Influence of wire rod dimensional accuracy on wire drawing process efficiency and optimization strategy

Introduction
Wire rod is a key raw material for metal product processing. Its dimensional accuracy is directly related to the efficiency and product quality of the subsequent wire drawing process. In the field of metal wire production, slight deviations in wire rod dimensions can lead to a series of problems during the wire drawing process, such as increased wire breakage rates and shortened die life. This article systematically analyzes the standard requirements for wire rod dimensional accuracy, explores the specific mechanisms that influence wire drawing process efficiency, and proposes practical optimization strategies to provide technical reference for relevant manufacturers.

I. Definition and Standard Requirements of Wire Rod Dimensional Accuracy
Wire rod dimensional accuracy refers to the degree to which its geometric parameters, such as diameter tolerance and out-of-roundness tolerance, conform to standard values. According to the national standard GB/T14981, the nominal diameter range of hot-rolled wire rod is 5.5mm to 14.0mm, corresponding to a cross-sectional area of ​​23.8-154mm². Taking 10mm wire rod as an example, the diameter tolerance range is plus or minus 0.40mm, and the out-of-roundness tolerance should be less than or equal to 0.50mm. These parameters directly determine the performance of wire rod in the wire drawing process.

Wire rod surface quality is also subject to strict specifications. Surface defects such as cracks and folds are not permitted, but minor indentations, localized bumps, dimples, scratches, and roughness are acceptable, with a depth of no more than 0.2 mm. These surface features may act as stress concentration points during the subsequent wire drawing process, affecting the surface finish and mechanical properties of the wire.

Theoretical mass calculations for wire rod use the formula W = 0.00617d² (d = diameter), and the standard steel density is 7.85 g/cm³. These standardized parameters provide a clear basis for wire rod production and quality inspection, and serve as fundamental indicators for evaluating the suitability of wire drawing processes.

Core Processes and Key Parameters of the Wire Drawing Process
The wire drawing process involves stretching and deforming wire rod through a die into wire of the desired fineness and precision. The core process includes multiple steps, including raw material screening, smelting, continuous casting and rolling, annealing, and surface treatment. Parameter control at each step is closely linked to the dimensional accuracy of the wire rod.

During the raw material screening stage, metal materials with a purity of at least 99.95% must be selected, and their surfaces must be free of oxide layers, oil stains, and mechanical damage. The smelting process utilizes a medium-frequency induction furnace with a temperature set between 1100-1150°C. The melt composition is regularly tested to ensure that impurity levels do not exceed 0.03%. These preliminary treatments directly impact the internal structural uniformity of the wire rod.

During the continuous casting and rolling stages, the mold cooling water temperature is set at 25°C, and the casting speed is controlled between 1.2 and 1.8 m/min. The ingot diameter tolerance must be maintained within ±0.5 mm, with a surface roughness Ra ≤ 3.2 μm. During hot rolling, the roughing mill starts at 850°C, and the ingot is refined to the target size through multiple rolling passes. The final rolling temperature is maintained at no less than 600°C to ensure grain refinement.

Annealing is a key step in adjusting material properties. The annealing temperature is set between 450-500°C, using a nitrogen-hydrogen mixed shielding gas. The wire running speed is maintained at 15 m/min, and the temperature gradient within the furnace must be controlled within ±5°C. Metallographic examination confirms that the grain size after annealing reaches ASTM grade 8 or above, and the Vickers hardness is maintained in the range of 65-75 HV.

During the surface treatment process, pickling is performed using a 10% sulfuric acid solution maintained at a temperature of 40-50°C. The current density in the electroplating bath is set at 2.5 A/dm², and the coating thickness is controlled between 3-5 μm. Systematic control of these parameters ensures the stability of the wire drawing process and the uniformity of the wire quality.

How Wire Rod Dimensional Accuracy Affects Wire Drawing Efficiency
Inadequate wire rod dimensional accuracy can affect wire drawing efficiency in several ways. First, exceeding the diameter tolerance causes uneven stress on the drawing die. When the wire drawing axis is asymmetrical with the die hole centerline, die wear is accelerated. Actual production data shows that dimensional fluctuations can shorten die life by over 30%.

Secondly, excessive out-of-roundness deviation can lead to uneven distribution of wire drawing surface reduction. When localized surface reduction exceeds a critical value, the die is prone to cracking or breaking. This cracking is often caused by the release of internal stress. When lubrication is inadequate and the temperature rises, it exacerbates material movement on the diamond die surface, increasing microstructure stress and ultimately forming macrocracks.

Thirdly, surface defects such as indentations and scratches exceeding the standard can cause abnormal friction with the die during the drawing process, accelerating die bore wear and potentially scratching the wire surface. Statistics show that a one-level increase in surface roughness can increase the wire breakage rate by 15-20%.

Uneven annealing, resulting in variations in wire hardness, is also a significant factor, causing premature fatigue damage to the die and the formation of annular grooves. A case study showed that when hardness fluctuations exceed 10%, die replacement frequency must increase by 2-3 times, severely impacting production efficiency.

Furthermore, dimensional accuracy issues can lead to frequent adjustments in subsequent processes. For example, during the tinning process, dimensionally unstable wire requires constant adjustment of the electroplating bath current density. Otherwise, the tin layer thickness will be uneven, significantly increasing the scrap rate.

II. Optimizing Strategies and Practices for Wire Rod Dimensional Accuracy
Improving Mold Processing Technology
Mold processing technology has a decisive impact on dimensional stability. Internationally advanced companies generally use high-speed mechanical grinders equipped with diamond-coated metal grinding pins to ensure stable equipment operation and standardized use of the grinding pins. The die hole dimensions are precisely measured using a profilometer and aperture gauge, and the inner surface finish of the die hole is inspected using a dedicated microscope. This high-precision processing can extend the life of the die by over 50%.

In contrast, many domestic manufacturers still use manual grinding of the die hole, resulting in large fluctuations in die parameters and difficulty in producing a straight working taper. Optimization efforts should include the introduction of automated grinding equipment, the establishment of standardized procedures for the use and repair of grinding pins, and the deployment of advanced testing equipment to achieve digital control of die hole dimensions.

Precise Control of Wire Drawing Process Parameters
Scientifically setting the wire drawing area reduction is crucial. Excessive area reduction can cause mold cracks, while too little can affect production efficiency. Experience has shown that a phased reduction in area reduction (e.g., from 20% to 12%) can balance efficiency and mold protection. Furthermore, using a nitrogen-hydrogen mixed shielding gas annealing process can stabilize grain size above ASTM grade 8 and control hardness fluctuations to within 5%.

Optimizing the lubrication system is also crucial. An online circulating filtration system, which automatically initiates waste liquid discharge when the metal ion concentration exceeds 5 g/L, can maintain lubricant cleanliness. One company's experience has shown that this improvement has reduced abnormal mold wear by 40%.

Establishing a Full-Process Quality Control System
At the raw material stage, GB/T 14981 standards must be strictly adhered to, with 100% inspection of wire rod diameter, out-of-roundness, and surface quality. Baosteel's practical experience has shown that using converter pre-desulfurization and phosphorus removal, vacuum degassing, and continuous casting electromagnetic stirring and soft reduction techniques can control the center segregation index below 1.05, significantly improving material uniformity.

In terms of process monitoring, the introduction of a PLC intelligent control system enables stepless speed regulation and constant tension control, reducing energy consumption by over 50%. Inverted wire drawing machines use laser diameter measurement to dynamically adjust tension, increasing production speed by 40%. Pulley-type equipment equipped with IoT sensors automatically optimizes parameters, reducing defect rates by 50%.

Standardizing Personnel Operating Procedures

Establishing strict operating procedures is fundamental to ensuring dimensional accuracy. These procedures include: centerline deviation calibration (≤0.05mm) during die installation; wire size and surface quality inspection every two hours; and standardized handling procedures for abnormal situations. Training and assessments have shown that standardized operations can reduce human error by 70%.

III. Typical Industry Case Studies

In the production of TS06 low-carbon wire drawing steel wire rod, Tiangang successfully produced wire rod that meets the high standards of galvanized steel wire by systematically optimizing converter endpoint control, LF ladle refining, and controlled cooling and rolling processes. Its key innovation lies in controlling the carbon content within a narrow range of 0.72±0.02%, while ensuring minimal fluctuations in the Mn and Si compositions (Mn±0.05%, Si±0.04%), and maintaining sulfur and phosphorus contents ≤0.010%.

Steel cord wire rod production demonstrates a solution to extreme precision requirements. Through techniques such as superheat control (15-25°C) and constant casting speed during the continuous casting process, the wire breakage rate is reduced to less than 1 break per ton. Particularly noteworthy is the strict control of non-metallic inclusions: CaO, MgO, MnO, and SiO₂ are permitted to contain 1000 units of impurities per square centimeter, while Al₂O₃ is limited to 3 units. Other impurities must not exceed 1μm.

Stainless steel wire drawing provides an excellent example of surface treatment. Pretreatment involves removing roller marks with 600-grit sandpaper and ultrasonic cleaning with an alkaline degreasing agent (humidity ≤ 60%). During the texturing phase, straight grains are sanded with a 120-grit sanding belt at a constant speed of 0.15-0.25 MPa, while random grains are sanded with an 80/150-grit sanding belt with a 30° offset. Post-treatment includes cleaning with anhydrous ethanol and electrostatic dust removal. This process maintains a stable product qualification rate above 98.5%.

IV. Conclusion and Outlook
There is a significant correlation between wire rod dimensional accuracy and wire drawing process efficiency. Analysis shows that dimensional accuracy issues primarily affect production efficiency through abnormal die wear, increased wire breakage rates, and reduced surface quality. Optimization strategies should encompass four dimensions: die precision machining, process parameter control, full-process quality control, and standardized operations.

Future development trends include: widespread use of intelligent testing equipment to enable real-time dimensional monitoring and automatic adjustment; the development of new die materials to further improve wear resistance and service life; and the introduction of big data analytics to establish predictive models linking process parameters and product quality. These technological advances will drive the wire drawing process towards higher efficiency and higher quality.

Manufacturers should establish a long-term mechanism for dimensional accuracy management, including regular calibration of measuring equipment, continuous optimization of process windows, and enhanced employee skills training. Only by combining technological innovation with management optimization can they maintain quality advantages and cost competitiveness in the face of fierce market competition.