Warm press forming method and automobile frame component

Abstract

By the present invention, during forming of a steel sheet having a tensile strength of 400 MPa or greater into a press-formed part comprising a flange part and other portions by press forming, by heating the steel sheet to a temperature range of 400-700°C and then press forming the heated steel sheet using crash forming, at which time the average temperature difference between the flange part and the other portions of the press-formed part immediately after forming is kept to within 100°C, shape changes such as springback can be suppressed, the dimensional precision of a panel can be enhanced, and the desired mechanical characteristics can easily be obtained in the press-formed part.

Description

technical field

[0001] The present invention relates to a warm press forming method capable of suppressing poor dimensional accuracy due to shape changes such as springback that occurs when high-strength steel sheets are press-formed.

[0002] Furthermore, the present invention relates to an automobile frame member manufactured by the above-mentioned warm press molding method. Background technique

[0003] The application of high-strength steel plates to vehicle components has been studied in order to balance the weight reduction of the vehicle body for the purpose of increasing fuel consumption ratings and the improvement of collision safety for passenger protection. However, high-strength steel sheets generally have poor press-formability, and have a large shape change (springback) due to elastic recovery after mold release, and are prone to poor dimensional accuracy. Therefore, the parts to which press-forming is currently applied are limited.

[0004] Therefore, in orde...

Examples

Embodiment 1

[0197] Steel plates with a thickness of 1.6mm and a tensile strength of 440MPa class to 1180MPa class were heated under the conditions shown in Table 1, and then formed into Figure 6 (a) The upper pressure plate of the center pillar, one of the car frame components shown. In addition, for comparison, under the conditions shown in Table 1, the forming of the center column upper plate was carried out by warm drawing forming and cold flangeless drawing forming at room temperature (the steel plate was not heated).

[0198] Here, an electric furnace is used for heating the steel plate. The time in the furnace was set to 300 seconds, so that the entire billet was heated with a uniform temperature distribution. The heated billets were taken out of the furnace, fed into a press after a transfer time of 10 seconds, and formed under the conditions shown in Table 1. Immediately thereafter, the temperature difference between the flange portion and the portion other than the flange port...

Embodiment 2

[0211] Molten steel having the composition shown in Table 2 was smelted in a converter and cast by a continuous casting method to produce a thick slab (steel raw material). These thick steel billets (steel raw materials) were heated to the heating temperature shown in Table 3, soaked and held, and after rough rolling, they were finished rolled and cooled under the hot rolling conditions shown in Table 3, and coiled into coils. Made into a hot-rolled steel plate (thickness: 1.6mm). It should be noted that the steel sheets a, i, k, and m are heated to 700°C in a continuous hot-dip galvanizing line, and then immersed in a hot-dip galvanizing bath with a liquid temperature of 460°C to form a hot-dip galvanized layer on the surface. , and then perform alloying treatment on the coating layer at 530° C. to form an alloyed hot-dip galvanized layer. It should be noted that the plating adhesion is 45g / m 2 .

technical field

[0001] The present invention relates to a warm press forming method capable of suppressing poor dimensional accuracy due to shape changes such as springback that occurs when high-strength steel sheets are press-formed.

[0002] Furthermore, the present invention relates to an automobile frame member manufactured by the above-mentioned warm press molding method. Background technique

[0003] The application of high-strength steel plates to vehicle components has been studied in order to balance the weight reduction of the vehicle body for the purpose of increasing fuel consumption ratings and the improvement of collision safety for passenger protection. However, high-strength steel sheets generally have poor press-formability, and have a large shape change (springback) due to elastic recovery after mold release, and are prone to poor dimensional accuracy. Therefore, the parts to which press-forming is currently applied are limited.

[0004] Therefore, in orde...

Examples

Embodiment 1

[0197] Steel plates with a thickness of 1.6mm and a tensile strength of 440MPa class to 1180MPa class were heated under the conditions shown in Table 1, and then formed into Figure 6 (a) The upper pressure plate of the center pillar, one of the car frame components shown. In addition, for comparison, under the conditions shown in Table 1, the forming of the center column upper plate was carried out by warm drawing forming and cold flangeless drawing forming at room temperature (the steel plate was not heated).

[0198] Here, an electric furnace is used for heating the steel plate. The time in the furnace was set to 300 seconds, so that the entire billet was heated with a uniform temperature distribution. The heated billets were taken out of the furnace, fed into a press after a transfer time of 10 seconds, and formed under the conditions shown in Table 1. Immediately thereafter, the temperature difference between the flange portion and the portion other than the flange port...

Embodiment 2

[0211] Molten steel having the composition shown in Table 2 was smelted in a converter and cast by a continuous casting method to produce a thick slab (steel raw material). These thick steel billets (steel raw materials) were heated to the heating temperature shown in Table 3, soaked and held, and after rough rolling, they were finished rolled and cooled under the hot rolling conditions shown in Table 3, and coiled into coils. Made into a hot-rolled steel plate (thickness: 1.6mm). It should be noted that the steel sheets a, i, k, and m are heated to 700°C in a continuous hot-dip galvanizing line, and then immersed in a hot-dip galvanizing bath with a liquid temperature of 460°C to form a hot-dip galvanized layer on the surface. , and then perform alloying treatment on the coating layer at 530° C. to form an alloyed hot-dip galvanized layer. It should be noted that the plating adhesion is 45g / m 2 .

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