What is Profile
Profiles are objects with a certain geometric shape made by rolling, extrusion, casting and other processes of iron or steel and materials with certain strength and toughness. This type of material has a certain appearance size, a certain shape in section, and certain mechanical and physical properties. Profiles can be used alone or further processed into other manufactured products, which are often used in building structures, manufacturing and installation. Mechanical engineers can select the specific shape, material, heat treatment state, mechanical properties and other parameters of the profile according to the design requirements, and then divide the profile according to the specific size and shape requirements, and then further process or heat treatment to meet the design accuracy requirements. The material, specifications and dimensions of the profile can refer to the corresponding national standards.
The concept of billeting has two meanings: blooming billeting and secondary billing. Blooming Blooming is steelmaking few large weight slab after blooming mill -rolled into blooms copper mill required. The secondary blooming is to further roll the blooms of the cross section into small billets and supply them to the finished rolling mill.
The purpose of heating is to reduce the deformation resistance of the metal, increase the plasticity of the metal, and improve the structural properties. Profile rolling is divided into rough rolling, intermediate rolling and finishing rolling. The task of rough rolling is to roll the billet into a suitable intermediate billet. In the rough rolling stage, the temperature of the rolled piece is relatively high, and the uneven deformation should be placed in the rough rolling pass rolling stage as much as possible. The task of the middle rolling is to make the rolled piece extend quickly and approach the finished size. Finish rolling is to ensure the dimensional accuracy of the product and the extension is small. The elongation coefficients of the finished hole and the pre-forming hole are generally 1.1 to 1.2 and 1.2 to 1.3 respectively .
Modern section steel production usually has the following requirements for the rolling process:
- A billet of one size is rolled into an intermediate billet of various sizes during the rough rolling stage. Rough rolling of section steel is generally carried out in a two-roll pass. If all the steel billets use continuous casting billets, from the perspective of the production organization of steelmaking and continuous casting, the size specifications of the continuous casting billets are as small as possible, and it is best to require only one specification. However, the more size specifications of the finished section steel, the stronger the company’s ability to open up the market. This requires rough rolling to have the ability to split a billet into billets of multiple specifications. Rough rolling can be used to widen and widen the profiled billet, or it can be narrowed and rolled. A typical example is the use of slabs to roll H- shaped steel.
- For profiled materials, try to use as many as possible 10,000 pass and multi-roll pass in the middle rolling and finishing rolling stages. Because the multi-roll pass and universal pass are beneficial for rolling thin and high sides, and it is easy to individually adjust the reduction of each part of the rolling piece section, it can effectively reduce the uneven wear of the roll and improve the dimensional accuracy.
- For continuous rolling of section steel, loopers cannot be used due to the large section coefficient of the rolled piece. The tension control between the frame is generally carried out by the current memory method or the torque memory method that drives the main motor.
- For most section steels, good low-temperature toughness and good weldability are generally required in use. To ensure these properties, the material requires low carbon equivalent. For these steels, low-temperature heating and low-temperature rolling can refine the grains and improve the mechanical properties of the material. Water cooling after finishing rolling also has obvious benefits for improving material properties and reducing cooling time on the cooling bed.
There are two processes for finishing profiles after rolling, one is the traditional hot sawing cut-to-length and cut-to-length straightening process, and the other is the newer long-length cooling, long-length straightening and cold sawing process.
The more prominent part of profile finishing is straightening. The straightening of the profile is more difficult than that of the sheet and pipe. The reasons are: First, during the cooling process, the bending caused by the asymmetry and uneven temperature of the section is large; the second is that the section coefficient of the profile is large, and the required straightening force is large. Due to the relatively large section of the rolled product, the roll distance of the straightening machine must also be large, and the straightening blind zone is large. Under some conditions, it will have a great impact on the use of steel. For example: the straightening blind zone of heavy rails is significantly reduced The full-length straightness of the heavy rail. To reduce the blind area of straightening, the measure on the equipment is to use the variable intercept straightening machine, and the measure on the process is the long-length straightening