Analysis of fastener material properties and uses

Carbon cold rolled hot rolled wire rod

The low-carbon SWRCH6~16A series are non-heat-treated cold heading and cold extrusion steels, which are mainly used to produce various types of fasteners with lower strength grades. Such products generally have a large amount of cold heading deformation and a complicated shape, and have high requirements for pickling and phosphating quality. When producing fastener products with a cold heading deformation amount ≥1/3, annealing treatment should be carried out in steel grades. In the selection of the customer, it is recommended that the customer select the grade with low carbon content (SWRCH6A) as far as possible, especially when producing fasteners with large deformation of cold heading, especially the selection of grades. In the selection of the wire material specifications, it is recommended that the customer select the similar specifications as much as possible to meet the product size requirements, so as to reduce the amount of drawing deformation and reduce the impact of work hardening.

Free return cold rolled steel hot rolled wire rod

In 2004, Maanshan Iron & Steel Co., Ltd. undertook the National 863 Program “Research on High Performance and Low Cost Cold Rolled Steel” (2003AA331030), aiming to develop online softening and low cost cold heading steel wire production technology with independent intellectual property rights in China.

High-strength fasteners of class 8.8 and above are usually made of medium carbon steel or medium carbon alloy steel. The typical production process is: hot-rolled steel spheroidizing annealing, cold-drawn deformation, cold-form forming, rolling and quenching and tempering. The main purpose of spheroidizing annealing is to obtain enough plasticity for the steel to meet the requirements of cold head forming. In the process of cold heading, the material tends to withstand a total deformation of up to 7080%. Therefore, the plasticity of the raw material is required to be as low as possible, and the general requirement is not more than HRB82. The spheroidizing annealing treatment is currently in the fastener manufacturing process. The most time-consuming and energy-intensive process, the cold-rolled steel wire rod is spheroidized and annealed in a batch or continuous processing annealing furnace with a cycle of about 1224 h. Therefore, the fastener manufacturing industry is eager to simplify the spheroidizing annealing process. The spheroidizing annealing treatment time is shortened or even the spheroidizing annealing treatment step is omitted.

Ma Steel's high-line aiming at the latest technology in the field of wire rod rolling, forming a unique hot-rolling process technology production line with independent intellectual property rights of Maanshan Iron and Steel Co., Ltd., and developing annealed SWRCH35K-M and CH35A-M hot-rolled wire rods. And annealed SWRCH35K-MT, CH35A-MT hot rolled wire rods for the production of fasteners exported to the US market. Among them SWRCH35K-M and SWRCH35K-MT can produce ∮ 6.5-16mm a total of nine specifications, CH35A-M, CH35A-MT can produce ∮ 16-20mm three specifications, free of annealing SWRCH35K-M, CH35A-M, SWRCH35K-MT and The CH35A-MT hot-rolled wire rod is suitable for the manufacture of hexagonal bolts or fasteners with the same amount of cold heading and hexagon socket head bolts. For fastener products with large deformation, the spheroidizing annealing process is still required. For the nut products, the no-annealed MFM-1 and MFM-3 hot-rolled wire rods for ordinary high-strength nuts have been successfully developed. The MFM-2 hot-rolled wire rod not only eliminates annealing but also eliminates quenching + tempering. The process directly produces 8-level nuts.

Non-regulated cold rolled steel hot rolled wire rod

Non-tempered cold heading steel is mainly used to manufacture fasteners such as 8.8, 9.8 and 10.9 high strength bolts. The use of non-tempered cold-rolled steel to manufacture high-strength bolt products can eliminate the annealing treatment before steel cold drawing and the quenching and tempering treatment after bolting in urban and rural areas. It greatly simplifies the production process, shortens the production cycle, reduces energy consumption, and avoids problems such as surface oxidation, decarburization and workpiece deformation caused by heat treatment, thus having significant economic and social benefits. Japan has carried out industrial mass production.

In 2005, Maanshan Iron & Steel Co., Ltd. undertook the National 863 Program Guided Project “Research and Development of Non-tempered Steel Wire for Low Temperature Controlled Rolling and Controlled Cooling Fasteners” (2005AA001110).

In 2008, Maanshan Iron & Steel Co., Ltd. undertook the National Support Program Project “Development of Low-Cost, High-Strength Non-Quenched and Tempered Cold-Rolled Steel Products for Steel Structure Joints” (2007BAE30B04).

The non-tempered steel series developed by Maanshan Iron & Steel Co., Ltd. is obtained by using micro-alloying, heat-controlled rolling, controlled cooling and other toughening methods to obtain ultra-fine grain structure. In the manufacture of fasteners, the annealing of the raw materials and the preparation process of the finished fasteners are omitted, and the product performance can meet the requirements and actual use of the current fastener mechanical performance standards (GB/T 3098.22-2009). Requirements. This new process route for the production of high-strength fasteners of grades8.8-10.9 can save a lot of energy and manufacturing costs, reduce environmental pollution, is a green product, and can also reduce quenching cracks and surface decarburization caused by heat treatment. defect.

Alloy cold heading steel

10B21, ML40Cr, SCM435 cold heading steel, mainly used to produce high-grade fastener products of grade 8.8-12.9. Through strict process control, the product has superior performance and high cost performance.

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