Common Terms in Steel Pipe Knowledge (1)

1. Technical conditions

The performance indicators and quality requirements stipulated in the standard are called technical conditions, such as chemical composition, external dimensions, surface quality, physical properties, mechanical properties, process properties, internal organization, delivery status, etc.

2. Quality certificate

The production of square and rectangular tube metal materials is the same as the production of other industrial products. It is carried out according to unified standards and regulations. The product factory inspection system is implemented, and unqualified metal materials are not allowed to be delivered. For the delivered metal materials, the manufacturer provides a quality certificate to guarantee its quality. The quality certificate of metal materials not only states the name, specification, number of delivered pieces, weight, etc. of the material but also provides all the inspection results of the specified guarantee items. The quality certificate is the supplier's confirmation and guarantee of the inspection results of the batch of products, and it is also the basis for the buyer's re-inspection and use.

3. Accuracy grade

For some metal materials, there are several dimensional tolerances stipulated in the standard, and according to the size of the dimensional tolerances, they are divided into several grades, called precision grades. According to the allowable deviation, the precision level is divided into ordinary precision, higher precision, advanced precision, and so on. The higher the precision level of the square tube, the smaller the allowable dimensional deviation.

4. Varieties

Varieties of metal materials refer to products with different uses, shapes, production processes, heat treatment states, and particle sizes.

5. Specifications

Refers to different sizes of the same type or type of metal material. The general size is different, and its allowable deviation is also different. In product standards, the specifications of varieties are usually arranged in order from small to large.

6. Edge state

The edge state of the square tube refers to whether the strip is trimmed or not. Those who trim the edge are trimmed strip steel, and those who do not trim the edge are called uncut strip steel.

7. The degree of softness and hardness of the material

Refers to the use of different heat treatments or work hardening degrees, resulting in different degrees of softness and hardness of the steel. In some strip steel standards, it is divided into extra soft steel strips, soft steel strips, semi-soft steel strips, low hard steel strips, and hard steel strips.

8. Theoretical quality and actual quality

These are two different methods of calculating delivery quality. The deliverer according to the theoretical quality is the delivery quality calculated according to the nominal size and density of the material. The actual quality of delivery refers to the delivery quality obtained by weighing the material.

9. Deviation and Tolerance

Because it is difficult to achieve the nominal size in actual production, there is an allowable difference between the actual size and the nominal size in the standard, which is called the deviation. A negative value of the difference is called a negative deviation, and a positive value is called a positive deviation. In the standard of rectangular tubes, the sum of the absolute values of the specified allowable positive and negative deviations is called tolerance. Deviation has directionality, that is, expressed as "positive" or "negative", while tolerance has no directionality.

10. Smelting method

Refers to what kind of steelmaking furnace is used for smelting, such as open hearth furnace, electric arc furnace, electro slag furnace, vacuum induction furnace, and mixed steelmaking. The meaning of the word "smelting method" in the standard does not include the concepts of the deoxidation method and pouring method.

11. Smelting ingredients

The smelting composition of steel refers to the chemical composition of steel in the middle of casting after smelting.

12. High-quality steel and high-grade high-quality steel

Also known as high-quality steel and high-quality steel, the difference is that high-quality high-quality steel is superior to high-quality steel in part or all of the following aspects: 1. Reduce the range of carbon content; 2. Reduce the content of harmful impurities; 3. Ensure higher purity 4. Guarantee high mechanical properties and process performance.