Preparation method of high-carbon extra-thick composite die blank

Abstract

The invention discloses a preparation method of a high-carbon extra-thick composite die blank. The method comprises the steps that weak cooling is carried out on the surface layer of a continuous cast blank leaving from a bent bridge section, the offline continuous cast blank is subjected to air cooling to 300-700 DEG C and then subjected to hot charging, rapid heating is carried out, the temperature of a heating section and the temperature of a soaking section are controlled to be 50-150 DEG C higher than AC3 temperature, and the heating time is 0.2-1 h; the discharge rapid cooling speed is controlled to 1-10 DEG C / s; the temperature of the stacking slow cooling stack position is 150-300 DEG C, and the time is longer than or equal to 8 h; a milling machine is used for milling the six faces of the steel blank, and fine milling is carried out for 1-2 mm after a metal substrate is milled on a composite interface; the composite blank is horizontally placed into a vacuum chamber for vacuuming, wherein the vacuum degree is smaller than 1*10<-2>Pa, and the vacuuming time is 20-30 min; the welding voltage is 20-100 KV, the welding current is 50-200 mA, the welding speed is 200-300 mm / min, and the depth of fusion of the composite blank is controlled to be 60-100 mm. On the premise of ensuring the good surface quality of the blank, the preparation method has the significant effect on effectively improving the production efficiency of steel for a die set, reducing deformation and cracking in the welding process and improving the composite steel blank yield.

Description

technical field [0001] The invention belongs to the field of metallurgical industry slab preparation technology, and in particular relates to a method for preparing a high-carbon extra-thick composite mold steel slab mother blank containing 0.42-0.60wt% of C, 0.20-0.80wt% of Mn and 100-1000mm in thickness . Background technique [0002] Die steel is a steel type used to manufacture various forging, stamping or die-casting workpiece molds. It has become an important product with a large amount of consumption and a wide influence in the world's industrial production. Affected by the characteristics of the mold, this type of steel has high requirements on the purity of the steel and the uniformity of the interface structure and performance of the steel. Formwork steel with C:0.42~0.60wt% and Mn:0.20~0.80wt% as the main components is a kind of mold steel with a large amount of consumption, and has a large specification coverage (mainly concentrated in 50~300mm group spacing) ,...

AI Technical Summary

Problems solved by technology

[0003] The problems in the production of steel ingots are that the yield rate caused by problems such as risers and rolling wedges is generally not high, and due to the internal defects of die-cast ingots, it is difficult to produce super-large unit weight (more than 30 tons) products

[0007] For the steel used for the formwork mentioned above, since the structure at room temperature is ferrite + pearlite, and the structure of the welding fusion zone has high carbon element characteristics, high carbon equivalent, and strong hardenability, the welding fusion zone is air quenched. Martensite is obtained. Due to the volume expansion brought about by the phase transformation process, stress is generated between the region and the surrounding non-transformed structure. When the stress exceeds the material strength limit, deformation and cracking will occur. Experience shows that this kind of cracking crack is visible to the naked eye after welding. It is extremely difficult to find, and it is difficult to detect through flaw detection and other methods. Once it penetrates the fusion zone after standing still after welding and subsequent heating and rolling processes, it will cause air leakage and directly lead to waste products.