Free-cutting steel casting powder and application thereof

Abstract

The invention relates to the technical field of steel smelting, in particular to free-cutting steel casting powder and application thereof, and the free-cutting steel casting powder contains F, CaO, SiO2, Al2O3, MgO, R2O and C; wherein the mass fraction of the F is 3%-4%; the mass fraction of the CaO is 20%; the mass fraction of the SiO2 is 30%; the mass fraction of Al2O3 is 15%; the mass fraction of MgO is 5%; the mass fraction of the R2O is 6%; the R2O is Na2O and / or K2O. According to the free-cutting steel casting powder, the viscosity of the casting powder is improved, so that the flowing uniformity of casting powder liquid slag is controlled, and the heat transfer effect of the casting powder is improved; further, by increasing the F <-> content in the casting powder, the thermal resistance of the casting powder is improved, the crystallization performance is enhanced, heat transfer between an initial blank shell and a copper cooling wall in a crystallizer is weakened, and the purpose of weak cooling is achieved; meanwhile, the melting point of the casting powder is increased, and the melting speed is reduced, so that the casting powder has a proper melting structure. After the free-cutting steel casting powder is adopted, the surface quality of a produced free-cutting steel continuous casting blank is good, the surface defects of the casting blank are effectively avoided, and the product quality is improved.

Description

Technical Field

[0001] The invention relates to the technical field of steel smelting, and in particular to a free-cutting steel protective slag and application thereof. Background Art

[0002] Free-cutting steel, also known as steel for automatic machine tool processing or simply automatic steel, is a type of alloy steel that adds a certain amount of one or more free-cutting elements (such as sulfur, phosphorus, lead, calcium, selenium, tellurium, etc.) to the steel to improve its cutting performance. With the rapid development of modern industry towards automation, high speed and precision, higher and higher requirements are placed on the cutting performance of steel. With the rapid development of the machinery manufacturing industry, cutting processing has occupied an important position in the production of parts. In order to improve production efficiency, reduce production costs and meet the needs of high-precision and high-quality products, higher requirements are placed on the cutting properties of steel. Free-cutting steel came into being in this context. By adding specific free-cutting elements, the cutting performance of steel is significantly improved, the tool wear during the cutting process is reduced, and the quality of the processed surface is improved.

[0003] Free-cutting steel is an energy-saving material that is increasingly widely used in the machinery manufacturing industry. It is mainly used in industries such as office equipment, home appliances, instruments, and automobiles that have large cutting volumes and high levels of automation. It is characterized by fast cutting speed, low tool loss, low processing costs, and high surface finish of finished products. In recent years, the types and process development of free-cutting steel in my country have made good progress. Domestic special steel companies have gradually developed high-grade lead-free sulfur-based free-cutting steel to replace imports. Due to its high oxygen, high sulfur, and high phosphorus composition characteristics, free-cutting steel is prone to defects such as subcutaneous bubbles, slag inclusions, and deep vibration marks in the ingot. The ingot grinding volume is large, and the surface quality of the wire rod is poor, which affects the product quality and increases the cost.

[0004] Therefore, it is of great significance to study how to improve free-cutting steel to avoid surface defects of ingots and improve product quality. Summary of the invention

[0005] The purpose of the present invention is to solve the problem that due to the high oxygen, high sulfur and high phosphorus composition characteristics of the existing free-cutting steel, the casting is prone to defects such as subcutaneous bubbles, slag inclusions, deep vibration marks, etc., the casting requires a large amount of grinding, and the surface quality of the wire rod is poor, which affects the product quality and causes an increase in cost, thereby providing a free-cutting steel protective slag and its application.

[0006] In order to achieve the above-mentioned object, in the first aspect, the present invention provides a free-cutting steel protective slag, wherein the free-cutting steel protective slag contains F, CaO, SiO2, Al2O3, MgO, R2O and C; wherein:

[0007] The mass fraction of F is 3%-4%;

[0008] The mass fraction of CaO is 20%;

[0009] The mass fraction of SiO2 is 30%;

[0010] The mass fraction of Al2O3 is 15%;

[0011] The mass fraction of MgO is 5%;

[0012] The mass fraction of R2O is 6%;

[0013] The R2O is Na2O and / or K2O.

[0014] Preferably, the binary basicity of the free-cutting steel protection slag is 0.6-0.7, wherein the binary basicity R2=ω(CaO) / ω(SiO2).

[0015] Preferably, the melting temperature of the free-cutting steel protection slag is 1200-1250°C.

[0016] Preferably, at a temperature of 1300° C., the viscosity of the free-cutting steel protection slag is 1.5-1.6 Pa·s.

[0017] Preferably, the melting rate of the free-cutting steel protection slag is 55s.

[0018] In a second aspect, the present invention provides a use of the free-cutting steel protection slag described in the first aspect in the production of free-cutting steel.

[0019] According to the above technical scheme, the present invention aims at the problem of crack defects in free-cutting steel wire rod after rolling, and clarifies that the main cause of the defects is the extension of the surface defects of the ingot caused by the mismatch of the protective slag. On this basis, the free-cutting steel protective slag of the present invention controls the uniformity of the inflow of protective slag liquid slag by increasing the viscosity of the protective slag, so as to improve the heat transfer effect of the protective slag; further, by increasing the F - The content of the protective slag is used to improve the thermal resistance of the protective slag, strengthen the crystallization performance, and weaken the heat transfer between the primary billet shell and the copper cooling wall in the crystallizer to achieve the purpose of "weak cooling"; at the same time, the melting point of the protective slag is increased and the melting speed is reduced to ensure that the protective slag has a suitable melting structure. After the free-cutting steel protective slag of the present invention is used, the surface quality of the continuous casting billet of the free-cutting steel produced is good, the surface defects of the casting billet are effectively avoided, and the product quality is improved.

[0020] Other features and advantages of the present invention will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0021] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0022] In a first aspect, the present invention provides a free-cutting steel protective slag, wherein the free-cutting steel protective slag contains F, CaO, SiO2, Al2O3, MgO, R2O and C; wherein:

[0023] The mass fraction of F is 3%-4%;

[0024] The mass fraction of CaO is 20%;

[0025] The mass fraction of SiO2 is 30%;

[0026] The mass fraction of Al2O3 is 15%;

[0027] The mass fraction of MgO is 5%;

[0028] The mass fraction of R2O is 6%;

[0029] The R2O is Na2O and / or K2O.

[0030] In a preferred embodiment of the present invention, the binary basicity of the free-cutting steel protection slag is 0.6-0.7, wherein the binary basicity R 2＝ ω(CaO) / ω(SiO2).

[0031] In the preferred embodiment of the present invention, since the melting point of the free-cutting steel protection slag can directly affect the thickness of the liquid slag layer, and then affect the thickness of the free-cutting steel protection slag liquid slag film, therefore, in order to further control the heat transfer uniformity and heat transfer effect of the free-cutting steel protection slag, it is proposed to increase the melting point on the basis of the original free-cutting steel protection slag to ensure that the free-cutting steel protection slag has a suitable melting structure. The melting temperature of the free-cutting steel protection slag is 1200-1250℃.

[0032] In a preferred embodiment of the present invention, since the thickness and uniformity of the liquid slag film of the free-cutting steel protective slag are closely related to the liquid slag viscosity, if the viscosity is too low, the slag film will be thickened and uneven; and if the viscosity is too high, the flow performance of the free-cutting steel protective slag will deteriorate, the liquid slag will have difficulty in flowing in, the slag film will become thinner, and the lubrication will be poor. The idea for improving the viscosity is: appropriately increase the viscosity, control the uniformity of the liquid slag inflow of the free-cutting steel protective slag, and improve the heat transfer effect. Under the condition of a temperature of 1300°C, the viscosity of the free-cutting steel protective slag is 1.5-1.6Pa·s.

[0033] In a preferred embodiment of the present invention, since the melting rate of the free-cutting steel protective slag can directly affect the thickness of the liquid slag layer, and further affect the thickness of the liquid slag film of the free-cutting steel protective slag, in order to further control the heat transfer uniformity and heat transfer effect of the free-cutting steel protective slag, it is planned to reduce the melting rate on the basis of the original free-cutting steel protective slag to ensure that the free-cutting steel protective slag has a suitable melting structure. The melting rate of the free-cutting steel protective slag is 55s.

[0034] In a second aspect, the present invention provides a use of the free-cutting steel protection slag described in the first aspect in the production of free-cutting steel.

[0035] Through the implementation of the above technical solution, the free-cutting steel protection slag of the present invention controls the uniformity of the inflow of the free-cutting steel protection slag by increasing the viscosity of the free-cutting steel protection slag, so as to improve the heat transfer effect of the free-cutting steel protection slag; further, by increasing the F - The content of the free-cutting steel protective slag is used to improve the thermal resistance of the free-cutting steel protective slag, strengthen the crystallization performance, and weaken the heat transfer between the primary billet shell and the copper cooling wall in the crystallizer to achieve the purpose of "weak cooling"; at the same time, the melting point of the free-cutting steel protective slag is increased and the melting speed is reduced to ensure that the free-cutting steel protective slag has a suitable melting structure. After the free-cutting steel protective slag of the present invention is used, the surface quality of the free-cutting steel continuous casting billet produced is good, the surface defects of the casting billet are effectively avoided, and the product quality is improved.

[0036] In addition to the above-mentioned key technical points which must be implemented as required, the present invention requires that other production processes be implemented in a conventional manner.

[0037] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0038] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0039] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A free-cutting steel protection slag, characterized in that: The free-cutting steel protective slag contains F, CaO, SiO2, Al2O3, MgO, R2O and C; wherein: The mass fraction of F is 3%-4%; The mass fraction of CaO is 20%; The mass fraction of SiO2 is 30%; The mass fraction of Al2O3 is 15%; The mass fraction of MgO is 5%; The mass fraction of R2O is 6%; The R2O is Na2O and / or K2O.

2. The free-cutting steel protection slag according to claim 1, characterized in that: The binary basicity of the free-cutting steel protection slag is 0.6-0.7, wherein the binary basicity R2=ω(CaO) / ω(SiO2).

3. The free-cutting steel protection slag according to claim 1 or 2, characterized in that: The melting temperature of the free-cutting steel protection slag is 1200-1250°C.

4. The free-cutting steel protection slag according to any one of claims 1 to 3, characterized in that: Under the condition of a temperature of 1300° C., the viscosity of the free-cutting steel protection slag is 1.5-1.6 Pa·s.

5. The free-cutting steel protection slag according to any one of claims 1 to 4, characterized in that: The melting speed of the free-cutting steel protection slag is 55s.

6. Use of the free-cutting steel protection slag as claimed in any one of claims 1 to 5 in the production of free-cutting steel.