The steel strand is a steel product composed of several steel wires. According to the needs, the galvanized layer, zinc aluminum alloy layer, aluminum coating, copper coating and epoxy resin coating can be added on the surface of carbon steel. Steel strand can be divided into: prestressed, unbonded, galvanized steel strand, etc. This paper only introduces the prestressed steel strand with the largest market circulation and consumption.
Structure and application of steel strand
Prestressed steel strand is a stranded steel cable composed of 2, 3, 7 or 19 high-strength steel wires, which has been stress relieved (stabilized). The main features are high strength and good relaxation performance. In addition, it is relatively straight when it is unfolded and suitable for prestressed concrete or similar purposes. It is widely used in infrastructure projects such as high-speed railway construction, expressway and national and provincial highway bridge. China’s prestressed steel strand industry originated in the 1960s, began to introduce western technology in 1988, and began to develop rapidly after 1995, mainly due to the sustained growth of China’s economy and the country’s policy of continuous investment in infrastructure. Now China has become the largest prestressed steel strand consumer market in the world.
Galvanized steel strand is usually used for messenger wire, guy wire, core wire or strength member, etc. it can also be used as earth wire / ground wire of overhead power transmission, barrier cable on both sides of highway or structural cable in building structure. The common prestressed steel strand in prestressed steel strand is uncoated steel strand for prestressed concrete, also galvanized, which is commonly used in bridge, construction, water conservancy, energy and geotechnical engineering, unbonded steel strand or monostrand is commonly used in floor and foundation engineering, etc.
The manufacturing process is divided into single wire manufacturing and stranded wire manufacturing. The (cold) drawing technology is used in the production of single wire. According to different materials of the product, it can be high carbon steel wire rod, stainless steel wire rod or medium and low carbon steel wire rod. If galvanizing is required, electroplating or hot plating shall be carried out on the single wire. In the process of strand manufacturing, multiple steel wires are twisted into products by a strander, and the prestressed steel strand needs to be stabilized continuously after forming. The final product is generally collected on the I-shaped wheel or completed as a reel less
Steel strand China market
At present, the production bases of steel strand are mainly in Tianjin, Jiangsu, Hebei and Henan, which account for 70% of the total output of the country. Tianjin has obvious location advantages, and the logistics in the center of the North-South channel is more convenient, which can easily radiate Beijing, Tianjin, Hebei, Shanxi, Inner Mongolia and northeast provinces. Due to the development of Tianjin strand industry cluster, B steel production of iron and steel enterprises in the region is driven, and Rongcheng steel and Aosen steel provide sufficient raw material supply in the region. Manufacturers along the Yangtze River mainly radiate to Jiangsu, Zhejiang, Shanghai, Fujian and Guangdong, benefiting from the developed inland water network transportation and low freight. There are Shagang, Yonggang, Wuhu Xinxing and other manufacturers in the area as raw material suppliers with sufficient supply.
According to Mysteel’s statistics, there are 54 sample steel strand manufacturers in total, with a total output of 5.6756 million tons in 2017, of which nearly 50% are concentrated in North China; the second is East China, accounting for 25% and central China, accounting for 12%; the third is Tianjin, with a total of 20 sample steel strand manufacturers, with a regional output of 2.37 million tons in 2017, ranking first in China, accounting for 42%; and Next, Jiangsu accounted for 12% and Hebei for 8%. Overall, the region is highly concentrated in North China, followed by East China, but with the construction of national projects, the southwest and northwest regions will be the key development areas in the future.
Future market of strand steel
With the continuous breakthrough of technical barriers in China’s steel strand industry and the involvement of a large number of private capital, the proportion of private enterprises continues to rise. In 2018, the industry expects that China’s new steel strand capacity will be about 400000, and the effective capacity will reach 6 million at the end of the year. In the future, the competition in the industry market will be particularly fierce, in which the large manufacturers and brand manufacturers occupy the high-end market through their own brand advantages and long-term customer resource advantages established through cooperation, while some private manufacturers adopt regional sales mode and low-cost cash sales to compete, resulting in the increase of many steel strand manufacturers’ output and the decrease of profits, or even losses. Therefore, the future market urgently needs the supervision and coordination mechanism.