In use, it is required to have good welding, riveting performance and comprehensive mechanical properties. The raw material billets for producing channel steel are carbon steel or low alloy steel billets with a carbon content of no more than 0.25%. The finished channel steel is delivered in a hot-formed, normalized or hot-rolled state. The specifications are expressed in millimeters of waist height (h) * leg width (b) * waist thickness (d). For example, 100485.3 means that the waist height is 100 mm, the leg width is 48 mm, and the waist thickness is 5.3 mm. Steel, or 10# channel steel. For channel steel with the same waist height, if there are several different leg widths and waist thicknesses, it is necessary to add a b c to the right of the model number to distinguish them, such as 25#a 25#b 25#c, etc.
Classification
Channel steel is divided into ordinary channel steel and light channel steel. The specifications of hot-rolled ordinary channel steel are 5-40#. The specifications of hot-rolled modified channel steel supplied by agreement between the supplier and the buyer are 6.5-30#. Channel steel is mainly used in building structures, vehicle manufacturing, other industrial structures and fixed panels. Channel steel is often used in conjunction with I-beams.
Channel steel can be divided into 4 types according to shape: cold-formed equal-edge channel steel, cold-formed unequal-edge channel steel, cold-formed inner curled channel steel, and cold-formed outer curled channel steel.
According to the theory of steel structure, the channel steel wing plate should bear the force, which means that the channel steel should be standing up instead of lying down.
serial number
① Use international chemical element symbols and national symbols to indicate chemical ingredients, and use Arabic letters to indicate ingredient content:
Such as: China, Russia 12CrNi3A
②Use fixed-digit numbers to represent steel series or numbers; such as: United States, Japan, 300 series, 400 series, 200 series;
③Use Latin letters and sequence to form the serial number, which only indicates the purpose.
Specifications
The specifications of channel steel are mainly expressed by height (h), leg width (b), waist thickness (d) and other dimensions. The specifications of domestic channel steel range from 5-40, that is, the corresponding height is 5-40cm.
At the same height, light channel steel has narrower legs, thinner waist and lighter weight than ordinary channel steel. No. 18 to 40 are large channel steels, and No. 5 to 16 are medium channel steels. Imported channel steel is marked with actual specifications, dimensions and related standards. The import and export orders of channel steel are generally based on the specifications required for use after determining the corresponding carbon steel (or low alloy steel) steel grade. Apart from specification numbers, channel steel does not have a specific composition and performance series.
The delivery length of channel steel is divided into two types: fixed length and double length, and the tolerance value is specified in the corresponding standard. The length selection range of domestic channel steel is divided into three types according to different specifications: 5-12m, 5-19m, and 6-19m. The length selection range of imported channel steel is generally 6-15m.
Shearing process optimization
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problem analysis
The 400mm unit in a steel plant is a profile unit that mainly produces medium-sized angle steel and channel steel, with an annual output of 650,000 tons, of which channel steel product specifications range from 638 to 1208, accounting for approximately 25% of the total output. The segmentation operation of the finished channel steel is carried out using a 400t cold shearing machine. The shearing quality of channel steel has a great influence on the subsequent process, especially the welding quality. If there are defects such as shoulder collapse, burrs, tears, and bevel cutting at the shear fracture, there will be a large gap when the channel steel is butted, affecting the welding. Quality, especially strength indicators, thus causing greater safety hazards.
As the production pace and output of Angang’s vertical 400mm unit increase, the above-mentioned shearing defects become more and more prominent, and the shearing quality internal control compliance rate is only 94.2%. Moreover, the service life of the shear blades is getting shorter and shorter, and they are replaced once per shift on average, resulting in increased production costs and employee labor intensity. In response to these problems, we carefully analyzed the process, technology and operation, and proposed corresponding improvement measures, achieving good results.
- Process reasons
The design capacity of this unit is 200,000 t/a, but the output has reached 600,000 t/a. The problem of insufficient production capacity in the cooling bed area is very prominent. Compared with the production of angle steel, the cooling speed of channel steel is slower, resulting in shearing. The temperature of the channel steel is high during cutting, which is prone to defects such as shoulder collapse, burrs, and tears, and has a greater impact on the life of the shearing blade. - Reasons for cutting blade design
The basic basis for the design of channel steel cutting edges is the pass shape of the finished channel steel, as shown in Figure 1 (taking 100# channel steel as an example). This design is prone to the following problems during the shearing process: First, the two shoulders of the channel steel are relatively thick compared with other parts, and the shearing force required is also large. The shearing blade wears quickly. After the shearing blade is used for a period of time, . This part has a relatively large amount of wear, resulting in a large gap between the shoulders and prone to shoulder collapse. Secondly, compared with the waist, the two legs of the channel steel are affected by the shearing angle. When the shearing amount is reduced, the shearing of the legs changes from normal shearing to tearing, and burrs easily appear on the end faces of the channel steel legs. Third, the slope of the upper and lower shearing blade legs is basically the same as the finished channel steel pass shape. In this way, the legs are basically stressed at the same time during shearing. The shearing force is relatively large and the shearing blades wear out quickly. On the one hand, the shearing indentations on the leg ends are serious. On the other hand, after the shearing blades are aged, the sheared parts of the channel steel will easily appear. There are many tears and burrs. The latter two points are the main reasons affecting the shear quality of channel steel.
improvement measures
In response to the above three problems, corresponding measures have been taken. - In order to solve the problem of slow cooling rate of the cooling bed, a water mist fan was added in the cooling bed area to increase the cooling rate of the cooling bed area. A set of water mist nozzles was added one meter in front of the shearing machine to reduce the cooling rate of the channel steel shear. temperature of the cutting part, thus avoiding shear defects caused by high steel temperature.
- In view of the problems existing in the design of channel steel shearing blades and combined with the actual production conditions, the shearing blades are designed into the shape shown in Figure 2 (taking 100# channel steel as an example). The width of the upper shearing blade is changed from 100mm to 99mm, which reduces the gap between the upper shearing blade in the left and right directions and improves the shearing quality of the two corners of the channel steel; the arc size of the two corners of the lower shearing blade is changed from R8mm to R7mm, which improves the shearing quality of the two corners of the channel steel. The amount of shear overlap improves the shear quality of the channel steel shoulder; the upper edge width of the lower shear blade is changed from 79mm to 80mm, and the lower edge width is changed from 97mm to 94mm, so that the slope of the lower shear blade leg end is smaller than the slope of the finished channel steel pass. , so that when the legs are sheared, the upper and lower parts of the legs will not be stressed at the same time, thereby reducing the shearing force and improving the shearing quality.
- Through data regression analysis on the actual shear quality and shear gap of each specification of channel steel, the shear gap specifications of each specification were formulated, specifically: 0.20~0.30mm for 63# channel steel, and 0.20~0.30mm for 80# channel steel. 0.20~0.35mm, 100# channel steel is 0.25~0.35mm, 120# channel steel is 0.25~0.40mm, and different gaskets with thicknesses of 0.20~1.00mm are made. Every time you replace the cutting blade, measure the gap first, and then select the corresponding gasket to ensure that the shearing gap is controlled within the range of process requirements.
