Cold-rolled metal strip is one of the key materials in modern industry. Due to its increased strength, accuracy, surface smoothness and a wide range of steel grades, it is widely used in a wide variety of industries, from automotive to microchip manufacturing. An important technological operation in its production is welding, which provides a cost-effective and flexible rolling process.
In this article, we will describe in detail the role of welding in the production of cold-rolled strip, consider the types of welding, and the characteristics of steels produced at PZPS.
What is cold rolled strip and where is it used
Cold-rolled strip is thin strips of metal obtained by cold rolling, in which workpieces are passed through rolls at a temperature below the recrystallization temperature. This process allows us to achieve the following results:
- minimum thickness tolerances (up to hundredths of a millimeter);
- high surface finish (suitable even for mirror polishing);
- excellent mechanical properties: strength, hardness and plasticity.
Main applications:
- Automotive and aeronautical equipment: used for the production of body parts, shock absorbers, fasteners.
- Construction: It is used as a reinforcing material, as well as for the manufacture of fences, architectural profiles, exterior and interior elements.
- Electronics and energy: used for the manufacture of transformers, windings, contact groups and other live parts.
- Home appliances: necessary for creating instrument cases, fasteners, heating elements and other internal components of various devices.
- Instrument engineering and mechanical engineering: due to its high plasticity and ability to maintain its shape after processing, the tape is ideal for production stamped parts.
Overview of steel and alloy grades produced by PZPS
PZPS offers a wide range of cold-rolled steel grades, each of which has its own application in modern industry.
Electrotechnical steels:
- 20895, 20880, 20860, 20832 — silicon-doped materials with high magnetic saturation and low hysteresis losses are used in transformers and generators.
- 21895, 21880, 21860, 21832 — varieties of the above brands with improved characteristics for high-frequency equipment.
Precision soft magnetic alloys:
- 50N, 50NP — nickel-based materials with high magnetic permeability are used in various sensors and relays.
- 79NM, 80NM, 81NMA — iron-nickel alloys with a narrow hysteresis loop and a low coercive field, ideal for working in alternating magnetic fields.
- 49K2FA-VI, 27KH — for rotor and stator parts.
Precision alloys with high electrical resistance:
- X15YU5, X23U5, X23YU5T — used for the manufacture of heating elements that are resistant to overheating and oxidation.
- X20N80N, X15N60N — used in instrument making, electric heaters, and industrial automation for the manufacture of devices operating at temperatures above 1000°C.
Alloys with a specified TKLR:
- 29NK, 33NK, 36N, 42N — used in electronic equipment, where dimensional stability is important when temperature changes. They are used in connections with ceramics and glass (for example, in radio lamps, electronic boards, thermoblocks).
Corrosion resistant steels:
- 12X18N9 — classic austenitic stainless steel, resistant to corrosion in atmospheric and slightly acidic environments. Used in chemical, food grade industries and medicine.
- 12X18H10T — modification with the addition of titanium, resistant to intergranular corrosion. Ideal for welded structures.
- 10X17N13M3T — increased resistance to aggressive environments, including saline and acid.
Corrosion-resistant steels are also widely used in modern construction for the manufacture of various decorative elements.
Why welding is irreplaceable in the production of cold-rolled strips
Rolling production lines work with metal coils, but each roll has a limited length. To ensure the continuity of the process and reduce costs, welding is used — a way to combine two rolls into one without compromising quality.
Key benefits of using welding:
- Improving the efficiency of the rolling process — long rolls reduce the time required to reconfigure equipment between batches, which speeds up the production process and increases efficiency.
- Production flexibility — joining several rolls of metal into one long roll makes it possible to obtain strips of the required length without the need for longer initial rolls.
- Saving material — joining coils makes it possible to effectively use raw materials, minimizing waste and reducing the amount of metal required to produce a given volume of products.
- Production optimization — lengthening metal coils makes it possible to optimize the use of raw materials and increase rolling productivity.
With the help of welding, manufacturers can optimize their processes, reduce costs and offer customers a better product.
Fact: welding one thin strip with a thickness of 0.3 mm requires an accuracy of fractions of a millimeter, and the welding zone itself must be strong, but not thicker than the main material, otherwise it will lead to defects during further rolling.
Types of welding used in the production of cold-rolled strip
In modern production, three main types of welding are used: contact welding, electric arc welding and laser welding. Each of them has its own peculiarities.
Contact welding
A method of joining metal, which uses the heat released when an electric current passes through the point of contact between parts. This process is accompanied by the application of mechanical pressure, which ensures a strong connection. Contact welding is used for thin steels, in mass production and on automatic lines.
Process steps:
- Surface preparation. To ensure good contact, the sheets to be welded are cleaned of rust, dirt and oxide films.
- Metal heating in the contact zone. A high-strength electric current is passed through the parts to be welded, which heats the steel to the melting point.
- Pressure application. The heated surfaces are pressed together with a certain force, forming a strong welded joint.
- Metal cooling and solidification. After the current supply is stopped, the metal cools down and hardens, and a strong welded joint is formed in the welding zone.
Benefits:
- Productivity. The high speed of the welding process can significantly reduce the connection time.
- Joint strength. To obtain a reliable seam, it is enough to fine-tune the parameters of the welding equipment.
- Cost-effectiveness. Contact welding does not require the use of electrodes and filler materials, which simplifies the process and reduces costs.
Disadvantages:
- Not suitable for thicker materials. Contact welding is most effective for joining materials of small thickness.
- Fine tuning of equipment and surface preparation. To obtain a high-quality seam, the welding parameters (current, time, pressing force) must be strictly observed. This requires a highly qualified operator and precise equipment.
- The difficulty of welding some materials. For example, alloys with high thermal conductivity or corrosion-resistant steels may be difficult to contact welding due to their specific properties.
In contact welding, the current can reach several thousand amperes, but the current will not last more than a few seconds. At the same time, the temperature in the contact zone is more than 1300°C — higher than the melting point of most steels.
Arc welding
The metal parts are connected due to the heat generated by the electric arc generated between the electrode and the metal being welded. The resulting arc melts the metal and makes it possible to combine materials. This method is widely used for joining various types of steel.
The process includes the following steps:
- Preparation. The surfaces to be welded are cleaned of dirt, rust and oxide films to ensure good contact between the surface and the electrode.
- Creating an electric arc. Using a welding machine, an electric arc is created between the electrode and the metal. The high arc temperature melts the metal in the welding zone.
- Weld formation. The molten metal joins to form a weld. After the power supply is cut off, the metal solidifies to form a strong connection.
Benefits:
- Suitable for various alloys and metals, including steel, aluminum, copper and others.
- Simplicity of equipment and availability. Arc welding machines are relatively inexpensive and easy to use, which makes this method popular.
Disadvantages:
- It requires protection from radiation. Welding releases ultraviolet radiation, which is harmful to the retina and skin, so it is important to use personal protective equipment.
- Dependence on the welder's experience. The quality of the welded joint depends heavily on the qualifications of the welder and the correct configuration of the equipment. The wrong choice of welding parameters leads to the formation of defects in the weld.
The average weld pool temperature during electric arc welding is about 1700°C, and the maximum welding arc temperature is 8000°C.
Laser welding
The most high-tech method. It is used in automated lines, especially when working with expensive and sensitive to deformations materials. It is based on the use of laser energy for local melting and fusion of materials.
The process consists of the following steps:
- Preparation. To ensure good contact and a high-quality weld, the surfaces to be welded are cleaned of dirt, rust and oxide films.
- Focusing the laser beam. The laser beam focuses on the contact point and melts the metal with minimal thermal effect. This allows the metal to melt accurately and quickly in the desired area.
- Welding. Under the influence of laser radiation, the metal in the welding zone melts and combines.
- Weld formation. After the laser beam is turned off, the molten metal cools down and solidifies, forming a strong compound.
Benefits:
- High accuracy and quality. Laser welding allows precise control of the metal melting process, ensuring high quality welds and minimizing the risk of damage to surrounding materials.
- Minimum heat-exposure zone. The laser beam is concentrated on a small area, which reduces the thermal effect on surrounding tissues and minimizes deformation.
- It is suitable for automation. Laser welding is easy to automate, which makes it possible to integrate it into production lines and increase the efficiency of technological processes.
- The ability to weld hard-to-weld alloys. This method is suitable for welding various metals and alloys, including those that are difficult to weld using other methods.
Disadvantages:
- Expensive equipment. Laser welding systems are expensive, which limits their use in some areas.
- It requires highly qualified staff. To work effectively with laser equipment, highly qualified operators who are familiar with the peculiarities of the laser welding process are required.
The focal spot diameter during laser welding can be less than 0.1 mm, which ensures jewelry accuracy even at high operating speeds.
Modern welding technologies: a look into the future
Modern welding is developing rapidly. Among the advanced solutions that are used or tested in the production of tape are the following:
- Hybrid laser-arc welding. It combines the advantages of a laser (accuracy) and an arc (penetration depth). It provides high strength and speed.
- Ultrasonic welding. Ideal for thin tapes and foils. It is used when it is necessary to combine materials without melting them, for example, for sensitive electronic components.
- Welding in an inert environment. It provides an ideal level of compound purity, especially when working with precision alloys and steels that are sensitive to oxidation.
- Induction welding. It is used for long longitudinal joints. The method is effective for rapidly heating and combining the tape on continuous production lines.
Why do they choose PZPS
The St. Petersburg Precision Alloy Plant is one of the leading suppliers of cold-rolled strip in Russia and the CIS. In ours product range more than 50 types of steels and alloys, from standard to unique precision materials. Thanks to modern equipment — automatic lines, high-precision rolling and welding machines — we can produce a tape of the length, width and thickness you need. Our process quality control ensures that all our products meet high industry standards.
Order cold-rolled strip with perfect welds today. Contact us to get a product that meets your industry requirements.
