LPDC mold nitriding treatment process, gas nitriding, soft nitriding, deformation control, aluminum adhesion improvement

LPDC mold nitriding treatment process, gas nitriding, soft nitriding, deformation control, aluminum adhesion improvement
The mold is subjected to long-term high-temperature alternating thermal shock, resulting in surface scratches, aluminum adhesion, wear, and cracking; Nitriding is a commonly used surface strengthening method for low-pressure molds. Many molds deform beyond tolerance after nitriding, the cavity size runs away, or the nitride layer is too brittle, resulting in peeling off during production.
1、 Nitriding process parameters, layer depth, hardness quantification standards
Gas soft nitriding: 570-580 ℃, insulation for 3-5 hours; compound layer 0.008-0.015mm, diffusion layer 0.15-0.25mm, hardness HV600-800, small deformation, suitable for nitriding after cavity precision machining.
Gas nitriding: 510-530 ℃, insulation 12-24h; diffusion layer depth 0.3-0.5mm, higher hardness, but longer cycle, higher deformation risk, suitable for long-term large-scale molds.
It is not recommended to use ion nitriding for complex deep cavity molds, as the nitriding in the corners of the deep cavity is uneven, resulting in color difference and discrete hardness.
Reserve deformation allowance before nitriding: leave 0.02-0.04mm grinding allowance after precision machining, and polish the size after nitriding.
Before nitriding, Xinfeng Machinery molds undergo stress relief tempering to release machining stress and reduce nitriding warpage deformation.
2、 Preparation before nitriding, furnace installation, polishing after nitriding, and usage taboos
Thoroughly clean the mold cavity of oil stains and residual release agents before nitriding. Oil stains may cause nitriding blind spots, insufficient hardness, and localized aluminum adhesion.
Stress relief tempering: Hold at 600 ℃ for 4-6 hours, slowly cool with the furnace, eliminate CNC machining stress, which is the core step of controlling deformation.
After nitriding: the compound layer is thin and cannot be polished excessively. Polishing wears through the compound layer, and the nitriding effect disappears directly; Only do mirror polishing.
Taboo: Nitriding molds are prohibited from rapid cooling. If the temperature difference during mold water cooling is too large, the nitride layer is prone to cracking and peeling off; The brittleness of the nitride layer is higher than that of the substrate, avoiding knocking and bumping.
3、 Differences in Nitrogen Control for Overseas Customers
Simplified nitriding of Southeast Asian molds without stress relief tempering, resulting in significant deformation after nitriding, requiring manual polishing to repair the mold cavity.
The North American customer's mold nitriding comes with hardness gradient and layer depth metallographic reports, and the nitriding deformation amount is included in the mold acceptance criteria.
European customers prioritize soft nitriding and deformation control, value dimensional stability, and do not blindly pursue deep nitriding.
Long term continuous production of molds in the Middle East, using hard nitriding, pursuing longer wear resistance life, and supporting strict heating and cooling curves.
4、 Nitriding failure chain
No stress relief tempering before nitriding → stress release during machining, cavity warping, and dimensional deviation;
Surface oil stains have not been cleaned thoroughly → Nitriding blind spots, low local hardness, priority for aluminum adhesion and pulling;
Overpolishing, grinding through the compound layer → nitriding failure, with little difference from non nitriding molds;
The nitride layer is too thick and the hardness is too high, resulting in high brittleness. Under thermal shock, the nitride layer peels off and falls into the mold cavity, forming slag inclusions.
5、 Long tail traffic layout ideas
Low pressure casting mold nitriding, soft nitriding, mold aluminum adhesion improvement, deep nitriding layer, aimed at mold masters and heat treatment engineers.
keywords LPDC mold gas nitrocarburizing、nitriding treatment for low pressure casting die；
Problem class: distortion control when nitriding aluminum casting mold;
Comparison class: Gas Nitriding vs Nitrifying Die for LPDC.
Suitable for special pages on mold maintenance and surface strengthening.
6、 Common misconceptions in the industry
Misconception 1: The deeper the nitride layer, the better. Deep nitriding is more brittle, prone to peeling off under thermal shock, and can also cause greater deformation.
Misconception 2: After nitriding, casually polishing and grinding through the compound layer will directly result in the loss of wear and adhesion resistance to aluminum.
Misconception 3: Nitriding can cure aluminum adhesion, while nitriding only improves it. Abnormal mold release agents and mold temperatures can still cause aluminum adhesion.
FAQ
Q: What are the common temperatures for soft nitriding?
A: 570-580 ℃.
Q: What is the thickness of the soft nitride compound layer?
A：0.008–0.015mm。
Q: Is there a necessary process before nitriding?
A: Stress relief tempering.
Q: What are the taboos for polishing after nitriding?
A: Do not over polish to prevent the compound layer from being worn through.
Q: Advantages of hard nitriding?
A: Deep diffusion layer, longer wear resistance life.
Q: What are the causes of nitride layer peeling off?
A: Hard layer, rapid cooling impact, and collision.
Q: Core benefits of nitriding?
A: Improve surface hardness, reduce aluminum adhesion and strain.
Q: Is complex cavity preferred?
A: Gas soft nitriding, controllable deformation.