Smelting process for controlling spring steel inclusions

A technology for controlling springs and inclusions, applied in the smelting field of spring steel, can solve the problems of difficulty in controlling spherical oxide inclusions, formation of cracks at the junction of substrates, no deformability, etc. Beneficial for shaping and reducing phosphorus content

Active Publication Date: 2018-12-28
NANJING IRON & STEEL CO LTD
View PDF3 Cites 20 Cited by
  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The traditional spring steel is deoxidized by strong deoxidation method to reduce the total oxygen content of the wire rod, but there are oxide inclusions of more than 30 μm on the wire rod of this deoxidation method, and the inclusions are not deformable, and cracks are easy to form at the junction with the matrix during the deformation process , leading to premature failure
Although high alkalinity slag is beneficial to the control of total oxygen, sulfide and alumina inclusions in steel, it is difficult to control spherical oxide inclusions

Method used

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
View more

Image

Smart Image Click on the blue labels to locate them in the text.
Viewing Examples
Smart Image
  • Smelting process for controlling spring steel inclusions
  • Smelting process for controlling spring steel inclusions

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0021] The process flow of the spring steel produced by the present invention: KR molten iron pretreatment → BOF top-bottom double-blowing converter → LF refining furnace → RH refining furnace → 220 m3 continuous casting CCM. By modifying the slag system, the plasticity of inclusions is optimized, the number and size of inclusions are reduced, and the shape of inclusions is as follows: figure 1As shown, the width size is less than 9 μm, the aspect ratio is 4, the total oxygen content is ≤15ppm, and the nitrogen content is ≤30ppm.

[0022] 1) After the molten iron is desulfurized by KR, the mass fraction of S is 0.0035%, which reduces the desulfurization pressure of the refining furnace and creates good conditions for the deoxidation of the refining furnace and the formation of acid slag.

[0023] 2) Before adding steel scrap to the converter, adjust the bottom blowing of the furnace body to the full-range argon blowing mode to avoid nitrogen increase during the smelting proces...

Embodiment 2

[0031] The process flow of the spring steel produced by the present invention: KR molten iron pretreatment → BOF top-bottom double-blowing converter → LF refining furnace → RH refining furnace → 220 m3 continuous casting CCM. By modifying the slag system, optimizing the plasticity of the inclusions, reducing the number and size of the inclusions, the total oxygen content of the prepared spring steel is ≤12ppm, and the nitrogen content is ≤25ppm; the projection of the inclusion composition on the position of the ternary phase diagram is as follows figure 2 As shown, it can be seen from the figure that the composition of the inclusions in the ternary phase diagram is closer to the low melting point region, the inclusions are easy to float up and removed, and the inclusions are smaller and easier to deform. Concrete preparation steps are as follows:

[0032] 1) The molten iron is desulfurized by KR with a mass fraction of S of 0.004%, which reduces the desulfurization pressure o...

Embodiment 3

[0041] The process flow of the spring steel produced by the present invention: KR molten iron pretreatment → BOF top-bottom double-blowing converter → LF refining furnace → RH refining furnace → 220 m3 continuous casting CCM. By modifying the slag system, optimizing the plasticity of inclusions, reducing the number and size of inclusions, the width size is less than 10μm, the aspect ratio is 3, the total oxygen content is ≤12ppm, and the nitrogen content is ≤25ppm; the inclusion composition is projected on the position of the ternary phase diagram as figure 2 As shown, it can be seen from the figure that the composition of the inclusions in the ternary phase diagram is closer to the low melting point region, the inclusions are easy to float up and removed, and the inclusions are smaller and easier to deform. Concrete preparation steps are as follows:

[0042] 1) After the molten iron is desulfurized by KR, the mass fraction of S is 0.0045%, which reduces the desulfurization p...

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
Login to view more

PUM

PropertyMeasurementUnit
flexural strengthaaaaaaaaaa
densityaaaaaaaaaa
flexural strengthaaaaaaaaaa
Login to view more

Abstract

The invention discloses a smelting process for controlling spring steel inclusions. The smelting process comprises the following steps of (1) KR molten iron desulfurization pretreatment, (2) BOF top-bottom double combined flowing converter smelting, (3) LF furnace refining, (4) RH furnace refining and (5) continuous casting process, wherein the mass fraction of S is controlled to be below 0.005% after molten iron is processed by the step (1); the step (3) is carried out by high-purity silicon carbide for diffusion deoxidation, and the refining slag alkalinity is controlled to be 0.6-0.9; a lowalkalinity slag process is adopted in the step (4), and the final slag alkalinity is 0.5-0.7; and it is ensured that a molten steel contact part is free of aluminum in the step (5), a double electromagnetic stirring process is adopted in a secondary cooling zone and a casting blank solidification end zone, and a central carbon segregation index is controlled to be below 1.15. The smelting processadopts molten iron pretreatment, converter catching carbon, refining low alkali slag, continuous casting protective pouring and special refractory materials. Through the control over the oxygen potential of molten steel, the inclusion form and the central carbon segregation, the spring drawing performance is improved, and the spring fatigue limit is increased.

Description

technical field [0001] The invention belongs to a method for smelting spring steel, in particular to a smelting process for controlling inclusions in spring steel. Background technique [0002] With the development of the automobile and other equipment manufacturing industry, the requirements for the spring of key components are getting higher and higher, and the quality of the wire rod produced by the spring is put forward higher requirements, and the microscopic inclusions become the source of fatigue cracks, which reduces the fatigue limit of the material , eventually lead to spring fracture, the size and quantity of inclusions is an important index to measure the spring steel wire rod, and the inclusion control is not only related to the smelting process, but also related to the continuous casting process. The traditional spring steel is deoxidized by strong deoxidation method to reduce the total oxygen content of the wire rod, but there are oxide inclusions of more than...

Claims

the structure of the environmentally friendly knitted fabric provided by the present invention; figure 2 Flow chart of the yarn wrapping machine for environmentally friendly knitted fabrics and storage devices; image 3 Is the parameter map of the yarn covering machine
Login to view more

Application Information

Patent Timeline
no application Login to view more
Patent Type & Authority Applications(China)
IPC IPC(8): C21C1/02C21C5/35C21C7/06C21C7/10B22D11/115
CPCB22D11/115C21C1/02C21C5/35C21C7/0006C21C7/06C21C7/10Y02P10/20
Inventor 李明李强尹雨群陶镳赵柏杰
Owner NANJING IRON & STEEL CO LTD
Who we serve
  • R&D Engineer
  • R&D Manager
  • IP Professional
Why Eureka
  • Industry Leading Data Capabilities
  • Powerful AI technology
  • Patent DNA Extraction
Social media
Try Eureka
PatSnap group products

Browse by: Latest US Patents, China's latest patents, Technical Efficacy Thesaurus, Application Domain, Technology Topic.

© 2024 PatSnap. All rights reserved.Legal|Privacy policy|Modern Slavery Act Transparency Statement|Sitemap