2 Technical Conditions The various performance indexes and quality requirements that a product should meet are called technical conditions, such as chemical composition, overall dimensions, surface quality, physical properties, mechanical properties, technological properties, internal organization and delivery status.
3 Guarantee conditions According to the Technical Conditions for Metallic Materials, the manufacturer shall conduct inspection to ensure that the inspection results meet the quality indicators such as performance, chemical composition and internal structure, which is called guarantee conditions.
4 Quality Certificate The production of metal materials, like the production of other industrial products, is carried out according to unified standards, and the product ex-factory inspection system is implemented. Unqualified metal materials are not allowed to be delivered. For the delivered metal materials, the manufacturer shall provide quality certificates to ensure their quality. The quality certificate of metal materials not only indicates the name, specifications, number of delivered pieces, weight, etc. All inspection results of the specified guarantee items are also provided.
The quality certificate is the supplier's confirmation and guarantee of the inspection results of this batch of products, and it is also the basis for the buyer's re-inspection and use. 5 Quality grades According to the allowable deviation requirements of steel surface quality, shape and size, the steel quality is divided into several grades. For example, first-class products, second-class products. Sometimes different grades are made for a certain requirement, such as the surface quality is divided into one, two and three grades, and the depth of decarburization layer on the surface is divided into one group and two groups, which all indicate the difference in quality.
6 Accuracy grade Some metal materials have specified several allowable dimensional deviations in the standard, and they are divided into several grades according to the different allowable dimensional deviations, which are called accuracy grades. Accuracy grades are divided into general accuracy, higher accuracy and advanced accuracy according to allowable deviation. The higher the accuracy level, the smaller the allowable dimensional deviation. When ordering, attention should be paid to writing the accuracy grade requirements into the contract and other related documents.
7 Brand The brand of metal material is the name of each specific metal material. The brand of steel is also called steel grade. The brands of metal materials in China can generally reflect the chemical composition. The brand number not only indicates the specific variety of metal materials, but also can roughly judge their quality according to it. In this way, the brand simply provides the same concept of the quality of a specific metal material, which brings great convenience to production, use and management.
8 Metal material varieties refer to products with different uses, shapes, production processes, heat treatment states and particle sizes.
The model of type 9 metal material refers to the code names of products with different shapes and categories, such as profiles and cemented carbide, which are expressed by Chinese phonetic alphabet (or Latin) letters and one or several numbers. Numbers represent the nominal dimensions of major parts.
LO specification refers to the different sizes of the same variety or the same model of metal materials. Generally, the allowable deviation is different with different sizes. In product standards, the specifications of varieties are usually arranged in order from small to large.
Ll surface states are mainly divided into bright and unlit states. Common in steel wire and steel strip standards, the main difference lies in bright annealing or ordinary annealing. There are also grinding, polishing, pickling, electroplating and so on as the surface state.
12 edge state The edge state refers to whether the strip is trimmed. Trimming is trimming strip steel, and untrimmed strip steel is untrimmed strip steel.
13 delivery status delivery status refers to the final plastic deformation or final heat treatment status of product delivery. Delivered products without heat treatment are hot-rolled (forged) and cold-rolled products. After normalizing, annealing, high-temperature tempering, quenching and tempering, solid solution and other treatments, it is collectively referred to as delivery in heat treatment state, or it is referred to as delivery in normalizing, annealing, high-temperature tempering and quenching and tempering state according to heat treatment categories.
The hardness of 14 material refers to the different hardness of steel obtained by different heat treatment or work hardening degrees. In some steel strip standards, it is divided into super soft steel strip, soft steel strip, semi-soft steel strip, low hard steel strip and hard steel strip.
15 longitudinal and transverse directions mentioned in the longitudinal and transverse steel standard refer to the relative relationship with the rolling (forging) and drawing directions, and those parallel to the machining direction are called longitudinal directions; Perpendicular to the machine direction is called transverse direction. Samples taken along the processing direction are called longitudinal samples; Samples perpendicular to the machine direction are called transverse samples. The fracture on the longitudinal specimen is perpendicular to the rolling direction, so it is called transverse fracture; The fracture on the transverse specimen is parallel to the machining direction, so it is called longitudinal fracture.
16 theoretical quality and actual quality These are two different methods to calculate the delivery quality. If the goods are delivered according to the theoretical quality, the delivery quality shall be calculated according to the nominal size and density of the materials. If delivered according to the actual quality, it is the delivery quality obtained by weighing (weighing) the materials.
17 Nominal dimensions and actual dimensions Nominal dimensions refer to the nominal dimensions specified in the standard and are ideal dimensions expected in the production process. However, in actual production, the actual size of steel is often greater than or less than the nominal size, and the actual size is called the actual size.
18 deviation and tolerance because it is difficult to reach the nominal size in actual production, there is an allowable difference between the actual size and the nominal size specified in the standard, which is called deviation. Negative difference is called negative deviation, and positive difference is called positive deviation. The sum of the absolute values of allowable positive and negative deviations specified in the standard is called tolerance. Deviation is directional, that is, it is "positive" or "negative", while tolerance is not directional.
19 delivery length There are four provisions on the delivery length of steel in the current standard: fixed length, where the steel length is within the standard range and there is no fixed length, it is called normal length. However, for the convenience of packaging, transportation and measurement, when cutting steel, it is best to cut it into several sizes with different lengths according to the situation, so as to avoid disorderly ruler, which is called short ruler length.
Smelting method refers to which steelmaking furnace is used for smelting, such as open hearth furnace, electric arc furnace, electroslag furnace, vacuum induction furnace and mixed steelmaking. The meaning of the word "smelting method" in the standard does not include the concepts of deoxidizing method (such as fully deoxidized killed steel, semi-deoxidized killed steel and boiling steel) and pouring method (such as injection, pressure injection and continuous casting).
2l Chemical composition (product composition) refers to the chemical composition of steel products, including main components and impurity elements, and its content is expressed by weight percentage.
22 melting composition the melting composition of steel refers to the chemical composition of steel in the middle stage of casting after melting (such as deoxidation in a tank)
23 Finished product composition The finished product composition of steel, also called validation analysis composition, refers to the chemical composition obtained by drilling or planing test pieces from finished steel according to the specified method (see GB/T222 for details) and analyzing them according to the specified standard method. The composition of finished steel products is mainly used by the user department or the inspection department when accepting steel products. General manufacturers will not analyze all finished products, but ensure that the components of finished products meet the standards. For some main products, sometimes due to some reasons (such as process changes, unstable quality, melting components close to the upper and lower limits, melting analysis has not been obtained, etc. ), the manufacturer also analyzes the composition of the finished product.
High-quality steel and high-quality steel (with the letter A) are also called high-quality steel and high-quality steel. The difference is that high-quality steel is superior to high-quality steel in some or all of the following aspects:
① Narrowing the range of carbon content; (2) reducing the content of harmful impurities (mainly sulfur and phosphorus); (3) ensure high purity (refers to less inclusion content); (4) Ensure high mechanical and technological properties.
Steel prospect
For the market prospect, there are differences among large domestic steel enterprises. Angang lowered the price of medium plate in April on March 18. Last week, Baosteel raised the futures prices of major products in April. However, the dominant varieties of WISCO and Shougang did not follow the pace of Baosteel, and Shagang even introduced a price reduction policy and gave subsidies.