Service HotlineT-bolts have been widely used in the fields of aviation, aerospace and defense due to their good positioning and anti-shedding effects. Its related standards have special requirements for accurate positioning, anti-falling off, and dimensional consistency of T-bolts. This requires that the position, size and shape and position tolerance of the anti-fall hole of the T-bolt shank must be controlled within a certain range. Therefore, the processing method of the anti-shedding hole is particularly important. Since the machined anti-shedding hole is located at the position of the rod, the milling processing efficiency is too low, the product cost is high, and there is a large machining error. When conventional drilling is used, the consistency of the anti-shedding hole size cannot be guaranteed. To solve the above problems of low efficiency and dimensional instability
The heating bolt pre-stretching method makes the bolt pre-stretch to the required deformation amount by heating, and then tighten the nut. After cooling, the bolt is shortened and the connection is pre-tightened. This is a commonly used fastening method in infrastructure installations. However, it is not suitable for devices that often need to be disassembled and adjusted, because during the disassembly process, the connected parts will be heated and elongated together with the bolts, and the use of open flame heating will be limited in some occasions; the use of electric heating will make the structure of the screw It becomes complicated and increases the investment, and even if it is difficult to disassemble, such as the propeller shaft of the ship, etc., the heating method is not suitable.
Existing bolt and nut connections usually use threads for connection, and this connection method has two main drawbacks. First, tools are required to be used to lock it during installation, and it takes a long time to complete, which is time-consuming and labor-intensive; Second, the installed bolts and nuts are prone to loosening after a period of time, resulting in loosening and shaking between the connecting parts. Therefore, there is a need for a bolt and nut fastener that is easy to install and can effectively prevent the loose fit of the bolt and nut, so as to solve the problems existing in the prior art.
China is the world's largest producer of carbon steel fasteners such as screws, nuts and bolts, and the EU is a major market for these products. In January 2009, the EU decided to impose anti-dumping duties of 26.5% to 85% on Chinese carbon steel fastener products. On July 31 of the same year, China resorted to the relevant EU legislation and anti-dumping measures to the WTO dispute settlement mechanism. The case became China's first lawsuit against the EU at the WTO. On July 15, 2011, the WTO Appellate Body issued a report and finally ruled that China won the case in the trade dispute with the European Union on fasteners. The head of the Department of Treaty and Law of the Ministry of Commerce of China welcomed the ruling on the 16th, and said that China's victory in the case is of great significance, which will help improve the competitive environment for Chinese companies in the international market including the European Union, and will also strengthen the WTO members' interest in the case. Confidence in WTO rules and the multilateral trading system. This is not only a victory for China's industry, but also a victory for WTO rules, the official said. The WTO Appellate Body found in its ruling report issued on the 15th that Article 9(5) of the EU's Basic Anti-dumping Regulations on individual tax rates violated WTO rules; at the same time, the Appellate Body overturned some of the panel's rulings and supported China's position , ruled that the EU's anti-dumping measures against Chinese screws, nuts, bolts and other carbon steel fasteners also violated WTO rules in terms of domestic industry identification, normal value and fair comparison of export prices. The head of the Treaty and Law Department of the Ministry of Commerce of China said that the EU is one of the WTO members that has initiated the most anti-dumping investigations against Chinese products in the world. unfair treatment. He said that China hopes that the EU will cancel the legislation and discriminatory anti-dumping measures that are inconsistent with WTO rules as soon as possible, treat Chinese export enterprises fairly, and effectively safeguard free trade and fair competition.
1) Scope This standard specifies the lock nut (referred to as nut), the size of the locking device, technical requirements, acceptance rules and measurement methods. This standard applies to the design, production, inspection and user acceptance of nuts and locking devices for tapered bushings. 2) Terminology The terms used in this standard conform to the provisions of GB/T 6930. This standard specifies the marking system, index, test method and marking of the mechanical and working performance of the effective torque section steel hexagonal lock nut. This standard is applicable to coarse thread 6H class nuts made of carbon steel or alloy steel, the width across the sides conforming to the provisions of GB 3104, the nominal height is ≥ 0.8D, and the guaranteed load and effective torque need to be specified, and the thread diameter is 3 ~ 39mm. Except for the effective torque part, the thread size and tolerance are specified in GB 193, GB 196 and GB 197. The working temperature range of the nut should be in accordance with: All-metal nut without electroplating treatment: -50℃～+300℃. All-metal nuts with electroplating treatment: -50℃～+230℃; nuts embedded with non-metallic elements: -50℃～+120℃. This standard does not apply to nuts with special performance requirements (such as weldability and corrosion resistance). For stainless steel and non-ferrous metals with fine pitch lock nuts or thin nuts made of carbon steel or alloy steel, the performance indicators and test methods of effective torque specified in this standard may be adopted by mutual agreement.
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