel 1215; The moisture content of the cold-pressed pellets is less than 0.5%; During the converter smelting process, it is added as a slag-reducing agent from the high-level silo of the converter when the smelting process is about 7 to 10 minutes into the "re-drying" period.

2. The cold-pressed pellets according to claim 1, characterized in that, The source of the iron oxide scale includes at least one of the following: iron oxide scale from steel rolling and iron oxide scale generated from wire drawing; And / or, the adhesive comprises at least one of sodium silicate, bentonite, and carboxymethyl cellulose.

3. The cold-pressed pellets according to claim 1, characterized in that, The dimensions of the cold-pressed pellets are 33mm~37mm×28mm~32mm×16mm~20mm.

4. The cold-pressed pellets according to claim 1, characterized in that, The average particle size of the residue from the large-batch casting is below 250 μm; And / or, the average particle size of the iron oxide scale is less than 250 μm; And / or, the average particle size of the lime is less than 250 μm; And / or, the average particle size of the adhesive is below 250 μm.

5. A method for preparing cold-pressed pellets as described in any one of claims 1 to 4, characterized in that, Includes the following steps: The mixture is cold-pressed to obtain cold-pressed pellets; The mixture includes slag from large-batch casting, iron oxide scale, lime, and binder.

6. The method for preparing cold-pressed pellets according to claim 5, characterized in that, The preparation of the mixture includes the following steps: Mix the slag, iron oxide scale, and lime from the large batch of casting, then add the binder and stir. The stirring speed is 30 rpm to 50 rpm, and the stirring time is 3 min to 5 min.

7. The method for preparing cold-pressed pellets according to claim 5 or 6, characterized in that, The cold pressing process includes the following steps: The mixture is pressed using a briquetting machine to obtain primary pellets, which are then left to stand to obtain cold-pressed pellets.

8. The method for preparing cold-pressed pellets according to claim 7, characterized in that, The linear pressure of the briquetting machine is 20kN / cm~30kN / cm, and the rotation speed is 16rpm~20rpm; And / or, the settling time is 24 hours or more.

9. The application of cold-pressed pellets as described in any one of claims 1 to 4 in the field of iron and steel smelting.

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