Heat treatment technology of ultra-long mandrel

Abstract

The invention discloses a heat treatment technology of an ultra-long mandrel used for a mandrel pipe mill, wherein the heat treatment characteristics of hot-work mould steel are considered according to the spot environment, the ultra-long mandrel adopts 4Cr5MoSiV1 steel (H13) as raw material, and the raw material is processed through forging, alignment, rough lathing with outside round surface and ultrasonic detection in turn and then is processed through heat treatment on a medium-frequency induction heating furnace. The heat treatment technology comprises the following steps: performing medium-frequency quenching once and tertiary medium-frequency tempering treatment three times. The beneficial effects of the medium-frequency heat treatment technology of the ultra-long mandrel are as follows: the technology is simple, the operation is convenient, the speed is fast, the oxidation and decarburization phenomenons are less, the material is saved; alignment is not needed to perform after the heat treatment, the production cost is low, the efficiency is high; the heating is uniform, the temperature difference on the surface of the mandrel is small, the temperature control accuracy is high, the four-quadrant hardness of the surface and the subsurface are uniform, the impact value can be increased by 10%, the cracking phenomena of the mandrel is delayed in use, the service life of the mandrel can be increased to twice of the common mandrel; and the technology is also applicable to the heat treatment of common floating mandrels and retained mandrels; and the energy consumption is low and pollution can not be caused to the environment.

Description

technical field

[0001] The invention relates to a mandrel heat treatment process for a continuous pipe mill, in particular to an ultra-long mandrel heat treatment process. Background technique

[0002] In the rolling process of seamless steel pipes, the mandrel is an important tool on the pipe rolling mill. In addition to being made of high-strength and high-wear-resistant materials, it also requires high surface quality. The mandrel works together with the roll to roll the perforated tube blank into seamless steel tubes of various sizes. According to different rolling methods of steel pipes, it can be divided into floating mandrel, semi-limited mandrel and limited mandrel. In the recent stage, the market demand for seamless steel pipes continues to grow, resulting in a linear increase in the consumption of mandrels on rolling mills, with domestic consumption reaching 40,000 tons per year.

[0003] The commonly used material for the mandrel is 4Cr5MoSiV1 steel (H13), which...