WO2007014516A1

WO2007014516A1 - A modified steel and its manufacture process

Info

Publication number: WO2007014516A1
Application number: PCT/CN2006/001830
Authority: WO
Inventors: Zhiping Xiao; Luwei Xiao
Original assignee: Zhiping Xiao
Priority date: 2005-08-03
Filing date: 2006-07-24
Publication date: 2007-02-08
Also published as: CN1718826A; CN100424211C

Abstract

A modified steel and its manufacture process. The modified steel comprises 2.5~3.0% C, 0.8~1.2% Si, 0.7~1.5% Mn, ≤0.03% S, ≤0.03% P, and balance Fe. The process is as follows: compounding the ingredients, melting, modifying using modifier, casting to form cast parts or cast ingots, and heat treating. The steel has the composition of iron, also has the microstructure and properties of steel. The steel is good in casting property, could sustain large deformation-stress, and could maintain extremely high strength and toughness even after quenching or tempering. The steel is low in cost, good in mechanical performance, could substitute for many alloy steels, and is a structural material which is worth developing and has wide application prospect.

Description

Deteriorated steel and production method thereof

Technical field

The invention relates to a metamorphic steel product in the metallurgical field and a production method thereof.

Background technique

The emergence of ductile iron since the end of the 19th century has made great changes in the application of ordinary cast iron in industry. In the late 20th century, due to the continuous improvement of the modifier, the graphite changed from a sheet to a dot (particle diameter in micrometers), and the concept of "dot graphite cast iron" appeared. The modified point-like graphite cast iron has improved performance in all aspects compared with ductile iron. However, there has been no substantial progress in the refinement of carbides, and the performance of cast iron has not been fundamentally improved. Despite extensive research and unremitting efforts over the years, the effect is still not obvious enough.

Summary of the invention

The technical problem to be solved by the present invention is that the cast iron is subjected to metamorphism treatment, so that the carbide in the internal structure of the cast iron after the metamorphism is sufficiently refined to be similar to some steel materials to form a new steel grade - metamorphic steel .

The technical solution of the present invention is to provide a deteriorated steel capable of achieving the above object and a method of producing the same. The sulphur and 0. 03% of the sulphur and 0. 03% of the sulphur and the sulphuric acid. Phosphorus, the balance is iron.

The production process of the modified steel is as follows:

ω, ingredients: according to the use of the workpiece within the above range of ingredients to select the appropriate ingredients for the furnace;

(2), melting: melting at a temperature above 1450 ° C;

The tempering treatment is carried out by the use of a smelting method or a direct addition, the amount of the smelting agent is 1. 4~1. 8 %. Then stir and let stand for 3 to 5 minutes;

(4), castings or ingots: casting, casting temperature 1300 ° ( _;

(5), heat treatment of castings or heat treatment of ingots:

Heat treatment of castings:

1 Annealing: 40CTC heating and holding for one hour, with furnace cooling (removing stress requirements), or heating at 950 °C for 3 hours, with furnace cooling (machining requirements); '

2 quenching: 950 ° C for 5 hours, cooled to 800 ° C water quenching.

Ingot heat treatment: homogenization annealing, thermal deformation, cold deformation, annealing, finishing, quenching and tempering.

The new metal material obtained by the above method, called metamorphic steel (also known as BZ steel), has the following characteristics:

(1), the composition is simple, no other alloying elements are added, and only a small amount of modifier is added during the deterioration treatment. And the quality of cast iron is not high, generally 14~18 can be cast, so the material cost is low.

(2) The 305 modifier used does not contain magnesium which is easy to produce flaming fumes, and the production environment is safe. After the cast iron is degraded, the deterioration effect can be maintained in the ladle for a long time, which is particularly advantageous for the smooth progress of the casting work. Moreover, the old materials can be returned to the furnace, and the old materials returned to the furnace can continue to maintain a considerable degree of deterioration effect, which is very beneficial for saving the deterioration agent.

(3) The ingot after deterioration must be subjected to high temperature annealing. The purpose is to control the morphology, quantity and dispersion of the modified carbide particles in the ingot to obtain a structure that is advantageous for further pressure processing or machining, so as to perform various forming processes (including forging and rolling) as needed. , stretching and car, pliers, satiety, milling, grinding, etc.).

(4) After the molding work is completed, various forms of heat treatment can be performed like alloy steel. Quenched For the tempered workpiece, the hardness of HRC 55-65 and the toughness of 4- lOJ/cm ² can be obtained.

(5) In order to meet certain special properties (such as improving wear resistance and corrosion resistance), a small amount of alloying elements can be added. For example, adding a small amount of Cr to the raw material can improve the acid resistance and improve the mechanical properties and hardenability. .

After the metamorphic steel has been modified, its carbide has been greatly "broken". Subsequent annealing treatment, only 950 ° C, 3 hours of heat preservation, can be basically dissolved, the matrix structure has become pearlite + ferrite, leaving only a small amount of undissolved carbide on the substrate. Since the metamorphic steel has a pearlite + ferrite matrix structure after annealing, this material has good pressure processing properties. The quenched structure of the metamorphic steel is a structure in which some fine residual carbides are distributed on the martensite matrix, which is similar to the structure of many steels. Its performance is determined by its (Si, Mn content and the heat treatment method used, its mechanical properties are shown in Table (1):

Table 1 )

The process properties of the modified steel are as follows:

1. The melting temperature is not too high, just over 1450 °C. The metamorphic treatment is carried out in a ladle by a flushing method, and since it does not contain Mg, there is no flare and a large amount of soot in the flushing process. Good environmental conditions.

2. Casting is carried out above >1300 °C, because the carbon content is close to the eutectic point.

3. After the ingot is annealed, the "broken" carbide is more soluble in the matrix. The large amount of ferrite makes the annealed ingot have excellent processing properties, not only for car, clamp, planing, Milling, grinding, and hot forging, molding, hot pressing, hot rolling, deformation capacity of up to >40%. Conducive to the processing of materials into sheets, strips, profiles, bars.

4. After forming the formed material, various types of heat treatment can be performed. Quenching + tempering increases the HRC of the material to 55-65. After high temperature insulation for a period of time, it is cooled to 800 °C, and the workpiece can be directly quenched into water without causing cracking and deformation.

5. Since BZ steel does not contain other alloying elements, the oxidation resistance is poor. If it is necessary to increase the oxidation resistance, add a small amount of A1. If there are other special properties, a small amount of other gold-containing elements may be added. For example, in order to improve the acid resistance, a small amount of Cr may be added. Cr not only improves acid resistance but also improves mechanical properties. That is to improve the deterioration effect.

6. Since the matrix structure of BZ steel is basically the same as that of steel, it has good weldability with steel, and the weld transition zone is metallurgical.

7. Deteriorated steel can greatly change the microstructure and properties of ordinary pig iron and gray cast iron. Its strength, hardness and toughness indicators have reached the level of certain alloy steels, which can replace alloy steel to a considerable extent. +

8. Deteriorated steel is not only a casting material with low cost and good performance, but also a processing type with high deformation ability. As long as you master the deterioration treatment and the corresponding heat treatment technology, you can achieve the intended purpose.

9. According to the current situation of various metals, especially the high price of Xigui Metal, it is very important to save the common elements of alloy steel such as Ni, Cr, Mo, V, Ti, W---. One of the advantages of metamorphic steel is that it is possible to replace part of the alloy steel. Therefore, vigorously promoting metamorphic steel is a matter of great significance to society.

The application prospect of metamorphic steel is expected: The modified steel has both iron composition and steel structure and properties; it has good casting properties and can withstand a large amount of deformation pressure, and can be obtained after quenching and tempering. To extremely high strength and toughness. Moreover, the modified steel has low cost and good mechanical properties and can replace a variety of alloy steels. It is a structural material that is worthy of vigorous development and has broad application prospects. See Table (2) for the applicable range of the following:

At present, metamorphic steel has been applied in some enterprises, such as making ball mill liners and grinding balls, rolls, feeding, stamping, die, mold and so on.

detailed description

Example 1, the composition of the modified steel of this example and its content are: 2.5% carbon, 0.8% silicon, 0.7% manganese, 0.025% sulfur and 0.025% phosphorus, and the balance is iron. The production process is as follows: (1), Ingredients: According to the above ingredients, the total amount is 200 kg, including carbon 5 kg, silicon 1.6 kg, manganese i.4 kg, sulfur 0.05 kg, phosphorus 0.05 kg, 18# pig iron 132 kg, scrap 59.9 kg ;

(2), melting: using 200kg medium frequency furnace, heating to 145CTC temperature to melt molten iron;

(3) Deterioration treatment: When the temperature of the molten iron reaches 145 CTC or more, 3 jin of the 305 modifier is added by the pulverization method to carry out the deterioration treatment. After the addition, the liquid metamorphic steel melted in the furnace is stirred, stirred and allowed to stand for 3 minutes;

(4), casting: casting casting, casting temperature > 1300 ° ( _;

(5), casting heat treatment: '

1. Annealing (stress relief): heating at 400 °C for one hour, cooling with the furnace; 2. quenching: 950 °C for 5 hours, cooling to 800 °C for 30 minutes water quenching. Example 2, the composition of the modified steel in this example and its content are: 3. 0% carbon, 0.8% silicon, 1. 2% manganese, 0.025% sulfur and 0.025% phosphorus, balance For iron.

The production process is as follows:

(1), Ingredients: According to the above ingredients, the total amount of ingredients is 10t, including carbon 300 kg, silicon 80 kg, manganese 120 kg, sulfur 5 kg, phosphorus 5 kg, 18# pig iron 8 t, scrap 1.49 t;

(2), melting: The melting furnace is a 10 ton intermediate frequency furnace, and the iron is melted at a temperature of 1450 ° C;

(3) Deterioration treatment: When the temperature of molten iron reaches 145 CTC or more, 150 kg of 305 modifier is directly added for modification. After stirring for 2 minutes, let stand for 5 minutes and prepare for casting;

(4) Ingot casting: casting ingot casting, casting temperature 130CTC;

(5), ingot heat treatment: homogenization annealing, thermal deformation, cold deformation, annealing, finishing, quenching, tempering, and tempering. The first few steps of the above ingot production are the same as the mold production, but the ingot is changed into an ingot mold suitable for the rolling sheet. The mold temperature should be greater than 400t:. The details are as follows: ' 1 Homogenization annealing: 950 C after 3 hours, the furnace is cooled.

2 Heating before hot rolling: heating at 950 ° C for 3 hours, rapid rolling. After the completion of this pass, it needs to be annealed again, and it can be annealed at 950 ° C for 30 minutes.

In addition, several important issues to be considered in the production process of deteriorated steel are:

(1), modifier: It is the key material for the production of metamorphic steel, which is composed of a variety of materials. A commercially available 305 modifier composed of rare earth ferrosilicon, ferrosilicon, silicon calcium alloy and trace elements should be used.

(2) After the metamorphic steel has been modified, it must be heat treated to obtain the best results.

(3) The most important feature of metamorphic steel is to make iron become the structure and performance of steel and its low production cost. Therefore, the development of metamorphic steel should fully consider this feature. '

(4), the deteriorated steel after quenching and tempering, not only has high hardness but also good toughness. ·

(5) The present invention can play a better role in replacing some alloy steels in the manufacture of rolling mill parts, automobile parts, and various molds.

In the industrial production tests of Examples 1 to 2, the raw materials were anhydrous, free of mud, oil-free, rust-free, and other contamination.

Claims

Claim

1. A deteriorated steel containing 2.5 to 3.0% carbon, 0.8 to 1.2% silicon, 0.7 to 1.5% manganese, 0.03% sulfur and 0.03% phosphorus, and the balance being iron. '

2. A method of producing a modified steel according to claim 1, wherein the method is the following production process:

(1), ingredients: according to the use of the workpiece within the above range of ingredients to select the appropriate ingredients for the furnace,

(2), melting: melting at a temperature above M50 ° C,

(3), modification treatment: When the temperature of the molten iron reaches 5CTC, the modification agent is used for the modification. The amount of the modifier is 1.4~1. 8 % of the total amount of the metal in each furnace. It is added by adding or directly adding, and then stirring. , then let stand for 3 to 5 minutes, '

(4), casting or ingot: casting, casting temperature 1300 ° (,

(5), heat treatment of castings or heat treatment of ingots:

Casting heat treatment:

1 Annealing: 40CTC heating and holding for one hour, with furnace cooling (removing stress requirements), or 95CTC heating for 3 hours, with furnace cooling (machining requirements),

2 quenching: 950 Ό heat preservation 5 hours, cooling to 800 ° C water quenching, · ingot heat treatment: homogenization annealing a thermal deformation a cold deformation an annealing a finishing one quenching a temper.

The method for producing a deteriorated steel according to claim 2, wherein the modificator is a 305 modificator.