The production of stainless steel ultra fine wires has developed rapidly over the past decade, with over 100 companies now engaged in this industry. Significant improvements have been made in product quality, variety, production processes, and equipment. The production capacity has shifted from being insufficient to exceeding demand. However, several issues persist, including unstable raw material
Current Status and Prospects of Ultra Fine Stainless Steel Wire Production and Market in China
Part Ⅰ
Abstract
The production of stainless steel ultra fine wires has developed rapidly over the past decade, with over 100 companies now engaged in this industry. Significant improvements have been made in product quality, variety, production processes, and equipment. The production capacity has shifted from being insufficient to exceeding demand. However, several issues persist, including unstable raw material quality, poor and high consumption of molds, outdated overall equipment, and low enterprise standards. The author calls for strict regulation and management of fraudulent behaviors in the current stainless steel market, such as substituting inferior products for superior ones and engaging in unfair price competition, in order to purify the market environment.
#### Keywords
Stainless steel wire, ultra fine wire, production, market status
With the rapid development of the national economy, scientific and technological advancements, and the gradual improvement of people's living standards, the application range of stainless steel wires has continuously expanded. Both the production volume and variety have steadily increased, along with a gradual improvement in quality. Notably, the development of stainless steel ultra fine wires (hereinafter referred to as ultra fine wires) has been even faster. Before the 1990s, there were only a few key state-owned enterprises producing ultra fine wires domestically. Since the mid-1990s, due to the high demand for products and the shortage of supply, many investors believed this project had a promising market, required low investment, small land area, offered high value-added benefits, was pollution-free, and could be quickly launched. Coupled with some misleading promotional hype, a surge in investments occurred. In just a few years, the industry expanded to over 100 ultra fine wire enterprises of various ownership types—including state-owned, private, collective, sole proprietorship, joint ventures, and township enterprises—scattered across the country, with significant differences in scale.
During these years of rapid development in the ultra fine wire industry, the market has also quietly shifted from a seller's market with product shortages to a buyer's market with excess supply. Reviewing the development and market changes in the ultra fine wire industry over the past few years reveals certain progress and numerous issues.
1 Current Status of Ultra fine Wire Production
1.1 Achievements and Progress
1.1.1 Formation of a Buyer’s Market and Increased Competition Leading to Improved Product Quality
Over the past few years, the number of ultra fine wire production enterprises has steadily increased, and production volumes have gradually expanded, providing users with a growing range of choices. Additionally, investments from foreign, Hong Kong, and Taiwanese investors have led to the establishment of several modern joint-venture and wholly foreign-owned wire mesh enterprises in China. Most of their products enter the international market, setting higher quality standards for ultra fine wires. Consequently, the main quality indicators of these products have seen gradual improvement.
The GB8605-88 "Industrial Wire Mesh Standard" has become almost obsolete and is rarely used as a reference. Instead, each user sets their technical requirements based on their specific needs, which suppliers then use as the basis for their wire production. Several key indicators have seen significant improvements:
(1). Reduction in Diameter Tolerance and Ovality:
- The tolerance range for wire diameter has generally reduced by approximately 1-3 ultra finemeters (u). Previously, according to the GB8605-88 standard, specifications ranging from Φ0.025mm to Φ0.08mm had tolerances of ±0.0015mm to ±0.003mm. Currently, these tolerances have tightened to ±0.001mm, indicating an enhancement in the precision of ultra fine wires.
(2). Increase in Single Coil Weight:
- Various specifications have seen their single coil weights increase by several times or even several dozen times. This increase reflects advancements in production efficiency and capacity to meet larger demands from consumers.
(3). Stringent Requirements for Surface Quality:
- There is now stricter criteria for surface quality compared to previous years. While standards such as GB8605-88 and some enterprise standards stipulated requirements like no scratches, burrs, scars, rust, folds, obvious defects, or oxidation colors on the surface, they did not specify the degree of surface glossiness or mottling. Presently, although there are no quantitative specifications for mottling, it has become a significant determinant of pricing. The reduction in mottling can lead to price decreases of up to approximately 50% compared to normal wires.
(4). Enhanced Intrinsic Performance Requirements:
- There has been a slight increase in requirements for intrinsic performance metrics such as tensile strength and elongation. Specifically, the upper and lower limits for tensile strength have slightly narrowed, while the minimum elongation rate has slightly increased.
These developments illustrate the continuous refinement and improvement in ultra fine wire production, driven by market competition and evolving customer expectations for higher
1.1.2 Continuous Improvement in Equipment Level and Technological Performance
Before the mid-1990s, most ultra fine wire production factories in China used double-tower pulleys with 12 stages, driven by DC motors with controllable silicon rectifier speed regulation. The wire drawing speed was 5-8m/s, and the single coil weight ranged from several tens of grams to around 200 grams. The process involved straight-line winding, fewer wire drawing passes, low production efficiency, small coil weight capacity, and frequent wear on the pulleys, resulting in inadequate process satisfaction. Some manufacturers used 4-tower pulley wire drawing machines, which, apart from more wire drawing passes, did not significantly differ in performance from the double-tower pulley machines. Heat treatment winding machines generally had 8-12 heads, using lineators or other mechanical devices with contact points, unable to be tilted, and incapable of producing heavy-duty finished products. Additionally, due to constant motor speed during winding, regardless of coil weight, the steel wire's furnace time constantly varied, preventing consistent heat treatment speeds. This represented the first generation of products.
Entering the mid-1990s, with the development of the wire mesh industry and the continuous improvement of ultra fine wire quality standards, higher demands were placed on the performance of ultra fine wire production equipment. Various equipment manufacturers began developing and producing new types of wire drawing machines and heat treatment production lines. The new wire drawing machines adopted double-tower pulleys with 15 stages, made from materials like corundum with surface hardening treatments, equipped with spray devices, and using frequency conversion speed regulation. They featured ball screw non-contact reversing, stepper motor wire arranging, micro computer-coordinated control of the entire drawing and wire arranging system, displaying production parameters. Non-contact tension sensors automatically adjusted tension, enabling the system to track and handle larger coil weights. The wire drawing speed also increased to 10-12m/s, with increased wire drawing stages improving production efficiency and enhancing adaptability to process requirements to some extent. Heat treatment furnaces increased to 10-18 tubes, and winding machines adopted non-contact screw stepper motors for tapered shaft winding, thereby increasing finished product coil weights. This marked the second generation of products.
These advancements illustrate the evolution and technological progress in ultra fine wire production equipment, driven by the need to meet higher quality standards and enhance production efficiency in response to market demands.
In recent years, the industry has seen the emergence of advanced four-tower wheel drawing machines with 20-22 drawing stages, trending towards intelligent operation. These machines employ variable frequency drives, programmable logic controllers (PLC), human-machine interfaces, stepper motors, and high-standard industrial control components. They achieve PLC system processing, synchronizing speed and wire arrangement systems during ultra fine wire production. These machines feature parameter input functions and fine-tuning and protective features for wire tension adjustment, giving them some intelligent processing capabilities and enabling larger spool winding.
Heat treatment winding machines have also advanced, capable of multi-head production with single-head control. The PLC system calculates the number of winding layers and automatically adjusts the winding speed to maintain a relatively constant heat treatment speed, ensuring stable and consistent product performance. This can be considered the third generation of equipment.
At present, various generations of ultra fine stainless steel wire production equipment are in use within China. However, the majority of enterprises still rely on first-generation equipment. Only a few enterprises have adopted third-generation equipment, indicating a significant gap in equipment modernization across the industry. Consequently, the path towards equipment upgrading and renovation for the ultra fine wire industry remains long and challenging, with substantial tasks ahead.
1.1.3 Strengthening of the Die Repair Process in the ultra fine Wire Industry
The importance of die repair in ultra fine stainless steel wire production was not adequately recognized until a few years ago. Many ultra fine wire production companies had weak die repair capabilities, outdated and rudimentary equipment, and some newly established enterprises even lacked a die repair process. In recent years, this aspect has received more attention.
(1). Strengthening Die Repair Teams:
- Various production plants have reinforced their die repair teams by adding more personnel. They have become more attentive to selecting appropriate grinding powder granularity and researching die repair processes. Corresponding equipment has been provided. For smaller molds, the common practice is to use a combination of horizontal ultra-light grinding and wire polishing, which improves the quality of the molds and enhances the efficiency of die repair.
(2). Improvement of Grinding Machines:
- Some companies have improved the originally widespread 10-head grinding machines (swing cars) used in the stainless steel ultra fine wire and tungsten-molybdenum industries. These have been upgraded to 20-head machines, making the bodies more compact, enhancing grinding efficiency, achieving better results, and providing more convenience in use.
These advancements indicate a shift towards acknowledging the critical role of die repair in maintaining and improving the quality and efficiency of ultra fine wire production.
1.2 Issues and Gaps
While the ultra fine stainless steel wire industry has made some progress in recent years, several significant issues persist, hindering its development. These problems can be summarized in six words: "unstable" and "high consumption."
**Unstable:**
- **Product Quality:** There is a lack of consistency in the quality of the final ultra fine wire products.
- **Raw Material Quality:** Variations in the quality of raw materials lead to inconsistency in the final product.
- **Mold Quality:** The molds used in production vary in quality, contributing to product inconsistency.
- **Equipment Performance:** Some of the equipment used in production does not perform reliably or consistently.
- **Company Stability:** The overall stability and sustainability of some companies in the industry are uncertain.
These instability factors are interconnected and mutually reinforcing, creating a cycle of cause and effect.
**High Consumption:**
- **Mold Consumption:** There is a high rate of mold consumption in the production process. This issue is closely tied to the instability mentioned above. Poor quality molds and raw materials lead to increased wear and tear on molds, driving up consumption rates.
The instability in raw materials and mold quality is particularly critical. These issues directly lead to inconsistent product quality and increased mold consumption, negatively impacting the economic efficiency of companies. This, in turn, contributes to the overall instability of the enterprises in the ultra fine wire industry.
1.2.1 Regarding Several Instabilities
Instabilities exist in many industries to varying degrees, but they are particularly prominent and severe in the ultra fine wire industry, with substantial impact. The reasons for this can be attributed to the unique characteristics of the ultra fine wire industry.
(1). Nature of Ultra Fine Wire Production:
- Ultra fine wires are a deep (fine), cold, and precision-processed product within the category of stainless steel wires. The greatest challenge lies in combining these three aspects: deep processing, cold processing, and precision processing.
(2). Challenges of Combined Processing:
- Deep Processing:If the focus is solely on deep processing, methods such as melting, casting, hydrostatic extrusion, and bundle (strand) drawing can be used. These methods allow for finer products, higher production efficiency, lower consumption, and reduced costs. However, they do not meet the principles of precision and cold processing because the product sizes are inaccurate, the surfaces are not smooth, and the shapes are irregular.
- Precision and Cold Processing:If the focus is solely on precision and cold processing, it can be easily achieved. Products like polished high-surface steel wires fall into this category, but they do not meet the principles of deep processing.
(4). Complexity and Constraints:
- The difficulty in ultra fine wire production stems from integrating industrial-scale mass production into a micro domain. This integration exposes and reflects many interrelated technical and conditional constraints. Achieving the necessary precision, surface quality, and shape regularity while maintaining deep and cold processing principles presents significant technical challenges.
These inherent complexities in the ultra fine wire production process create numerous points of instability, significantly impacting the overall industry.
(5) Ultra fine wires production enterprises are small and numerous, and they are widely and sparsely distributed.
In recent years, some investors have only seen the "short, flat, and fast" aspects of ultra fine wires projects while neglecting the inherent rules and difficulties of ultra fine wire production. They lack rational scrutiny and clear understanding. With little knowledge of the industry and the market, and even less understanding of basic stainless steel knowledge, they hastily started projects. After a period of operation, various problems emerged one after another, which they were unable to solve, leaving them bewildered. As time passed, their working capital was exhausted, rendering them unable to continue operations, and they had no choice but to shut down. Some enterprises operated for as short as two to three months. Currently, apart from a few major key enterprises, most ultra fine wire production factories in the country are small-scale. The size of these enterprises varies greatly, ranging from just a few pieces of equipment and a few people to dozens of pieces of equipment with hundreds or even thousands of people. There are also unregistered individual enterprises. The ownership of enterprises takes various forms, and these enterprises are scattered across the country. With so many enterprises, vast differences in scale, scattered locations, various forms of ownership, different corporate cultures, different business philosophies, different ways of thinking, and different quality awareness, the complexity is evident. There is neither an effective industry standard, industry policy, nor a practical product technical standard that meets user needs. In the ultra fine wire industry, there is too much freedom and a lack of necessary unification; too much arbitrariness and a lack of basic control; excessive disorder and a lack of proper regulation; and biased publicity with a lack of correct guidance. This situation inevitably leads to instability in enterprise and product quality.
(6) Ultra fine wire production requires "ultra-clean, ultra-fine, and homogeneous" raw materials.
Currently, the raw materials used for ultra fine stainless steel wire production mainly include low-carbon and ultra-low-carbon stainless steels, such as 304, 304L, 316, and 316L, with a small portion using other steel types. Some of these materials are imported wire rods from Japan, South Korea, France, and Taiwan, which are processed into fine wires by domestic manufacturers. Another portion is domestically produced wire rods processed into fine wires, and a small amount of fine wires are directly imported from abroad as ultra fine wire raw materials. These materials are typically produced using general stainless steel smelting methods, which can meet the needs for producing coarse, medium, and fine wires. However, for ultra fine wire, the finer the material specifications, the more problems arise, especially for ultra-fine wires smaller than Φ0.025mm. Using these materials makes it difficult to maintain normal production. Issues include frequent breakage, low spool weight, poor surface quality, low production efficiency, and high consumption. The degree of these issues varies between batches, furnace numbers, and even individual spools, indicating significant fluctuations in raw material quality along their lengths.
Practical experience shows that the type, morphology, and size of inclusions in the raw materials have a significant impact on the production and mechanical properties of ultra fine wires. Therefore, it is essential to use high-purity, highly homogeneous raw materials with very few non-plastic inclusions and no metallic carbides. Currently, smelting methods cannot meet these ultra-clean and homogeneous requirements, so special processes are needed. These include using electroslag remelting, vacuum induction melting, double vacuum induction melting, and potentially powder metallurgy (micro metallurgy) methods to produce high-quality raw materials. While this approach increases costs significantly, it is worthwhile for producing ultra-fine wires (with diameters less than 0.025mm) that have relatively low consumption but much higher added value compared to regular ultra fine wire.
(7) Ultra fine wires production requires highly wear-resistant and high-precision molds.
The drawing of ultra fine wire generally uses several types of molds, including natural diamond, CVD (chemical vapor deposition) diamond, synthetic single crystal, and synthetic polycrystalline diamond. Synthetic diamonds are only used for intermediate or coarser molds, while natural diamonds are used for the final product molds. Currently, the main issues with the natural diamond molds used by various enterprises are: a) significant quality differences and low average lifespan; b) outdated mold inspection equipment and low manufacturing precision.
(8) The equipment used in ultra fine wire production consists mostly of various non-standard products.
Most ultra fine wire production factories in the country use wire drawing machines, wire take-up machines, and heat treatment furnaces that are non-standard equipment in constant need of improvement. These vary in type, grade, and performance. For products like ultra fine wires which require high precision and high stability, using these non-standard devices makes it difficult to stably produce high-quality ultra fine stainless steel wire.
The main issues are as follows: some domestic electronic components in the microcomputer-equipped control systems do not meet standards, resulting in poor system anti-interference capabilities and a relatively high rate of soft faults. The lubrication and cooling of the wire drawing machine are inadequate, leading to poor performance. The capstan wheels have significant bouncing and poor stability, their surface wear resistance is low, and their service life is short. The design of capstan levels and taper ratios does not meet the needs of drawing ultra fine stainless steel wire of different steel grades and specifications, causing unreasonable stretching and sliding of the wire during drawing. In summary, the design of wire drawing machines focuses more on purely mechanical issues while neglecting the finer details closely related to process requirements. The main problems with the equipment are its low degree of meeting process requirements and poor adaptability.
1.2.2 Regarding the High Consumption of Molds
The reasons for this problem, aside from the comprehensive quality of the molds themselves (mold blanks, processing methods, structure) previously mentioned, include the following factors:
1. **Raw Materials**: The intrinsic quality, composition, purity, and the type and quantity of non-plastic inclusions in the raw materials used for ultra fine wire production have a significant impact on the lifespan of molds. Using low-quality, low-cost raw materials to reduce costs actually increases mold consumption, which is unwise.
2. **Heat Treatment Quality of Raw Materials and Semi-Finished Products**: The energy conditions during the heat treatment process, such as heating temperature, time in the furnace, and the status of protective gases, play crucial roles.
3. **Design of the Drawing Process Route**: This includes the selection of total and partial compression ratios and the appropriateness of handling various small details in the mold usage and management processes.
4. **Type and Quality of Lubricants**: The usage and circulation status of the lubricating liquid also affect mold consumption.
5. **Drawing Speed and Distribution During the Drawing Process**: How the speed and distribution are managed during drawing affects mold wear.
6. **Mold Repair Process and Equipment**: The condition of the mold repair equipment, the experience and intuition of the repair personnel, and their coordination with the drawing process are all important factors.
7. **Design and Installation of the Wire Drawing Machine Mold Structure**: Proper design and installation of the mold structure in the wire drawing machine are crucial.
Each of these factors can affect the lifespan of molds to varying degrees. Currently, there are many issues in these areas within the ultra fine wire production process that need to be adequately addressed and effectively resolved.