Method for controlling formation of cross grain in large gauge low carbon wire rod
By controlling the temperature and deformation of the heating, rolling and finishing processes, the content of harmful elements in molten iron and steel billets is precisely controlled. By adopting recrystallization-type controlled rolling and cold feeding and cold charging processes, the problems of iron oxide scale cracking and transverse defects in the production of large-size low-carbon wire drawing materials are solved, and the surface quality of products and production stability are improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- YANGCHUN NEW STEEL CO LTD
- Filing Date
- 2024-07-30
- Publication Date
- 2026-05-29
AI Technical Summary
In the production of large-size low-carbon wire drawing materials, improper rolling temperature control can lead to iron oxide scale cracking and transverse defects. After cold working, bending and bursting problems may occur. In addition, the high requirements for warehousing and logistics make it prone to corrosion.
By controlling the temperature and deformation of the heating, rolling and finishing processes, recrystallization-type controlled rolling is adopted to precisely control the content of harmful elements in molten iron and steel billets. Low-Cr, low-Ni ore and low-S molten iron are used, and cold delivery and cold charging processes are employed to avoid iron oxide scale cracking caused by thermal stress. Cold billet rolling and cold delivery and cold charging processes are also adopted.
It effectively controlled the transverse grain defects of large-size wire drawing materials, improved the surface quality of products, reduced quality disputes, and lowered the defect rate in the production process.
Abstract
Description
Technical Field
[0001] This invention relates to the field of steelmaking technology. Specifically, it relates to a method for controlling the formation of cross grain in large-diameter low-carbon wire drawing. Background Technology
[0002] In the production of low-carbon wire drawing materials, high-temperature rolling is generally used to ensure good ductility and relatively low tensile strength. The temperature is typically controlled at 955±20℃. The rolling process, from roughing to final rolling, generally does not change significantly when the wire diameter increases from φ5.5mm to φ14mm, achieving the desired specifications by reducing the number of rolling passes. However, this operation leads to the following problems:
[0003] (1) During the production of large-size low-carbon wire drawing materials, the rolling temperature is controlled online. When the ambient temperature is low, the thermal stress generated during the cooling process of the steel causes some of the iron oxide scale to crack and regenerate a layer of iron oxide scale. After excessive oxidation of the surface, "horizontal lines" will appear at the cracked part of the original iron oxide scale. After cold working, defects such as bending, cracking, and horizontal lines will appear at the horizontal lines.
[0004] (2) In order to minimize the appearance of horizontal lines on the steel, the requirements for warehousing and logistics are extremely high. It is necessary to cool in a constant environment to avoid thermal expansion that could damage the iron oxide scale, and to avoid a humid environment to reduce corrosion. The rolling process needs to be completed within two to three months after the rolled material is produced. Summary of the Invention
[0005] The purpose of this invention is to provide a method for controlling the formation of cross grain in large-size low-carbon wire drawing materials.
[0006] Specifically, the method for controlling the formation of transverse striations in large-size low-carbon wire drawing materials involves the following production processes: molten iron, converter, refining, continuous casting, heating, rolling, and finishing. In the heating process, the soaking temperature is controlled at 1010±20℃. In the rolling process, the finishing rolling temperature is 850±15℃, the wire drawing temperature is 915±15℃, the temperature at the insulation hood is 780±30℃, the temperature at the insulation hood is 650±30℃, and the temperature at the bottom coil is 540±30℃.
[0007] In this invention, recrystallization controlled rolling is adopted, with roughing deformation controlled at 50%, intermediate rolling deformation controlled at 15%, final rolling deformation controlled at 2%, and wire drawing speed at 85 m / s.
[0008] Furthermore, controlling harmful elements in the refined molten iron is crucial to reducing cracking in low-carbon wire drawing materials. Specifically, the P% + S% in the molten iron should be controlled to <0.045%, and the sum of trace elements should be <0.1%. The trace elements are Cr, Ni, Cu, As, and V. Trace element control should begin from the initial molten iron input, requiring the use of low-Cr and low-Ni ores. Ore blending should be conducted half a month in advance, and adjustments must be made promptly if the trace element content of the molten iron does not meet the requirements. Low-S molten iron should be used during steelmaking, and P should be below 0.022% at tapping.
[0009] To control harmful elements in low-carbon wire drawing materials, during the refining process, the oxygen level at the refining station is controlled to be ≤120 ppm, and the oxygen level at the outlet is controlled to be ≤30 ppm; and the nitrogen level in the finished product is controlled to be ≤45 ppm.
[0010] Furthermore, when the diameter of low-carbon wire exceeds φ11mm, cold billet rolling is required to control harmful elements in the billet. The rolling process adopts a cold feeding and cold charging process.
[0011] Advantages of this invention:
[0012] This invention does not require additional equipment; precise control of key points is sufficient to achieve the desired result.
[0013] This invention effectively controls the quality of large-size wire drawing products, eliminating horizontal grain issues in mass production and resulting in smooth product surfaces after surface treatment. In contrast, the original process resulted in 2-3 instances of horizontal grain quality issues per month, and even quality disputes. Detailed Implementation
[0014] The present invention will be further described below with reference to specific embodiments.
[0015] The production process for large-size low-carbon wire drawing materials includes molten iron, converter, refining, continuous casting, heating, rolling, and finishing. Specifically, in the heating process, the soaking temperature is controlled at 1010±20℃; in the rolling process, the finishing rolling temperature is 850±15℃, the wire exiting temperature is 915±15℃, the temperature entering the insulation hood is 780±30℃, the temperature exiting the insulation hood is 650±30℃, and the final coil temperature is 540±30℃.
[0016] In this invention, recrystallization controlled rolling is adopted, with roughing deformation controlled at 50%, intermediate rolling deformation controlled at 15%, final rolling deformation controlled at 2%, and wire drawing speed at 85 m / s.
[0017] Furthermore, harmful elements in the refined molten iron are controlled to reduce cracking in low-carbon wire drawing materials. Specifically, the P%+S% ratio is controlled to be <0.045%, and the sum of trace elements is controlled to be <0.1%, with the trace elements being Cr, Ni, Cu, As, and V.
[0018] Control methods:
[0019] 1. Raw material control: Select low-Cr and low-Ni ores, and complete ore blending 15 days in advance;
[0020] 2. Production should be organized according to the condition of the molten iron, with Cr+Ni≤0.05;
[0021] 3. Low-S molten iron is selected during steelmaking, and P ≤ 0.022% is used when tapping steel.
[0022] To control harmful elements in low-carbon wire drawing materials, during the refining process, the oxygen level at the refining station is controlled to be ≤120 ppm, and the oxygen level at the outlet is controlled to be ≤30 ppm; and the nitrogen level in the finished product is controlled to be ≤45 ppm.
[0023] Furthermore, when the diameter of low-carbon wire rod exceeds φ11mm, cold billet rolling is required to control harmful elements in the billet. The rolling process adopts a cold-feeding and cold-loading process, where the billet needs to be stacked offline for 48 hours before being cold-fed to the rolling mill. Specifically, in the steelmaking process, when the rolling specification is ≥11mm, the billet is not hot-fed and directly rolled after passing through the heating furnace. Instead, the billet needs to be stacked offline for more than 48 hours to release internal stress before being sent to the rolling mill for rolling.
Claims
1. A method for controlling the formation of cross grain in large-format low-carbon fiber drawing materials, characterized in that, The production process for large-size low-carbon wire drawing includes molten iron, converter, refining, continuous casting, heating, rolling, and finishing. In the heating process, the soaking temperature is controlled at 1010±20℃. In the rolling process, the finishing rolling temperature is 850±15℃, the wire drawing temperature is 915±15℃, the temperature at the insulated hood is 780±30℃, the temperature at the insulated hood is 650±30℃, and the lower coil temperature is 540±30℃. In the molten iron process, the P%+S% content in the molten iron is controlled to be <0.045%, and the sum of trace elements is <0.1%. The trace elements are Cr, Ni, Cu, As, and V. The rolling process uses recrystallization-controlled rolling, with roughing deformation controlled at 50%, intermediate rolling deformation controlled at 15%, and final rolling deformation controlled at 2%. The wire drawing speed is 85 m / s.
2. The method for controlling the formation of cross grain in large-format low-carbon wire drawing materials according to claim 1, characterized in that, in In the refining process, the oxygen level at the refining station is controlled to be ≤120 ppm, and the oxygen level at the outlet is controlled to be ≤30 ppm; and the nitrogen level of the finished product is controlled to be ≤45 ppm.