Permissible deviation of hot-rolled steel plates and strips (GB/T709-1988)

The allowable deviation of hot-rolled steel plates and strips (GB/T 709-1988)

Introduction

Steel strips and steel plates are two very popular steel products in a wide variety of sectors. Hot-rolled steel strips and steel plates are commonly used in construction and metallurgical engineering, as well as other engineering applications. The surface quality, mechanical properties, and dimensional accuracy of these hot-rolled steel products are of great importance. Grade GB/T 709 expresses the accuracy requirement of hot-rolled steel plates and strips; the surface quality and geometry of these steel products are specified in the standard. The main purpose of these provisions is to identify the allowable tolerances for surface quality, width and thickness, flatness and straightness.

Allowable deviation

The allowable tolerance of the hot-rolled steel plates and strips, which comply with standards GB/T 709-1988, with regard to surface quality, width, thickness, flatness and straightness is given in the standard.

In terms of surface quality tolerance, Clause 6 of the standard stipulates that there should be no defects on the surface of the steel, such as cracks, bumps, scratches and rust. In terms of tolerance for width and thickness, Clause 7 stipulates that the maximum width and thickness of the steel plate should be within the range specified in the contract. In addition, the thickness tolerance of the steel plate is also limited to 0.1mm.

In terms of flatness tolerances, Clause 8 stipulates that the maximum deviation of the flatness of the steel plate should be 0.1% of the width of the steel plate. With respect to straightness tolerances, Clause 9 stipulates that the maximum straightness deviation of the steel plate should be 0.2% of the total length of the steel plate.

Conclusion

The allowable deviation of hot-rolled steel plates and strips specified in GB/T 709-1988 involves the surface quality, width, thickness, flatness and straightness of the steel. The surface quality should not have any visible defects. The maximum tolerance for the width and thickness should be within the range specified in the contract. The flatness and straightness tolerances should be 0.1% and 0.2% of the width and length of the steel plate, respectively 。

GB/T709-1988 Hot Rolled Steel Plate and Strip Tolerances

GB/T709-1988 Hot Rolled Steel Plate and Strip Tolerances specifies the allowable deviations in sizes, shapes, weights and allowance of deviation of center line and corner radius of hot-rolled steel plates and strips.

The content of this standard includes the following sections: Scope, Normative Reference, Terms and definitions, Permissible Deviations of dimensions and shapes of hot-rolled steel plates and strips, Permissible deviations in length, Permissible deviations in width, Permissible deviation in thickness, Permissible deviation in straightness, Permissible deviation in weight, Permissible deviation in allowance of deviation of center line and corner radius.

This standard applies to hot-rolled steel plates and strips with a thickness of 2.5mm~12.2mm and a width of 100mm~2000mm produced by the following methods: thermomechanical rolling and finishing rolling. This standard does not apply to PS steel and checkered sheets.

Deviations in dimensions and shapes of hot-rolled steel plates and strips should be in accordance with the table of GB/T709-1988. Deviations in length should not be more than - 0/+2mm. Deviations in width and thickness should not be more than ±1.5%, and deviations in weight should not be more than 4.5% of the theoretical weight. The permissible deviation in allowance of deviation of centreline and corner radius should not be more than ±2.5%.

Adherence to the permissible deviations specified in this standard will ensure that hot-rolled steel plates and strips are within acceptable size, shape and weight dimensions. This standard is applicable to domestic manufacturers, users and quality inspectors.