At present, the lightweight of vehicle body is an important challenge faced by the whole car factory. As one of the important solutions of lightweight, high-strength steel has the advantages of enhancing the strength of vehicle body and improving the collision safety performance. However, difficulties in forming and serious springback of high-strength steel have brought great troubles to tooling manufacturing and debugging.

In this case, the emergence of thermoforming steel has become the perfect choice to solve the above problems. After special processing technology, the thermoformed steel shows excellent strength and toughness under high pressure and heavy load. It has high strength and can effectively resist external pressure and impact; At the same time, due to the heat treatment, the springback problem of the hot formed steel has been better improved, which makes the difficulty of tooling manufacturing and debugging greatly reduced.

Composition and Properties 

of Thermoformed Steel Plates

Thermoforming steel plate is a kind of steel plate through special manufacturing process, thermoforming steel plate is mainly composed of carbon, silicon, manganese, sulfur, phosphorus and other elements, which has a high carbon content, usually between 0.10% and 0.25%. In addition, a small amount of alloying elements, such as chromium, nickel, molybdenum, etc. may also be added to the thermoforming steel to adjust the performance of the steel plate.

An example from the field of automotive manufacturing illustrates the performance of thermoforming.

Suppose that in the body structure of a car, a material needs to be used to make the body beam to ensure that the vehicle has sufficient strength and safety in the event of a collision. In this case, thermoformed steel can be chosen as the material for the body beam.

The performance advantages of thermoformed steel in automotive manufacturing are as follows:

• High strength: After special processing technology, the hot formed steel has small and uniform grains, which has high tensile strength and yield strength. This enables the body beam to absorb energy effectively in the event of a collision, reducing the impact of the collision on the vehicle and its occupants.
• Excellent toughness: The toughness of the thermoformed steel is excellent, which means that the body beam can bend and deform without breaking during a collision. This helps prevent the collapse of the vehicle structure and protects the safety of the occupants of the vehicle.
• Good plasticity: The plasticity of the thermoformed steel allows the body beams to adopt complex shapes and designs to adapt to the needs of different vehicle types and body structures. In this way, car manufacturers can choose different shapes and sizes of body beams according to the requirements of different models.
• Good welding performance: Thermoformed steel usually has excellent welding performance, and the body beam can be connected into the overall structure through welding and other processes to improve the overall rigidity and stability of the car.

Thermal Forming Parts Manufacturing Process Flow

1.Blanking sheet production

The blanking sheet is the blanking sheet with a specific profile produced on the uncoiling blanking line, and then the blanking sheet is transported to the thermoforming line, and the blanking sheet is sent to the coding machine through the vacuum sucker by the robot, and then placed on the conveyor line and transmitted to the heating furnace.

2. Austenitizing of metallographic structure

The metallographic structure of the initial boron steel is ferrite and pearlite, we can see from the figure above that in the Austenization stage of hot forming process, the first temperature to 930-950℃ and then heat preservation makes the internal structure of the sheet material completely austenitic, and the plasticity of the austenitic structure is very good, low strength, very suitable for stamping processing.

3. Hot stamping processing

The sheet material from the heating furnace will be quickly sent to the cavity of the hot forming die by the manipulator clamp for stamping processing. The key difference between the hot forming die and the cold stamping die is that there is more water cooling system. During the process of pressure holding cooling (quenching), the metallographic structure of the sheet will be completely changed into martensitic structure. The strength and hardness of martensitic structure are very high, the tensile strength of thermoforming parts can reach 1500MPa, and the surface hardness of parts can reach 52HRC.

4. Laser cutting

Due to the strength and hardness of hot forming parts, the traditional cold stamping die is used for trimming and punching, and the die parts wear seriously and the life is seriously shortened. The current solution is to equip 3-4 laser cutting robots at the end of the thermoforming line for trimming and punching.

5. Post-processing

Because in the process of thermoforming, the surface of the part is oxidized to form an oxide film when it is in a high temperature state, it is generally necessary to clean the part by shot peening.

The above is a general thermoforming parts manufacturing process flow, the specific process and steps may vary depending on the type of product, materials and requirements.

The application field of thermoforming steel is very wide, especially in high pressure and heavy load scenarios. In aerospace, Marine, nuclear energy, energy and other fields, thermoformed steel is widely used in the manufacture of high pressure vessels, structural parts with high strength requirements. In the automotive industry, thermoformed steel is used to manufacture body structures and body safety components, providing vehicles with greater compression and crash-resistance.

In the future, with the continuous progress of science and technology and the continuous innovation of technology, the application prospect of thermoforming steel will be broader. The advantages of thermoformed steel in high-pressure and heavy-duty scenarios will be continuously exploited, bringing more possibilities and opportunities to various fields. At the same time, the green environmental protection and sustainability of thermoforming steel will also receive more attention and attention. Let us look forward to the brilliant performance of thermoformed steel in the future, and contribute more to the development and progress of human society!