How to Improve Insufficient Strength and Brittleness of Electrode Paste (from Both the Formulation and the Process Side)-FAQ-Graphite Electrode and Electrode Paste Supplier | Rongxing Group-Graphite Electrode and Electrode Paste Supplier

Abstract

Typical signs of insufficient strength after sintering: poor impact resistance in the lower section of the electrode, frequent hard breaks, fracture-surface particles that "crumble at a pinch", and high porosity of the sintered body. In terms of the indicator, the compressive strength of the sintered body should generally be ≥ 20 MPa (measured after sintering at 1200℃). Improvement must start from the formulation and the process sides simultaneously; changing only one side usually fixes one problem and creates another.

Keywords

Electrode paste strength；sintered-body compressive strength；formulation optimization；paste plant process control；Rongxing Group

Last updated

2026-11-10

Owner

Rongxing Group Technical Team

1. Formulation perspective

Adjustment	Working mechanism	Recommended value / notes
Increase the pitch proportion	Higher coking yield, denser binding bridges between aggregate grains	Binder 20%–24% (upper limit for sealed-furnace paste); too high worsens volatilization and smoking
Add graphite scrap / graphitized coke	Improves electrical and thermal conductivity, lowers thermal stress, improves thermal shock resistance	5%–15% addition; take the upper limit for high-power furnaces
Switch the aggregate to electrically calcined anthracite + calcined petroleum coke	Dense, low-ash, thermally stable, high skeleton strength	Ash ≤ 5% (≤ 4% for sealed-furnace paste); reject metallurgical coke / green coke
Optimize the grain-size gradation	Close packing of large and small particles, lower porosity	Design coarse : medium : fine for "closest packing"; maximum block ≤ 1/10 of the cross-section dimension
Add pitch coke or butt (residual electrode) powder	Fine powder fills the gaps and forms a continuous carbon network after coking	Butts must be clean and free of impurities, otherwise the impurities introduced outweigh the benefit
Control the volatile matter window	Too low: insufficient coking; too high: more pores	13%–17% (fine-tuned according to how well sealed the furnace is)

2. Process perspective (production at the paste plant)

Process step	Key control	Typical parameters
Kneading	Insufficient temperature → uneven pitch distribution; insufficient time → raw material entrained	180–190℃, 60–75 min; pressurized kneading preferred
Temperature equalizing and ageing	Let the paste from the kneader stand to equalize temperature and relieve thermal stress	Equalize so that forming takes place at 140–145℃
Forming pressure	Insufficient pressure → low bulk density of the green paste	Formed-body density ≥ 1.60 g/cm³ (depending on the formulation)
Block size and shape	Large blocks sinter poorly at the core and easily leave a "raw core"	8–15 kg per block; large furnaces change to cylindrical / elliptical paste
Cooling and setting	Quenching creates internal stress and cracking during transport and storage	Gradient cooling; avoid quenching with water

3. Process perspective (on-site use by the customer)

Paste temperature management: when transport and stockpile temperatures fall below 0℃ in winter, paste blocks become brittle; store them in a warm shed (≥ 10℃) for more than 24 h before adding;
Baking regime matching: the paste's volatile matter must match the furnace's baking heat source (furnace-mouth radiation / fin-plate current / furnace gas preheating) — do not use high-volatile paste in sealed furnaces, nor low-volatile paste in semi-closed furnaces;
Incoming inspection: test bulk density and block breakage rate for every batch; send sintered strength for third-party testing quarterly.

Principle of judgement: first establish where the "blame" for a strength problem lies — if the same batch of paste shows normal strength on other furnaces, the problem is mostly at the user end (tamping, cooling, baking regime); if multiple batches are brittle on different furnaces, the problem lies in the formulation and the production process.

How to Improve Insufficient Strength and Brittleness of Electrode Paste (from Both the Formulation and the Process Side)

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