CN104451370B - Vanadium-containing hypereutectic high-chromium cast iron and preparation method thereof - Google Patents

Abstract

The invention discloses a vanadium-containing hypereutectic high-chromium cast iron, which belongs to the technical field of high-chromium cast iron. It is obtained through deoxidation treatment and inoculated by a bottom-wrapping method, and its chemical composition expressed in weight percentage is: carbon C3. 5～4.4%, manganese Mn 0.1～1.2%, chromium Cr15.5～21.5%, silicon Si0.5～1.5%, vanadium V5.5～7.5%, phosphorus P≦0.06%, sulfur S≦0.06%, and the rest iron. The cast iron can be used to manufacture parts subject to strong wear such as slurry pump flow parts, the manufacturing method is simple and economical, the product quality is stable, and has broad market prospects.

Description

Vanadium-containing hypereutectic high-chromium cast iron and manufacturing method thereof

technical field

The invention relates to the technical field of high chromium cast iron.

Background technique

High chromium cast iron is a kind of important wear-resistant material that is widely used. It is widely used in various wear parts in the fields of metallurgy, mining, water conservancy, electric power, chemical industry, etc. impellers, jackets and guards). There are a large number of high-hardness M ₇ C ₃ carbides in the structure of high-chromium cast iron, so it has excellent wear resistance. improved. The chromium in high chromium cast iron can not only effectively improve the corrosion resistance of the material in the slurry, but also a large amount of chromium-containing M ₇ C ₃ carbides can effectively improve the wear resistance of the material and increase the service life of the wetted parts. The increase in the number of carbides in high-chromium cast iron has an important impact on the improvement of the erosion and wear resistance of wetted parts. However, when the number of carbides increases to a certain extent, coarse primary carbides will appear in high-chromium cast iron, resulting in The toughness of high chromium cast iron drops sharply, which makes hypereutectic high chromium cast iron lose its use value. Therefore, the high chromium cast iron currently used for this type of wetted parts is usually a hypoeutectic high chromium cast iron whose carbon equivalent does not exceed the eutectic point as the upper limit, such as KMTBCr26 and KMTBCr15Mo3 cast irons in my country's national standards for wear-resistant materials.

Due to the presence of brittle, hard and coarse carbides in hypereutectic high chromium cast iron, the strength and toughness are low, and casting defects such as cracks are prone to occur. These defects limit the application of hypereutectic high chromium cast iron in wear-resistant parts. To maintain the high hardness of hypereutectic materials and improve their strength and toughness, the best way is to refine their primary carbides. Therefore, refining carbides and changing their distribution form is an important means to improve the toughness of hypereutectic high chromium cast iron.

The Chinese patent application number 200710178680.6 discloses a cast high-carbon high-chromium cast iron and its preparation method, wherein the chemical composition of the high-carbon high-chromium cast iron is (% by weight): C 4.5-5.5, Cr 22.5-30.8, V 3.0～5.0, Mn 0.7～1.2, Nb 0.2～0.5, Ti 0.5～1.0, Mg 0.08～0.20, Na 0.05～0.20, Re 0.05～0.20, Si＜1.0, the balance is iron and unavoidable trace impurities, and Chromium to carbon ratio ≥ 5.0 and ≤ 5.6. The main feature of this patent is to increase the carbon content in high chromium cast iron and increase primary carbides, thereby improving its wear resistance. However, since the patent contains 0.5-1.0 Ti, and the Ti element is very easy to be oxidized, the castings are prone to defects such as slag inclusions. In addition, in the preparation method provided by this patent, when the alloy melt is out of the furnace, it needs to be inoculated with vanadium-iron particles and modified with rare earth magnesium alloy and sodium salt compound, which increases the difficulty of manufacturing, and the performance of the material is not easy to control.

Patent WO2004/103608 introduces a method of producing hypereutectic cast iron with lost foam, which can be used to produce components of equipment such as slurry pumps, cyclones and crushers. The disadvantages of this method are: the mold investment is large, and it is not suitable for the production of single-piece and small-batch slurry pump components; the maximum amount of inoculant that can be added is limited (generally no more than 1%, and the maximum is no more than 2%); The particle size of the agent is small, generally no more than 100um, and there are relatively many impurities such as oxides on its surface, but under the conditions of the invention, these impurities remain in the casting, which has an adverse effect on the toughness of the material.

Patents WO4047760-A1 and EP147422-A1 disclose a kind of wear-resistant hypereutectic high-chromium cast iron. The Cr content in the cast iron is too high. 100 degrees beyond its liquidus), the size of the obtained primary carbide is about 75 μm. Due to the need to use a lower pouring temperature, it is difficult to form when pouring thin-walled or complex parts, and defects such as cold shut, insufficient pouring and cracks are prone to occur during casting production.

The Chinese patent application number 201210182532.2 discloses a high-carbon and high-vanadium wear-resistant steel, the mass percentage of which is: carbon (C) 2.0% to 2.6%, vanadium (V) 8.0% to 9.0%, chromium (Cr) 5.5% %～6.5%, molybdenum (Mo) 2.0%～3.0%, nickel (Ni) 0.5%～1.0%, niobium (Nb) 1.0%～2.0%, silicon (Si) 0.4%～1.0%, phosphorus (P)＜ 0.04%, sulfur (S) <0.04%, and the balance is iron (Fe). Due to the addition of precious elements such as Mo, Ni and Nb, the steel has a high cost.

US Patent "Microstructurally refined multiphasecastings" Publication No. 5803152 describes a method for refining primary phases applicable to alloys of all eutectic phases (aluminum/silicon, copper/silver, especially for white cast iron). The process is to add an inoculant to the molten metal while pouring the casting. The disadvantages are: the amount of inoculant added is high, and impurities such as oxides on the surface generally remain in the casting, which has an adverse effect on the toughness of the material; in addition, the pouring temperature of this method is low, and the fluidity of the alloy liquid is not good. Well, it is not very suitable for the production of complex parts such as slurry pump flow parts.

R.J.Llewellyn et al published a paper titled "Scouring erosion resistance of metallic materials used in slurry pump service". This paper introduces a hypereutectic high-chromium cast iron produced by a conventional casting process. The cast iron has good corrosion resistance and erosion resistance, but the paper does not introduce the method of refining primary carbides.

To sum up, although the prior art has research on vanadium-containing cast iron, hypereutectic cast iron and high-chromium cast iron, there are still various defects such as high cost, complicated process, narrow applicability, and unsatisfactory effect, especially the lack of A material with high wear resistance, high toughness and high hardness suitable for manufacturing wet parts and wear parts.

Contents of the invention

The technical problem to be solved by the present invention is to provide a vanadium-containing hypereutectic high-chromium cast iron and a manufacturing method thereof. The hypereutectic high-chromium cast iron has high wear resistance, high toughness and high hardness. Features, it can be used to manufacture parts that are prone to strong wear, such as the flow parts of slurry pumps. The manufacturing method is simple and economical, and the product quality is stable.

In order to solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a hypereutectic high-chromium cast iron containing vanadium, which is obtained through deoxidation treatment and inoculated by the method of pouring into the bottom of the cast iron, and its chemical composition expressed in weight percentage for:

Carbon C 3.5～4.4%, Manganese Mn 0.1～1.2%,

Chromium Cr 15.5～21.5%, Silicon Si 0.5～1.5%,

Vanadium V 5.5～7.5%, Phosphorus P≦0.06%,

Sulfur S≦0.06%, the rest is iron.

As a preference, the chemical composition expressed in weight percent of the above-mentioned vanadium-containing hypereutectic high-chromium cast iron is:

Carbon C 3.99%, Manganese Mn 0.81%,

Chromium Cr 20.51%, Silicon Si 0.86%,

Vanadium V 6.1%, Phosphorus P 0.028%,

Sulfur S 0.024%, the rest is iron.

The above-mentioned manufacturing method of vanadium-containing hypereutectic high-chromium cast iron has the following steps:

(1) Using scrap steel, steelmaking pig iron, high-carbon ferrochromium and high-carbon ferromanganese as raw materials, the raw materials are melted into molten iron at a temperature of 1500-1600 °C;

(2) Add aluminum powder for deoxidation to molten iron in an amount of 0.08-0.12% of the weight of molten iron;

(3) Add ferrovanadium preheated to 470-580°C into the molten iron, melt all the ferrovanadium at a temperature of 1400-1450°C and evenly disperse it in the molten iron, and then raise the temperature of the molten iron to 1500-1600°C and released;

(4) The molten iron is inoculated by the method of pouring into the bottom. The inoculant is ferro-titanium particles with a particle size less than 10mm accounting for 0.2-0.5% of the weight of the molten iron; The molten iron is poured into the sand mold to cast the mold; the chemical composition of the finally obtained cast iron expressed in weight percentage is:

Carbon C 3.5～4.4%, Manganese Mn 0.1～1.2%,

Chromium Cr 15.5～21.5%, Silicon Si 0.5～1.5%,

Vanadium V 5.5～7.5%, Phosphorus P≦0.06%,

Sulfur S≦0.06%, the rest is iron.

Preferably, the heating equipment in the above step (1) to step (3) is a medium frequency induction furnace.

The beneficial effect produced by adopting the above-mentioned technical scheme is that: this method creatively adds vanadium to high-chromium cast iron, thereby obtaining a vanadium-containing hypereutectic high-chromium cast iron, which has high wear resistance, high toughness, high Due to the characteristics of hardness, the heat treatment process can be omitted after casting, and it can be used to manufacture parts that are prone to strong wear, such as the flow parts of slurry pumps. The manufacturing method is simple and economical, and the product quality is stable, which has broad market prospects.

Description of drawings

Fig. 1 is the metallographic photograph of cast iron of the present invention in embodiment 3;

Figure 2 is a metallographic photograph of the comparative alloy in Example 3.

detailed description

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Example 1:

A method for manufacturing vanadium-containing hypereutectic high-chromium cast iron, which has the following steps:

(1) Add 205kg of high-carbon ferrochrome (FeC55C600II), 110kg of pig iron for steelmaking (L04), and 127kg of scrap steel into a 500kg medium-frequency induction furnace, and heat them to melt them into molten iron;

(2) Raise the temperature of the molten iron to 1500-1600°C, and add 0.5kg of aluminum powder to the molten iron;

(3) Preheat ferrovanadium (FeV50-B) with a weight of 58kg to 470-580°C and add it into the molten iron, melt all the ferrovanadium at a temperature of 1400-1450°C and evenly disperse it in the molten iron, and then put The temperature of molten iron is raised to 1500-1600°C and released;

(4) Put 2.0kg of ferro-titanium particles with a particle size of less than 10mm in the bottom of the bag, and use the flushing method to inoculate the molten iron; after the inoculation is completed and the slag is removed by sedation, pour the molten iron into furan at a temperature of 1360°C In the resin sand mold, the flow parts of the slurry pump such as guard plates and sheaths are produced, and the impact toughness samples are cast along with the mold. The sample size is 20 mm×20mm×110mm.

The chemical composition and mechanical properties of the cast iron produced by the above method are shown in the following table 1 in weight percent:

Table 1.

Example 2:

A method for manufacturing vanadium-containing hypereutectic high-chromium cast iron, which has the following steps:

(1) Add 155kg of high-carbon ferrochromium (FeC55C1000II), 90kg of pig iron for steelmaking (L04), 179kg of scrap steel and 3kg of high-carbon ferromanganese (FeMn78C8.0) into a 500kg intermediate frequency induction furnace, and heat them to melt them into molten iron;

(2) Raise the temperature of the molten iron to 1500-1600°C, and add 0.5kg of aluminum powder to the molten iron;

(3) Preheat ferrovanadium (FeV50-B) with a weight of 73kg to 470-580°C and add it into the molten iron, melt all the ferrovanadium at a temperature of 1400-1450°C and disperse it evenly in the molten iron, and then put The temperature of molten iron is raised to 1500-1600°C and released;

(4) Put 2.0kg of ferro-titanium particles with a particle size of less than 10mm in the bottom of the bag, and use the flushing method to inoculate the molten iron; after the inoculation is completed and the slag is removed by sedation, pour the molten iron into furan at a temperature of 1400°C In the resin sand mold, the flow parts of the slurry pump such as guard plates and sheaths are produced, and the impact toughness samples are cast along with the mold. The sample size is 20 mm×20mm×110mm.

The chemical composition and mechanical properties of the cast iron produced by the above method are shown in the following table 2:

Table 2.

Example 3:

A method for manufacturing vanadium-containing hypereutectic high-chromium cast iron, which has the following steps:

(1) Add 200kg of high-carbon ferrochromium (FeC55C600II), 188kg of pig iron for steelmaking (L04), 50kg of scrap steel and 2kg of high-carbon ferromanganese (FeMn78C8.0) into a 500kg intermediate frequency induction furnace, and heat them to melt them into molten iron;

(2) Raise the temperature of the molten iron to 1500-1600°C, and add 0.5kg of aluminum powder to the molten iron;

(3) Preheat ferrovanadium (FeV50-B) with a weight of 60kg to 470-580°C and add it into the molten iron, melt all the ferrovanadium at 1400-1450°C and disperse it evenly in the molten iron, and then put The temperature of molten iron is raised to 1500-1600°C and released;

(4) Put 2.0kg of ferro-titanium particles with a particle size of less than 10mm in the bottom of the bag, and use the flushing method to inoculate the molten iron; after the inoculation is completed and the slag is removed by sedation, pour the molten iron into furan at a temperature of 1390°C In the resin sand mold, slurry pump flow parts such as guard plates and sheaths are produced, and impact toughness samples are cast along with the mold. The sample size is 20 mm×20mm×110mm.

Taking the sample in Example 3 as an example, compare the vanadium-free comparative alloy with this sample, wherein the comparative alloy also adopts the same pouring temperature and the same sample size as in Example 3, and the results are shown in Table 3 below :

table 3.

The metallographic diagram of the vanadium-containing cast iron in Example 3 is shown in FIG. 1 , and the metallographic diagram of the comparative alloy sample is shown in FIG. 2 .

It can be seen from the comparison that the primary carbides of the vanadium-containing hypereutectic high-chromium cast iron in Example 3 are obviously refined, and have higher hardness and impact toughness, so it is more suitable for use in the manufacture of slurry pump flow parts, etc. The cast irons of Example 1 and Example 2 also have similar characteristics to those of Example 3. The cast iron manufacturing method is simple and economical, the product quality is stable, the heat treatment process can be omitted after casting, and the cast iron has broad application prospects.

Claims (4)

1. A vanadium-containing hypereutectic high-chromium cast iron is characterized in that: it is made by deoxidizing treatment and inoculated through the bag bottom punching method, and its chemical composition expressed in weight percent is: Carbon C 3.5～3.99%, Manganese Mn 0.1～1.2%, Chromium Cr 15.5～21.5%, Silicon Si 0.5～1.5%, Vanadium V 5.5～7.5%, Phosphorus P≦0.06%, Sulfur S≦0.06%, the rest is iron; The vanadium-containing hypereutectic high-chromium cast iron is prepared according to a method comprising the following steps: (1) Using scrap steel, steelmaking pig iron, high-carbon ferrochromium and high-carbon ferromanganese as raw materials, the raw materials are melted into molten iron at a temperature of 1500-1600 °C; (2) Add aluminum powder for deoxidation to molten iron in an amount of 0.08-0.12% of the weight of molten iron; (3) Add ferrovanadium preheated to 470-580°C into the molten iron, melt all the ferrovanadium at a temperature of 1400-1450°C and evenly disperse it in the molten iron, and then raise the temperature of the molten iron to 1500-1600°C and released; (4) The molten iron is inoculated by the method of pouring into the bottom. The inoculant is ferro-titanium particles with a particle size less than 10mm accounting for 0.2-0.5% of the weight of the molten iron; Next, pour the molten iron into the sand mold to cast the mold. 2. The vanadium-containing hypereutectic high-chromium cast iron according to claim 1, characterized in that: its chemical composition expressed in weight percent is: Carbon C 3.99%, Manganese Mn 0.81%, Chromium Cr 20.51%, Silicon Si 0.86%, Vanadium V 6.1%, Phosphorus P 0.028%, Sulfur S 0.024%, the rest is iron. 3. the manufacture method of vanadium-containing hypereutectic high-chromium cast iron described in claim 1, is characterized in that: has the following steps: (1) Using scrap steel, steelmaking pig iron, high-carbon ferrochromium and high-carbon ferromanganese as raw materials, the raw materials are melted into molten iron at a temperature of 1500-1600 °C; (2) Add aluminum powder for deoxidation to molten iron in an amount of 0.08-0.12% of the weight of molten iron; (3) Add ferrovanadium preheated to 470-580°C into the molten iron, melt all the ferrovanadium at a temperature of 1400-1450°C and evenly disperse it in the molten iron, and then raise the temperature of the molten iron to 1500-1600°C and released; (4) The molten iron is inoculated by the method of pouring into the bottom. The inoculant is ferro-titanium particles with a particle size less than 10mm accounting for 0.2-0.5% of the weight of the molten iron; The molten iron is poured into the sand mold to cast the mold; the chemical composition of the finally obtained cast iron expressed in weight percentage is: Carbon C 3.5～3.99%, Manganese Mn 0.1～1.2%, Chromium Cr 15.5～21.5%, Silicon Si 0.5～1.5%, Vanadium V 5.5～7.5%, Phosphorus P≦0.06%, Sulfur S≦0.06%, the rest is iron. 4. The method for manufacturing vanadium-containing hypereutectic high-chromium cast iron according to claim 3, characterized in that: the heating equipment in the step (1) to the step (3) is a medium-frequency induction furnace.