Impregnated graphite blanks for shops that machine their own carbon graphite parts — job shops, seal reconditioning works and component OEMs. Huahao Sealing has produced carbon graphite since 2006 and supplies extruded rod and tube, molded ring blanks, isostatic block stock and near-net-shape blanks, in unimpregnated, phenolic/furan/epoxy resin, antimony, copper or Babbitt impregnated condition. Unimpregnated base density 1.55-1.70 g/cm³ with 8-15% porosity, below 2% after impregnation. We machine to customer drawing and advise on pre- versus post-impregnation machining routes, carbide versus PCD tooling and stress relief.
| Blank Forms | Extruded rod & tube / molded ring / isostatic block / near-net-shape |
| Base Density | 1.55 – 1.70 g/cm³ (unimpregnated) / 1.75 – 1.80 (resin) / up to 2.20 (antimony) |
| Porosity | 8 – 15% before impregnation, < 2% after impregnation |
| Impregnant Options | None / Phenolic / Furan / Epoxy / Antimony / Copper / Babbitt |
| Machining Hardness | 60 – 95 HS (unimpregnated) / 70 – 105 HS (impregnated) |
| Service Temperature | -200°C ~ 220°C (resin) / 400°C (copper) / 500°C (antimony) / 600°C (carbonized) |
| Thermal Conductivity | 8 – 70 W/m·K (grade and direction dependent) |
| CTE Anisotropy | ≈ 1 × 10⁻⁶/°C within layer planes vs ≈ 27 × 10⁻⁶/°C across layers |
Four blank forms — extruded rod and tube, molded ring blank, isostatic block and near-net-shape stock, covering seal rings, bushings, three-part rings and custom parts
Impregnation state as ordered — unimpregnated cuts easiest; phenolic/furan/epoxy resin, antimony, copper or Babbitt can be applied after roughing or before finishing to avoid a second setup
Pre-relieved stress and pre-machining verification — graphite is graphitized above 2500°C, where in-plane CTE is about 1 × 10⁻⁶/°C against about 27 × 10⁻⁶/°C across the layers; cooling plus impregnant cure locks residual stress into the blank, which releases and distorts after roughing, so blanks are stress-relieved and rough-verified before shipment
Batch-to-batch consistency you can check — lot sampling reports for density and porosity (base 1.55-1.70 g/cm³, 8-15% porosity) prevent out-of-spec porosity that blocks impregnant penetration and density scatter that shows up as wall-thickness variation after machining
Material and machine time saved — near-net-shape blanks hold stock down to what final grinding needs, cutting expensive graphite removal and PCD cycle time on production quantities
In-house seal rings — machine shops turn the OD and grind the face of molded ring blanks to make pump seal rings
Bushing and guide-sleeve stock — bored from extruded rod to replace metallic bushings on pump shafts
Three-part and split seals — cut to length and slotted from tube stock to make spring-loaded split rings
Contract manufacturing — CNC shops machine custom carbon graphite parts to end-user drawings
Spares and reconditioning — reverse-engineer a failed part and re-cut blanks so small urgent lots stay on schedule
| Grade Code | Temperature | Notes |
|---|---|---|
| Unimpregnated | 350°C | Cuts easiest, carbide tooling is enough; 8-15% porosity means the finished part still needs impregnation and finishing stock |
| Phenolic resin | 220°C | Tg 160-190°C — excessive cutting heat softens the resin skin; drop the speed, cool the cut, or finish before impregnating |
| Furan resin | 220°C | Tg 260-300°C, Td5 340°C, 65% char yield — holds up better than phenolic at the cutting edge, the usual choice for post-machining impregnation |
| Antimony | 500°C | 85-105 HS — highest tool wear; run PCD and leave roughing stock rather than roughing from the impregnated condition |
| Copper | 400°C | 80-100 HS — the copper phase smears and loads the tool; use a sharp rake and generous chip clearance for clean surfaces |
| Babbitt | 200°C | 70-90 HS — soft alloy deflects under the cut; take light multi-pass finishing depths to hold size |
Pricing is quoted per specification, impregnation condition and quantity, with no fixed threshold. Single prototypes and small reconditioning lots are accepted. Isostatic block and near-net-shape blanks are quoted individually from the part geometry and stock allowance, and on production volumes they usually cost less overall than machining from full-size rod. Send quantities, outer and bore dimensions and the impregnation requirement, and we will propose the blank size.
Yes, in three supply conditions: raw blank (sawn to length), near-net-shape blank (grinding stock left), or machined to final drawing (stress relief, impregnation, finishing and inspection included). Drawings or samples are both accepted. For thin-wall parts, internal cavities and long bushings we recommend one verification piece to confirm distortion before releasing the full order.
Decide by whether tolerance or final property consistency governs. To guarantee the pores are filled and properties are uniform, finish first and impregnate after. For larger volumes where dimensional stability matters most, buy impregnated stock and finish in one setup. Unimpregnated blanks at 60-95 HS and 8-15% porosity cut freely with carbide tooling; antimony-impregnated material at 85-105 HS and copper at 80-100 HS raise tool wear sharply, so use PCD and leave roughing stock. With resin grades control cutting heat: phenolic Tg is 160-190°C, furan Tg 260-300°C with Td5 340°C and 65% char yield, so furan tolerates the cutting zone better.
Three checks: require lot-by-lot sampled density and porosity data (unimpregnated base 1.55-1.70 g/cm³, 8-15% porosity; below 2% porosity after impregnation); weigh every piece in a mixed lot and compare — outliers point to uneven pressing or baking; cut a section and inspect grain uniformity and lamination. Uneven density is what causes impregnant that will not penetrate and wall-thickness variation after machining, so these two checks catch most blank failures.
Carbon graphite has low impact resistance, and thin walls, three-part rings and sharp corners chip first. Blanks are packed individually with cushioning separators so they cannot touch or stack under load; inspect OD and faces on receipt, and if chipping appears photograph it and keep the packaging and inserts so each piece can be judged as grindable or needing replacement. On the design side, breaking sharp corners into small radii and avoiding very thin walls cuts transit and clamping losses noticeably.
