The failure analysis of cold roll forming

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What is cold roll forming?

Cold roll forming is a forging technique used to shape metallic materials at near room temperature. Forming metals at lower temperatures preserves or enhances the tensile strength of the material while still allowing for a high level of a complex operation. Cold forming is a high-speed process that enables manufacturers to produce large volumes of metal products in a fast, consistent and cost-effective manner. Cold forming products are harder, yield higher, tensile strength higher, and surface finish higher than high temperature forming methods.

In this process, the bar is roughed to remove defects on the surface of the material and the bar is prepared for grinding. After this, the turning blank is straightened to minimize any changes in the bar and then ground to the final blank size at the optimum balance between the expected root and the finished part outer diameter. Once this is done, the roller performs the final moulding process to create more complex details, such as precision gear teeth. These details are created using displacement rather than cutting or grinding. By modifying the bar with great pressure, the grain structure of the material is compressed rather than removed, thus increasing the ultimate tensile strength of the final part. The process maximizes the use of materials and significantly reduces production waste.

Failure analysis of cold roll forming

Due to the high wear resistance and minimal plastic deformation of the cold roll, the surface of the cold roll is required to have a high hardness and a thick hardening layer. The material of the cold roll is 9Cr2Mo. The surface hardness of HS96 is obtained by surface quenching and tempering. The surface of the roll is hard and brittle. At the same time, poor thermal stability, and high cracking sensitivity. The thermal impact strength, tensile strength and contact fatigue strength of roll directly affect the quality of the roll. In the process of using the roll, when there is an accident such as belt damage and foreign matter entering, the surface of the roll will be subjected to thermal impact. This situation can not be completely avoided at present, so the thermal impact resistance has become one of the most important characteristics of cold roll forming.

Strip fracture or roll sticking is caused by a large amount of strip accumulation between the work rolls, which will cause local pressure on the rolls, resulting in strip and roll surface welding. This will cause a thermal impact on the surface of the roll, and the degree of roll damage depends on the severity of the accident. The factors that cause the crack depending on the performance of the roll and the cause of the crack. Conditions of use. The cracks caused by the defects of the roll itself appear inside the roll, while the surface and subsurface cracks appear due to improper operation.

Reason of roll peeling during cold roll forming?

Due to the limited working conditions of cold rolls, high surface hardness, good thermal shock resistance, spalling resistance and wear resistance are the main criteria for the selection of cold rolls. In China, high hardness cold rolls generally use 9Cr, Mo, 9Cr, MoV and other chromium-based high carbon forged steel materials. 9 Cr, W, et cetera. Chromium alloy occurs during the quenching of high carbon steel. When alloy austenite is transformed into alloy martensite, the volume of hardened parts increases because of the larger martensite. The roller surface is affected by internal tension and controlled by compression stress. After quenching, martensite is formed on the surface and volume expands. The inner core has no such change, so the surface has an impact on the roller body. One is the tension that increases the volume, and the other is the tension in the weak part of the metal. Cracks are easy to create. With the development and expansion of crack, roll surface will peel off, even fracture.

Leading manufacturer supplier of cold roll forming machine

Foshan Te Xiang Machinery Co., Ltd is a China leading manufacturer of metallic processing machines, including slitting line, cut to length line, stainless steel polishing line, ERW tube mill line, roll forming machines, embossing line and etc.

TX has experience in developing and manufacturing the roll forming machines for more than 30 years, so far the types of profiles that are produced by TX roll formers are more than 7,000. Customized solution is provided based on the individual need of each customer.

The types of roll formers above mentioned are merely the types of representation. TX has developed many other types that are too many to be mentioned here like angle iron bending line, adjustable C/U/Z channel/purlin roll forming machine with auto pinching, octagonal roll forming machine, highway guardrail beam roll forming machine, floor deck roll forming machine, drywall roll forming machine(with in-line punch and fling cut-off) etc. You are welcome to inquire with the drawing or sample. If you are looking for a high-performance roll forming machine, feel free to send an inquiry to contact us.

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