Preparation method of gradient coating for surface strengthening of blanking die

Abstract

The invention discloses a preparation method of gradient cladding for blanking die surface reinforcing. The preparation method comprises the following steps that a die is preheated, cleared and machined; TRD salt bath salt preparation is conducted, specifically, a salt bath formula comprises, by mass, 70-75% of borax anhydrous, 8-12% of a chrome supplying agent, 4-6% of a niobium supplying agent,3-6% of a reducing agent and 8-10% of an activating agent; salt bath chrome and niobium co-soaking treatment is conducted, specifically, the die is soaked in a molten salt bath, the temperature of thefirst stage is 880-910 DEG C, and the heat-preservation time is 2-3.5 h; the temperature of the second stage is 930-940 DEG C, and the heat-preservation time is 2-3 h; the temperature of the third stage is 980-1040 DEG C, and the heat-preservation time is 3-4 h; and the die is taken out and then tempered after being subjected to oil quenching. According to the preparation method of the gradient cladding for blanking die surface reinforcing, the phenomenon that stress transition of the cladding is uneven is avoided, the service performance of the die is improved, and the service life of the die is prolonged.

Description

technical field [0001] The invention relates to the technical field of metal materials, in particular to a preparation method of a gradient coating used for surface strengthening of a blanking die. Background technique [0002] With the continuous development and use of fine blanking technology, especially the stamping of thick steel plates has attracted widespread attention due to its high productivity, superior stamping quality and rich economic benefits. It provides semi-refined blanks for cutting, It has many comprehensive benefits such as saving processing hours and energy consumption, reducing costs, and improving product quality. Compared with thin plate punching, thick plate punching requires greater punching force, and surface wear and heat generation are also more serious. For some molds with sharp corners, lugs or folded intersections, the contact stress during punching is much greater than The average stress, even exceeding the allowable compressive stress of th...

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Problems solved by technology

[0003] At present, the common mold surface heat treatment process schemes include traditional carburizing, nitriding, carbonitriding, PVD, CVD, electroplating, etc., but compared with TRD (Thermal Reactive Diffusion) technology, the surface coating formed by it has hardness. Insufficient (carburizing, nitriding, carbonitriding), poor bonding strength (PVD), etc., some will cause serious pollution (electroplating, etc.) and produce toxic products

The carbide coating prepared in the TRD salt bath has high hardness, strength, wear resistance and corrosion resistance. Zhang Wenjie and others invented a salt bath co-penetration agent (CN 103103476B), which overcomes the single chromizing and single chromizing. The disadvantage of infiltrating niobium is that Cr can be obtained on the metal surface 3 C 2 -NbC gradient coating, but with underlying Cr 3 C 2 The thickness of the layer is thin (1-2μm), and the ratio of the thickness of the niobium layer (8-9μm) to the thickness of the chromium layer is too large (about 4.5), resulting in poor overall continuity of the coating and uneven distribution of the phase structure. Shows inhomogeneous transition of cladding hardness, cladding cross-sectional hardness from matrix-Cr 3 C 2 Layer - NbC layer changes from 600HV-1400HV-3100HV, Cr 3 C 2 The hardness difference between the NbC layer and the NbC layer is large (△=1700HV), and there is uneven stress transition in the coating layer, which is prone to problems such as cracks, peeling, and cracking in the coating layer.

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