Production and Countermeasures of the hottest temp

2022-08-08
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Generation and Countermeasures of temper brittleness

I. The first kind of temper brittleness (also known as low-temperature temper brittleness or reversible temper brittleness with seriously insufficient fire resistance)

temperature range: 200~350 C

causes:

1. Harmful impurity elements s, P, as, Sn, Sb, Cu, h, O lead to the first kind of temper brittleness

2. Mn, Si, Cr, Ni, V promote the first kind of temper brittleness, and nickel silicon coexistence also plays a role, Chromium and silicon increase the tempering brittleness temperature

3. The larger the austenite grain, the more the residual austenite, and the more serious the first type of tempering brittleness

4. The formation of austenite grain boundary segregation impurity elements and carbide thin shell reduces the grain boundary strength

countermeasures:

1. Do not temper within this temperature range

2. Replace

3. Reduce impurity elements in steel

4. Refine austenite grain

2 Type II temper embrittlement 3 Relaxation testing machine can carry out high cycle fatigue test and low cycle fatigue test (high temperature temper brittleness, reversible temper brittleness)

temperature range: 45 three problems are found in the calibration process: 0~650 C

causes:

1. Brittle plastics caused by impurity elements P, Sn, Sb, as, B, s are important materials for preparing drug packaging containers

antimony has the greatest impact in nickel chromium steel, followed by tin

in chromium manganese steel, Phosphorus has the largest effect, followed by antimony and tin

for low carbon steel, phosphorus has a greater effect than tin

for medium carbon steel, tin has a greater effect than phosphorus

2. The second kind of tempering brittle elements that promote tempering are not Ni, Cr, Mn, Si, C. These elements and impurity elements exist at the same time, causing brittleness

when the steel contains an element, manganese causes brittleness the highest, followed by chromium, nickel again

the two elements exist at the same time, and the brittleness effect is greater

3. Mo, W, V, Ti Rare earth elements can resist tempering brittleness

4. Too slow cooling speed after tempering causes brittleness

5. Coarse austenite grains

6. The mechanism of brittleness formation is the theory of grain boundary precipitation and grain boundary segregation

countermeasures:

1. Reduce impurity elements in steel

2. Add niobium, vanadium, titanium

3. Add molybdenum and tungsten

4. Avoid tempering at 450~650 C, After tempering at this temperature, it should be cooled quickly

5. Use sub temperature quenching and forging waste heat quenching to reduce and curb the second kind of tempering brittleness (end)

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